HH ss 0 1OHAy Varah NM NATURE AND EXTENT OF FOULING OF SHIPS’ MOU LOMS se seis): >: : 2 : By J. Paul Visscher From BULLETIN OF THE BUREAU OF FISHERIES, Vol. XLIII, 1927, Part II Document No. 1031 : Mr ea A (4 J yy Pe tate tink IOGRAP Bp 4 NSTIT i UK B%, PRICE 35 CENTS Sold only by the Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. SS A SS SS SS U.S. GOVERNMENT PRINTING OFFICE 5 SHhaes Seu Bes > : 3: +: WASHINGTON : 1928 ee “ha lbs el hie ie 2 ope haha aaa eT rem aT oe Ne pre vcrean ae oa) J r x v ng tae tana \ aint in dente pene tre oatpemoe Jorcstpaae Snel ptt Nao Pie he aaa op nga Rai yes oe a boo hematin ‘ : ; x ; race Pat ARs ’ ' : % ert ae ase aiid aatie ice cide an ‘ oe ae i rev intunnd tha Ae Bersted vee erica ee bse, Baty ety i yusbdy NATURE AND EXTENT OF FOULING OF SHIPS’ BOTTOMS me By J. Paun VisscHER For the Bureau of Construction and Repair, U. S. Navy Department Bo CONTENTS Page Page Tntradiction= S222 oy 2k ee oe 193 | Factors that determine fouling—Contd. Statement of the problem__________ 193 Poison paints, ete.—Continued. History of the problem_-_-__-__-_____ 195 Poison paints. 2222222 ess 230 Methods ets Jai o ucts Ole) BO eae 198 Effect of poison on larval INatunevot fouling. 2202) kee ee a 198 barnacles________-._=__ 234 Extent of fouling-__.-___.__--.------- 203 Surface films___=__-__________ 236 Effects of fouling__-=—.---....--------s 213 Metals_________ e psialale uae et at 237 Factors that determine fouling _________ 215 Light and colors__________________ 238 Relation of duty of ship to fouling - ea PAs Submerged test panels _______ 939 ees ae a oars of Paes ean 217 Submerged colored tiles_._______ — 242 oe ee Woods Hol, Mass. 282 Wat oe, aun ak, AN 293 Beaufort, N. C__---_-___. 243 aters cruise Reacti f th id | f Seasons and rate of growth________- 225 Seek u A tat ce ae eee Sansome netodneiy. 0. 296 barnacles to spectral colors... 244 Rate of growth... 998 Reactions of larval barnacles to RLS AAI on oe DEES 998 light at time of attachment___ 246 Siemon Gaim 928 Process of attachment of the Data from ships__-___________ 928 larvee of barnacles_______ 246 _ Experimental data__.________- 229 | Discussion and conclusions_____________ 247 Poison paints, metals, and surface Summary 20 2). SS os Saya ie eee 248 Eur Ss fea he EIN ele POSKO) 4 |S BSN oY Kay eee oY aly yee eS a a ae ie os 249 INTRODUCTION STATEMENT OF THE PROBLEM Fouling of ship’s bottoms is an accumulation of plant and animal organisms, which attach and grow on both wooden and metal ships. This accumulation of material consists of many species of animals and plants, which find the bottom of a vessel a favorable place of abode. All who have ever been‘at a seacoast have noted the crowded growths of “‘seaweed,’”’ barnacles, ‘“‘moss,”’ corals, and the like that frequently cover almost all structures that are either totally or partially submerged and that afford a place of attachment. It is this type of growth, in the main, that attaches to the hulls of boats and causes them to be ‘fouled.’ In its broadest usage, this word covers not only the effects of organisms that grow on ships, but also of those that burrow into them (in the case of wooden vessels), and has even been used to include the deleterious effects of corrosion on metal ships. In this paper only the first and original idea of this term will be considered, inasmuch as 193 194 BULLETIN OF THE BUREAU OF FISHERIES the effect of marine borers recently has been studied extensively by others (Atwood, 1924), while the problem of corrosion has but little relation to this biological study. The economic importance of the fouling of ships’ bottoms rarely is realized by anyone who is not informed regarding the very special problems relating to the maintenance of ships. The factors that contribute to the importance of this problem may be outlined briefly, as follows: 1. Speed diminished up to 50 percent. . 2. Voyage delayed from 10 to 50 per cent of total time. 3. Increase in fuel consumption up to 40 per cent additional. 4, Increase in wear and tear on machinery. 5. Necessity for dry docking, cleaning, and painting after every six or eight months. 6. Loss of time for above, amounting to about one month out of every year. It has been estimated conservatively that more than $100,000,000 is spent annually by the shipping interests of the United States alone because of fouling. When one realizes that fouling often increases the resistance of a ship In water, so that the fuel consumption must be increased 30 per cent in order to maintain a given speed, and that for more than half of the time between dry dockings for any vessel that operates at sea, after the first month, such costs probably are increased by a minimum of 10 per cent, the expense due to increased fuel consumption alone assumes large proportions. It is the practice of most shipping concerns to “‘clean” the bottoms of their _ vessels every six or eight months. In order to do this the bottoms are exposed to view, either by the use of dry docks or marine railways. The former are of two types—the graving dry dock and the floating dry dock. Lighter craft frequently are removed from the water by a marine railway. The cost of maintaining and operating such equipment can be charged largely to fouling. The large sums of money involved can be realized when one learns that it costs approximately $100,000 to dry-dock, clean, and paint the bottom of a vessel such as the Leviathan or the Majestic, for these ships have more than an acre of surface exposed to the action of the sea and which must be cleaned and painted every time these vessels are dry- docked. It must not be forgotten, also, that durmg the period in dry dock the cost of maintaining the ship and its crew remains constant, while the operating income is reduced to nothing. ‘The time spent in dry dock varies with conditions from three days to three weeks, or more; but for the ships listed in this report the average is seven or eight days. This process of cleaning is illustrated in Figure 1. In addition to its economic importance, this problem has an important relation to the question of national defense. An able Navy has long been held to be the greatest force for defense that a country such as the United States can possess. Under present conditions, speed of such vessels is of increasmg importance. If, then, fouling decreases the speed by as much as 40 per cent, the efficiency of such crafts is lost and critical delays might result. From a biological point of view, this problem has several interesting aspects. The ecology of the organisms that live at some depth in the ocean has been difficult to study, because it has been impossible to bring them to the surface in sufficient ezel ‘9 oung ‘praex AABN HOMON 0G} 1810 ‘S‘S°N UL “SUpoop-Arp 10jJe Crys v Jo [[NY oy} SuraeaI Jo ssoooIgd—"T “OI (TS0L 20d) “Il 3d “2061 “WT “A “S “O 7794 FOULING OF SHIPS’ BOTTOMS 195 numbers accurately to determine their relations as life communities. When, however, the bottom of a ship is raised out of water, these communities, in their entirety and uninjured, can be seen and qualitative and quantitative studies can be made. The effect of depth in producing distinct zonations may be studied easily on ships’ bottoms, and these special groups of organisms can be studied thus in detail. The study of this problem also presents data for the solution of the problem of geographical distribution. It has long been a debated question whether a given species of barnacle or other organism attached to the bottom of a boat can survive transportation to another port and continue to live and reproduce its kind. Whether one can explain the mundane distribution of some species of organisms in this manner never has been determined. Data have been obtained that have a specific bearing on the question of the effect of pollution in our harbors and the ability of some types of organisms to sur- vive. The rate of growth of different kinds of organisms can be studied from these data, as can also the problem of seasonal variation in their abundance. The effects of various poison paints, of sunlight, temperature, salinity, and of tidal currents are all of interest in a biological study of this problem and have been considered wherever possible during this investigation. : The author was assisted in the examination of ships by F. A. Varrelman and in some of the experimental studies by R. H. Luce. To the authorities of the Bureau of Fisheries and of the United States Navy, as well, and especially to Capt. Henry Williams, he is very grateful for many courtesies and continued interest in this work. For the use of laboratory facilities during the course of this investigation he is grateful to the directors of the zoological laboratory of the Johns Hopkins University, of the United States Fisheries laboratories at Woods Hole, Mass., and Beaufort, N. C., and of the biological laboratory of the Western Reserve University at Cleveland, Ohio. HISTORY OF THE PROBLEM The problem of foulmg growths on the hulls of ships naturally is not a new one, for fouling has occurred ever since ships first were used. We seem to have no record regarding the earliest methods of prevention, but Atheneus (200 B. C.), quoted by Ewbank, informs us that “‘the ships of Archimedes were fastened everywhere with copper bolts and the entire bottom [of wood] was sheathed with lead.’ Alberti fn his work on architecture, published in the fifteenth century] tells us that a ship called “‘Trajans ship” was salvaged from Lake Riccia, where it had been submerged for more than 1,300 years, and that “over all, there was lead, fastened on with copper nails.” Young (1867) records the fact that a Roman ship, sunk in the Lake of Nemi, was found to have been coated with bitumen, over which sheets of lead had been nailed. The seams of the vessel were caulked with “‘tow and pitch,”’ the hull being made of larch wood. In the reign of Henry VIII (1510 to 1547) vessels were covered with a coating of loose animal hair, attached over pitch, over which a sheathing board about an inch in thickness was fastened to keep the hairinits place. In the reign of Charles II (1660 to 1685) “‘the Phoenix and 20 other of His Majesty’s ships were sheathed with lead and fastened with copper nails.’’ That these methods were not satisfactory 196 BULLETIN OF THE BUREAU OF FISHERIES is seon from the fact that none has persisted, for we find that during the eighteenth century the sheathing generally in use “was a doubling of the skin of a ship with wood, which was kept constantly’ payed with tar and grease, or mixtures of such compounds.” The prevention of fouling, then, has been a problem persisting through the centuries, which has taxed the skill of ingenious sea captains for hundreds of years; and the fact that it still occurs indicates the extremely difficult nature of its solution. In earlier times it was the general practice for vessels to be cleaned by the scouring action of the surf. A favorable beach was selected and the vessel carefully beached in such a manner that the surf, loaded with sand and broken shells, would scour the sides of the vessel and rid it of its fouling materials. Other vessels were run into fresh water at frequent intervals (a method still employed to a limited extent) and the organisms normally living in salt water would die and in some instances fall off, thus ridding the hull of its fouling. More recently the vessels were beached at flood tide and, allowing the vessel to list as the tide ebbed, were cleaned as the water would leave the vessel high and dry. It has been the goal all along, however, to prevent the attachment of these organisms. ‘That many people have been interested in this problem is indicated by the fact that in England, previous to 1865, according to Young (1867), more than 300 patents had been issued for antifouling materials; while in America 166 patents were issued prior to 1922, as found by Gardner (1922). The followimg quotation from his paper (p. 43) will serve to give some idea of the great variety of materials that have been employed within the last century. Amongst the many materials for prevention of fouling and corrosion of iron ships which have had patents taken for their use or been experimented with will be found silicates, quicksilver, plumbago, gutta percha, asphalte, shellac, guano, cow dung; now comes a powerful compound consisting of ‘‘clay, fat, sawdust, hair, glue, oil, logwood, soot, etc.,” mixed, “to be plastered on the ships’ bottoms”; then we have ‘‘emery, shellac, and castor oil”; next “pitch, tar, and shellac”; next comes another peculiar mixture, ‘‘baryta, litharge, arsenious acid, asphaltum, oxide calcium, and creosote’’; than another, ‘‘Burgundy red earth, grease, lime, unburnt earthenware, chalk, or Roman cement.” Next follows a very curious composition consisting of “‘grease from boiled bones, kitchen stuff, and butter without salt, mixed with poisonous materials.” Now we have the grand chef-d’oevre of the whole, which is described thus: ‘‘Sugar, muriate of zinc and copper, and the sirup of potatoes or sugar with powdered marble quartz or feldspar.” The last one, which will be noticed consists of ‘‘asafoetida with pitch, tar resin, and turpentine smeared over the bottom, and then coated with paper or cloth.’”” Who will say, after this, that poisoning and physicking have not had their fair chance? More modern methods, however, have centered around the idea of poison paints, for with the advent of iron ships the use of metals as sheathing was rendered impossible because of the electrolytic action in sea water and the consequent dis- integration of the iron of the ship. Many types of antifouling paints containing posions are offered under various trade names, but none has yet been found which is satisfactory under all conditions. Indicative of the types of many of these paints are the two following, used by the Navy as its standard antifouling compositions in 1922 and 1925, respectively : FOULING OF SHIPS’ BOTTOMS 197 1922 NAVY STANDARD ANTIFOULING PAINT | 1925 NAVY STANDARD ANTIFOULING PAINT (Per gallon of paint) (Per gallon of paint) 2,248 cubic centimeters denatured ethyl | 1,196 grams mineral spirits. alcohol. 306 grams pine oil. 355 cubic centimeters pine tar oil. 564 grams coal tar. 355 cubic centimeters turpentine. 923 grams resin. 680 grams gum shellac. 923 grams zinc oxide. 680 grams zinc oxide, dry. 616 grams iron oxide. 680 grams iron oxide. 410 grams mercuric oxide. 336 grams mercuric oxide. 515 grams cuprous oxide. 329 grams silica. Even before the use of steel ships, methods employed to limit the extent of foul- ing made use of various paints, many of which contained copper and mercury as poisons. In reviewing the methods followed until recently for the prevention of fouling one can not but be impressed with the fact that these methods have been governed largely by haphazard experiment and rule-of-thumb procedure. Pre- cedence apparently has been relied upon more than any analysis of the factors involved. Progress under these conditions naturally is a matter of tardy develop- ment and slow improvement. Consequently, in an attempt to obtain more efficient paints the United States Navy has undertaken an extensive investigation of the entire problem, using a great variety of posions in as many paints. It was soon realized, however, that a careful study of the organisms responsible for the foul condition would be of considerable value, and at the request of the Navy Depart- ment, and with its support, this investigation of the fouling agencies has been made under the direction of the United States Bureau of Fisheries. Although foul conditions on the bottoms of ships have been studied for many years, such studies have related almost entirely to the effects of fouling and to means of preventing it. Thus we find treatises such as that by Young (1867) on ‘The Fouling and Corrosion of Iron Ships,” and many articles, from time to time, in transactions of such organizations as the British Institute of Naval Architecture and the American Society of Naval Architects and Marine Engineers. One of the most recent and comprehensive of such papers is entitled, ‘‘Notes on Fouling of Ships’ Bottoms, and the Effect on Fuel Consumption,” by Capt. Henry Williams, C. C., U.S. N. (1923). Many articles dealing with the effect of fouling, especially with its relation to resistance, have appeared in these journals (McEntee, 1915), but these have not concerned the nature or extent of fouling. The growths on the bottoms of ships have been studied by many naturalists interested in collecting rare species of organisms and in systematic studies of various groups of animals and plants. Thus, Charles Darwin (1853) and H. Pilsbury (1916), in their respective treatises on barnacles, both record many of their specimens as having been secured from ships’ bottoms. At the time this investigation was begun (September, 1922) no study was known that dealt with the nature and extent of these growths. Since that date, however, two articles by Hentschel, working at Hamburg, have appeared, which 198 BULLETIN OF THE BUREAU OF FISHERIES deal with ‘‘Growths on Marine Vessels.” The former (1923) is an ecological study based on the examination of 48 vessels, while the second (1924) is a preliminary study of seasonal distribution of the organisms that cause fouling of ships, made while on board a vessel cruising from Hamburg to the West Indies and Central America. METHODS In order to determine adequately the nature and extent of fouling of ships on the Atlantic coast, it was arranged that the author be notified of the proposed dry docking of all the larger naval craft at several of the United States navy yards, and also by the United States Shipping Board regarding many of their vessels. This enabled the author or an assistant to be present at the time of docking of more than 250 vessels. Notations were made in each case of the relative amount of fouling and its distribution on the various parts of the hull. Collections of repre- sentative samples were made, which were preserved and carefully examined later in the laboratory. Since the material was frequently in a very poor condition when collected, due, usually, to pollution of the harbor waters and to consequent death and partial decay of the growths, exact determinations were not always possible, especially with hydroids, where one often found only empty ‘“‘stems.’”’ For deter- mination of the total amount of fouling present, known areas were scraped carefully and the material collected, measured, and weighed while wet; and in some eases © the relative amounts of each of the fouling agencies were determined. In addition, the itinerary of each vessel was secured whenever possible, and the date of previous docking also was obtained. For the great majority of vessels examined the paint used was the ‘United States Navy standard” (used by the Shippimeg Board as well as the Navy), and notation was made of all exceptions. On the data thus obtained the following report is based. However, in order to determine more accurately the validity of some of the theories that presented themselves during the course of this investigation, consider- able experimental work was carried on simultaneously, and the results of these experiments also are included in their appropriate places. NATURE OF FOULING As previously stated, the fouling of ships’ bottoms is caused by growths of both plants and animals. Among the workers at the dry docks one hears the terms “‘orass,’”’ “‘moss,” and ‘‘corals’”’ as describing the types of growths found on ships. It is quite evident that the term ‘‘grass’’ is commonly applied to the stems, or coeno- sares, of hydroids, and that the term ‘‘moss’’ is applied to the various seaweeds, usually green algw, which are found so commonly near the water line. The term “‘shells”’ includes all shelly growths, such as barnacles, oysters, clams, mussels, and even certain Bryozoa; but more commonly barnacles are recognized as distinct from the other ‘‘shells,”’ while the corals so frequently mentioned are probably Byrozoa, for coral itself has been found rarely. These groups of organisms, then—barnacles, alge, hydroids, mullusks, Bryozoa, and tunicates—make up the preponderance of the growths that are found on the bottoms of ships. In the determination of the forms collected it has often been quite impossible to ascertain the exact species with finality. This was due to the fact that FOULING OF SHIPS’ BOTTOMS 199 many of the growths either were dead, and all their soft parts entirely gone, or they were but recently dead and in a putrid condition when the ship was docked and the collections made. LIST OF THE SPECIES OF ORGANISMS COLLECTED FROM SHIPS’ BOTTOMS Animals—Continued. Phylum BR YOZOA— Class ECTOPROCTA— Animals: Phylum ARTHROPODA— Class CIRRIPEDIA (barnacles)— Balanus improvisus. . eburneus. . amphitrite. . tintinabulum. . crenatus. . harmeri. . tulipiformis. . perforatus. Balanus sp.? Chthamalus fragilis. Lepas anatifera. L. anserifera. L. hillii. Conchoderma aurita. C. virgatum. Pecilasma crassa. eelerloeesiuslivliee) Bugula turrita. Bowerbankia caudata. B. gracilis. Anguinella palmeta. Aleyonidium mytili. A. gelatinosum. Membranipora monostachys. M. lacroixii. M. liniata. Membranipora sp.? Lepralia pertusa. Crissia sp.? Phylum ANNELIDA (worms)— Class POLYCH ATA— Hydroides hexagonis. Hydroides sp.? Phylum MOLLUSCA— Class PELECOPODA— Mytilis edulis. M. hamatus. Nereis pelagica. Glycera sp.? Phylum CHORDATA— Class TUNICATA (sea squirts) — Mya sp.? Ostrea elongata. Anomea ephippium. Anomea sp.? Class GASTEROPODA— Crepidula fornicata. Nudibranchiata sp.? Phylum COKLENTERATA— Class HYDROZOA (hydroids)— Eudendrium ramosum. Eudendrium sp.? Tubularia crocea. T. couthouyi. Tubularia sp.? Campanularia amphora. C. portium. C. vorticellata. Campanularia sp.? Bougainvillia carolinensis. Obelia commissuralis. O. gelatinosa. Obelia sp.? Perigonimus jonsii. Podocoryne sp.? Class ANTHOZOA— Metridium sp.? Segartia lucie. Astrangia sp.? Plants: Molgula manhattensis. M. arenata. Botryllus arenata. B. schlosseri. B. nigrum. Ciona intestinalis. Division ALGA— Class CYANOPH YCHA— Oscillatoria lsetevirens. Class CHLOROPHYCEA— Cladophora sp.? Enteromorpha intestinalis. E. torta. E. chetomorphoides. E. marginalis. Enteromorpha sp.? Ulothrix flaca. Ulva lactuca. Vaucheria sp.? Acrochetium sp.? Class PH ZOPH YCEA— Ectocarpus sp.? Fucus sp.? Class RHODOPH YCEA— Polysiphonia nigrescens. P. violacea. Polysiphonia sp.? Phylum PROTOZOA— Class INFUSORIA— Vorticellide. Folliculina sp. ? In the foregoing list are given the organisms collected from ships’ bottoms and identified as far as the condition of the material would permit. By referring to this list it will be seen that 48 species of animals have been found, in addition to 13 types that could be classified only as to genera; while all of the plants found were alge, of which 16 kinds were recognized. 200 BULLETIN OF THE BUREAU OF FISHERIES As will be seen, the largest number of forms is found in the group of barnacles. (Figs. 2 and 3.) These organisms vary greatly in size and shape, many kinds never growing more than one-fourth inch in diameter, and often not so high. Some species, however, notably those that attach on ships in tropical waters, grow to a very considerable size—4 inches in diameter and 6 inches in height. Very frequently they are found growing one upon another, so that the height of a cluster occasionally may reach 8 or even 10 inches. Most barnacles are protected by means of hard calcareous plates, which surround the animal, forming a sort of shell. These plates vary in number, with the kind of barnacle, from four to very many; but the more common forms (Balanus) all have six plates or compartments forming the walls of the shell and two pairs of plates that comprise the top or covering of the shell, and which are arranged like valves. Between these valves the animal extends its thoracic appendages when feeding. (Fig. 4.) This peculiar habit has given rise to a popular description of a barnacle as an “animal which stands on its head and kicks its food into its mouth.”’ Some barnacles, however, do not form heavy calcareous shells and are very much elongated. (Fig. 5.) These are commonly called “gooseneck”’ barnacles and include the last six species of barnacles listed on page 199. Since the ‘‘neck” or stalked portion of this type of barnacle is not protected by shelly structure, such growths fall off upon the death of the organism; but all other types of barnacles leave behind them their shells or houses, which frequently persist for many years if not forcibly removed. Barnacles have a complicated life history. The eggs are fertilized within the body chamber of the adult and held in lamellar folds until the young are hatched. The almost microscopic larval organism is free-swimming, with three pairs of ap- pendages and a single median eye, and is known as the “nauplius.” (Fig. 6 A.) After a period varying from 1 to 10 days, or more, these nauplii metamorphose into tiny bivalved forms called the ‘“‘cyprid” larve. (Figs. 6 B, C, and D.) At this time the larval barnacle has six pairs of appendages, like the adult, and two long antenne with many sensitive hairs or bristles. The median eye is sometimes lost, and paired compound eyes are always present. These young barnacles, resembling miniature clams, float and swim about for a considerable time, often for two or three months, and finally attach by use of appar- ently adhesive pads on the tips of the two antenne. (Figs. 6 B and ©.) After attachment, they metamorphose into the adult stage, miniature at first but grow- ing rapidly to full size. At the time of this radical change the eyes apparently are lost in some forms. It is the study of these cyprid larve at the time of attach- ment, of course, which is of fundamental importance in an investigation of the fouling of ships’ bottoms. It is of interest to note that of the 150 species of barnacles listed by Charles Darwin in his monograph of 1853, only 15 kinds have been found on ships examined for this investigation, and that all of the commonest are typical shore forms, normally . inhabiting shallow water (and rarely living at depths in excess of 10 fathoms), such forms as are found in most harbors and sheltered coastal areas. The hydroids are the next most numerous animal group, with 15 types found during the investigation. Hydroids usually are colonial in their growth and have an even more complicated life history than do the barnacles. These growths begin Buuu. U. §. B. F., 1927, Pt. II. (Doc. 1031.) = Fic. 2.—Sizes and shapes of sessile barnacles found on ships, bottoms. 1, Balanus tintinabulum; 2, B. crenatus; 3, B. im- provisus; 4. B. eberneus; 5, B. amphitrite b av 1. SHOOG LON AYNLYN AGNLS.. Fic. 3.—Sizes and shapes of sessile barnacles found on ships’ bottoms. A cluster of B. tintinabulum Burm Us se be ke LO Pty ll (DocwlOsie) Fic. 4.—Internal structure of a typical sessile barnacle. (After Darwin) Fic. 5.—Stalked barnacles collected from ships’ bottoms. 1, Conchoderma; 2, Lepas FOULING OF SHIPS’ BOTTOMS 201 after attachment of a free-swimming larva, which changes its form completely upon fixation and produces a stalked growth or stolon. In many forms this stalk branches profusely and forms a treelike structure, often attaining a length of 6 or 8 inches. (Fig. 7.) Here, too, the living animal is inclosed within a chitinous sheath, which | \ Fic. 6.—Larval stages in the development of barnacles and the condition of the antennz at the time of attachment. 4, dorsal view of the nauplian larva of Balanus perforatus (after Groom); B, cyprid larva of Tetraclita divisa (after Nilsson Cantell); C, cyprid larva of Scapellum (after Nilsson Cantell); D, lateral view of a cyprid of Lepas fasiculatus, showing internal anatomy (after Willomoes, as in Hoek) persists (especially in the case of Tubularia) for many months after the death of the organism. Since these colonial organisms obtain their food by means of feeding polyps, which are situated at the ends of the stalk or its branches, and since all other parts of their bodies are protected by the chitinous hydrotheca, it is apparent 202 BULLETIN OF THE BUREAU OF FISHERIES that after attachment, in the case of these organisms as well as of the barnacle, they are completely resistant to any ingredients of a paint film. The problem of pre- vention of fouling accordingly resolves itself into one of prevention of attachment of these forms. Bryozoa are a group of organisms abundantly present on all marine coasts but much less abundant now than in prehistoric times. The great majority of them form colonies of thousands of relatively small individuals, each of which is surrounded by a more or less chitinous or calcareous shell. They may be either aborescent in their form of growth, as Bugula (fig. 8 A), or more commonly they form an encrusting lamellar growth, as in the case of Membranipora. (Figs. 8 B and C.) These growths frequently vary greatly in their form and may produce “sea mats” and coraline structures, which may form growths 6 to 8 inches in height and 12 inches in diameter. Each colony originates from a single minute larva, which has a free- swimming period persisting from one to many hours. Tn the case of mollusks, such forms as oysters and anomia attach duvedly to the surface of the vessel and may grow to considerable size. ‘Thus, oysters have been collected fully 5 inches in length and 3 inches in width. (Fig. 9.) Such forms as Mytilis, on the other hand, attach by means of byssal threads, and although they grow to a very considerable size (fig. 9), upon the death of the organisms the shell drops off, although the byssal threads may still persist for many years, leaving a telltale story of their former presence. These forms, also, at the time they attach, are minute, free-swimming larve, which in several cases are known to be sensitive to light. Of the annelids, only one type occurs at all abundantly, this bemg the serpulids, which form calcareous, tube-shaped shells. (Fig. 10 6.) Hydroides tubes have been found fully 3 inches long, and on a few ships in large numbers. This is the only type of this group that has been found attaching directly to the hull, the other forms listed being only casual inhabitants of the rich growths, both faunal and floral, that are found on some ships. The Protozoa, unicellular forms, are indicative of the environment in which the ship has been. The Vorticellide, in particular, indicate a putrid environment and on some ships were very abundant. The tunicates, or sea squirts, are both solitary and colonial in type. The former were found more often and frequently grew to large size. (Fig.10 A.) The colonial forms are incrusting types and do not produce as large an amount of growth as the other forms. These, too, are free-swimming organisms at the time of attachment. The alge were the most ever-present form, with the possible exception of the barnacles. They frequently formed heavy mats of growth, extending from the water line to from 1 to 8 feet below. Although individual growths might be of little conse- quence, the large numbers frequently made the mass appear much like a beautiful lawn. In many cases the growths of alge, especially the Enteromorpha, would attain a length of 7 to 10 inches. It is interesting to note that both the Enteromorpha and Cladophora are remarkable for the fact that many of their species are found indif- ferently in both salt and fresh water, and that they are characteristic plants of the littoral zone, rarely, if ever, extending into the sublittoral. 0 Aaysnya v ‘g feIIB ae 9 e STAMeRE DEG Jo 1aysnyo v ‘gE feLIePNGNy, Jo so\sNJo BV ‘VY “DpLuOPT “SS *O OY} WOIy poyooyfoo ‘su10}}0q ,sdiys uo punoy splo1pAy Jo sodA L— 2 “Ola Mina VaOw 4 41 Uodn JurMo1d snsqo1dunr snuvjog JUIMOYs ‘spray *S “S °M 04} JO [[NY 94) UO poydessoj0qd viodiaviq -M1aJA JO AuO[oo ‘OH {1aJOUIRIp UI SaoUT 9 0} F MOI VIOdIULIQUIOT\] JO SolMO[Od [BIOAVS ‘q ‘ejngng jo Auojoo ‘y ‘sui04j0q ,Ssdiys Uo SuI[Noy osnvd 4eVyy (vozkjod) voz0dig Jo sodA T—'s ‘oly CTSOL 90d) ‘Il 4d ‘226T “A a “8S “A “TIOg SOMA ‘“€ :eImOouy ‘Z {BatjsQ ‘T “su0}}0q ,sdiys UO ZuI[NoJ sv punoy sySni[ou Jo sodA |. —é ‘OI (TE0L 90) “Il Yd ‘L261 “A “A SO T10gG B. F., 1927, Pt. Il. (Doce. 1031.) Fic. 10.—Types of fouling. A, clusters of the tunicate (sea squirt) Ascidia. B, numerous speci- mens of the serpulid worm Hydroides, showing the calcareous tubes in which they dwell pe[Noy ATS INO “GS “S “Q ‘“SdrIYs uO Sur[Noj Jo sjunowe satyrjey— TT “Oly (TE0L 9°) II 4d “2661 “A “A S A WIE pornos Ajoyes1opoum paw AABN H[OJION oy} 4B oF1vq y “sdIys UO ZUL[NOJ jo syuNoMe oAtyvIOY—'ZT “Ol CTSOL 90d) ‘II 4d ‘2261 “A “A ‘“S “N “TIE Pano} A[Avoy wazsayg “S*g°Q ‘SdIYs uO SuINOj jo syuNowe oAVIaY—'el ‘O1a] (TESOL 90d) “Il 3d “2261 “A “d “S “0 “T19E Fic. 15.—Amount and type of fouling. Heavy accumulation of hydroids, tunicates, and barnacles on propeller and struts FOULING OF SHIPS’ BOTTOMS 203 EXTENT OF FOULING The prevalence and amount of fouling is surprising to anyone who witnesses for the first time the docking of marine vessels. In earlier times it was not uncom- mon for ships to have their entire bottoms incrusted with organisms to a depth vary- ing from 5 to 9 inches, with estimated weights of 300 tons or more. In recent years, due especially to more regular and frequent dry docking, such conditions are experi- enced but rarely; but even to-day, after vessels have been at sea for 6 or 8 months, they frequently accumulate growths from 2 to 3 inches in depth, and vessels with from 50 to 100 tons of fouling are seen frequently. When one realizes that all ships become foul if submitted to the usual environment, the extent and prevalence of fouling can be realized. In Figures 11, 12, and 13 are shown conditions typical of lightly, moderately, and heavily fouled ships, while in Figures 14 to 19 are seen the kinds of growths contributing to these conditions. In Table 1 is given a list of all of the vessels examined during this investigation, with notations regarding the amount of fouling on each. By reference to this table it can be seen that there is great variation in the amount of fouling on various ships. The reasons for this will be discussed under separate headings in another section of this paper dealing with the factors that determine fouling. 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SNIIIG sexe wo x MeN | 0% 09 0% G26I 2% “Gea | 77777oTedBg, SCA ALWis | cacaee Ba oar enil nc Seg | Be SPR ewe ee SRR TeeuVIIE}Ipoy-WOA MON | 0S Ou 06 Sz6l ‘Tg ‘“uBr Beer one aon sa eNeTT Am s}iod o14,eg—yI0X ASN | 91 0°¢ ¢'9 czel ‘0g “uer "BINZ[OTA ‘sepenieg 490149 U9XIs-AJOUIN ‘Ioqrey YIOX MeN | 02s 0% OF opr *sjossnur ‘sejoenieg 400119 puodes-AjUeASS ‘10qIvE AIOX MON | 0 2 0@ 0% S@6L 66 “uer ‘[euBHO vureued ‘ese ‘sopemieg | 7 Pers Ree ate ser BIA ‘sejej]g poeyIUA JO 4sB0d 4SeAA—yIOA AON | OT 0° 0'8 G61 9 “uef "BTA[OTATS SO [OC 0G Gen lascaans oe | pian sateen | ee [toe | oe mere graeme os punog joyonjUeN | > | 09 PEI Fe (09d "goz0xkIg | > 77> =-puvjs] HooTq—-viqdjepeliqg—yioz MON | 0% 0's 09 P26T OL ‘ed S80 [08018 Cit Rasaeeevar| cade asad io SNe [nae earl mst Ree eee BOlIJV JO 4SB0d 4S9AA—HIOK MON | 9° 9"9 09 F261 OL “99 eiudjepelid—yi0x MON | 0S pees LONE 761 6 "00M ‘seOBUeY eINULTAT BoLIyy INoOS-yIoOX MEN | OT o's Ou Piaraal earings PAOD eetm $SO[O BULB Cs Bees [ONATS | ecrercea | an wena | iNet iinig || = Nee || gnetiain geen mn nanccnae s 1OqIBH YIOX MON | 0 SS OT 0°9% PEL F "00 od x SOIPUT 4S0M—HLO}ION—-HIOX MON | 91 ST 0'€ Fe61 & “99M ‘od Kia | Sr aoe | eorengee aa | Mears nee rae meee IOpv.iqey—-y10zX MON | 0's oT oF FBI ‘9% “AON “So[OBOIB g See | Saag ane casos es acoia eer Ara ueqnO-y10 XK MON | OT 0@ 0'€ F261 ‘02 “AON ‘od x --=-BolIoury [B1JUsO—HIOX MON | 0'P oh OIL ¥26I ‘61 “AON TOAOIGSOC, [U7 surydoy *SO[D BULB GI S DIOL DATE Ty | scsse macnn | ea meee (cere Scmeel | ee nin [none = eeu een Shanna PURIST HoOTg—yIoR MON | (2) | (2) | F661 ‘SE “AONE | dtusqusry | 82 "ON JOrou CepLablOUNE [Po Po Ruling sera Sees puvlel1T—yIOX AON | 0°9 09 (tas ¥E6T (LT “AON puourygory "SopOBUIe || RO ao Rec le ea ea ig ae pear puLlsuq MeN—yIOX MON | 0S 0% 07 F260 ST “AON ‘od ‘BOlIFV JO 4SBOD JSOM—HIOR MON | 9° gg 0°9 #261 ‘9 “AON od SIOJBA JUEOBIPB PUB PIB A AAVN' AIOX MONT | 0'9T |O0'9r | Fe6T‘62 “490 *s193sXo ‘sopeureg SOIPUT JSOMA-PUL[SU MON-HIOZ AMON | 0'8 0% 0 ST FOI ‘LZ “390 ‘so,voruny ‘sopvnieg VOMOULY [BIMeD—HIOX MON | 0° 07 0'IT PGI ‘ES “900 Jepue} jJeI0ITY ‘sprorpAy ‘sopovure g ~~ =s}tod oIe@A-A1OX MON | 0" 0% 09 F061 ‘2S “400 SEE MEI CHC “0 [OBUAU CSOs UOTUT (It | patece sa | pantera Rien una |e Cen |e Tgeeercecesr ye. peel op---~~ 08 0'8 0'IT P26 ‘02 “320 -~-19£01)80q, ‘splorpAy ‘soqeorang, wOoIOULy [eIjUEQ—yIOX MON | OL 08 OL | ¥26r ‘or “400 777 dedeoms euryAL GF fayann qu G52) che cikcfey | aoc a hepsi reel me pe al et engin yr oar UvOUBIIOJIPSTT-AIOR MON | 9 P q"¢ 06 7261 ‘9 490 IO} SOI re se BI[opelmd—HIOR MON | — 77 PBL SF 4OO | OSI | pBometqTe IAT ‘eoz0kig ‘sojoeureg ----@01I}V JO 4SB0d ISOM -—HIOX MON | OT 0'¢ 0'9 HOGI ‘6S “9dEg |----7 IOPSIOTT | -7 7 qourelqyeO ‘sprorpAq ‘soyeoruny, 4UIOd PleYUIODO—AIOX MON | (2) (2) | 0°6 F261 12 “4deg diqsqusrt a OT ON Jenext oO *BOIUOTUNIGe SO]OUM TG Cs | mcrae eemieeen | ane org eterna Reetinmere enim RP ERERGGE 4 eae (9 0% 0's 001 HOB Tele] 10 S| neces mee OD iaaes|pes a “shorqdum yy ‘w3]B ‘sopoeureg BoWeULy [eIUeD-HIOA MON | 09 0's (Whee | ee op---~~ I9A014S9C, | Gyo) Fualeli Glehu eect eg Pee [io ree | [Bee ee UVOUBIIO}IPOT—YIOK MON | 9° 0's g's HOI ‘OL “9eg | 1904S 1017 ‘SONU MABGHOITLUT TAT | ec eee eeapemee sai eee |g ase | ese ems ee BIydiepelmq—-yiox MON | 09% |--- 0°92 Foor ‘9 “Ades ref£01459q *sprorpAy ‘sepovureg ---BOLIJV JO S800 JSaM—HIOX MON | 0'T OF 0'¢ PGI ‘F “deg |7-7 77 IE, SIOI 7 SB ITiS LO WA = seca | See | CE ee | owe toae oat soe er eee ae piex AABN YIOX MON | 08 [77 0's FEBL‘G “3GOg: | tT IOSMID “wav BoTIOULY YINOg UI0yION—HIOX MON |---~—- ~~ 09 09 P61 ‘% “ydeg j-- IOI SIOIT "SO[DSUIB Chis | na fee aeeae ial Remi | geen nes Seems aE eS Ss HIOX MON ts {4 {2 ¥26T (OL an SOG ie tad | aga a aE | RD NS oes OE ieee 1OqivH AIO MON: éh 4) 4) | ¥26T ‘2% drgsyqsrT *SPIOTPAUMSA[O SUL IG Gio | annette | abet ee eek | aaa al | eee ioe BOLIJV JO S800 JSOM—HIOR MON | OT 0°¢ 09 POST ‘ZL “BMY | IOI SII --=-9UI}[OSSOH 480M Sed [Wan | esa eee etc cee mea pea ema ce eee ie | ZIMOGIeEYO-HIOX MON |--=-- = 08 08 FC6I ‘8 resuessed a *“sojoBnIeg ---[RURO BUILUR BIA ‘VUITO-FIOX MON | OT q'g CLS ae OP sea Ren aeons Saree man OP metasni|ieee BULLETIN OF THE BUREAU OF FISHERIES 208 “sploipAy ‘sepoeuieg *so/DBuIe “sploipAyq ‘sepoeuieg “eZ[e ‘sopenieg nat “spjoipAy ‘sopoenieg ‘ealV *sojoemieg ‘aZ,y ‘ea[8 “soz0s1g “ed[e ‘sojoenieg *Boz0A1g ‘sojoBuieg ‘sploipAg ‘ea,y Mistues10 AuI{Noj Jo ods} dayjeulMOperg ae eee euON | 44317 on Avo AUTO} Jo eo1d0q, op----- Sai emciners fet barca SIT PUBIST 104849 WOJSUIYSBAM—HIOX MON OUIBIA-HIOX MON AAUIOTA pus JOqIB_ YIOA MON pestnso s1038 Ay One) |SRSETTTF 0% 0@ 0? 09 OT 09 0% g- ot 0° OMFS) [SETI 0% Q° oT 02 LE (Gili) | Sea 0% One: =i | Sasa =5=5 0% OnO8 |e 098 0°21 OT 08 0's 0% 0% 0'T 0% 09 0@ 9% oF OT 0'IT 0 21 0 01 0% 0 ZI 0T 0'8 06 qa0d uy |Zutstn10} oun OMT | SUL | 18301, (sqjuour ut) ¥O0p Jo qno pofieg penuyu0j—y] aravy, 926I ‘6a GZ6L ‘2% conte SZ61 SZ6I ‘8 S26 ‘Z SBI 96 9261 ‘9% ABTA, cat AON 906 GZ6I ZBI ‘8S * S261 26 * 9261 ‘02 “Idy S@6L ‘ek “Idy S%6L°L “dy pouturexo o18q Weer enna aK IOJY SOIT eyes 10A019S0q, efeiteecintee deta Joy qsIO1 Aa qaneaee Soe Bn} [BABN Sasesecescse diys 07189 Squiesaeesat ae: RCW CHG § SSSFSFS55E55 dyqseyy4e ¢ Sarr 1901489, See tee Jopue, drqsyqayy edéy, ee poo args pt age noe | Hog, Critics GSsseresess 4qa!T U10jseq Epc t sees eae B20A Buty. U. 8. B. F., 1927, Pt. II. (Doe. 1031.) Fic. 16.—Type and amount of fouling on ships’ bottoms. Many small sessile barnacles, some clusters of Bryozoa and hydroids, and numerous conspicuous stalked barnacles (Lepas) Fig. 17.—Type and amount of fouling on ships’ bottoms. A typically dense growth of hydroids Buu. U. S. B. F., 1927, Pt. Il. (Doe. 1031.) Fic. 18.—Type and amount of fouling on ships’ bottoms. Large clusters of tunicates (sea squirts) @ we. i! Fic. 19.—T ype and amount of fouling on ships’ bottoms. Numerous tunicates, typical clusters of hydroids, many small barnacles, and colonies of Bryozoa FOULING OF SHIPS’ BOTTOMS 209 By analyzing the data in this table regarding the extent of fouling we find that 87 per cent of all ships were fouled to some extent, and accordingly only 13 per cent were clean. A more detailed analysis of these proportions is given in Figure 20. By referring to this figure it will be seen that while 13 per cent were clean, 39 per cent were lightly fouled, 27 per cent moderately fouled, and 21 per cent heavily fouled. TOTAL NUMBER OF eC Er 2 0 SHIPS EXAMINED (100%) NUMBER OF SHIPS pepe, 5 2 HEAVILY FOULED (21%) NUMBER OF SHIPS eperpecemecmecens 6 7 MODERATELY FOULED (272) NUMBER OF SHIPS = uae 2 8 LIGHTLY FOULED (39%) NUMBER OF SHIPS peppers 33 NOT FOULED (132) Fic. 20.—Total number of ships examined and relative number in each of the four groups classified according to the amount of fouling on each vessel TaBLE 2.—Total amount of fouling, by weight Aun Total amount .. Date exam- < ew) ; Amount of Ship area Length} Width | Draft Breas Size of areas measured fouling per area mie Metrie | que ured States Feet | Feet | Feet Q , Kilos ‘ons Proteus___------ Sept. 28,1922 | 552.0 62 27.7 4)1 usher wide, water line | 60 kilograms__| 8,000.0 8.82 ‘0 keel. Fish Hawk.---- Noy. 7,1922| 147.0 27 11.0 Pe ea (ay) es A as ar ie ea 5 kilograms____ 415.0 46 yoming----.- Dec. 17,1922 | 562.0 93 28.5 4 | 1 square meter 2 kilograms. 5, 954.0 6. 55 West Virginia__| Nov. 21,1922 | 624.0 97 30.5 Cee domes 3 kilograms___| 10,612.5 | 11.67 Leviathan-___-- May 18,1923 | 906.9 100 23.7 4) er dale 22-22 2.5 kilograms 9,987.0] 10.98 _| Mar. 1,1924 | 906.9 100 23.7 See dose 212 3 grams-_-_-____ 12.0 - 013 Feb. 24,1923 | 668.0 74 22.8 5)|---@.doz=2__-. 10 grams-_--__- 28.2 -310 Dec. 19,1923 | 668.0 74 22.8 57)----. (a Coys is Se ae es ae ers al 1 gram _—____-__ 2.8 . 003 The exact amount of fouling on individual ships has been difficult to determine because of complicating conditions at the time of dry docking. A fairly accurate determination was made, however, for each of the eight ships listed in Table 2. The amount of fouling on each was determined by calculations based upon accurate measurements of the total amounts on limited areas, the sizes of which are indicated for each vessel in the above table. The total amount of fouling on the entire ship was then calculated on the basis of a knowledge of the length, width, and draft: of the ship and calculation of its wetted surface. It will be seen by reference to this table that fouling was very severe on ships like the Proteus, a collier in the naval transport service; while a passenger ship like the America had only a very small amount of fouling. None of the vessels listed in this table indicates the maximum amount of fouling occasionally found on ships. This has been estimated by reliable authorities to exceed 500 tons per vessel occasionally, but fortunately few ships are now permitted to become so foul before redocking, regardless of time intervals. 210 BULLETIN OF THE BUREAU OF FISHERIES TABLE 3.—Distribution and frequency of various organisms on first 100 ships examined 3 Ee : : : h 8 A = bl std 3 q es IES 8 bo s\S i=} i) 2 be aS) 44] 2) Ep a =| ® r=] lol. Fouling material ARGISEE 2/2 2182 S]8 ole SE lelslslslelPiSisl- Ke Se Slklaolels laa SlsleleiOl SiR ia] 8) a|S/S leplenlesl Sale| Slelele le 218|2 ArslololS|H) Pole S)Slola|a 8] 0/9) oc) Q 3s FE SIE YS | I Le I eI ft a 1 Mf Ve Ia fc fs J 1) 2|3)| 4) 5) 6) 7} 8) 9 |10)11)12)13)14/15}16)17/18)19)20)21) 22) 23)24)25/26 '29}30)31/32)33/34 Barnacles: Balanus eburneus ae improvisus_ = amphitrite -__ tintinabulum crenatus-_-_ _-- Perigonimus jonsii--_-__- Podocoryne sp., unident Metridium sp., unidenti fied__ gelatinosum __-_-__ Membranipora lacroi: Sp.) unidentified ==. ---- desc Mollusca: Ostrea elongata____ Mytilis edulis____ Nudibranchiata sp. ?___..--------------- Annelida: Hydroides hexagonis ---_-__------------- oe Nereis pelagica_______-_ Glycera sp., unidentifie: Protozoa: Alge: lve lactucas ee sean --|--|X|X|--]--|X]--]X]--]--|-- Vaucheria sp. ?.._--__- x Enteromorpha intestinalis_ sp., unidentified _____ Ulothrix flaca _____-__-- Polysiphonia nigrescens___-__ Acrochstium sp., unidentified_ Syphonales sp., unidentified _ -_ ed ee <|_ x by (mel b-4 lanl improvisus... 3 ee x amphitrite__- te tintinabulum__ crenatus____- tulipiformis-__-- Balanus cyprid lar Balanus sp., undetermine Lepus hillii-----.-------- Conchoderma aurita_ Poecilasma crassa_._-.--------- z Hydroids: Eudendrium ramosum_-_ Tubularia crocea--_- > 4 aa eee Alcyonidium mytili- Membranipora mona: Tacroixii_ ‘sp., unidentified _ Mollusca: Ostrea elongata_ Protozoa: Vorticellidg -_--_- peas) Gel ee}ise|Eal elles eessls4)ieel HEIs Polysiphonia nigr Cladophora sp., unidenti 1 No record for ship. 212 BULLETIN OF THE BUREAU OF FISHERIES TABLE 3.—Disiribution and frequency of various organisms on first 100 ships examined—Contd. Fouling material { Saint Mihiel | Eastern Leader | Edenton | Chinook | Neptune | McFarland { S.-11 | Sands || Reuben James | Hopkins | Independence | Cantigne ( Wright | William Penn | Bird City { Western Plains | West Virginia { West Nestleton | Tulsagas o oO 3 I =) 8 a3 — Cs I on a a a I oo 3 Ss 00 = 8 EA FS oO ot co a g oo oo oO oO s Oo = Pale 195)96|97/98) [ Barnacles: wo 2 5 g ~~ A “o a a g B 5 i} a i = Hydroids: Eudendrium ramosum _-_---__---___-_.- Tubularia crocea- -_---- sp., unidentified_-_- is Campanularia amphora_ --|--- portium==--2220—~ w|--|--[--]-=|--|==|=-|-=)~=]--]--|-=]--|-~- Vorticellatasn ae TO TE fap Sa ESSN US PSL] Sa [dd | a aa | a len GP Oc sp., unidentified__ Bougainvillia carolinen Perigonimus jonsii__-_---__- Podocoryne sp., unidentifi Metridium sp., unidentified Segartia sp., unidentified _ Astrangia sp., unidentified_-_ = Orr wOoMO WHOM i} 1 1 1 8 3 Bryozoa: il Bugula turrita___---------- Bowerbankia caudata_ 3 Anguinella palmeta___ 6 Alcyonidium mytili-----------_----_-___. 1 Polatinosuot see ea ES 5 Membranipora monastachys-___---______- 3 Vacroixiie = on eee ca Re eae 1 Spy unidentified asses 14 Lepralia pertusa__-------------_--____-___ 16 Mollusca: 1 Ostrea elongata_------------------_-____-- a Mytilis edulis---__ x<|L- | =ae))7/ Nudibranchiata sp. ay ---|13 Annelida: 2 Hydroides hexagonis-_- -__--------------_-_ Olsiead ea sp., unidentified_ ys ee 1B Bea) 8) Nereis pelagica __ ----_---------_-__ 22 (2) ey Glycera sp., unidentified ea ee ee =--| 1 Protozoa: Wel y Morticellidset2 5 2225 es ees erg | Geek Molliculing es soos = eee eos Ne eB fl ft ie) fel (al el feel | fea fecal al fe ate fesl eal ete ec icaleal ale dealt oils |F=PS RSIS 10 Tunicates: SVP ale A ay doe tiatn alice aati alll ag ia pean Lm iii i 2 Molgula manhattensis___----.---------_--]_- xIxI--|__]- arenata___--------- Ea) Sa] ea] | a] | aD a ahead | aaa ||| eas | eo a 9 Botryllus schlosseri_. Hi] S| S| 2] |e ea 2] sy | ae | ea | ea aa a a 4 Algae 0 ey ee EGE STUNT Sana ease a ans si TESA aT Fat tea it | 1 Ulva lactuca____- Vaucheria sp. ?_- ech Enteromorpha in ae|) 2 sp., unidentified__--_- z eed Ulothrix flaca______-_-- ---|19 Polysiphonia nigrescens-_-_-_- ---| 4 Acrochetium, sp., unidentified__. ---| 4 Syphonales sp., uni i eof it Cladophora sp., unidentified___ -| 1 Oscillatoria sp., unidentified__-_-._-______|_- 2 ; 1 No record for ship. pe Figure 21 is shown a comparison of the relative importance of the various kinds of fouiing growths, based upon data given in Table 1. It will be seen that of the 217 vessels that were foul 152 had barnacle growths, 105 were foul with alga, FOULING OF SHIPS’? BOTTOMS 213 91 with hydroids, 87 with Bryozoa, 37 with mollusks, 22 with tunicates, and 17 with Protozoa. It is clearly evident, however, that for most vessels barnacles are the most important fouling agent, while the hydroids and alge form the next groups, in order of importance. These relations are shown in Table 3, where the occurrence of each kind of organism is tabulated for each of the first 100 ships. 0 50 100 150 200 250 TOTAL NO. SHIPS EXAMINED Sp NY PE TST ETE ERE 2 250 TOTAL NO. SHIPS FOULED 217 SHIPS WITH BARNACLES 152 SHIPS WITH ALGAE 105 SHIPS WITH HYDROIDS 91 SHIPS WITH BRYOZOA 87 SHIPS WITH MOLLUSCS 37 SHIPS WITH TUNICATES 22 SHIPS WITH PROTOZOA 17 Fig. 21.—Number of ships fouled by each of several groups of organisms . EFFECTS OF FOULING As Capt. H. Williams has very aptly stated, “‘considering the fact that frictional resistance is the most important element in the resistance to propulsion of practically all ships, it is surprising that there has been little investigation of the possibility of reducing skin friction to a minimum. Ship owners seem satisfied that everything is accomplished by the present system of docking ships periodically,” and the subsequent cleaning of their bottoms and painting with antifouling compositions. He states, further, that “the effort to drive foul ships at full speed has burned many tons of fuel; the normal fuel consumption of ships is in excess of what this consumption would be with clean, freshly painted bottoms. While probably it is not possible to prevent fouling and the consequent increase in fuel consumption, there is room for definite improvement over existing conditions.” A few studies on the effect of fouling, as regards increased resistance, have been made. Thus, McEntee (1915) studied the relation of fouling to increased frictional resistance by submerging, near the navy yard at Norfolk, Va., a series of steel plates, each weighing 10 pounds and measuring 2 by 10 feet. After periods ranging from 1 to 12 months he removed the plates from the water, shipped them to Washington, D. C., and, at the experimental model basin, tested their resistance at speeds ranging from 2 to 8 knots. The maximum increase in resistance was found to be four times as great as when such plates are clean and freshly painted. The amount of fouling was determined in all cases, and the maximum foul condition of these plates would be roughly comparable to the condition listed as slightly less than ‘moderately fouled”’ in previous tables and elsewhere in this paper. 214 BULLETIN OF THE BUREAU OF FISHERIES Although the author is not aware of any detailed studies on the effect of fouling, as regards increased resistance and consequent increased fuel consumption im ships in actual operation that are moderately or heavily fouled, recent investigations by the Navy Department show a considerable increase in fuel consumption for boats only eight weeks out of dry dock and on which only small amounts of fouling could possibly have accumulated, as the trials were made early in spring in the cold waters near Bos- ton Harbor. The results of tests with a new submarine off Provincetown, Mass., are given in Figure 22, from which it can be seen that the speed attained with a low propeller action was decreased from 9.85 to 9.25 knots; and at high energy input (1,050 kw.) this was reduced from 15 to 14.5 knots. If there is so great a reduction in KILOWATT INPUT TO PROPELLERS S.00 10.00 1.00 12.00 13.00 14.00 15.00. SPEED INKNOTS Fic. 22.—U. S. Submarine S-34. Standardization trials, measured mile. Provincetown, Mass., May 16-18, 1928. Vessel out of dock 56 days for run with foul bottom. Motor efficiency disregarded as virtually constant. - with foul bottomiy,=-822-25 with clean bottom speed when the amount of fouling is barely noticeable, the proportionate decrease in the speed of vessels heavily fouled must be very great indeed. These results are in accord with the observations of McEntee, quoted above, who tested the resistance of recently submerged plates, with no discernible fouling, and yet found a very noticeable increase in resistance, which for the plates used in his experiments he calculated at an increase of almost 2 per cent per day. That similar results are obtained by actual tests with ships is seen from the state- ment by Sir Archibald Denny, published as part of the discussions that follow the McEntee paper. Denny states that “‘at their shipyard on the river Leven, a tribu- tary to the Clyde, they have found an increase in resistance at the rate of nearly » FOULING OF SHIPS’ BOTTOMS 215 one-half of 1 per cent per day for periods as long as three months.”” This would mean an increase in resistance of almost 50 per cent by the end of this period, while ‘‘exam- ination of the bottoms of the vessels in dock revealed no apparent fouling.” That such practical tests are fully in accord with theory, as based upon experimental data, is shown by the additional studies of McEntee (1915) on the use of graphite, soaps, and oils as a coating for the wetted surfaces of a model ship. He found that all of these produced greater resistance than a smooth, shellacked surface. For an analysis of the resistance of ships, the work of Hovgaard (1908) is one of the more recent, while a very excellent bibliography on this subject is given by Rigg 1915). FACTORS THAT DETERMINE FOULING The factors that determine the presence and the amount of fouling on a given vessel are very numerous and variable. ‘The major factors, however, may be classi- fied with some degree of accuracy. The season of the year, the weather, and the temperature of the water constitute one group of factors. The condition of the water in various harbors, both as to salt content and pollution, also affects fouling. The contour of the ship, which is correlated with the duty and speed of the vessel, and also the waters cruised, all affect the amount of fouling. The length of time between successive dry dockings and the proportion of this time spent in cruising or in port are very important factors. The nature of the material of which the ship’s bottom is made, as well as the paints or other materials that protect it, also are of importance. Inasmuch as life is more abundant and rapid in its growth in tropical regions, it follows that boats that travel in tropical waters become more heavily fouled and in a shorter time than do similar vessels in more temperate latitudes. Likewise, ships in port during the spring and summer show heavier growths than those that are idle in port during the autumn and winter. It will be impossible to consider all of the factors that condition fouling in all its variations, but the following pages will be devoted to a discussion of some of the major ones, with special reference to the effectiveness of paints, both as regards their poisonous properties and their protective properties from a biological consideration of the reactions to them of the larve of the various forms that cause fouling. We shall discuss the relation of foulmg to (1) duty, including the factor of “‘dry-docking period’’; (2) seasons; (3) fresh waters; (4) paints and surface film; and (5) light and color. RELATION OF DUTY OF SHIP TO FOULING The “duty” of a ship determines, in large measure, the amount of fouling that will accumulate on its bottom. This is due to several factors, which include the effect of hull contour, of relatively much or little time spent in port, of the ship’s speed while cruising, and, finally, the effect of the waters cruised. By examining Table 1 it will be noted that there is a marked difference in the amount of fouling on ships belonging to different classes; i. e., having. different duties. ‘Thus, it was found that passenger ships with regular schedules were by far the least foul of any group. ‘This applies not only to vessels plying between America and Europe, but to those carrying trade from New York to South American ports as well, and can be stated as a general rule. 216 BULLETIN OF THE BUREAU OF FISHERIES Freight vessels and most of the active naval vessels form the next class of ships. These ships frequently lie in one port or another from one to three weeks, or even longer, and offer ample opportunity for a dense “‘set’’ of fouling growths to take place. The degree to which these organisms continue to grow depends very largely upon the amount of time in excess of 10 days that is spent in any one port and to an equal degree upon the successive ports visited after the acquisition of the original “‘set.”’ If these ports should be im close proximity, the growths will continue to develop as if the ship were in the original port (with some exceptions), but if con- siderable distance (500 miles or more) separates them, most, if not all, of the fouling is killed, and if less than 2 weeks old almost all will drop off when dead. PER CENT OF NUMBER OF SHIPS INEACH GROUP Tre OF SHIP 0. 10 20,30 40 50°60 70,80 90 108 DESTROYER SE FREIGHTERS | | Waa eda ot sex COLLIERS OUT OF COMMIS SION BATTLESHIPS LIGHT-SHIPS RSkRERSo Say PERS 0 LIGHT MODERATE HEAVY FOULING FOULING FOULING FOULING Fic. 23.—Relation between type (and related duty) of a ship and the amount of fouling, disregarding factor of time Another class of ships, including commercial ships lying idle in port either for overhauling, repairs, or other reasons, as well as many of our naval craft (in peace times), forms the group that is fouled most heavily. This is due largely to the fact that frequently they lie in a given port for from 1 to 6 months, affording ample time for the original set of fouling material to develop and grow, so that all types of sessile marine growths that normally occur in that harbor frequently are found in luxurious growth on the bottoms of such ships. An analysis of the data in Table 1, as regards the relation of fouling to the above classes of vessels, is given in Figure 23, which shows the percentage of the total number of ships in each of the eight classes, grouped according to the relative amount FOULING OF SHIPS’ BOTTOMS 217 of fouling on each. It will be seen at a glance that passenger ships average a very light amount of fouling, while lightships and battleships show a very heavy growth. The percentages given for each group do not show an exactly comparable relation- ship, because data gathered from all the sources are included. If one were able to exclude all data from the Philadelphia Navy Yard, with its polluted, fresh-water harbor, and also omit those ships that enter dry dock after an unusually short interval (because of accident), the relative percentages in each group would show a steady and proportionate increase in amount of fouling. However, in any chart of this kind more than one factor is represented. The fact that the average docking interval for passenger ships is about 7 months, for freighters about 8 months, for naval craft about 9 months, and for lightships about 11 months, must be taken into consideration. This factor, however, will be discussed separately below. Regardless of many of these complicating factors, the uniform difference in the amount of fouling is of real significance and, as will be shown, is probably related more to the effect of the relative amount of time spent in port than to any other one factor. Having seen that there is a significant difference in the amount of fouling on ships belonging to the various groups, an analysis of some of the factors that deter- mine this difference will be considered. Since the materials for construction are comparable, the paints usually the same, and the environmental factors, such as seasons, ports, and temperature, are similar in the main, the really significant dif- ferences are clearly related to the different duties of these vessels, and this relation to fouling can be analyzed by consideration of four main factors: (1) Hull design, (2) speed of ship while cruising, (3) dry-docking period and use of intervening time, and (4) the routes or waters cruised. HULL AND CONTOUR OF SHIP The construction of any ship plays a considerable part in the matter of fouling. The amount of fouling rarely is uniformly dense over the various portions of the hull. This is due not only to differences in structural relations of the various parts of the hull but to specific characteristics of the fouling organisms in attaching in definite zones. Thus, we find that there is a very definite and clearly defined vertical grada- tion noticeable in growths on ships’ bottoms. Certain forms, like Enteromorpha and some varieties of Balanus, are found characteristically in a rather narrow zone around the vessel and extending from the water line to a depth of about 3 feet. ‘Hydroids, ascidians, and the stalked forms of barnacles are found rarely in this zone. This, however, is the zone most commonly fouled, for in almost all classes of lightly fouled vessels this was the only region fouled. Often it is covered with a dense growth of alge, whose filaments often extend 5 to 6 inches. In such thickets one often finds a bevy of animals, including such forms as amphipods, annelids, isopods, and even canceroid crabs (probably Panopeus). Occasionally this algal zone extended much deeper than usual. On several ships this growth extended from the water line for fully 10 feet, almost to the bilge keels. It has been impossible to correlate these few cases with any seasonal variation as suggested by Hentschel (1923). 218 BULLETIN OF THE BUREAU OF FISHERIES Below the algal zone one finds a scattered growth of barnacles and incrusting Bryozoa on almost all ships that are lightly fouled, but on such ships these growths usually are very sparse, especially on the more perpendicular sides of the hull. How- ever, on all parts not so perpendicular as aft (on the “quarter” or near the “run,” etc.) these growths often were noticeably more abundant. As previously noted, some ships that were otherwise clean had small amounts of growths only in the seams formed by the overlapping of the steel plates. (See fig. 24.) On most ships barnacles and Bryozoa were found here, if at all. On some, as the Paul Luckenbach (June 12, 1924), large clusters of worm tubes (Hydroides) were found in these seams. The third vertical zone would include those growths that occur on the more horizontal portion of the hull—the true bottom of most ships. In the case of heavily fouled ships, this portion was also the most heavily coated. Hydroids are found in great abundance, while mussels, Ascidia, and often barnacles also are found here in great quantities. In the case of moderately fouled ships, this region is again most heavily coated, as a rule, with sessile barnacles, hydroids, and Bryozoa, and if from certain routes, with stalked or goosenecked barnacles. In the case of but lightly fouled ships, the growths here were of secondary importance to the algal zone but were always most severe in the region directly under the bilge keels and in the “run” of the ship. The factors that determine this distribution are numerous, no doubt, but some may be pointed out at this time, of which several will be discussed under separate headings. The presence of the algal zone only at the upper limit of growth is determined rather largely by the fact that these organisms are dependent upon sunlight for continued existence and growth. Light also may play a part in determining the activities of the larve at the time of setting, and so determine the location of later growths. The distribution of animal life is affected by the factors that determine the place of attachment of the young larval forms as well as by the conditions provid- ing the food necessary for continued growth. The effect of too strong a current of water, as when a vessel is cruising, probably may cause many of the more tender growths to be torn off. This undoubtedly accounts in part for the presence of growths in the seams behind the overlap of the steel plates in vessels that are in constant service. It is a fact that most barnacles, hydroids, and tunicates attach in largest number below the bilge keel and on other shaded parts of the bottom. This would indicate that relative light intensity plays some part in determining the place of attachment on the bottom. In view of these considerations, it will be seen that the contour of the vessel is an important factor in the matter of fouling. Flat-bottomed ships of shallow draft often are more foul than boatsof similar design but greater draft; while vessels designed so as to permit the effective sweep of the water while cruising to play on the entire surface usually are more free from fouling under similar conditions than are vessels with deep “‘runs.”’ Directly associated with the type of hull and the contour of the ship is the factor of speed of the ship while cruising. That this factor has some effect on the amount of fouling can not be doubted, but evidence on this point has been very difficult of obtainment without complications. The tremendous pressure exerted on the sides and prow of a vessel as it progresses at the rate of 30 knots undoubtedly saqerd ay jo dey -10A0 0} AG POUIIOJ MIVAS OY) UI LOZOAIG PUL SopovUAR JO ddUASAId BUIMOYS ‘MOTA PosIL[US “YF “SY}AOAT SUI[NOJ JO WOTYVOOT O1}SToJORIVyO BULMOYs ‘saquld [oo}s [BloAos *W “FBT ‘22 ATUNIGog ‘WOySOg 4R Yoop Arp Ul UMYZNLAaT OY} JO SMOTA “BUL[NOJ puv UsISop [[NY jo adA} UoVAJoq UOTyLloy—' Fs “OLT (TEOI 20d) “Il td ‘4261 “A “da “S “A “TING FOULING OF SHIPS’ BOTTOMS 219 kills most of the living organisms attached to it in exposed places. As indicated previously, the most usual place for fouling to be found on rapidly cruising vessels (passenger ships) was in the groove made by the overlapping of the metal plates of the hull. Here, then, is a case where the effect of friction through water is much reduced or entirely absent, and a merely local growth of fouling results. The notice- able absence of hydroids, tunicates, and other relatively soft-bodied organisms on rapidly cruising vessels indicates that such forms probably can not withstand the pressure, and consequently only shelly growths, such as barnacles and seruplids, are found on such vessels. LENGTH OF PERIOD BETWEEN DRY DOCKINGS The amount of time spent in port, in relation to the amount of time spent under way, obviously is related to the duty of the ship. It has long been known PERCENTAGE OF SHIPS (ACTUAL NUMBER INBRACKETS) On 10).205, 30) 40,50 605570180: 90; 100 | TV AZ ARES 2 COTS Ee ea SSR Ss NO FOULING LIGHT FOULING MODERATE HEAVY FOULING FOULING - Fic. 25.—Relation between the degree of fouling and the amount of time spent in port between dry dockings' that while idle in port boats frequently accumulate heavy growths of fouling; while similar vessels, on the high seas during an equal period, remain relatively free from fouling. In the past this fact has been associated more with the length of the period that elapsed since the previous dry docking than with the relative amount of cruising done during a given period, a relationship that is of secondary importance only, as will be shown. ; From the records of the ships that have been considered in this study, it has been estimated that passenger ships spend more than 60 per cent of their time cruising, while freighters spend an average of about 40 per cent of their time on the high seas. Naval craft vary greatly in this regard, but from the data given in Table 1 it can be seen that destroyers spend about 30 per cent of their time cruising, 220 BULLETIN OF THE BUREAU OF FISHERIES cruisers about 20 per cent, battleships about 15 per cent, and colliers about 10 per cent, while it will be realized that lightships and ‘‘out-of-commission’’ ships spend virtually none of their time cruising. That this factor is of great importance can be seen from a careful study of the list of ships, their docking periods, cruising time, and amount of fouling, given in Table 1. It has been considered desirable, however, to present this information ~ more fully and compare it from several points of view. Accordingly, in Figure 25 the amount of fouling in relation to the time spent in port, regardless of all other factors, is represented in the form of a diagram. As can be seen from this diagram, fouling increases in direct relation to the amount of time spent in port. TIME PERCENTAGE OF SHIPS IN EACH GROUP 0 10 20 30 40 50 60 70 80 90 100 IN OS | A 7-1 OR MONTHS 4-6 |__13_ WZZZZZZEU RRR OT OY 08 08 OR 108 OS Ot ae SINCE 7-9 [9 WLC LLL AREA PREVIOUS 13-15 LZ AZAR SORES > 0°O'O'0'O'O OG OOOO OO COSS | r us ie DRY- 16-18 BSSSSSRst 6 SSSSSe lene 1 DOCKING 19-21 CLEAN LIGHTLY MODERATELY HEAVILY FOULED FOULED FOULED Fic. 26.—Relation between amount of fouling and amount of time between dry dockings In Figure 26 the amount of fouling im relation to the total period that elapsed since the previous dry docking is shown. It can be seen, by referring to this dia- eram, that there is a fairly steady increase in the amount of fouling with the lapse ~ of time, regardless of all other factors. Although this diagram presents only rela- tive values, and at best approximate, it shows clearly, however, that the rate of fouling is virtually constant from the moment one dry-docking period ends to the time the next begins. (If the protective paints used have a definite “length of life” for efficiency as an antifouling agent, as is generally maintained, then, there should be a marked turn at some point in the diagram, presumably after six or eight months, on the basis of customary dry-docking schedules.) In Figure 27 is shown the relation of fouling to the amount of time spent cruis- ing. This diagram is the reverse of that shown in Figure 25 and will serve to emphasize the significance of cruising in its effect on fouling. It will be seen that the amount of fouling is decidedly less the longer the period of time spent cruising. FOULING OF SHIPS’ BOTTOMS 221 That this is due not so much to the actual effect of cruising as to the fact that such boats are not in harbor sufficiently long to accumulate heavy growths is seen by comparison of this diagram with those given in Figures 25 and 26. CRUISING PERCENTAGE OF SHIPS IN EACH GROUP 0 10 20 30 40 50 60 70 80 90 100 TIME 0-3 | 10 W772 TZ MONTHS 4-7 NT | GAZ eATVOEBRT RRS IN 8-4 WOW YW 7 ORR 2-15 | 2 | |W oD $s Jn FI. FBS Y Lno A icut El mopERATE Bc avy FOULING FOULING FOULING FOULING Fic. 27.—Relation between time at sea and amount of fouling In Figure 28 is shown a combination of Figures 26 and 27, indicating a more accurate relationship between cruising and fouling. As indicated, this table shows 1-4 % je) ea S279) a =) & 30-59 Zz E 60-79 Oo v 80-89 = F 90-94 = S 95-98 kn (=) pS = o re oO. 99-100 suscoscaue PER CENT OF TOTALNUMBER OF SHIPS INEACH CLASS. OO 20 30) AO) 1 5060) ne 80 JOP NO® | 3 13 FESS SO ih DAA ONES See oe BSERSSSSEEL S| | 6) WLAN ZAR RR YL 8 WAAI¥.aYaewaaZ RAS [_] CLEAN RSS] MODERATELY FOULED WA \NGHTLY FOULED [RM HEAVILY FOULED Fic. 28.—Relation between the amount of fouling and the per cent of total time since last dry docking spent in cruising 222 BULLETIN OF THE BUREAU OF FISHERIES the relation of the amount of fouling to the amount of time spent at sea. It will be seen easily that this relationship is constant and that the proportions appear to vary inversely as the percentage of time spent cruising. In Table 4 is shown a classified list of the various types of ships, indicating the number in each group, with their respective amounts of fouling in relation to the length of the last dry-docking period. Of the ships that docked within three months after a previous dry docking it will be seen that in all groups, excepting the battle cruisers, the majority of the ships were clean or only lightly fouled (for those docking), while in the next three months (i. e., from three to six months after previous dry docking) the majority were found to be in the classes of lightly or moderately fouled ships. It is also of interest to note that in columns 6 and 7, the periods longer than 18 months, the preponderance of heavily fouled vessels;is: very conspicuous, especially in the case of vessels “out of commission.” eth From these tables it is seen easily that the time between dry-docking periods is of great significance, but the use made of this time, either in cruising or in port, is of even greater importance. It can be seen, im addition, that the amount of fouling increases with the length of time that elapses since the previous dry docking (fig. 26) but becomes proportionately less with any increase in the percentage of time spent cruising. (Fig. 28.) Taste 4.—Analysis of the difference in docking periods for diverse types of ships and the relative amount of fouling on these ships, grouped according to length of tume elapsed since previous dry docking [H, heavily fouled; M, moderately fouled; L, lightly fouled; N, no fouling; X, aberrant cases, due to putrid waters of the Phila- delphia Navy Yard] 1to3 3 to6 6 to 9 9 to 12 12 to 18 18 to 24 . Class of vessel months | months | months | months | months | months Colliers and miscellaneous naval craft___.|_.-.--------|------------ 1 Hed aes AGE 2 222| Bt ees pipe es ‘Battleships: i: --5=220 ses te cee ee Destroyersiiesoe 2s Sea Passenger vessels Freighters’ 2s 220! S22 A oes FOULING OF SHIPS’ BOTTOMS 223 WATERS CRUISED Associated directly with the duties of a vessel is the cruising record, indicating by its log where the vessel has been and what ports were visited. Thus, of the boats examined for this report the passenger vessels were on the trans-Atlantic service or the South American or Mediterranean routes, while the freighters had an even wider range of routes. Some of those examined plied regularly between New York and the west coast of South Africa, others between New York and the Mediterranean or New York and our west coast, or even New York and the East Indies. Naval craft, as a rule, do not have regular definite routes, consequently much of the data in Table 1 is of little use in an analysis of the relation between routes and the amount of fouling. In those cases, however, where it has been possible to study the effect of dif- ferent routes traversed by different ships it has proved to be one of the most in- teresting problems encountered during the entire study. Just as the flora and fauna of the Tropics is different from that of the Arctic regions, and just as the trees of California are different from those found in Maine, so the growths attaching to ships in the China Sea are markedly different from those attaching in the North Atlantic or from those of any other geographic region. In other words, each vessel, if foul, shows at the time of docking, by the growths found on its bottom, a visible record of its cruise. ' This report is not the place for a discussion of the geographic range of various species of organisms but a discussion of their effect on fouling will be in order. _ One of the effects which was noticed early and was confused on many occasions is that found when a ship fouled in a tropical port arrives in a northern port, or vice versa. On such ships all growths are dead, either in a putrid condition or leaving behind only their skeletons or shelly growths as a reminder of the once abundant life. (Nevada, January 5, 1923.) Even ships moving from one port to another 500 miles away usually exhibited a similar state. (Leviathan, May 18, 1923, Norfolk to Boston.) While it can be stated as a general rule that vessels that remain only a few days in one port and then move on to another remain free from fouling, there are certain noticeable exceptions. This is the case with freighters of the United States Shipping Board, which ply between New York and the west coast of Africa. Almost without exception these vessels were found to be heavily fouled, in spite of short dry-docking periods (five to six and one-half months), and in spite of the fact that rarely did they remain in any one port for more than three or four days. By an examination of Figure 29, which indicates the geographical relationship of the routes taken by these ships, it will be seen that although they moved from port to port almost daily yet these ports are very close together and most are in the same latitude; that is, they are in a similar geographical area, with environmental conditions comparable if not identical. It is evident, consequently, that the effect of change of port on growths causing fouling would be very slight, if any, and it is very evident, as seen by the records of examination of such ships, that the barnacles and hydroids that attach 69861—28——_3 224 BULLETIN OF THE BUREAU OF FISHERIES in these ports continue to grow in the neighboring harbors just as rapidly and luxu- riantly as if the vessel had remained in the original port during the entire interval. Tt is doubtful if a series of ports can be found anywhere else in the world having so similar environmental factors that determine the ecological conditions for rapid growth of fouling organisms. In contrast with this route, vessels returning from South American ports are frequently clean, or at best only lightly fouled. Vessels in the trans-Atlantic service, whether passenger or freight, rarely show heavy fouling unless delayed in some port for a considerable length of time. Fic, 29.—Route taken by certain of the freighters operated by the United States Shipping Board. Many of the ports are in the same latitude and all are in a similar geographic area The type of fouling is very specific for certain routes, or at least for certain waters. Thus, naval vessels that practice in southern drill grounds at Guantanamo Bay, Cuba, West Indies, have characteristically large numbers of Balanus impro- visus, B. amphitrite, and Membranipora lacroxii. Vessels that remain in the western Atlantic, north of the Chesapeake, have characteristic growths of B. eburneus and Tubularia. Vessels that visit the ports of the east coast of South America usually have growths of B. tintinabulum and B. amphitrite, although if no extended time was spent in these ports, or if these were river ports, such vessels would have clean bottoms. It can be stated definitely from all data available that vessels that visit ports in tropical regions usually are more foul than those that ply more temperate zones. FOULING OF SHIPS’ BOTTOMS 225 Also, both from an examination of the logs of ships and a study of the organisms found on their bottoms, that ships foul almost entirely while in harbor, and that these growths usually die if the vessel leaves the original port where fouling first attached, provided such movement carries the vessel to a port at some distance from the original one (see Maryland and Nevada) or into a port with different ecologi- cal factors, such as fresh water, polluted water, or any water considerably different in temperature and related salt content, as found in most ports 500 miles or more apart. It is thus seen that the log of a ship tells in a large measure, to those able to read it, the degree of fouling likely to be found on a ship at any given time, and an exami- nation of the fouling material from the bottom of a vessel shows fairly accurately where the vessel has been and how long it remained in various harbors. SEASONS AND RATE OF GROWTH That fouling would occur more severely at certain periods of the year than at others is self-evident to all who study nature’s laws. It is a well-known fact that for most animals there is a limited breeding season, occurring, as a rule, but once each year. Similar periodicities are found in most marine organisms, some of which have been carefully studied; as, for example, the oyster (Brooks, 1880), the clam worm, Nereis (Lillie and Just, 1912), and the Chitin (B. H. Grave, 1922). It seems probable that all living organisms that are subject to marked seasonal changes in climate, such as temperature and salt content of the water for marine organisms, as well as to seasonal changes in food, either in kind or amount, have seasonal perio- dicities related to reproduction. Very little is known, however, regarding the exact details of this question as it applies to those organisms that cause fouling on ships’ bottoms. Such knowledge involves a careful study of the breeding periods of many species of these organisms, as well as an accurate knowledge of the habits of the larve from the time of hatching to the time when they attach and begin life as sessile organisms. However, some studies that have a bearing on this problem have been published recently. Caswell Grave (1920 and 1923) has studied the activities of the larve of four species of tunicates. He found that all had limited breeding periods during the summer months for the region about Woods Hole, Mass. He was able to demon- strate that in the species studied the larve have a relatively short, free-swimming period, varying from 1 to 28 hours. Of this time, during the first portion, in all cases, the organisms reacted toward light and against the influence of gravity; but toward the end of the free-swimming period all reversed these reactions and were negative to light and positive to gravity. At the end of the short, free-swimming period, these organisms become attached, metamorphose, and develop at a rapid rate into the typical adult form. The recent work of Fish (1925) is also of interest in showing the periodicity in the presence of different types of barnacle larve and other fouling agencies in the waters immediately south of Cape Cod. His data show that the larve of various barnacles are found for almost 10 months of the year. Itis for only about five of these months, however, that the cyprid forms are found. Since of the forms listed only Balanus crenatus and B. eburneus are serious fouling agents, and since they attach 226 BULLETIN OF THE BUREAU OF FISHERIES only while in the cyprid stage, it is apparent that fouling by barnacles could occur only from July to late September in this region. Of the three hydroids listed in his report, which are occasionally found on ships’ bottoms, it is of interest that the major- ity are also present as larve during the late summer months. Although a few additional scattered references to similar data could be listed, they are extremely meager, and there are almost no data available on the subject of seasonal distribution and periodicity (especially with reference to the larve) that are at all comparable to the complete study of this subject with reference to the boring mollusks (Teredo and Bankia), which so severely attack all marine struc- tures, especially piling, buoys, and wooden vessels. (See Atwood and Johnson, 1924.) SEASONAL PERIODICITY During this investigation, while examining the bottoms of more than 250 ships, it has been possible to secure some additional data, but relatively few are of an BOSTON=-—- NEW YORK == NORFOLK=----- BEAUFORT—--— JAN. FEB. MAR. APR. MAY JUNE JULY AUG, SEPT. OCT. NOV. DEC. Fic. 30.—Prevalence of the larve of organisms that cause fouling at Boston, New York, Norfolk, and Beaufort, N. C. From data gathered from ships’ bottoms and test panels exact nature because few ships are docked within 90 days of their previous docking, consequently it was only on rare occasions that the exact time of attachment for specific organisms could be determined. However, from the few ships that docked within 30 days of their last previous dry docking, as well as from vessels that were in a given port continuously, it has been possible to prepare some incomplete but fairly accurate charts for fouling in the harbors at Boston, New York, and Norfolk, and at Beaufort, N.C. These are given in Figure 30. By referring to this chart it will be seen that the periods of active fouling vary with the kinds of fouling. Thus, the hydroids and alge are late winter and early spring forms; while many of the barnacles, the oyster, and the bryozoan Bugula are late spring and summer forms, and some barnacles and the tunicate Molgula are late summer or early autumn forms. Each of these is found earlier in southern a FOULING OF SHIPS’ BOTTOMS 227 waters, as at Beaufort and Norfolk, than in the cooler and more northern waters, as at New York and especially Boston. It will also be noted that the barnacles and some of the others have a more extended breeding period in warm waters than in those north of New York, where these periods are limited sharply for most organisms. It is apparent, however, that for the barnacles and the more serious types of fouling, measures employed to prevent their attachments should be most effective during the early summer months, varying the date according to the latitude of the locality. The above data are admittedly not accurate in every detail but serve to indicate the significance of such studies. A more comprehensive study of this problem has been begun by the author, and preliminary results are appended as a preliminary report on seasonal fouling, as determined from panels submerged in various ports by naval vessels. Early in the course of this investigation it was realized that accurate data for determining the periods of active fouling could not be gathered by a study of ships’ bottoms alone, and it was accordingly recommended that such information for various harbors be ascertained by submerging panels from vessels visiting such ports. In conformity with these plans, 10 sets of panels were prepared by the Navy Department (New York and Norfolk yards), and these were issued to as many ships with instructions to submerge a set of two panels in each port visited, provided the vessel remained there three days or longer. Of these panels only three sets have as yet been received for biological study. Of these one set had but three boards and showed no results. The third set received was likewise small and com- pletely dried out when received so that results were difficult to evaluate. The second set, however, showed definite and significant results. These panels had been submerged by the U.S. S. Sirius and represent fouling conditions for limited periods at the San Diego, Mare Island, Bremerton, and New York Navy Yards. The data are tabulated in Table 5. By referring to this table it can be seen that fouling is severe at Mare Island in October, while it is very slight during June. At San Diego growths attach in moderate numbers in June and July, while no fouling, apparently, occurs during November. These data would indicate that at Bremerton, Wash., fouling is moder- ate in late June, while at the New York yard none occurs during late September. It is inter- esting that all of the above data substantiate general conclusions drawn from examination of ships’ bottoms. TaBLE 5.—Results obtained, with reference to seasonal fouling, from panels submerged by the “‘Sirius”’ Date of Date Depth «4. Fanel submer- | when Te- Place of submersion sub: | Curent and condition, Type of fouling i sion move! merge pus 5 | San Diego Slimy scum; few barnacles. Pee |e desees ew barnacies and hydroids. ae ome wee oni todo O. June 1 Single hydroid. eee (oe doses sedi ap Few hydroids. Seae|bae (eee Ree Scum only. July 11 15 minute barnacles. eee |e do_--- peeao do 25 barnacles on panel. eee SS Gopsgs |e do 125 barnacles on panel. July 28 Few minute barnacles. Seo Bes dose ay do Barnacles and few hydroids, ee do A single hydroid. Sept. 23 Clean. sees bee Go-22_ di ree Suma only. Bere eae do. .-- do- 0. ? Oct, 30 500 minute barnacles. _ A asso do___- do do -| 25 barnacles and few minute hydroids. SON dorle ITE do... Tp { aot barnacles and few hy- Ol 19_.--| Nov. 22 | Nov. 28 7 Clean. 20na=2| pee OOnee=| ae do_--- do do Do. olen | nee domes |22e douse = Do. 228 BULLETIN OF THE BUREAU OF FISHERIES RATE OF GROWTH The rate of growth of various organisms is of importance in any study of the fac- tors that determine fouling, because of the fact that organisms become much more resistant to changes in their environment as they grow older (within limits) and as such are not killed off by the moving of a vessel from one port to another as easily as when the growths were young and succulent, and also because of the fact that increase in size increases the resistance of the ship. It is surprising, perhaps, to learn that barnacles grow to sexual maturity in less than 90 days and often attain large size in less than that time, as can be seen by refer- ring to Figure 31 F, which shows the size of some barnacles collected from the Nevada after she had spent 60 days in the harbor at Rio de Janiero. Figures 31 A to E, represent the rate of growth of barnacles at Beaufort, N. C.; and in Figure 32 is shown the amount of fouling that accumulated on a piece of wood at this harbor in 60 days. Very little accurate information is recorded regarding the rate of growth of these forms, although B. H. Grave (1924) has made a recent study of some of the forms that cause fouling, but these results have not been published as yet. FRESH WATER HISTORICAL DATA It is a firmly established belief among mariners that if a “fouled vessel is placed in fresh water the growths on its bottom will be removed and the boat again become clean.’”’. When the cruises for vessels were less exactly timed than at present, ex- perienced sea captains often put into a fresh-water harbor for this single purpose; and even to-day ships passing through the Panama Canal are known frequently to spend an extra day or more in the fresh-water lakes, and it is commonly understood that sea captains are anxious to have their vessels in fresh-water ports whenever possible. According to Capt. Henry Williams (1923), however, unfortunately there is no definite information on this subject. Itis known that certain marine organisms can and do survive in fresh water; as, for example, the eel, the salmon, or the shad, all of which spend a part of their lives in fresh water and the remainder in salt water. Similarly, such alge as Enteromorpha and Cladophora live indifferently in fresh and salt waters; but such forms are very few in number in comparison to the vast number of marine organisms that soon die if placed in fresh water. Among the organisms that cause fouling, almost all are strictly marine forms with but a small percentage able to survive in brackish waters. There can be no doubt, then, that many of these organisms are killed if the vessel to which they are attached is transferred to fresh water for a period of time sufficient to secure this effect. DATA FROM SHIPS During the course of this investigation it was apparent on many occasions that the unusually clean condition of the boat was no doubt explicable on the basis of visits into fresh waters. Thus, in the case of the Western World (March 8, 1924) its regular Buu. U. S. B. F., 1927, Pt. II. (Doc. 1031.) ARTHUR Ho THOMAS COMPANY LABORATORY APPARATUS AND REAGENTS PHILADELPHIA < ; 2 3 4 . RE ANS pobotububdhotubotub tate Fic. 31.—Rate of growth for barnacles. A and B, one month’s growth of Balanus eberneus on glass slides 3 by 1 inch, June 5 to July 4, 1924, at Beaufort, N. C. C and D, two months’ growth of B. ebernews on wood at Beaufort, N. C., May 17ito July 16, 1924. E, three months’ growth of B. ebernews. May 17 to August 17, 1924, at Beaufort, N. C. we approximately three months’ growth of B. tintinabulum from Rio de Janiero, as collected from the hull of the .S. 8. Nevada Bui. U. S. B. F., 1927, Pt. Il. (Doc. 1031.) Fic. 32.—Amount of fouling accumulating within 60 days (May 15 to July 15, 1925) on a board 4 inches wide by 1 inch thick and 26 inches long. A, entire board, indicating average low tide line (x); B and C, enlarged views of growths FOULING OF SHIPS’ BOTTOMS 229 visit to Sante Fe (Argentina), far up on the Salado River, very probably explains the absence of fouling on this route, while vessels that do not visit fresh-water ports usually acquire heavy fouling. Similar explanations would account for the conditions found on the Hastern Pilot (March 25, 1924), the Zarembo (April 11, 1924), and also the Hastern Sword (April 11, 1924). The lightship tender Hawthorne (March 10, 1925) was found to be almost clean, in marked contrast to most vessels of her group. The fact that she spent consider- able time in the Connecticut rivers probably explains this condition, on the basis of the effect of fresh water. While there can be no doubt that fresh water kills many of the organisms that cause fouling, yet that does not imply in any way the natural conclusion that such ships would then be clean. On the contrary, many ships have been observed where the fouling growths were very probably killed by the entrance of the ship into a fresh- water harbor, but fouling on such ships often remained severe for a considerable period. ‘The shelly growths of barnacles, oysters, Mytilis, and even of Bryozoa, and the chitinous “‘stems” of hydroids have been seen on ships that had been in the fresh-water harbor of Philadelphia for more than 12 months. The most notable example of this is the case of the destroyers Parker and O’Brien (November 28, 1922), where many barnacle shells were scraped from their bottoms after more than 20 months in polluted fresh water. It is thus evident that although fresh water kills the growths that cause fouling, it does not remove them or clean the ships unless such growths are succulent or very young, in which cases the entire ship probably is cleaned by this process. EXPERIMENTAL DATA Tn order to ascertain more exactly the period that it is necessary a vessel spend in fresh water in order to secure such desired results, the following experiments were conducted. Various types of organisms were removed from their normal salt-water habita- tion and placed in containers, through which a slow current of fresh water passed constantly. A contimuous circulation of water was found necessary, both to supply the required oxygen and to prevent putrefaction from affecting the more resistant organisms. Death pomt was determined if after transfer to normal environment resuscitation did not occur. In Table 6 is given the list of the organisms tested and the period of exposure necessary to kill. The first column indicates the time at which the first were ob- served to succumb, and the second column indicates the maximum period during which these organisms were able to live in fresh water. The number of trials is also indicated in each case, many organisms being used in each trial. It will be seen from this table that many of the organisms that cause fouling can be killed by transfer to fresh water for a period of 24 hours. ‘This is especially true for most larval and young forms. It will be noted, however, that several important organisms such as Balanus eburneus, Ostrea, and Enteromorpha, often are not killed in less than four days, although in several tests it was found that the larve and younger forms of all but the last of these were killed within that period. 230 BULLETIN OF THE BUREAU OF FISHERIES TaBLeE 6.—Illustrating the resistance of marine organisms to the effects of fresh water, indicating in hours the length of time that certain forms, common on ship’s bottoms, were able to live in circulating fresh water F Number | Minimum | Maximum Cheeiue of trials period period Hours Hours Balanus eburneus 4 72 96 B. amphitrite-------_- 5 12 24 B. balanoides (1) - - ------ 4 36 48 Chthamalus stellatus (2). é 2 48 60 Tubularia erocea__------- 4 2 12 24 Budendrium -------------------- S 2 6 12 Obelia geniculata___ uD 1 12 Membranipora sp.?- ace 4 12 24 Bowerbankia gracili A 3 6 12 Ostrea elongata_______-------------------------------+----------------------------~------------ 2 48 96 Enteromorpha (8) -.--.----------------------+-+-------+-------------------~-------=-+-----=-= 3 72 ? Norr.—(1) and (2) are not common on ship’s bottoms but are listed for the sake of comparisons. (3) is a variable, depending waon:fie previous environmental conditions. Death determined by inability to revive after being returned to original environ- Accordingly, it can be assumed that much fouling is killed by a stay of one day in fresh water. If the growths present are all young, a larger percentage will be killed and most or all of them will disappear completely. If on the other hand, they are mature forms of more than two or three months, many of such growths may not be killed in less than 72 or 96 hours; and even if killed, their shelly structures will still remain, often for a long period of time. Inasmuch as the resistance to a ship is caused by these structures, whether alive or dead, little benefit will accrue from such visits to fresh water, except that these growths will no longer increase im size. It, is accord- ingly evident that fresh water will kill most forms that cause fouling but will not remove many of the growths already present, unless these are minute and not heavily calcified or chitinized. POISON PAINTS, METALS, AND SURFACE FILMS POISON PAINTS The practice of painting ships’ bottoms has been in vogue so long that its value hardly can be questioned. As stated in the introduction, ships probably have been painted since the first ship was launched, but the nature of this paint has varied from time to time. These paints have been utilized as much or even more for the preservation of the wood or metal of which the hull is made than for the prevention of marine growths. Thus, on steel vessels to-day it is the practice to cover the ship first with a coat of ‘‘anticorrosive’’ paint and subsequently with a second coating of some “‘antifouling’”’ paint. The former is for the preservation of the metal while the latter is applied in the hope of preventing the growth of fouling agencies, and contains the various poisons used for that purpose. ; Before metal vessels came into use poison paints were resorted to primarily to prevent the attachment of the marine borers, which, even in recent times, have caused so much destruction to piling and other harbor equipment (see Atwood and Johnson, 1924) and which, until steel ships were first employed, caused even greater damage to the hulls of wooden vessels. FOULING OF SHIPS’ BOTTOMS 231 That copper poisons are especially efficacious in preventing the attachment of the young larve of these forms, provided the paint has been applied recently, is acknowledged generally. Many copper and mercury salts are extremely toxic to most animal and many plant organisms. It would be supposed, naturally, that these would be effective against those organisms that cause fouling, although no experiments to prove such a contention have. been tried, as far as the author can learn, on any of the organisms as they exist at the time of attachment. Recently, Bray (1923) studied the resistance of the earliest larval stage of a single barnacle (Balanus eburneus) to various poisons, the results of which study will be considered below. That the efficacy of poisons has been doubted by many is indicated by the following quotation from Lewes (1889), of the Royal Naval College of Great Britain: On examining the conditions under which a vessel is put when coated with a composition which relies for its antifouling powers on metallic poisons only, we at once see the reasons which must make such a coating of little orno avail. In the composition we have drastic mineral poisons— probably salts of copper, mercury, or arsenic—which have been worked into a paint by admixture with varnishes of varying composition, and each article of poison is protected from the action of sea water by being entirely coated with this mixture; that this must be so is evident, or the com- position would not have sufficient cohesive power to stick on the ship. As a rule, care is taken to select fairly good varnishes, which will resist the action of sea water for, perhaps, two or three months before they get sufficiently disintegrated to allow the sea water to dissolye any of the poison; whilst even with the accidental or intentional use of inferior varnishes, three or four weeks will pass before any solution can take place and any poison liberated to attack the germs. A ship is dry-docked, cleaned, and her antifouling composition having been put on, she goes probably into the basin to take on cargo. Here she is at rest and, with no skin friction or other disturbing causes to prevent it, a slimy deposit of dirt from the water takes place, and this, as a rule, is rich in the ova and germs of all kinds of growth whilst the poisons in her coating are locked up in their restraining varnish and are rendered inactive at the only period during which they could be of any use. _ After a more or less protracted period the ship puts to sea, and the varnish being aided by friction of the water the poisonous salts begin to dissolve or wash out of the composition; but the germs have already got a foothold, and with a vessel sweeping at a rate of 10 to 12 knots through the water the amount of poison which can come in contact with their breathing and absorbing organs is evidently so infinitesimally minute that it would be impossible to imagine it having any effect whatever upon their growth. If the poison is soluble, it is at once washed away as it dissolves; if it is insoluble, then it is also washed away, but there is just a chance that a grain or two may become entangled in the organs of some of the forms of life and cause them discomfort. As the surface varnish perishes, the impact of the water during the rapid passage of the vessel through the water quickly dissolves out or washes off the poisonous salts and leaves a perished and porous, but still cohesive, coating of resinous matter, which forms an admirable lodgment for anything that can cling to it; and by the time the vessel lays-to in foreign waters, teeming with every kind of life, the poison which would now again have been of some use is probably all washed away, and a fresh crop of germs is acquired, to be developed on the homeward voyage, and a “bad ship” is reported by the person who looks after her docking. It is evident that a poison, even if it had the power of killing animal and vegetable life in all stages, could only act with the vessel at rest, unless it were of so active a nature as to burn off the roots and attachments of the life rooted to it, and if it did this, what, may I ask, would become of the protective composition and the plates of the vessel? And I think it is also evident that any poison so used must be under conditions in which it is very unlikely to be in a position to act when it might do good. The practical proof, given by experience, that poisons alone are unable to secure a clean bottom soon led many inquirers to the conviction that it was exfoliation in the case of copper which had acted in giving fairly good results, and in many compositions the attempt has been made to provide a coating which will slowly wash off, and, by losing its original surface, shall at the same time clear 232 BULLETIN OF THE BUREAU OF FISHERIES away germs and partly developed growths and so expose a continually renewed surface, in this way keeping the bottom of the vessel free from life. There is no doubt that when this is successfully done a most valuable composition will result, but the practical difficulties which beset this class of antifoulers must not be overlooked. In order to secure success, the composition must waste at a fairly uniform rate, when the ship is at rest, and also when she is rushing through the water; and this is the more important in the case of service vessels, as in many cases they spend a large percentage of their time at anchor, or in the basins of our big dockyards. If a composition is made to waste so rapidly that it will keep a vessel clean for months in a basin, then you have a good composition for that purpose; but send the vessel to sea, and under conditions where you have a higher temperature, and the enormous friction caused by her passage through the water exerting its influence upon the composition, and you will find that the coating which did its work so well for six months at rest in the basin will, in the course of one month under these altered conditions, be all washed away, and fouling will be set up. Noting this result, the manufacturer renders his composition more insoluble—less wasting—and so obtains a coating which, when the vessel is in motion, scales just fast enough to prevent fouling, and good results at once follow; the composition is then put on the same or other vessels, and they take a rest in the basin, and bereft of the aid of a higher temperature and the friction of the water, the composition ceases to waste fast enough, and bad results at once have to be recorded. (Gardner, 1922-23, pp. 47 and 48.) Apparently little consideration has been accorded the fact that all growths that attach to ships have a protective layer of material, frequently of a composition similar to limestone, between their bodies and the film of paint, and that in adult forms, at least, food is taken in from a very considerable distance from the sides of the ship. It is apparent to anyone with knowledge of the structure and habits of the animals that cause fouling that the only time a poison carried in a paint film could possibly be effective must be at the time of attachment. When it is realized that barnacles (which are, as previously demonstrated, the most serious factor in fouling) attach by means of long antenne, and that they do not take any food or even have any functional mouth during the period of attachment (that is, until metamorphosis has been completed) it can be seen that the effect of poison must be either as a direct irritant during this process or else the poison must be in such concentration in the surrounding water that the little organism, after attachment and subsequent metamorphosis, is poisoned by it with the food it takes from a distance of at least 1 millimeter from the surface of the paint. The amount of poison necessary to build up a concentration sufficient to be toxic at so great a distance, when submerged in an ocean of water that is usually in motion, and to hold such a concentration for a period of weeks or even months, as is demanded, would probably need to be much greater than the amount used. Hven as early as 1867 Charles ¥. T. Young questioned the efficacy of poison paints, as can be seen from the following quotation (p. 68): “Tt has been remarked somewhat dogmatically that for protecting iron vessels against corrosion and the adhesion of barnacles the use of a poisonous paint is in all cases indispensable, and this paint must be slightly soluble in water.” But he Maintains that ‘‘The primary requisite qualification for all paints or patented com- positions laid over the bottoms of iron ships is necessarily the ‘preservation’ of the iron.” It is accordingly apparent that the use of poisons as antifouling agents for steel ships has been based either entirely on a priori evidence, without adequate founda- tion, or else is a hold over from the custom of painting wooden vessels, and its efficacious use can be legitimately questioned. FOULING OF SHIPS’ BOTTOMS 233 The effects of many kinds of commercial paints have been observed during this investigation, but not in sufficient numbers to make it advisable to contrast their effectiveness, except in the comparison with the ‘‘Norfolk standard’’ used by both the Navy and the Shipping Board, whose vessels comprise more than 90 per cent of those examined in this investigation. It can be stated, however, that no paint, with the possible exception of “Moravian” (Litchfield, April 10, 1924), has proved to be superior to the ‘“‘Navy standard.” The “amalgamated” was used on the Benguela (September 4, 1924), and this vessel was much more severely fouled than the West Hestleton (August 12, 1924), both of which, as seen from their records, had similar duties, cruising records, and itimeraries, and were operating at almost the same season of the year, a factor that may have had some influence. The effect of the ““Red Hand’’ paint was seen on such ships as the Hopkins and Kane (December 7, 1923), Goff and Gilmer (November 21, 1923), and Fox (April 10, 1924), as well as on others; but adequate comparisons could not be made. In several cases, however, similar ships with similar duties but with ‘‘Navy standard” paint showed somewhat less fouling than the above. The “‘International’’ paint was used on several lightships and tenders, includ- ing the Relief (April 24, 1924), Northend (June 2, 1924), Lotus (August 7, 1924), Hawthorne (March 10, 1925), and Lightship 108 (April 4, 1925), and m most cases these were badly fouled. No comparison could be made, as none were painted with the ‘‘Navy standard.” The problem of continued effectiveness of paint is one that has been pondered long. The number of factors that enter into the problem of fouling apparently have clouded any accurate determination of this matter; and even in this investigation with respect to only a few ships could the question be answered positively, as negative data were inconclusive. 2 In the case of the Maryland (October 12, 1922), a heavy set of barnacles had occurred within the 70 days that elapsed after a previous dry docking, and in the case of the Sturtevant (November 20, 1924), a similar heavy growth of Balanus improvisus occurred during the 90 days after the previous dry docking. In the few other cases of short docking intervals (usually occasioned by some accident to the ship) light fouling, due to alge, was observed. It is evident, however, from these two cases, as well as from the experimental test plates, that fouling frequently occurs even within 20 days of the time of painting, indicating that the effectiveness of the poisons apparently was lost by that time. Many steel panels coated with various poison paints have been submerged, both by the Navy Department and by the American Society for Testing Materials, in order to determine the relative efficiency of such paints as antifouling means. Although the final report on the experiments conducted by the Navy Depart- ment has not been seen by the writer, the report of Bray (1923) contains a list of many of the poisons used and the period of exposure when examined. These poisons were used as ingredients of paint films and were employed in concentrations of 4, 8, and 12 percent. The following selections will give some idea of the range of materials tested: HgO, ZnO, CuO, naphthalene, zinc cyanide, poke root, NaOH, cupric oxide, sodamid, thymol, hydroxylamine sulphate, strychnine sulphate, quinine sulphate, uranium nitrate, Portland cement, T. N. T., phenol, capsicum, arsenated bakelite, 234 BULLETIN OF THE ‘BUREAU OF FISHERIES aluminum sulphate, barium sulphate, sodium silicate, sodium chloride, hexamethy- lenamine, and copper sulphate. Many of them showed heavy fouling in less than 150 days, although a few, especially the mercury and copper oxides, showed less than the other materials tested. In a tentative report regarding these results Captain Williams (memorandum, July 25, 1923) stated that “of all the different substances tried the most effective are mercuric and cuprous oxides.” The American Society for Testing Materials has appointed a subcommittee (No. 23) for investigating antifouling pats. Five annual reports have been sub- mitted, which include the results of many experiments with submerged panels and some tests on ships’ bottoms. One definite result that they record is that ‘‘differences in fouling and corrosion are as appreciable in underwater paints by varying the vehicle as they are by varying the pigment.’’ This fact would indicate the relatively minor effect of the toxic agents and the major importance of the condition of the paintfilm. Their final recommendations to date indicate a conclusion only in regard to the toxic compounds to be employed. They recommend as follows: Antifouling paints shall contain, in each gallon of paint, copper and mercury in not less than the following amounts for varying service of ship: Service f Copper | Mercury Ounces | Ounces 14 7 Gyn eel ce et nee he ee ce oe etn = soe bbee oat encetocintiesctarneeoacass IN (oa serosa VEU ee ean Ree es a SE Se A SS eae Soe steel 25 1.5 South Temperate waters---- ai8 20 5 UD o ee NE Sa eee Se 2h ee ee SS SS SS ane: SSS Se sotSS se sesrsee sce 14 14 The compounds of the metals are not specified, excepting that they ‘shall be present in the form of compounds which are not soluble in distilled water at 20° C, to a greater extent than 1 part per 15,000 parts of water, by weight (0.067 per cent = 0.00067).”’ Effect of poison on larval barnacles.—Bray (1923) has studied the effect of various poisons in differimg concentrations on the first larval stages of one of the barnacles that causes fouling (Balanus eburneus). He collected large numbers of the newly hatched nauplii and tested their resistance to known dilutions of many supposedly poisonous substances. The actions of the naupli were carefully noted under a microscope, and the time taken to bring about complete cessation of movement was considered to be the amount of time necessary for the given solution to exhibit its toxic effects. In Table 7 the results of some of his experiments are shown, The author states that these data may be ‘‘interpreted very diversely, according to the particular conception one has of the fouling process and the time and manner of the action of the toxic agent or the anticorrosive flm.’’ While virtually all were effective at saturation, this was not the case for such compounds as cobaltous oxide and car- bonate, both of which are fairly soluble in sea water, or for such compounds as anti- mony trioxide and copper carbonate, which are almost soluble. ‘‘Some are very effective at high concentrations but rapidly lose their toxicity on dilution—e. g., arsenious pentasulphide and calcium fluoride.”” Others, though but slightly soluble, “‘seem effective at a great dilution—e. g., copper cyanide, mercury arsenate, phenyl arsenious oxide; and especially worthy of note is clorvinyl-arsenious oxide.” FOULING OF SHIPS’ BOTTOMS 235 TABLE 7.—Resistance (in minutes) of larval barnacles (nauplii) to several concentrations of various compounds (from report of A. W. Bray) Percentage strength of solution Toxic agent 100 50 25 10 5 1 0.1 0.01 | 0.001 Mrercuricichlorided 4-2 a aS ok VRereUTICOXIGO een na se RON TACT Dae eee eS Mercuric arsenate-_-__- Copper O-nitro benzoat Copper P-nitro benzoat Lead O-nitro benzoate__ Ferric O-nitro benzoate_ Cuprous cyanide--_--....-._.---.-_--__-_----__-.___- Cupric cyanide__ Paris green. ____- Cupric chloride-_ Cuprous chloride-_ PECTIC ACL ee ee ee EE ELECT st CAWAUE ORHAN [Yale CR a BSE ea a a Pr Barium arsenate_____---_- Phenyl arsenious oxide--- Chlor vinyl arsenious oxid Dipheny] arsenious oxide____ Diphenyl amine arsenious oxide_-__________________- INapthalenosssees sia ee ee vie Lo eee ES 1 Hours. Thus, it is seen that Bray has shown that certain compounds have a very toxic effect on the earliest larval stages of barnacles, provided the concentration is sufficient in the medium surrounding the organism to have its maximum effect. It must be understood at this time that the barnacles attach by means of long antenne, and that in the case of mercurial compounds a concentration of more than one part per hundred thousand must be maintained in order to have any effect at all. With the entire ocean as a solvent, and less than 14 per cent of an extremely thin film to act upon, it seems questionable if such poisons can build up a concentration sufficient to be lethal for any considerable period of time. Of course, it is remotely possible that chemical action with sea water might have some effect, as suggested by Gardner (1922, p. 55). He states: The toxicity of free substances such as mercury and copper compounds to young organisms does not necessarily give a true indication of their toxicity when mixed with other ingredients of a paint, and the influence of the component parts of the sea water upon the toxic substance through longer periods may render it more or less toxic by dilution or by chemical interaction * * *. It is well known that when two substances are mixed together in varying proportions the resulting mixture is frequently more toxic than the same quantity of either component if used separately. The ‘‘why”’ of this action is not known; it is merely an empirical result. However, this type of speculation has no evidence whatsoever for its support and perhaps is indicative of the methods sometimes employed in the preparation of antifouling paints. Many paints have been tested by actual application on the bottoms of ships, both by the United States Navy and by the American Society for Testing Materials, through cooperation with the United States Shipping Board. In such tests the vessel to be painted usually was marked off into four divisions, and the forward port quarter and aft stern quarter were painted with the test paint while the other two quarters were painted with the regulation “‘Navy standard;”’ or vice versa, as the case might be. In such tests a true comparison of the relative efficiency of the two paints could be determined. 236 BULLETIN OF THE BUREAU OF FISHERIES The report of the American Society for Testing Materials, subcommittee No. 23 (1925), records the results with 11 vessels partially or completely covered with test paints, and in addition to these 7 have been examined in the course of this investigation. From the data given in their report it can be seen that in most cases there was no noticeable difference in amount of fouling, although in almost every case the experi- mental paint film did not “‘hold up” as well as the “‘standard.”’ These data indicate not only the ineffectiveness of poisons but also the very significant effect of the nature of the surface film in the matter of fouling, a subject that will be considered next. SURFACE FILMS Since the major importance of the problem of fouling of ships’ bottoms centers about the question of frictional resistance of the surface of the ship in passing through the water, the nature of the film covering this surface is of prime importance. It has been recommended by many people that paints of a greasy character would be advantageous, on the theory that there is no adhesion between the films of oil and of water. However, McHntee (1915) maintains, from his experimental data, that the most favorable coating for ships’ bottoms, as far as skin friction is concerned, is a paint that offers a permanent, hard, smooth surface. From a biological point of view, as far as the attachment of larval forms causing fouling is concerned, the nature of the surface film also is of great importance. In the course of the examinations considered in this paper it was noted that foulmg was most severe in regions where the surface was not smooth. Thus, im the areas where paint had peeled off, as shown in Figure 33 A the growth frequently was heavy, provided corrosion had caused a roughened surface. Frequently the number of barnacles that attached to a colony of Bryozoa (fig. 33 B), or even to other barnacles, would be much larger than on the adjoining smooth surface of the ship’s hull. In other cases, where the pigment of the paint had not been mixed properly before applying, the resulting rough surface often was fouled more heavily than in regions where the paint offered a smooth surface. (Figs. 33 C and D.) These observations are confirmed by reference to the report of Adamson (1922), in which he presents data to show that the ‘‘problem [of fouling] covers physical properties as well as chemical properties of the paint film.” In the summer of 1922 Bray (1923) made some preliminary tests on the effects of various surfaces in relation to the attachment of barnacles. He set out two sets on separate racks at Beaufort, N. C.; but, he concludes, ‘‘unfortunately, the length of time the racks were exposed, due in part to the lack of material and to an accident which caused them to lose rack A, after nearly four weeks exposure, renders any attempt at anything but tentative conclusions oi little value.’ These tests included such surfaces as glass, beeswax, eseter gum, and shellac, with various types of poisons and combinations. He, however, concludes that “there seems little doubt that a film of a ‘waxy’ nature is capable of greater retention of the toxic agent than a thinner, harder film.’”? This point is brought up at present, without reference to the question of poison, only to show the superior results obtained with “waxy’’ surfaces. The writer has observed barnacles attach to metal surfaces of many sorts, provided no electrolysis was present, to wood, stone, tile, glass, rubber, and shells of more than 30 species of animals—in fact, to everything that is found submerged at Buu. U. S. B. F., 1927, Pt. II. (Doe. 1031.) Fig. 33.—Effect of surface film on fouling. A, portion of the hull of the U. S.S. New York (Norfolk, Va., April 3, 1924), showing heavy set of barnacles where paint had peeled. B, also from the New York, showing attachment of barnacles on rough surface of a bryozoan colony. C and D, two test panels submerged at Beaufort, N. C., for identical periods of time, both with poisons but one (C) with a rough surface and the other (D) with a smooth surface FOULING OF SHIPS’ BOTTOMS 237 proper seasons and in favorable waters, with the exception of certain alge. However, not all alge are free from such attacks. Darwin records the occurrence of a special form of barnacles grown on the southern coast of Africa, and the author has found another variety growing in abundance on the fucus on the breakwater at Beaufort, N.C. Nevertheless, the question of selective attachment of the larve of barnacles has proved a fascinating one for experimental work. Knowing that barnacles attach while in the cyprid stage, by means of an adhesive secretion thrown out from the tip of the antennz, the possibility of finding some substances to which this “glue” would not adhere presented an interesting phase of the problem. It has been found that the larve of certain barnacles (Chelonibia testudinaria) attach only to the backs of turtles; others (Chelonibia patula) to the shells of crabs; others (Dichalaspis miilleri), again, to the gills and in the gill chamber of certain species of crabs; and that one type of barnacle (Balanus galeatus) grows only on a special kind of coral. Likewise, other barnacles are found only above low tide line (Balanus balanoides), and others, again, only below low tide line (Balanus crenatus). Considering these possible factors, and especially the relation of the adhesive substance of the barnacles to the nature of the surface to which it attaches, some experiments have been made, using more than 12 different compounds, including several decoctions made from different marine alew and which show conclusively that no barnacle can attach to these films (at least within three weeks) during a heavy ‘‘setting” period, when all other surfaces were being coated with young barnacles. It is also of interest in this connection that the presence of a slime film on the experimental panels, as well as on ships’ bottoms, has been considered by some. to be advantageous in preventing fouling, while others take the opposing view. Recent work done at the University of Washington by Miss Hillen (1923) would indicate that this slime is of bacterial composition, and she even maintains that ‘without this slime the barnacle would not settle upon the object (test panel) or develop upon it, as the slime is used as food material for the young barnacle in its first development.”’ Further evidence on these points seems to be needed. METALS Different metals have been used as a means of preventing fouling since early times, as was described in the introduction to this paper. Copper and zine were used abundantly on wooden ships, but with the adoption of steel vessels the use of these metals created electrolytic action that proved disastrous to the iron. That copper has a protective function toward certain growths is seen from the record of the Denver (March 16, 1923), Cleveland (April 10, 1921), and the Phalarope (August 19, 1923), all of which are wooden ships that were partially or completely plated with copper sheathing. On these vessels barnacles were found as abundantly on the copper as elsewhere, but alge and hydroids were conspicuously absent. Bry- 0zoa and serpulids were present occasionally, but were not nearly so prevalent as on the propeller blades and the struts, which were of alloy composition, probably bronze. ‘This difference was often noted on the propeller blades of iron ships, as on the Florida (March 15, 1923), where a very dense growth of hydroids covered the entire bottom but none were present on the propeller blades. 238 BULLETIN OF THE BUREAU OF FISHERIES A complete study of the relation of various metals to fouling has been made recently by Parker (1924), who submerged panels of zinc, iron, aluminum, tin, lead, and copper. He found more or less fouling on all of them except the copper, and only a small amount on zinc. He explained this difference on the basis of ionization of these metals in salt water and the solubility of the resultmg compounds. Thus, he states: The poisonous effects of these metals on marine animal life will depend upon the intrinsic toxicity of their ions, relatively high for all heavy metals, and the solubility of their hydroxides and basic carbonates in sea water. These solubilities in the case of:Fe, Sn, and Al are in amounts inappreciable; in other words, these metals in sea water are not surrounded by a layer of poisonous ions, and hence animals may grow upon them. In the case of Zn and Cu, on the other hand, the corresponding compounds are appreciably soluble in sea water, and the poisons thus liberated prevent the growth of animals upon these metals. His experiments with metal couples, however, have shown results that indicate a means of preventing fouling, even if an impractical method. He found that by coupling copper with metals higher in the electromotive series this metal can be rendered chemically imactive in sea water, and under such circumstances animals will grow freely upon it. Similar results were obtamed with other couples, so that Parker concludes that ‘‘marine animals will grow upon any heavy metal, provided that metal does not liberate ions or soluble compounds.” Conversely, it would accordingly be apparent. that any electrolytic action causing ionization would serve to prevent fouling. LIGHT AND COLORS During the course of the examination of the second ship observed in dry dock it was observed, as previously noted in this report, that fouling was most severe in the region of the run and beneath the bilge keels of the ship. This increase in amount of fouling on lightly or moderately fouled ships in all areas that might be considered s “shaded” has been one of the most outstanding points noted during the whole investigation. More than 50 per cent of all examinations showed such results very strikingly. Other explanations have been offered to explain this intensification of growth in restricted areas, as, for example, the protection afforded in such locations. The writer, however, has held that the main factor was the influence of light. This contention no doubt was influenced greatly by previous knowledge of various biological studies on related phenomena. The reaction to light of animals and plant organisms has long been a ie study of biologists, because of the fact that most organisms react to this stimulus, as well as because of the ease with which the stimulating agent can be controlled. Lord Avesbury (Sir John Lubbock, 1904) was one of the first to demonstrate the fact that animals of many sorts react to light of different colors, finding, for example, that bees “prefer” blue flowers and that the tiny water fleas, Cladocera, gather in the region of the red if given a choice of all the colors of the spectrum. More recently Mast (1911) and others have shown that reaction to light is a property common to almost all living things, both plant and animal. He showed, among other experiments, that the larve of one of the hydroids (Kudendrium) common on ships’ bottoms react negatively to light, while the spores of certain plant forms (alge), also common on ships’ bottoms, are positive in their reaction to FOULING OF SHIPS’ BOTTOMS 239 light. More recently, Caswell Grave (1920 and 1923) and his students have shown that the larve of several tunicates (Amaroucium, Perophora, and Botryllus) are positive to light upon liberation from the mantle chamber of the adult, but at the time of attachment all are definitely negative to light. Thus Grave and Woodward found for Botryllus (a tunicate common on our North Atlantic coast) that the free- swimming period for these larve persisted for from 1 to 27 hours, and that during this time they react positively to light for a “comparatively long period,” and then are indifferent. or nonresponsive and finally negative to light for a “‘period of short duration just before metamorphosis begins.’ Some work has been done on the reactions of the barnacle larve to light, notably by Jacques Loeb (Groom and Loeb, 1890); but this work was done only on the early larval stages (nauplii) and consequently has little bearing on the problem, as the cyprid stage is the condition in which the barnacles attach to ships’ bottoms. In his studies of the ‘‘nauplean larve”’ it was found that they were usually positive to light upon liberation from the parent, but that reversal of reaction frequently occurred, probably dependent on environmental factors. That practical tests have been made on ships’ bottoms regarding the effect of colors is recorded by Holzapfel (1923), who concludes that the advantageous effect, if any, is too slight to warrant any serious consideration. However, the report of Captain Macauley (1923) would indicate that not all nautical men would so minimize its practical importance. As this problem (the effect of light on fouling) seemed one that offered consider- able possibilities, and inasmuch as no controlled experimental data were available regarding it, considerable time has been spent on its study. This work has been of four kinds. First, the use of steel plates coated with variously colored paints, submerged in a tidal channel whose waters were heavily infested with fouling organ- isms; second, the study of the effect of a submerged electric light on the attachment of organisms (the results of this experiment were so inconclusive, due to various difficulties, that they are not presented here); third, the use of colored tiles under similar conditions in order to eliminate the possible effect of the constituents of the paint film, leaving only the effect of light; fourth, laboratory studies of the reactions of the cyprid larve of various species of barnacles to light of known intensity and spectral distribution; and finally, as a corollary of this, the study of the actual process of attachment and the effect of light at the time of attachment. SUBMERGED TEST PANELS Attachment of fouling growths on steel panels painted with materials of different colors has been studied by several workers. Soon after beginning this investigation a conference of men working on the various aspects of the problem of fouling of ships’ bottoms was held at Beaufort, N. C., on October 25, 1922, where large numbers of panels had been submerged to test the effectiveness of as many different paints. Already at this time a series of panels painted with different colored paints had been submerged at the suggestion of H. A. Gardner. As he states in his circular (1922) recording the fact that these were submerged, but without recording any results, these were submerged “‘to determine the effect of colors upon attachment of barnacles. It is believed that the barnacles might seek, through protective colora- 69861—28-—4 240 BULLETIN OF THE BUREAU OF FISHERIES tion, certain colors and avoid other colors against which they might present a more obvious appearance.” However, at the time of the first examination by the author these plates showed results that were quite inexplicable on the basis of adaptive coloration but proved sufficiently interesting from a biological viewpoint so that a preliminary report by the author was submitted at that time (December, 1922), from which the following paragraphs are quoted: In order to test this hypothesis a series of 12 steel panels had been exposed. All were painted with two coats of standard anticorrosive paint and a third coat which contained the desired pigment. All of the pigments, as well as the paint mixtures used, were nontoxic. (See H. A. Gardner, 1922.) All plates were exposed on the same day, and each panel was suspended separately from a rack built in a tidal channel, where the water flows at between 4 and 6 miles per hour whenever the tide is running. They were submerged in water about 6 feet deep, being held in a vertical position about 12 inches from the bottom. They were arranged in a row, end to end, about 2 or 3 feet from each other and parallel to the water currents in the channel. The plates extended in a line approximately north and south. Both sides of each plate, consequently, received about the same amount of light during the course of the day. Examination was made about two months later. As all of the plates had been treated alike, except for the colored pigments, and as all factors influencing them were the same, it may be concluded that any difference in the amount and nature of the fouling would be dependent on color. The results obtained are presented in a table (No. 8) and may also be seen in the photographs. (Fig. 34.) The colors of the plates shown in the photographs are as follows: 201, white; 202, yellow; 208, red; 204, green; 205, blue; and 206, black. By referring to the photographs and to the table it will be seen that there was much more fouling on the dark plates than on the lighter colored plates. The contrast between the white and black plates was very marked. TasiLe 8.—Organisms found on test panels that differed in color of paint Color of paint Clean area Alger Worm tubes Bryozoa Gusts Barnacles White (201) ------- oa (65 per | Abundant-------- Very few_----- OL ERE) Seth bes O21 A Be 0. cent). Yellow (202)------ ark (40 per | Very scattered----| Abundant_--_} 0_---.-_--.----_- O4SSt AAs 0. cent). Red (203) --------- Few and small (5 Very few. per cent Green (204)_------ Extensive_—---~----|----- Few. Blue (205)_----.--- Few, medium (15 di Fairly numer- per cent.) ous. Black (206) ------- INone=22 2-2 e-en==- Very abundant. Tt will be noted that the clean areas were most extensive on the white (65 per cent) and yellow (40 per cent) plates. The growth of very fine alge was present only on the lighter colored plates and was abundant only on the white plates. It formed almost the only growth present on these plates. The worm tubes (irregular, slender, white formations seen in the photographs), formed by an annelid worm of the genus Hydroides, appeared very numerous on all the plates except the white and black. The latter may have had as many worm tubes as any other plate, but because it was so densely covered by other growths the appearance of any tubes was obscured. The Bryozoa (characteristic circular patches seen in the photographs) were noticeably most abundant on the red plates, although all others, except the white and yellow, were also heavily infested. Not a single specimen was found on the white and but a few on the yellow plates. The hydroids (grass) were absent from all but the red, blue, and black plates, and were abundant only on the last. The barnacles were the most striking in their distribution. Only on the blue and black plates were many of them found, and they were most abundant on the black. Buy. U. S. B. F.,° 1927, Pt. If. (Doc. 1031.) Fic. 34.—Relation of color to amount of fouling. For description see p. 240 of text. Variously colored plates submerged at Beaufort, N. C., for 244 months, August to October, 1922 FOULING OF SHIPS’ BOTTOMS 241 It can be seen clearly then that there is a very definite relation between the color of the plates and the kind and amounts of growths on each. The barnacles and hydroids apparently attach only to dark-colored surfaces, while Bryozoa and worms attach to somewhat lighter surfaces as well, but apparently prefer the red and yellow, respectively. Since the white barnacles were found most abundantly on the black plates, and since neither the barnacles nor the worm tubes, both of which are conspicuously white, were found on the white plates, it would seem that there is no evidence of protective coloration. The apparent selection of the darker surfaces can best be accounted for by astudy of the behavior of the larve of these organisms. The newly hatched lary of almost all sessile marine animals (as well as many others) react positively to light; that is, they swim toward the source of light. This period of positive reaction, however, is of only limited duration. (It appears to be only long enough to carry the young organism to the surface of the water, there to be carried about and dis- tributed by the ocean currents.) Most of these larvee then become negative to light. It is in this period that they attach and molt into sessile organisms with characters similar to those found in the adult. This fact has been demonstrated experimentally for certain hydroids, annelids, and . tunicates. It is also known that lights of different wave lengths have different effects on various organisms. Some go toward red, others toward blue, green, etc., depending on their relative stimulating efficiency on the specific organism. On this hypothesis one can readily explain the results found on the plates described above. It would seem (from the limited evidence at hand) that barnacles are strongly negative to light at the time of attachment. Hydroids (grass) are likewise so. The Bryozoa, although negative to white light, are apparently “‘attracted” especially by the red, and the worms (Hydroides) apparently by the yellow-red light waves. It would appear that this selection or “tropism,” holds good for the animal forms only, as the algze were found extensively on the white plates. As this hypothesis is in accord with observations made on ships’ bottoms, where one finds the densest growths in regions least exposed to light, it seems safe to conclude that most organisms commonly found attached to the bottoms of ships become attached there because of a relative decrease in the amount of light given off by such areas. Tt was realized that these notes and tentative conclusions were based on very limited evidence, and it was hoped that this problem might be investigated more thoroughly by experiments in which many of the unknown factors would be more definitely controlled. Sources of error in the above experiments were numerous, although probably more or less equal for all. The relative amount of light, the amount reflected from other plates of different colors and composition in the im- mediate vicinity, are all unknown factors that should be eliminated in future tests. The behavior of pelagic larve of different ages was not known for any of the species commonly found on ships’ bottoms. It was believed, accordingly, that such studies, with controlled factors, would be of value both from an economic and a purely scientific viewpoint, and a few were carried out subsequently, as described in the following ages. ae Although several successive series of panels were submerged, not all presented as clear-cut results as did the series recorded. This lack of differentation was especially noticeable after the plates had been exposed for several months (if in spring or summer months), which, no doubt, can be explained by the fact that once the plate is heavily coated, colors lose their influence, and, consequently, within a relatively short period during the season of the year when fouling is most severe, all of the plates become very heavily fouled, regardless of color. However, as less than 10 per cent of all active vessels become heavily fouled, and those that become moderately foul do so, as a rule, only after a considerable period out of dry dock, it will be realized that under practical conditions the relative influence of colors will be greatly prolonged. 242 BULLETIN OF THE BUREAU OF FISHERIES A similar series of panels was exposed in the following summer (1923) at Woods Hole, Mass. (fig. 35), with the results shown in Table 9 in which is shown their relative efficiency on the basis of the area free from fouling. All films were in excellent condition. No corrosion was evident anywhere. Fouling was caused largely by Bugula, with some Alga and a small amount of Obelia. Although no barnacles attached during this period of the year, the same relative differences in amount of fouling are seen here as in the plates at Beaufort. TABLE 9.—Results of plates exposed at Woods Hole, Mass., submerged on May 31, examined July 26, 1928, painted with two coats each of the “photographic” color paints, as prepared by Henry A. Gardner Percentage No. Plate color Film Fouling of surface not fouled 8 10 7 20. 4 20 5 20 3 30 1 hite. --do.. 50 6 | hight) greenSss.c2¢ fo hes EPA ee -do 60 bs Wah 0 a nip dea vip uk ey Ses Dag a do 90 It was soon realized, however, that these results were open to various explana- tions, for the material employed to produce a given color was different in each case, and this factor alone might account for the differences in fouling. Accordingly, other methods of attack on this question were planned. These included, first, a submerged electric light with colored panels on each side; second, a set of colored tiles; and, third, a series of experiments in which the active cyprid larve were exposed in the laboratory to light of known wave length and intensity. SUBMERGED COLORED TILES Woods Hole, Mass.—During the summer of 1923 a series of colored tiles, with both glazed and unglazed surfaces, were submerged by the author at the biological station of the United States Bureau of Fisheries at Woods Hole, Mass. Tiles were used in these experiments to eliminate all possible effects of any toxic action that might have resulted from the use of pigments needed as coloring matter in the paints employed in the previous experiments with panels. These tiles were sub- merged in two sets of panels—eight glazed in one panel and five unglazed in the other. The regulation size was 6 by 6 inches, but a few were half size, measuring 3 by 6 inches, and about one-half inch in thickness. These tiles were submerged on May 13, 1923, and were examined from time to time until July 25. The amount of fouling was noticeably less on the lighter- colored plates. However, there were several apparent inconsistencies, the glazed, black tile having less fouling than any of the others, excepting the two white tiles, whereas the unglazed, black tile was the most heavily fouled. However, the follow- ing gradation, from least to most, was noticeable in amount of fouling: (a) Glazed set: White, black, light green, yellow, pink, blue, green, red, and dark green. . (6) Unglazed set: White, yellow, red, dark green, and black. pel ‘AT ‘de018 HIVp “ {(xouv}N}) OPA ‘wy SHovlq So oyepoooya Sq fuser AOD cases se tone eee esac ee aia 419 993 1,118 23, 914 1, 259 1,123 1 Omitted. It is evident from this table, which shows the average results of all tests, that the darker the surface the more barnacles are found attached. These results may be seen even more clearly in Figure 36. While a light surface is by no means a cure-all, it will be realized that anything that reduces the fouling 50 per cent is a very important factor. Especially is this true when one realizes that on less than 5 per cent of the ships (on the basis of an examination of 250 vessels) may one find a growth of barnacles at all comparable in number to those obtained at Beaufort in less than one week. Glazed tiles also were used by the author, but conflicting results were obtained, similar to those recorded in the memorandum report by Perry and Bray of August, 244 BULLETIN OF THE BUREAU OF FISHERIES 1923. That these results are not valid, because of the varying amounts of light reflected, depending upon the position of the sun and brightness of the day, can be seen easily by referring to Figure 37, which shows photographs of these glazed tiles, taken in front of a south window in bright but diffused light (not direct sunlight). It will be noticed at once that, optically, there is little difference, under these conditions, between the amount of light reflected from a white or a black surface, as seen in Figure 37, A and B, and even red is optically almost as ‘“‘light” as white under these conditions. It is thus evident that any experiments based upon the use of such tiles are of little value in judging the effect of relative light intensities. Accordingly data from unglazed tiles only have been considered of value in these experiments. REACTIONS OF THE CYPRID LARV OF BARNACLES TO SPECTRAL COLORS The reactions of the cyprid larve of two types of barnacles that cause fouling (Balanus amphitrite and B. improvisus) were tested by exposure to monochromatic light of known intensity. Light filters were selected that possessed a narrow trans- mission band and were of known composition and thickness. In Table 11 is given a list of all the filters used, with the limits of light transmissions and the dominant wave length of each filter. A copper sulphate filter was used to cut out the infra- red light waves. TasBLe 11.—List of filters used in experiments on reactions of the cyprid larve of barnacles to spectral colors, showing total spectral transmission and dominant wave lengths [The letter ‘‘C” after a filter denotes a Corning glass filter. The numbers after the Corning glasses refer to the transmission curves shown in Bureau of Standards Technological Paper No. 148. The letter ‘“W” denotes a Wratten filter, and the number refers to the transmission curves found in the booklet ‘‘ Wratten Filters,” published by the Eastman Kodak Co.] Dominant Dominant Filter Total transmission wave Filter Total transmission wave length length Mu-mu Mu-mu Ultra, ©'83 22: - - 225 315-423 mu-mu and 609 red 355 || Blue-green, C 56__-_- 340-700 mu-mu-_-_--_--------_ 505 end. Green, © 520222225) 425-670 mu-mu____ 530 Purple, C 69-------_- 310-485 mu-mu and 690 red 370 || Green, W 58___ -| 485-635 mu-mu__ 540 end. Yellow, W 15_ -| 500-700 mu-mu__ : 590 Purple, W 35_------- 300-475 and 650-700 mu-mu__ 420 || Orange, W 22__ -| 545-700 mu-mu-__ = 620 ‘Blue, W' 49 404-1285) 400-510 mu-mu_-_--__--------- 440 || Orange, C 38__ _| 540 red end__-_ =e 640 Blue; C60: Hee eee 335-640 mu-mu___----------- 460 || Red, C 19___------_- 620 red) end ae ere 700 Blue, G-59_----------- 335-690 mu-mu-____---------- 480 In order to separate the effect of color from that of intensity it was necessary to determine the total amount of light energy transmitted by each filter. The calibra- tion of these filters was very kindly done by the United States Bureau of Standards. By use of this information the total light energy transmitted through one filter could be balanced by that transmitted through any other filter by moving the source of illumination. By using two beams of light at right angles to each other, and each of equal intensity, the relative effects on large numbers of cyprids were determined for all the filters. The results of these experiments are summarized in Figure 38, which clearly indicates a great difference in the stimulating efficiency of various spectral colors. In the region of the spectrum between 500 and 600 mu-mu, or from light blue to Buu. U. S. B. F., 1927, Pt. Il. (Doc. 1031.) Fig. 37.—Optical effects of glazed tiles, demonstrating their uselessness for these tests. A. 1 glazed white; 2, glazed black; 3, unglazed white; 4, unglazed red; 5, unglazed black. B. Al glazed tiles. 1, white; 2, black; 3, pink; 4, yellow; 5. light green; 6, dark green; 7, red so Ns FOULING OF SHIPS’ BOTTOMS 245 yellow, the stimulating efficiency is equal to more than 50 per cent that of white light; while between 530 and 545 mu-mu it is more than 90 per cent, or virtually a eee PERCENTAGE 100- (ava oa te eee h i ea Ce INDIVIDUALS pl ito| i He be | b REACTING spa | baldnrtal “yt Late (es FILTER 60- WHITE 50 shi bs ed o ee 4 i Fe a — = 5 Eas BE ue il = WAVE DSIRE BiG tO Uae ee bt Udieaht it LENGTHS 350: ; 400; § 1500 tt 1600; |! '700 BALE He oat ae tiated thotbantlh. cd. Lu ate t} MILLI-MCRA Se cGrrEe & 2S a S 8&8 a > vm m™m m mm ~ Seal acy iin ae ie eS 7s fo} Q 3 m™ m ee] = mom mt Fae eCity ean eens ait, ern fi o oO ROW OT UM SU Weitovesleas as w oO ao Oo 2 te) Nm ow or ins) Les} pes) Fic. 38.—Distribution of the stimulating efficiency of equal energy values among the various parts of the spectrum for the cyprid larve of certain barnacles equivalent to white light. On the other hand, light of wave lengths of 700 mu-mu has less than 5 per cent of the efficiency of white light, and likewise at 420 mu-mu A. B. C. @ERES Fic. 39.—Attachment of barnacle larve with reference to source of illumination (indicated by arrows) t the stimulating efficiency is very much reduced. For a more complete account of these experiments see Visscher and Luce (1928). 246 BULLETIN OF THE BUREAU OF FISHERIES It is evident, therefore, that light rays in the field of blue-green have a much ereater effect in activating the cyprid larve of barnacles than the light rays in other fields of the visible spectrum. REACTIONS OF LARVAL BARNACLES TO LIGHT AT TIME OF ATTACHMENT It has been demonstrated that the larval barnacles are sensitive to light and respond more vigorously to light in the blue-green portion of the spectrum than to light of other color. That these organisms are negative to light at the time of attach- ment was demonstrated by isolating a number of the cyprids and placing them in small cubical aquaria, which were then covered with black paper on five of their six sides. ‘The uncovered side was exposed to light from a north window. The results of these experiments, which were repeated on several occasions, can be seen in Figure 39. It will be noted that in each dish the cyprids attached in that half of the container away from the source of light, and that in each case the individuals were so oriented as to be directed away from the source of illumination. Tt can be seen clearly from these experiments that for the two types of barnacles that were tested, light is an important factor in determin- ing the point of attachment, and that they orient themselves with their anterior ends directed away from the source of light. It would appear evident from the results of the submerged colored panels, from the sub- merged tiles, from the experimental data on reaction of cyprid larve to spectral color, and, finally, from the above experiment, in which it is shown that cyprid larve become negative to light at the time of attachment, that paints larva at the time of “‘selecting” a place of attach- varying from a light blue to yellow would ar accumulate the least amount of fouling, and that a light green paint probably would be the most efficient, all other factors being equal. Process of attachment of the larve of barnacles—After a free-swimming period of from three days to several weeks, the cyprids attach to some substratum and meta- morphose into the adult type of barnacle. When the internal physiological con- ditions necessary for attachment are present, apparently correlated with the “lipoid” content of the organism, the larve have been observed, on many occasions, to “walk”? on the substratum, apparently hunting a place for attachment. This re-' markable performance is accomplished by alternate attachment and release of the adhesive tips of the antennz, combined with the relaxation and contraction of the set of appendages, which result in giving the organism a forward movement. (Fig. 40.) In this manner these organisms have been observed to ‘‘walk” for considerable distances, and have been seen to “‘test’’ various areas for a period of more than an hour before finally attaching. FOULING OF SHIPS’ BOTTOMS 247 On several occasions the writer has been fortunate in seeing the actual process of metamorphosis while observing through a microscope. It was observed that after attachment by means of the antenne the organism would “kick” vigorously for some time, but without effecting release. The animal then appeared to become fixed and metamorphosis followed. The two-valved shell of the cyprid stage was thrown off, as was also the exoskeleton of the appendages and usually the paired eyes as well. From this almost amorphous mass, the young barnacle soon emerges. A secretion continues to be laid down on the formerly ventral surface. and the rudiments of a coating (the future shell) appear around the sides of the mass. Whereas, when attached, the appendages extend downward, they now extend upward, and the mouth parts also have changed their position. A more complete account of this process and related phenomena is given by the author (Visscher, 1928). It is thus apparent that barnacle larve ‘‘test’’ the surface to which they attach, and at no time do the bodies of these organisms come into direct contact with the surface to which they attach. DISCUSSION AND CONCLUSIONS From the data presented in this report it is apparent that fouling occurs almost entirely when ships are in port. For this reason passenger ships were found to be almost free from fouling, while ships temporarily out of commission, and battle- ships, were consistently the most severely fouled. It is accordingly apparent that vessels should be held in port as short a time as possible. Fouling growths usually are killed if the vessels move from one port to another at a considerable distance. This is due, no doubt, to the differences in temperature, salinity, and dissolved salts of various kinds. However, the death of the organism does not necessarily free the ship from its fouling. Only the living portions are killed and the shells often remain for many months. If, on the other hand, a vessel moves into another port while the fouling growths are still young and succulent, such growths probably die and fall off completely, thus ridding the vessel of all fouling matter. Fresh water also has been shown to cause the death of most organisms that produce fouling. However, the same results are found here as above; namely, that if heavy calcareous shells have already formed, the fresh water merely stops increase in growth but does not remove most of the material already there, unless it is very young and its parts are still soft. Metal has been shown to remain free from fouling growths as long as electro- lysis takes place and its ions are liberated. As this occurs normally, in sea water, for copper, this material will not foul heavily with most types of organisms unless such ionization is inhibited. It is evident, then, that to be effective it must be in such a condition that it will be wasting away continually, going into solution. The efficacy of poison paints has been questioned because of biological considera- _ tions relating to the activities of the larve at time of attachment. It bas been shown - that the only time when a poison carried in a paint film can be effective is at the time of attachment of the fouling material. Immediately after this a film of calcareous or allied material is deposited by the organism and separates its tissues from the paint. Many vessels and experimental plates have been observed that had become 248 BULLETIN OF THE BUREAU OF FISHERIES foul within 30 days from the time of painting with an antifouling composition. This would indicate the relative ineffectiveness of such material after a very short period. Much more important is the nature of the surface film in its relation to the method used for attaching the larve of the organisms that cause fouling. The beneficial effects of the paints now used very probably can be attributed far more to the nature of the surface (when in water) than to any peculiarly poisonous property that they may possess. It seems probable that undue emphasis has been placed upon the use of poisons in paints on steel ships, which is probably a hold over from their use on wooden vessels, and that the proper nature of the surface film is the desired goal. Finally, this report presents data that demonstrate clearly the relation between light and the attachment of fouling organisms. The experiments with submerged panels of different colors, with submerged colored tiles, and with the cyprid larve exposed to equal energies of spectral colors, all show that barnacles are more sensitive to light colors than to dark, and that at the time of attachment they react away from this stimulus. Inasmuch as red is optically almost as dark as black, it is evi- dent that a worse color could hardly have been selected. Yet red and brown are the colors of more than 90 per cent of the commercial antifouling paints used for steel ships. It is admitted that the red iron oxide so universally used makes an ideally inert “body” for such paints, but if a substance of a lighter color could be found as an adequate substitute, it seems very probable that its use would be advantageous. SUMMARY 1. The fouling found on ships’ bottoms is composed of both plant and animal organisms, with the latter the more important group wherever fouling is at all extensive. 2. Barnacles, hydroids, alge, tunicates, Bryozoa, mullusks, and Protozoa are all found abundantly and in frequency and abundance usually in the order named. 3. Fouling organisms are almost exclusively those commonly found on rocks and other submerged structures near shore, especially in harbors. 4. Fouling occurs almost entirely while vessels are in port. 5. Passenger ships with regular schedules that permit them to remain for only very brief periods in port are the least foul of any group of vessels. 6. Most ships are moderately fouled after six to eight months from the date of dry docking. 7. Heavily fouled ships frequently carry more than 100 tons of fouling materials and occasionally more than 300 tons. 8. It is conservatively estimated that the annual cost of fouling to the shipping industry of our country is in excess of $100,000,000 per year. 9. Under optimum conditions vessels foul within 30 days of the time of dry docking and the application of poisonous antifouling paints, indicating the hypo- thetical value of antifouling paints. 10. The time that elapses between dry-docking periods is of great significance, but the use made of this time, whether in cruising or in port, is of even greater im- portance, for fouling is proportionally more severe as the length of time since pre- vious dry docking is increased, but it is decreasingly heavy in proportion to the time spent cruising, FOULING OF SHIPS’ BOTTOMS 249 11. Vessels that are never in port for more than a few days at a time, and whose next port of call is at a considerable distance, rarely if ever accumulate much fouling. 12. Each vessel shows at the time of dry docking the visible record of its cruise by the diverse types of organisms found on her hull. : 13. Fresh water kills most of the organisms that cause fouling within 72 hours, but if calcareous or chitinous growths already have been formed, such materials remain and the resistance is not materially lessened. 14. Certain species of barnacles grow at a very rapid rate, attaining a size of 2 inches and becoming sexually mature within 60 days. 15. Fouling can be predicted from a knowledge of seasonal abundance of larval organisms in given ports. 16. Certain barnacles are found attached on certain substances and in limited regions, indicating a relation between attachment and the nature of the surface. 17. Light has been found to be an important factor governing the attachment of the larve of the forms that cause fouling. 18. At the time of attachment the larve of Balanus improvisus and 8. amphitrite are negative to light. (Most of the forms found on ships’ bottoms probably are of a similar nature.) 19. Light in the field of green and blue has been demonstrated to have the maximum stimulating efficiency for the cyprid larve of several barnacles. 20. 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