THE ECOLOGY AND DISTRIBUTION OF ROCK-BORING PELECYPODS OFF DEL MONTE BEACH, MONTEREY, CALIFORNIA

Gregory See ley Booth

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THE ECOLOGY AND DISTRIBUTION OF ROCK-BORING PELECYPODS OFF DEL MONTE BEACH, MONTEREY, CALIFORNIA.

by

Gregory Seeley Booth

Thesis Advisor

E. C. Haderlie

June 19 7 2

App.iove.cf faon public neXoxii, z; diAttub Litton imtmit.Q.d.

The Ecology and Distribution of Rock-Boring Pelecypods

off Del Monte Beach, Monterey, California

by

Gregory Seeley ^ooth Lieutenant, United States Navy B.S., Naval Postgraduate School, 1971

Submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE IN OCEANOGRAPHY

from the

NAVAL POSTGRADUATE SCHOOL June 19 72

ABSTRACT

Divers using SCUBA gear gathered and identified rock- boring pelecypods found in the subtidal outcrops of Monterey silicious shale off Del Monte Beach, Monterey, California. Underwater photographs were taken of all the recognizable species present.

A species distribution and mapping survey was made. along two transects, one of which would be subjected to radical ecological change after isolation from the open sea by a proposed breakwater project.

Most species found are common to both transects. Their distribution is variable and depends to a great extent on the character of the substrate, which varies from soft, carbonate-rich mudstone to chert. However, within this framework of distribution dependent on sub- strate, there are inconsistencies which remain unresolved

TABLE OF CONTENTS

I. INTRODUCTION 8

A. HARBOR DEVELOPMENT PLANS 8

1. Reasons for Development ■ 8

2. Plans for Construction and Use 8

B. MONTEREY BREAKWATER STUDY 11

II. NATURE OF THE PROBLEM ■ 15

A. OBJECTIVE 15

B. SPECIES DETERMINATION AND RECOGNITION— 15

C. UNDERWATER MAPPING ■ 16

III. EQUIPMENT AND METHODS 18

A. CLIPBOARD AND RECORDING SLATE 18

B. PROBES 18

C. DIGGING TOOLS — 19

D. REFERENCE LINE — 19

1. Description • 19

2. Installation 19

a. D Transect 19

b. C Transect 20

E. PHOTOGRAPHY 21

IV. PRESENTATION OF DATA 23

A. GENERAL 23

B. ACCURACY-- — 23

1. Errors in Species Identification 23

2. Errors due to Poor Visibility 23

a. General 23

b. Sewage 2 4

c. Plankton Blooms 24

d. Wave Turbulence 25

e. Sun Angle 25

3. Lack of Detail 25

V. RESULTS 26

A. SPECIES DISTRIBUTION AND RECOGNITION CHARACTERISTICS 26

1. Parapholas californica 26

2. Chaceia Qvoidea 27

3. Zirf aea pilsbryi 29

4. Barnea subtruncata 30

5* Nettas tome 11a rostrata — 30

6* Penitella conradi •- 30

7* Penitella gabbi 31

8. Penitella penita — 31

9. Lithophaga plumula ■ 32

10. Bo tula f alcata ■ 32

1] . Nestlers 33

B. SUBSTRATE 34

1. Background 34

a. Monterey Formation 34

b. Tularcitos Fault 35

2. Observations 35

C. DISTRIBUTION DEPENDENCE ON SUBSTRATE 37

D. OTHER BIOLOGICAL OBSERVATIONS 3 8

1. Sea Mouse 38

2. Abalones 39

3. Sea Hares 39

VI. DISCUSSION 40

A. CONCLUSIONS ABOUT DISTRIBUTION • 40

B. ECOLOGICAL IMPACT — ■ 40

1. General ■ 40

2. Impact on Borers 40

a. Salinity Fluctuations 40

b. Temperature Variation 40

c. Wave Surge ■ 41

d. Food Supply 41

e. Pollution ■ — 41

VII. SUGGESTIONS FOR FURTHER STUDY ■ 42

APPENDIX A: TRANSECT MAPS 43

APPENDIX B: SELECTED PHOTOGRAPHS 77

BIBLIOGRAPHY 10 4

INITIAL DISTRIBUTION LIST ■ 107

FORM DD 1473 ■ l08

LIST OF FIGURES

1 Present Harbor Area, Monterey, California-- 9

2 Proposed Breakwater and Mole Structures 10

3 Location of Transect Lines 12

4 Triangulation System Used in Transect Station Location 13

5-36 Transect Maps ■ 45

37-77 Selected Photographs — • 78

ACKNOWLEDGEMENT

The author wishes to express his appreciation to Dr. Eugene C. Haderlie whose assistance and guidance were particularly valuable; to Mr. Jack Mel lor without whose suggestions and assistance the study might never have been completed; to Mr. Anthony Weaver of Hopkins Marine Station for generous loan of equipment; to Miss Janine Haderlie for timely and professional photo-processing work; and to my friends Bob Bornholt, Archie Cambell, Mark Hovermale, Clark Wilson, Brian Cronyn, Larry Gardiner, Buford Howell, and Steve Kramer who , by giving up leisure time to dive, made this study possible.

I. INTRODUCTION

A. HARBOR DEVELOPMENT PLANS

1 . Reasons for Development

For several years there have been plans to construct two additional breakwaters so as to enlarge the protected harbor area at Monterey, California. Although the size of the fishing fleet has declined since the disappearance of the sardine in the late 1940 's, recreational boating and sport fishing craft have filled the harbor, resulting in long waiting lists of people wishing to rent slip space at Monterey. Also, the lack of a harbor of refuge along the coast from San Francisco to Santa Barbara represents a hazard to mariners. It is in response to these needs that the present breakwater project has been planned.

2 . Plans for Construction and Use

Figure 1 shows the present layout of Monterey Harbor. The present structures provide adequate protection to larger boats anchored in the outer harbor and to small craft in the marina. Figure 2 shows the Army Corps of Engineers plan which is still awaiting funding. The new breakwaters of granite block construction will form a protected basin several times the size of the existing harbor. The construction of the breakwaters will be the first phase of the plan with the addition of the earth and rock filled moles anticipated several years later. The central mole will be the heart of the project. From-

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it, numerous floating docks will provide access to the 1,7C0 slips proposed in the plan. In addition, parking, hotel, and restaurant facilities are planned for the central mole. The smaller mole at the end of the eastern break- water is designed to provide pier space for oceanographic research vessels. B. MONTEREY BREAKWATER STUDY

In order to determine the ecological effects of the proposed breakwaters, a comprehensive study under the direc- tion of Dr. Eugene C. Haderlie is being conducted by students and faculty of the Department of Oceanography at the Naval Postgraduate School. The purpose of the Monterey Breakwater Study is to establish ecological base lines in this relatively undisturbed area so as to have a basis for comparison for post-construction studies (Haderlie , 1971) .

The study is structured about a set of four transect lines upon which 15 individual stations have been surveyed (Fig. 3) . These stations were charted so as to include all types of bottom substrate with water depths ranging from 2 to 15 m. A grid of 12 navigation poles, in conjunction with the markers delineating the transects, facilitates location of the stations to within a few square meters (Fig. 4) . On applicable stations, sediment grain size and sediment depth are monitored on a periodic basis. Vertical plankton hauls are made regularly. Parallel to the transects, dredges and balloon trawls are used to collect bottom dwellers and demersal fishes. A Smith-Maclntyre benthic grab is being

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used to sample the infaunal assemblage (Haderlie , 1971) . Divers have measured and outlined with polypropylene line two stations with exposed shale bottoms. These two stations have been intensively studied with divers gathering, identi- fying, mapping and counting the specimens of the some 160 species found (Minter , 1971) .

Wave data, tide records, and continuous traces of temperature and salinity are also available as additional inputs to the study. The ecological studies of the pilings of Wharf No. 2, done over the past few years by the students of the Naval Postgraduate School, and the extensive studies by Haderlie (1968,1969,19 70) of the local fouling and wood boring fauna will supplement the data gathered in the Monterey Breakwater Study itself. Thus, prior to the start of construction of additional harbor facilities, an extensive and reasonably accurate data base will be avail- able to which post-construction studies can be compared.

This author has completed a small portion of the over- all study and the results are reported in this thesis. Work was divided into two major areas; first, detection, identification, and recognition of rock-boring pelecypods and second, mapping and in situ observation. Fifty- three SCUBA dives were made by this author to accomplish the objectives .

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I I . NATURE OF THE PROBLEM

A. OBJECTIVE

As a part of the Monterey Breakwater Study the objec- tive of this work was to examine and document the distri- bution of rock-boring pelecypods in the area to be affected by the construction of additional wave barriers in southern Monterey Bay. The problem of species recognition had to be solved before meaningful data could be taken.

B. SPECIES DETERMINATION AND RECOGNITION

Species determination for most bivalves is a relatively easy and accurate process. Valve morphology is the usual key to identification while only infrequently are the soft parts of the animal used for taxonomic purposes. For common bivalves of the Pacific Coast of North America, the book by Keen (19 6 3) is a useful morphological guide.

The identification and in_ situ recognition problems with rock borers are varied, some apparent, some more subtle. The obvious problem is that the siphonal tips are the only parts of the animal presented to view. The not so apparent problem arises from the paradox that al- though the pholads are able to bore into reasonably durable rock, the valves of some species are as fragile as egg shells. In addition, the animal may have bored to a depth of more than 2 ft. Extracting an undamaged, living speci- men from its tapering conical burrow in 2 ft of rock is not a simple task.

15

However, the identification and in situ recognition problems are not insoluble. In Turner's (19 54,1955) excellent works on the family Pholadidae, there is for each species some mention of the appearance of the poste- rior end of the siphons. The siphon tips vary from very distinctive (Chaceia , Parapholas) to relatively indistinct (Penitella sp.) . Siphon size and i_n situ recognition accuracy are directly related. The shells of the smaller pholads, although generally more fragile, are only a matter of inches beneath the surface of the rock and are relatively easy to extract. Once the complete shell is available, identification is simplified. Emphasis should be placed on the complete shell, which includes the two main valves and the accessory parts. The pholads, usually upon reach- ing the end of the boring phase of their life cycle, form these accessory parts as covering and protection to muscles and visceral areas that were exposed or exterior to the valves during boring. Although rarely is more than one species present in a given locality for each genus, where two or more species of the same genus are found together (as is the case at Monterey with the genus Penitella) the accessory parts are essential to correct species identification.

C. UNDEPvWATER MAPPING

The underwater mapping was done along the C and D transects (Fig. 4). Well marked polypropylene line was

16

laid down along a transect and anchored. Divers then pro- ceeded to observe and record the species and relative abun- dance of the rock borers and the character of the substrate. In areas of exposed rock, samples of the shale were brought back to the laboratory to determine their relative hardness. In sandy areas sand depth measurements were made, especially if pholads were boring the rock beneath.

In observing and mapping the pholads, detection, was the main problem. The siphons of all the local ::ock borers ex- cept Chaceia , Parapholas , Zirf aea, and Barnea are on the order of a few millimeters in diameter when in the full open posi- tion. They protrude very little from the substrate and may even be several millimeters below the surface even when open and feeding. When alarmed in any way the siphons first close, and if further alarm stimuli are received they can be withdrawn well into the burrow, if not all the way within the valves. Common sources of alarm are attack by crabs or fish, strong wave surge and rapid pressure fluc- tuations caused by the bubble collapse of a diver's exhaled air. The bubble collapse problem is most severe with the species Barnea subtruncata. However, the most persistent problem is wave surge, which not only causes reduced visibility but also causes grains of sand to roll into or shower upon the siphons causing them to close or even retract. Moderate surge in sandy areas greatly reduces the number of species and specimens seen.

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III. EQUIPMENT AND METHODS

A. CLIPBOARD AND RECORDING SLATE

As in a previous study (Minter, 19 71) an inexpensive fiberboard clipboard was used to which a soft lead pencil was attached by a nylon line. As suggested by Minter, white bakelite, 0.04 inches thick, cut to standard size, was used as a recording slate. In addition to the strong- wide clip, several elastic rubber bands were used to secure the bakelite sheet to the clipboard after one such sheet was lost in the surf zone.

B. PROBES

Two probes were used in this study. Constructed of 3/16- and 3/8-inch diameter drill rod with welded T handles, they were scribed every centimeter, double scribed every 10 cm, and marked with blue paint every 20 cm. Each was 90 cm in length and had a tapered pointed tip. The smaller diameter probe was used for determining bore depths and sand depths where the cover was not too thick. The larger probe was more rigid and was used to determine the depth of thick sand cover. Whenever sand depths were recorded, multiple measurements were taken so as to reduce the possibility of erroneous measurement resulting from the probe entering an unoccupied pholad bore.

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C. DIGGING TOOLS

For digging out borers or obtaining rock samples a variety of hammers and chisels were tried. For extracting deep-boring pholads, a hand-held pneumatic hammer, adapted by Anthony Weaver of Hopkins Marine Station, Pacific Grove, California, for use with a conventional SCUBA tank, was fitted with a standard 1-inch steel-cutting chisel modified with an extra long shaft. For gathering smaller specimens a 1-inch wide stainless steel chisel and a short handled mallet were used with good success. For carefully chipping away the rock surrounding a pholad in its burrow, a sharp tool-steel drill punch was used to localize the force of the hammer's stroke. Frequently this was unnecessary as the piece of weakened shale would split right through the pholad burrow.

D. REFERENCE LINE

1. Description

The piece of equipment at the heart of the map- ping survey was a carefully marked length of 1/4-inch yellow polypropylene line. It was marked every meter with a wrapping of blue vinyl tape and every 5 m with a 1-inch wide strip of white nylon. These 8-inch white nylon "flags" were marked with a permanent marker and attached to the line with short pieces of soft stainless wire.

2 . Installation a. D Transect

The 320 m line was put in place using a 13-ft skiff and outboard motor. It was first placed along D

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transect so that the shoreward end would be at the first exposed shale, 80 ra short of station D2 (Fig. 3) . It was anchored with 100 lb of lead at the zero mark where the wave surge was greatest; 50-lb lead weights anchored the middle and far end of the line. After the shoreward anchoring weights were attached to the line and dropped in place, the line was unreeled along the transect. After a slight tension was put in to straighten the line, the far end anchor was dropped. Divers then attached 2-lb weights every 25 m and attached the center anchoring ball at the 160-m mark. After the mapping, photography, and observation were completed along D transect, the weights were removed and the line was checked for wear, b. C Transect

A different procedure was used to lay the line along C transect. Whereas D transect is relatively free of the giant kelp Macrocystis pyrif era , C transect has a heavy growth of it (Fig. 4) . The line was rerolled on a metal reel and unreeled along the bottom by divers using a compass bearing and frequent checks at the surface for navigation. With the 100-m mark just east of station C2 (Fig. 3) , the line was anchored in the same manner as along D transect, except that the weights were attached as the line was unreeled.

,This method of putting the line in place was less accurate and, unlike the case for D transect, it could not be straightened due to the columns of kelp

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stipes. The line has been left in place on C transect, attached to the lead weights with stainless steel shackles.

E. PHOTOGRAPHY

A Nikonos 35-iran camera in conjunction with a Subsea Mark 150 battery powered strobe unit was used for all underwater photographs. In the often murky., turbid water, results were generally poor except for properly illuminated close-up pictures. The use of the Nikonos is quite flex- ible for close-ups. Although the basic camera and lens can focus only into a range of 2.75 ft, by using the Nikonos extension tubes various image sizes can be achieved The largest image size is achieved when using the 1-to-l extension tube where an object 25 mm in size is reproduced on 2 5 mm of the negative. Whereas total width of field is only as wide as the negative (35 mm) , very small objects can be photographed with good clarity and resolution. The extension tubes are not without one disadvantage; changing extension tubes requires opening up the camera. Thus, selection of an extension tube must be made when the dive is planned, and the decision has to be based on what the diver expects to photograph, not what he actually finds to photograph. Most of the photographs in Appendix B were taken using the 3-to-l extension tube (35 mm of negative represents 105 mm of subject when in proper focus.) .

Most photographs were taken using High Speed Ekta- chrome color reversal film (ASA 160, 23 DIN) made into slides. Best results were obtained using a strobe setting

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of 100 w-sec at 12 inches and camera settings of f 22, 1/60 sec and 2.75 ft when using the 3-to-l extension. Some longer range pictures were taken when visibility permitted. Good results came from settings of 150 w-sec for the strobe and 1/60 sec, varying the f stop for dif- ferent distances (3 ft, f 11; 4 ft, f 8; 5 ft, f 5.6). All slides remain on file with the Department of Ocean- ography at the Naval Postgraduate School.

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IV . PRESENTATION OF DATA

A. GENERAL

The raw data collected along C and D transects during this study are presented in Appendix A as individual sets of strip charts showing the character of the substrate and the major topographic features in addition to a sym- bolic plot of the distribution of the rock-boring pelecypods

B . ACCURACY

1. Errors in Species Identification

Many factors, such as valve and accessory part morphology, visible siphon characteristics, and bore depth, were used in identification of the rock borers. This does not, however, preclude the possibility of misidentif ication. In situ identification accuracy should be considered very high for specimens recognized as Chaceia , Parapholas , or Barnea as their siphons are very distinctive. In addition, the siphons of Zirf aea are distinctive when the size factor is included. Conceivably, young Zirf aea could be misiden- tif ied as mature Penitella sp. as their in situ recognition characteristics are similar. Hopefully, errors of misidentif ication have been kept to a minimum.

2 . Errors Due to Poor Visibility a. General

Visibility in the area under study was generally poor. This author's estimate of average

23

visibility of 6 to 8 ft is based on one year's diving experience in the study area. Reduced visibility was a product of several superimposed factors.

b. Sewage

The City of Monterey sewage outfall line runs approximately parallel to D transect and empties into the Bay at a point about 600 m northeast of station D2 . A large surface slick was usually visible from the bluff behind the beach or from the air. Under the influence of the prevailing north winds and weak local currents, the sewage effluent was spread back along the beach and to the west (Trumbauer ,1966) . It contributed materially to the poor visibility.

c. Plankton Blooms

Although the nutrients added by the sewage effluent may contribute to a higher sustained plankton level in the area, the effects of the spring and fall plankton blooms were still noticeable. Divers reported during the middle two weeks of October 19 71 that lumines- cence was so intense throughout the water column that visibility was reduced to zero as long as the diver was moving through the water. Although visibility was 10 to 15 ft when the diver was still, as he moved, the turbulence around his faceplate triggered the bioluminescent reaction in the planktonic organisms (presumably Noctiluca) . A motionless diver could observe a moving diver enveloped in a brilliant blue cloud and seemingly exhaling blue bubbles.

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The bottom turbulence generated by long period swell also caused the organisms to luminesce, blanketing the substrate with a blue fog. Benthic observation was impossible as each wave of turbulence approached and passed.

d. Wave Turbulence

In addition to the special case of poor bottom visibility due to wave turbulence described above, long period swell generates its own brand of poor visibility. The turbulent water motion caused by the interaction of the horizontal surge and the rough bottom puts all the finer sand, silt and algal detritus into suspension. Another wave-generated visibility problem is that the diver is being moved back and forth with the surge and remaining stationary relative to the bottom while observing benthic organisms varies from annoying to impossible.

e. Sun Angle

The foregoing reasons coupled with a low sun angle during the winter months all contribute to the production of error due to poor visibility. 3. Lack of Detail

Time limitations, coupled with less than adven- tageous environmental factors, have precluded a more detailed distributional survey of the rock-boring pelecypods in the study area. Further researchers should be wary of attempts at greater detail with respect to in situ benthic surveys of organisms that are difficult to both detect and recognize.

V. RESULTS

A. SPECIES DISTRIBUTION AND RECOGNITION CHARACTERISTICS 1 . Parapholas californica

Parapholas is the most widely distributed and most obvious rock borer in the study area. It is easily distinguished by its cylindrical, flat-tipped united siphons. The incurrent siphon is three times the diameter of the excurrent siphon and is surrounded by numerous branched cirri which give it a lace-like appearance. The excurrent siphon protrudes a few millimeters above the flat disk of the siphons and is nearly smooth. A second ring of short cirri surround the combined siphons making it look like a coin with a reeded edge. Color varies from a uniform dark red-brown to pure white. Turner (19 55) states that Parapholas is found to depths of 30 ft, yet this author has found large colonies of animals at depths of 60 ft. These deepest specimens were found in soft shale at D-306 (Fig. 36) at the base of the outcrop, and nearly the entire colony was pure white. Since other white specimens are found among pigmented ones throughout the area, conclusions should not be drawn concerning pigmen- tation versus available light.

Parapholas is found boring into the soft shales and its bore is rarely more than 11 inches deep. Since the soft shale erodes rather rapidly, the mature animal

26

forms a calcareous tube or "chimney" which lines the walls of its burrow (Fig. 45,48). This tube, which thickens with age, stabilizes the shale immediately surrounding the burrow. As the shale later erodes, the cement-like chimney, protruding 1 to 2 inches above the eroding surface of the shale, provides a protective housing into which the animal can withdraw. Parapholas are able to live normally with a sand cover of up to 6 inches. It appears that the siphons are unable to extend more than 6 inches above the top of the bore, although with a thicker sand cover it cannot be assumed that the animal is unable to feed and respire using percolation water in the sand (Fig. 37-49) „ 2 . Chaceia ovoidea

One of the largest pholads, this animal according to Turner's description can extend to a length of more than 3 ft. The siphons are joined except for the posterior 2 inches. When open, the excurrent siphon has the shape of the bell of a musical horn and the incurrent siphon looks like a short length of pipe (Fig. 65,67). Both are usually a uniform deep mahogany red with a white interior. Although there were few dense concentrations of Chaceia along the transects, the area between the transects has many concentrations, mostly along ledges. This author noted that Chaceia appear to be light sensitive. When the beam of a standard underwater light is aimed at a specimen with it siphons open, the animal will often close its siphons and may even withdraw into its burrow.

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Although there are many Chacela boring vertically on flat shale, there are many more boring horizontally into the soft shale below ledges. Many of the ledges in the area, especially the ledges in the very rough area northwest of station D2, appear to have been undercut by Chaceia. Many horizontal bores in that area that were probably 2 ft long when the active animal stopped boring are now only 6 to 10 inches long. The large volume of the siphons no longer fits comfortably within the bore and, when unalarmed, up to 4 inches of warty, wrinkled siphon is exposed and dangles from the bore. To this author it appears that Chaceia bores horizontally, either seeking a darkened habitat under ledges or because, in the layered substrate of hard and soft rock, the animal can bore within a layer to full adult size, . whereas vertical boring might be stopped short of full size by a hard layer of rock. This supposition is supported by limited data on bore depths of 19 animals which appeared of similar size to the diver. The average bore depth of the animals boring hori- zontally was 22 inches while that of those boring vertically was 15 inches.

Surprisingly few Chaceia were observed living with a cover of sand. This probably occurs, not because sand has any effect on the living animal, but because the settling preference of the species keeps it out of areas where periodic sanding occurs (Fig.' 59-68).

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3. Zirf aea pilsbryi

Another of the large pholads, Zirf aea can bore to a depth of more than 2 ft. Also found in abundance in the tidal mud flats of Elkhorn Slough 14 miles to the north, this vertical borer is limited in the study area to boring in the softest shale and mudstone. More than half of the hundreds of specimens observed were covered with up to 12 inches of sand. The average maximum bore depth as measured from the surface of the rock was 19 inches, although this figure is based on only eight large animals .

The animal will not tolerate sand showers and will withdraw its siphons with even moderate surge. The first time divers mapped D transect, no Zirf aea were seen as turbulence was moderate. On later occasions during calm conditions, hundreds were seen along D, although no dense colonies were found as are common for Parapholas and Chaceia. A density on the order of five Zirf aea per m2 is an average maximum. During calm wave conditions this author, while examining the cirri on the siphon of one animal, observed a small circle of sand start to shift and boil. After about 4 sec the siphons of another Zirf aea rapidly emerged, stopping about 1 inch above the surface of the sand. It appeared as though the animal was ejecting water so as to loosen and unconsolidate the sand and facilitate the upthrust of its siphons. The cream- colored siphons marked with reticulations of dark

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red-brown are easily missed as they blend well with the sand (Fig. 49-58) .

4 . Barnea subtruncata

Barnea is a somewhat smaller-valved pholad but a large adult can extend its siphons 2 ft. The siphons are a mottled dark red-brown grading to white at the very tip. The distinctive i_n situ recognition feature of Barnea is a crown of ten reddish unbranched papillae surrounding the incurrent siphon. Specimens were observed in exposed shale and in areas of 6 to 8 inches of sand cover. No specimens were observed along D transect where wave surge is generally greater. As mentioned earlier, Barnea is particularly sensitive to high frequency pressure changes. The bubble collapse problem may be in part responsible for the fact that only 11 specimens were sighted. Little can be said about distribution except that the species is not abundant in the area (Fig. 69) .

5 . Nettastomella rostrata

This pholad is too small to be detected by a diver as the siphon tips are on the order of 1 or 2 mm in diameter. The distinctively sculptured valves with characteristic calcareous siphonoplax of two dead specimens were found while gathering rock samples. Nothing can be said about distribution except that the species is present in the study area and is probably rare (Fig. 77) .

6 . Penitella conradi

This species is fairly common in the study area but its siphons are too small to be detected by divers.

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The mature animal adds a chitinous sheath, the siphonoplax, to the posterior edge of the valves, and the siphons do not extend out of these short protective flaps. The distinguishing characteristic is the small accessory part, the mesoplax, which is pointed anteriorly, truncate poste- riorly, and lacks lateral wings (Turner , 1955) . Little can be said about its distribution except that it is not rare and has been found in rocks from both transects (Fig. 72)

7 . Penitella gabbi

This species is also fairly common in the study area. Although the siphons are visible, they are difficult to identify in_ situ. When removed from the shale, P^_ gabbi is easily identified by the round pustules that cover the exterior of the combined siphons. Also, the mesoplax is distinctive, being pointed anteriorly, rounded posteriorly, and having broad lateral wings. Like P_^ conradi , it is found along both transects in water less than 40 ft deep (Fig. 74,76) .

8 . Penitella penita

This species, reputed to be the most common member of the family Pholadidae along the west coast of North America, is not abundant in the study area. Although isolated valves of dead specimens were found in rock samples, no living specimen was taken. The animal does exist in the study area with unknown distribution (Fig. 75) .

31

9 . Lithophaga plumula

This pelecypod is not a member of the family Pholadidae, nor is it a trie borer, as boring implies rotation of some type of tool about an axis to cut or wear away the medium being bored (Nair,1968). Because of its extremely fragile shell, Lithophaga has adapted to using chemical means to hollow out a protective burrow. Formerly thought to secrete a strongly acidic polysaccharide which reacted with carbonates, it has been shown that the secretion by Lithophaga is a nearly neutral mucoprotein which complexes with calcium (Jaccarini and Bannister, 1968) .

Lithophaga is very abundant throughout the study area and can be distinguished i_n si tu by bone-white siphons with several flap-like appendages.

10 . Botula f alcata

This mytilid is thought by some authorities to be only a nestler. However, this author feels that Botula must be able to enlarge an existing pholad bore to a great extent. Of the hundreds of specimens dug out of the shale, most filled the burrow rather tightly. Some specimens fit exactly and tightly in the shale while still retaining the valve morphology distinctive of the species. Although there is evidence of wear at the beaks, the tight and exact fit with slightly crescent- shaped valves indicates possible chemical activity. It must be pointed out that these suppositions are based

32

on in situ observation, not on scientifically documented fact.

Botula is very abundant in the study area and is found with Lithophaga in rock containing carbonates (Fig. 70,71) .

11. Nestlers

Kellia laperousi , Sphenia pholadidea, and Hiatella arctica are common nestlers occupying pholad bores after the deaths of the original inhabitants (Fig. 73) .

33

B. SUBSTRATE

1. Background

a. Monterey Formation

A knowledge of the submarine geology of the study area provides the key to understanding the inhomo- geneous distribution of the borers.

The subject area is the only shallow water outcrop within Monterey Bay of the Miocene marine unit known as the Monterey Formation. Although the Monterey Formation underlies most of Monterey Bay south of the Monterey Submarine Canyon, it is covered in most places with several hundred feet of more recent assorted sands and gravels. The Miocene rock is a resistant, brown, silicious mudstone composed mainly of diatomite and diatomaceous shale, interbedded with beds of opaline chert (Greene , 1970) .

Structurally, the study area represents the most complex geology of the southern Monterey Bay area. The contact between the Miocene Monterey silicious shale on the east and the Cretaceous Santa Lucia grano- diorite on the west lies parallel to and immediately east of Wharf No. 2. In a narrow band east of the contact, seismic reflection profiling shows that the Monterey Formation is complexly faulted and folded with synclines and anticlines generally plunging northwest. Away from the contact the Monterey Formation is essentially homo- clinal and contains a layer which, based on its seismic

34

reflection, Greene (1970) believed to be chert. This chert layer lies about 300 ft below the estimated top of the Miocene strata.

b. Tularcitos Fault

Approaching Monterey from the southeast, the Tularcitos Fault becomes discontinuous and difficult to chart. Probably still active today, the Tularcitos exhibits essentially vertical movement with the eastern block down dropped. The conclusion to be made is that the folded and deformed condition of the subtidal outcrops of the Monterey Formation is associated with the Tularcitos Fault, the Tularcitos Fracture Zone offshore, and the contact between the granodiorite and the marine strata (Greene, 1970) .

2 . Observations

Although the contact between the shale and the granodiorite is covered with sand, shale outcrops are exposed midway between transects A and B. Even though most of the shale west of B transect is covered with sand, the flat shale areas that are exposed are being bored by all the species that are found further to the east. This is significant because these areas are alter- nately covered and swept free of sand, probably depending on the variation of the deep water wave direction from one Pacific storm to the next. Evidently even the small borers are able to either get their siphons up through the sand if it is thin or exist at a probably reduced

35

metabolic level using percolation water if the sand cover becomes thick.

The most rugged area topographically lies between transects C and D. Most of the area is characterized by hummocks and ledges roughly parallel to the trend of the Tularcitos Fracture Zone. Some of these ledges are contiguous features several hundred meters long. Many of the ledges have been undercut by rock-boring pele- cypods and assorted crevice dwellers, such as sipunculid and polychatae worms.

Rock samples were gathered from along C and D transects and from many locations between them. The rocks were not tested chemically except that the dilute hydrochloric acid test was used to detect the presence of carbonates. Time limitations prevented more sophis- ticated relative hardness tests as were done by' Evans (1966b). However, an attempt was made to determine hardness using a Rockwell hardness testing machine, normally used to test metals. All samples tested were too brittle and shattered under load. However, scratch testing provided a rough idea of the range of hardness exhibited by the different samples.

Internally, all the samples, as though over- stressed, appear cracked and shattered. Although of non-crystaline structure, they often cleave with planar or nearly planar surfaces orthogonal to the bedding plane.

By examining the seismic reflection profiles

36

upon which Greene (19 70) based his report, it appears that the layer of chert 300 ft below the top of the Miocene strata should surface within the study area. Probably the most significant geological observation of this study is that chert does exist in the subtidal Miocene outcrops. However, in the closest exposed subaerial Monterey shale, chert is not found. In fact, Dr. Robert S. Andrews of the Naval Postgraduate School states that, to his knowledge, subaerially-exposed chert is rare in the Monterey area.

Rock samples other than the chert vary from soft mudstone containing abundant carbonates to gray and black silicious shales of varying hardness. The bedding in the subtidal outcrops is essentially planar, and the thickness of individual layers varies from a centimeter or less to a meter or more with the layers of hard rock tending to be less than 20 cm thick.

C. DISTRIBUTION DEPENDENCE ON SUBSTRATE

With a knowledge that layers of chert and other hard silicious rock are found in the study area, most of the borer distributional inhomogeneiti.es can be easily explained. All the various species easily bore the carbonate-rich mudstones. These soft mudstones only rarely exhibit an encrustation of coralline algae or sponges, indicating that the rock is eroding at a rapid rate, making encrustations unstable. Although the large holdfast of Macrocystis pyrifera is able to attach to

37

the softer rock, other sessile algae are found anchored only to more durable rock.

The mechanical borers are able to attack the softer silicious shales. As the shale becomes harder the pholads become stunted, thick-valved, and misshapen. Finally there are the hardest shales and the layered chert in which the borers are unsuccessful. These hard rocks are usually encrusted with corallines and sponges.

There are a few areas, however, such as C 225-249 (Fig. 17,18), where the reason for the absence of borers is not apparent. The flat rock is not heavily encrusted, and samples indicate that it is relatively soft and contains some carbonates. Samples of it appear essentially similar to samples taken from adjacent areas presently being bored. The factors which, in general, explain the borer distribution are inadequate to elucidate these anomalies.

D. OTHER BIOLOGICAL OBSERVATIONS 1. Sea Mouse

While investigating the unfamiliar siphons of the cockle Clinocardium nauttalli , the author unearthed a sea mouse from under 4 inches of sand. This polychatae worm, Aphrodita aculeata , was approximately 4 inches long, 1 inch wide, and 1/2 inch thick. For locomotion it was equipped with 20 to 30 sets of parapodia, each parapod sporting 4 to 6 retractable, 1/2-inch, black setae. Protecting its dorsal surface were two rows of brass-colored spines. •

38

2 . Abalones

Minter (1971) states that as a result of sea otter predation the population of red abalone in the Del Monte kelp bed has been annihilated. Although none exist in unprotected areas, this author has sighted more than a hundred mature specimens living deep in caves too narrow for otters to enter. Many of the narrow caves appear to have been formed by pholads boring out the soft rock from between layers of rock too hard for borers to attack. In addition to the red abalone (Haliotis rufecens) , specimens of the pink (H. corrugata) , black (H. cracherodii) , and pinto (H. kamtschatkana) abalones were examined and returned to their habitat.

3 . Sea Hares

The largest of the sea slugs found in California waters, Tethys californica, commonly called the sea hare, was rarely seen by divers in the study area. Yet during the first week of April 19 72 divers observed literally hundreds of these foot-long gastropods in the vicinity of C transect. On subsequent dives, April 10 and 11, only a few were seen. Since that time they have been seen only rarely. Although it is thought that they come together in large numbers to breed (Johnson and Snook, 19 27) , where they came from and why they carne to that one site are .unknowns .

39

VI. DISCUSSION

A. CONCLUSIONS ABOUT DISTRIBUTION

The variation of hardness and amount of carbonates of the Miocene marine strata known as Monterey shale is the main factor underlying the inhomogeneous distri- bution of rock-boring pelecypods in the study area.

B. ECOLOGICAL IMPACT

1 . General

The general ecological impact of the proposed breakwaters at Monterey, California, has been treated by Haderlie (1971) and Minter (1971). It is expected that the population of rock borers will be affected.

2 . Impact on Borers

a. Salinity Fluctuations

Many of the species of rock borers live in the low intertidal zone in areas where an appropriate substrate is available. The salinity variations are greater there than are those expected within the proposed harbor. The probable range of seasonal salinity varia- tions should have little effect on the boring population.

b. Temperature Variation

For the same reasons as above, temperature variation is not likely to affect the borers.

40

c. Wave Surge

Loss of wave surge at the bottom and the consequent deposition of silt will eventually alter the population of borers. Although it is possible that borers can live when buried under sand too thick for their siphons to project into the water, it is doubtful that normal growth and reproductive ability are not seriously derogated. Even assuming that the borers now living are not directly killed by the silting, future generations will find no suitable substrate to which they can attach. Areas that are not swept free of deposits will eventually be devoid of rock borers.

However, only a fraction of the exposed rock is located within the perimeter of the breakwaters, and tidal currents between the east and north breakwaters may be sufficient to prevent deposition of silt in that channel .

d. Food Supply

The expected decrease in the available planktonic food supply, when coupled with the filtering action of sand over the siphons, may hasten the demise of the rock borers in quiet water.

e. Pollution

The extent of damage to the borers attrib- utable to oil and gasoline spills, sewage, and solid wastes from 1,700 boats and their operators cannot be predicted.

41

VII. SUGGESTIONS FOR FURTHER STUDY

The results of this study suggest several areas where further study is appropriate. The most obvious work will be done after construction of the breakwaters to analyze the ecological impact on the area.

For the biochemist, an explanation of the boring mechanism, if any, of Botula f alcata could confirm or deny this author's suppositions concerning that species

For the geologist, a more detailed analysis of the exposed Miocene strata with respect to hardness and chemical composition might suggest answers to distribu- tional anomalies left unresolved in this thesis.

\

42

APPENDIX A: TRANSECT HAPS

In this Appendix the distribution of the rock borers along with the character of the substrate is presented in two series of strip charts, one for each (C and D) transect. The plotting commences at the mean of higher high water line (MHHW) and proceeds seaward across the sand to the first exposed rock, then along the reference line to the 320-m mark. All specimen plotting is sym- bolic and information needed to interpret the charts is included in the following list.

1. The words no, solitary, occasional, several, many, large numbers, colony, dense colony, and very dense colony are used to denote the relative abundance of the borers along the transects.

2. The 1 m width (50 cm either side of the reference line) has a horizontal exaggeration of 3.75:1 for ease

in plotting.

3. Comments about substrate and borer distribution are in the left and right columns respectively.

4. The symbols used to represent the borers are:

O Parapholas

A Chaceia

-^ Barnea

O Zirf aea

P Penitella sp.

L,& Lithophaga and Botula

The small arrows (j) drawn across ledges point to the

43

low side. Dotted lines and ledges show the approximate boundaries of the type of substrate described in the left column.

5. Individual animals are not plotted except those labeled solitary. Symbols show only that the species is found in that location.

6. Tube worm mounds are frequently large piles of

2

sand (20 ft in area and 1 to 2 ft deep) surrounding the

hook-shaped tubes of Diopatra ornata.

44

VIORE THAN THREE FEET _ DF SAND

NO BORERS

MHHw

1 meter

Figure 5. C MHHW - 0 (approximately 170 m)

45

LEDGE, (OWE FOOT)

SHALE WITH PATCHES OF THIN SAND COVER

?-o

1 5

DEPRESSION FILLED WITH ROUNDED PIECES OF BROKEN SHALE

10 —

SHALE

LEDGE, (ONE FOOT)

TUBE WORM SAND MOUNDS

s ■

SAND

i.8

^

LB

L&

I

*,B

A

L.B

fc

LARGE NUMBERS OF LITHOPHAGA AND

PENITELLA

SOLITARY BARNEA

SOLITARY CHACEIA

£ — 1 meter

SOLITARY BARNEA

NO BORERS

Figure 6. C O - 20 The ledge at the 7-m mark is the first exposed shale on the transect.

46

fc>

35

LANE OF SOFT SHALE BOUNDED BY ^0 SAND ON BOTH SIDES

as -

i-.fc

o

o

? oP

L©

O

o

VERY DENSE COLONY OF PARAPHOLAS WITH SOME LITHOPHAGA AND

PENITELLA

SOLITARY BARNEA

V

2o

o o°oon°oo

i R o ° o 0 ° L/5 O OP o °

o o 0 •; o o

S&

*

1 meter

SOLITARY BARNEA

SOLITARY BARNEA

Figure 7. C 20 - 40 This is a striking contrast to the- previous figure where there are no Parapholas.

47

~&0

SHALE, PARTLY SAND COVERED

LEDGE, (TWO FEET)

5<r-

SAND AND TUBE WORM MOUNDS

LEDGE, (ONE FOOT)

So-

SIX TO TWELVE INCHES DF SAND COVERING SHALE

4S

LANE OF SOFT SHALE BOUNDED BY SAND

4o

LB ° O

4,6

o

«-,*

o

o

P o

o

A

o

o o

o ° o

0 O c> 0 h

P o

o °0°

MANY LITHOPHAGA AND PENITELLA, SEVERAL

PARAPHOLAS

SOLITARY CHACEIA

NO BORERS

SEVERAL PARAPHOLAS

NO BORERS

o

o

L,*

1 meter — ^

JE

VERY DENSE COLONY OF PARAPHOLAS WITH SOME

LITHOPHAGA AND

PENITELLA

Figure 8. C 40 - 60

48

SERIES OF SMALL, LOW LEDGES OF CHERT

7S-

SHALE, PARTLY SAND COVERED

70~

ZERO TO FOUR INCHES DF SAND COVERING SOFT SHALE

O 0

°0° O°o~o °£

0& O00°r? 0

°00 0 o°o^O

o

o o

o o

O o

A ° o °

o o

a

o

Go

0

O O

O

D

o

o

o

o □

1 meter

OCCASIONAL PARAPHOLAS IN SOFTER SHALE BELOW LEDGE LIP

VERY DENSE COLONY OF PARAPHOLAS AND

OCCASIONAL ZIRFAEA AND CHACEIA

LARGE NUMBERS OF PARAPHOLAS AND

OCCASIONAL ZIRFAEA UP THROUGH SAND COVER

SOLITARY BARNEA

Figure 9 .

O

60 - 80

49

Too

TUBE WORM MOUNDS AND SAND

S *

SERIES OF LOW LEDGES OF CHERT

90-

FLAT SHALE

SAND

SS-

SERIES OF SMALL, LOW LEDGES OF CHERT

90

a

a

D

o

a

□

o

SEVERAL ZIRFAEA UP THROUGH SIX TO TWELVE INCHES OF SAND

NO BORERS

SEVERAL ZIRFAEA AND PARAPHOLAS

NO BORERS

1 meter

1

OCCASIONAL PARAPHOLAS IN SOFTER SHALE BELOW LEDGE LIP

Figure 10. C 80 - 100

50

SAND

SHALE

SAND

\1o

itf-

iiO—

A COMPLEX SUBSTRATE OF EXPOSED SHALE PATCHES, SAND, I oS- AND TUBE WORM MOUNDS

□

D

a

P

o

a

*

o 0 ° o ° 0 o o u o

0 °

D

D

□ 0

D

a

>oo

a

o

□

SEVERAL ZIRFAEA AND OCCASIONAL PARAPH OLA S UP THROUGH SAND

SOLITARY BARNEA

SOLITARY BARNEA

COLONY OF PARAPHOLAS

0 0% O°o0o0° °0 0 o o o o o v °

a a

£ — 1 meter -r— 5>

D <-,Q

SEVERAL ZIRFAEA UP THROUGH ZERO TO SIX INCHES OF SAND

COLONY OF PARAPHOLAS

SEVERAL PENITELLA, LITHOPHAGA AND

ZIRFAEA

Figure 11.

100

120

51

I HO

'3H

SAND

130-

\2>-

a

lao

D

OCCASIONAL ZIRFAEA UP THROUGH FOUR INCHES OF SAND

>V

1 meter

SOLITARY BARNEA

Figure 12. C 120-140

52

SAND

LEDGE, (ONE FOOT)

\Uo

\SS-

ISo-

l«tf-

□

a

o

° o A

D

0

SAND

/Vo

O

D

D

O

0

D

a

o

a

1 meter

OCCASIONAL ZIRFAEA AND LARGE NUMBERS OF PARAPHOLAS UP THROUGH

ZERO TO FOUR INCHES OF SAND

LARGE NUMBERS OF PARAPHOLAS AND

SEVERAL CHACEIA IN VERTICAL FACE OF LEDGE

OCCASIONAL ZIRFAEA UP THROUGH FOUR INCHES OF SAND

Figure 13. C 140-160

53

LEDGE, (ONE FOOT) '8°

FLAT SHALE

TUBE WORM MOUNDS

SHALE

BAND

ns-

170—

165"-

>

o o oO

O O © o 0 io O o 0

0

a

D

0

□

a

o

/Go

o

a

o

D

O

1 meter

VERY DENSE COLONY OF PARAPHOLAS

OCCASIONAL ZIRFAEA AND PARAPHOLAS IN SHALE AND UP THROUGH THIN SAND

Figure 14. C 160-180

54

2oo

D

O

a o

o

l<K -

ZERO TO FOUR INCHES DF SAND COVERING SHALE

a

o D

a

o

o a

OCCASIONAL ZIRFAEA AND PARAPHOLAS UP THROUGH SAND

iqo —

i

IBS- FLAT SHALE

Oo 0

O 0 °

LARGE NUMBERS OF PARAPHOLAS AND SOME

o

o o ^

LITHOPHAGA

o

V-' <_J

180

4-— 1 me

J

ter — ^

__— _~— — 1

Figure 15. C 180-200

55

210

SAND

-XiS-

2\o —

LEDGE, (ONE FOOT)

a

205-

ZERO TO TWELVE INCHES OF SAND COVERING SHALE

2oo

a

o

a

o

o

a

D

< — 1 meter

NO BORERS

LARGE NUMBERS OF PARAPIIOLAS LOCALLY

ON VERTICAL FACE OF LEDGE

OCCASIONAL ZIRFAEA AND PARAPIIOLAS UP THROUGH SAND

Figure 16. C 200-220

56

2l-fO

235-

VERY FLAT SHALE

230-

ii$-

LEDGE, (THREE FEET)

SAND

?1o

NO BORERS

1 meter

MANY PARAPHOLAS AND SEVERAL CHACEIA ON VERTICAL FACE OF LEDGE

Figure 17. C 220-240

57

'XioO

FLAT SHALE

2SS-<

150 —

LEDGE, (ONE FOOT)

VERY FLAT SHALE

■xtz-

SEVERAL LOW LEDGES

lio

«V&

h*

0

L,*

OCCASIONAL PARAPHOLAS

AND LITHOPHAGA

1 meter — 5

NO BORERS

Figure 18. C 240-260

58

^%o

BIG, FLAT BLOCKS OF

NO BORERS

SHALE

X]$-

LEDGE, (ONE FOOT)

J

^

VERY DENSE COLONY OF

PARAPHOLAS AND

SEVERAL CHACEIA

270—

oQoo croog

$!&

0

,L,&

FLAT SHALE

0 0

L B

OCCASIONAL PARAPHOLAS

> J

AND LITHOPHAGA

2.W-

o

0 0

240

< — 1 meter — fc

Figure 19. C 260-280

59

3oo

BROKEN SHALE RUBBLE

w-

FLAT SHALE

i^o —

LEDGE, (ONE FOOT)

FLAT SHALE

o° 0° rPn °0 OO O U 0 O 0600°o°0

NO BORERS

DENSE LOCALIZED COLONY OF PARAPHOLAS

-x^ -

LEDGE, (ONE FOOT)

BIG, FLAT BLOCKS OF SHALE

2S0

t

1 meter — S

NO BORERS

Figure 20. C 280-300

60

FOUR TO OF SAND SHALE

TWELVE INCHES COVERING

3iS -

1lO-

FLAT SHALE

3o5-

CAVE DEPTH

LEDGE, (FOUR FEET) UNDERCUT MAKING TEN FOOT CAVE

O

O

o

0

o

o

0 0

0

o Og o o

o ° o

0

o

0

o

3 00

0 " o o^o 0 O o^,

i-

MANY PARAPHOLAS IN SHALE AND UP THROUGH SAND

DENSE COLONY OF PARAPHOLAS

OCCASIONAL PARAPHOLAS

1 meter —

DENSE COLONY OF PARAPHOLAS IN MOUND OF SOFT SHALE ABOVE CAVE ROOF; HOWEVER, NO BORERS IN LAYER OF CHERT ACTUALLY FORMING CAVE ROOF

SEVERAL PARAPHOLAS AND CHACEIA ON FLOOR AND REAR WALL OF CAVE

Figure 21.

300-320

61

o

MORE THAN THREE FEET _ OF SAND

NO BORERS

M H H W

1 meter

Figure 22. D MHHW - 0 (approximately 2 80 m )

62

'AO

ONE TO THREE FEET OF SAND 10

LEDGE, (TWO FEET)

LEDGE, (TWO FEET) SAND

NO BORERS

£ — 1 meter

SEVERAL CHACEIA AND PARAPHOLAS IN VERTICAL WALLS BELOW LEDGES

Figure 23. D 0-20 The ledges are the first exposed shale on D transect,

63

Figure 24. D 20-40

64

To"

SHALE

LEDGE, (ONE FOOT)

CALCAREOUS SHELL RUBBLE

SHALE

LEDGE, (ONE FOOT)

PARTLY SAND COVERED

L.B

^

L.8

? o

Ss?-

K-

SAND

<±0

L B

A

O l,B

SEVERAL PARAPHOLAS , PENITELLA, AND LITHOPHAGA

SOLITARY CHACEIA

SEVERAL PARAPHOLAS AND MANY PENITELLA AND LITHOPHAGA

NO BORERS

1 meter

Figure 25. D .40-60

65

LEDGE, (THREE FEET)

~W

SHALE

LEDGE, (ONE FOOT)

SAND

SHALE

SAND

7*

70-

&

ROUNDED, BROKEN CHUNKS OF SHALE IN A DEPRESSION IN THE SHALE

(oO

DENSE COLONIES OF CHACEIA AND PARAPHOLAS ; MANY LITHOPHAGA AND

1 meter

NO LIVING BORERS; MANY LARGE ROUNDED DEPRESSIONS SHOWING THE BOTTOMS OF EARLIER BORES

A FEW PARAPHOLAS

Figure 26. D 60-80

66

vO

<tfH

ZERO TO TWELVE INCHES OF SAND WITH MANY EXPOSED SHALE AREAS

c(0

0

A

a

O

□

A

A

A

a

LEDGE, (ONE FOOT) SAND

SHALE LITTERED WITH BROKEN SHALE RUBBLE

20

SEVERAL CHACEIA, PARAPHOLAS AND ZIRFAEA

a

a

a

a

1 meter

SEVERAL PARAPHOLAS

SEVERAL ZIRFAEA

Figure 27. D 80-100

67

no

LEDGE, (ONE FOOT)

ki<-

ZERO TO EIGHTEEN INCHES OF SAND WITH FEW EXPOSED SHALE AREAS

lio—

lo£-

O

o

o

AO o q 0 o

o

o o

D

D

a

a

a

□

100

VERY DENSE COLONY OF PARAPHOLAS AND SEVERAL CHACEIA

MANY ZIRFAEA UP THROUGH SAND

0

1 meter — S

Figure 28. D 100-120

68

Wo

FLAT CHERT

NO BORERS

LEDGE, (FIVE FEET)

VERY DENSE COLONIES OF PARAPHOLAS AND

UN-

CHACEIA IN VERTICAL

BROKEN SHALE RUBBLE

□

0' ■

0

□ o

FACE BELOW LEDGE

130-

TWO TO THIRTY- SIX

MANY PARAPHOLAS AND

INCHES OF SAND

ZIRFAEA UP THROUGH

o a

SAND

n

US —

0

Q

Q

110

* — 1 meter — £

Figure 29. D 120-140

69

1U6

D °

0

a

\SS-

a

D

TWO TO TWENTY-FOUR INCHES OF SAND

o

a

MANY ZIRFAEA AND OCCASIONAL PARAPHOLAS UP THROUGH SAND

1*0-

a

o

a

a

.

D

IfS"-

o

LEDGE, (ONE FOOT) LEDGE, (THREE FEET)

LEDGE, (THREE FEET)

FLAT CHERT

\H0

o — ^ A OA T

LARGE NUMBERS OF CHACEIA AND PARAPHOLAS BELOW LEDGES

NO BORERS

* — 1 meter — ^

Figure 30

D 140-160

70

180

HfT-

TWO TO THIRTY- SIX INCHES OF SAND

WO —

M

TWO LARGE BOULDERS

GRANITIC

D

□

a

a

a

SEVERAL THROUGH

ZIRFAEA UP SAND

O

a

\<oO

1 meter

Figure 31. D ■ 160-180

71

2^0

2^-

ZERO TO THIRTY-SIX 2yX INCHES OF SAND WITH FEW EXPOSED SHALE AREAS

□

a

a

a

iw-

il2.

a

a

1 meter — 5>

OCCASIONAL ZIRFAEA UP THROUGH SAND

Figure 32. D 180-240

72

'J GO

°°oi$%°°o

DENSE COLONY OF

2.S£-

0° o°0 o°o°0o0o

PARAPHOLAS UP

THROUGH FOUR INCHES

OF SAND

0

□

ZERO TO TWENTY-FOUR

o a

INCHES OF SAND 2S0—

O D

OCCASIONAL ZIRFAEA AND PARAPHOLAS UP

□

THROUGH SAND

a

-

0

*zh£-

□

o

□ o

2.40

< — 1 meter — 5

Figure 33. D 240-260

73

aso

O

o

o o

o o

ROUGH SHALE WITH FEW SAND AREAS

W-

0 O

o

o

MANY PARAPHOLAS

LEDGE, (FIVE FEET) SHALE RUBBLE

270—

a ^»~~ rr~~~~ 1

VERY DENSE COLONY OF PARAPHOLAS AND MANY CHACEIA BELOW LEDGE

00 A o°0o0

a

0

D

SAND

2l£-

O

0

a

OCCASIONAL ZIRFAEA AND PARAPHOLAS

2<°o

.

sr~ _l m g Ler ' j

Figure 34. D .260-280

74

SAND

ROUGH SHALE

SAND

300

X\S-

2Ho —

2gS-

ROUGH SHALE PARTLY SAND COVERED

aso

NO BORERS

u o O

o 0

1 meter — $

MANY PARAPHOLAS

Figure 35. D 280-300

75

FLAT CHERT

LEDGE, (THREE FEET)

LEDGE, (TWO FEET)

SHALE RUBBLE

3.£ -

LEDGE, (TWO FEET)

310-

FLAT HARD SHALE AND CHERT

LEDGE, (EIGHT FEET)

SHALE BLOCKS AND RUBBLE

3o.T—

SAND

3oo

NO BORERS

MANY PARAPHOLAS AND SEVERAL CHACEIA

SEVERAL PARAPHOLAS

NO BORERS

o o o 0 0 & „

1 meter

DENSE COLONIES OF CHACEIA AND PARAPHOLAS

Figure 36. D 300-320

76

APPENDIX B: SELECTED PHOTOGRAPHS

In this Appendix photographs are presented of most of the species described in section V of this thesis. For the borers whose siphons were too small to photo- graph, pictures of the valves are presented. Degree of magnification or an actual dimension is provided.

77

Figure 37. Four Parapholas showing pigmentation variation (x 1 1/2)

Figure 38. Three Parapholas showing crowding (x 2)

78

Csl

X

C

o

U XX

I

nD CD

u

£ rd

QJ -P ■H

en

rd H

O

a

rd M rd

on

CD M

Cn

•H En

79

Figure 40. White Parapholas at D-306 (x 1/3)

80

Figure 41. Two Parapholas in sand (x 2)

Figure 42. Parapholas (no chimney) protrudinrr from bore (x 1 1/2)

81

eg X

c

■H

o

U

Cn C ■H

O

w

W

rC

rH O

.c

a.

ro

rrj ft

U •H

Figure 44.

Four Parapholas showing cylindrical pseudofeces (x 1 1/2)

Figure 45. Parapholas chimney (x 1)

83

MW-

Figure 46. Dorsal view of young Parapholas valve showing chitinous flaps on posterior margin (x 1 1/2)

..:;<!-" pwp vp. ;p; . ' pppp p '.. ';p p<:; *

Figure 47.

Ventral view of young Parapholas valve showing pedal gape (x 1 1/2)

84

Figure 48. Parapholas chimney into which a Lithophaga has bored (x 2/3)

Figure 49. Parapholas and Zirfaea in inudstone (x 1 1/2)

85

Figure 50. Zirfaea (x 1 1/2)

■ ** ,

Wk,

m

Fiqure 51. Zirfaea in sand (x 1/3)

86

Figure 52. Zirf aea and worm tentacles (x 1 1/2)

Figure 53. Zirf aea in sand (x 1 1/2)

87

Zirfaea in sand

x 1 1/2)

Figure 56. Two Zirfaea in thin sand (x 1 1/2

Figure 57. Zirfaea in sand (x 2)

89

ittfe**?

V

* MS

y

<£• * . % >

Figure 58. Zirfaea in sand (x 2

Figure 59. Several Chaceia in eroding bores (x 1/2

90

X

0) rC

M-l

•H tSI

£

0)

o

flj A U

o

CD P

91

Figure 61. Siphons of 3 Chaceia (x 1 1/2

Figure 62. Chaceia in horizontal, eroding bore (x 1 1/2)

92

0)

u

C

-P

a

o

N •H

u

0 X!

Cn C •H

O X!

U

o

•H fa

93

Figure 64. Chaceia protruding from bore (x 1/3)

94

Figure 65. Chaceia (x 1 1/2)

Figure 66. Chaceia Note chitinous spots on siphon exterior (x 1 1/2)

95

Figure 67. Chaceia (x 1 1/2)

96

u

(0

4-1

o u

0)

+J ft' 0J

0)

rd

B

o

N

■H

O B

■H

o

X!

rO •H

<U U

rj

u

on

fd

!h CD

> ro

<u r.

00

u

o

97

Figure 69. Barnea Note ten unbranched papillae (x 3) .

98

Figure 70. Botula siphons (center and top left) (x 3)

Figure 71. Botula valve with chitinous covering (x 1 1/2)

99

■ v ■

Figure 72. Dorsal view of Penitella conradi valve with siphonoplax and callum (x 3)

Figure 73. Both valves of Kellia laperousi (x 3)

100

■

mmm&.

Figure 74. Penitella gabbi valve (x 2)

101

■'■'■.'

:x::'?::: ■■"■ '->f. ::>> ' \ ::>:'::::> r '■'• x S : . ■ '■: ; 'W. ■i^w^::''. '': V'JV': -V¥: -X» y'

■ '■'• '•:•. :::■.■:

•■•:■ v.-. v. .■:■ •.-.-:•:•:■:•■.

Figure 75. Penitella penita valve (x 3)

102

'

■■• ■•■■.•:■■•

• < i .kO?v*tf ' ■,**■■■■■?>■$??.

-

Figure 76. Ventral view of Penitella gabbi valve showing row of thickened imbrications on margin of pedal gape (x 3)

■ ■ ■'■'■• '■■

Fiqure 77. Both valves of Nettastomella (x 3)

103

BIBLIOGRAPHY

Allen, J. A. , "Observations on size composition and breeding of Northumberland populations of Zirphaea crispata (Pholadidae: Bivalvia) ," Marine Biology , v. 3, p. 269-275, July 1969.

Church, R. , "Underwater Photography: A Mirror in the Sea," Oceans, v. 4, p. 9-32, May-June 1971.

Clapp, W.F. and Kenk , R. , Marine Borers: an annotated bibliography, ACR-74, Office of Naval Research, Department of the Navy, 1963.

Cox, K.W., California Abalones , Family Haliotidae,

California Department of Fish and Game Fish Bulletin No. 118, 1962.

Evans, J.W. and Fisher, D., "A new Species of Penitella (Family Pholadidae) from Coos Bay, Oregon," The Veliger , v. 8, p. 222-224, 1966a.

Evans, J.W. , The Ecology of the Rock-Boring Clam Peni- tella penita, Ph.D. Thesis, University of Oregon, 1966b.

Evans, J.W. , "Relationship between Penitella penita

(Conrad, 1837) and Other Organisms of the Rocky Shore," The Veliger, v. 10, p. 148-151, 1967.

Evans, J. W. , "The Role of Penitella penita (Conrad

1837) (Family Pholadidae) as Eroders Along the Pacific Coast of North America," Ecology , v. 49, p. 156-159, 1968a.

Evans, J.W. , "Growth Rate of the Rock-Boring Clam Peni- tella penita (Conrad 1837) in Relation to Hardness of Rock and Other Factors," Ecology , v. 49, p. 619- 628, 1968b.

Fitch, J.E., Common Marine Bivalves of California,

California Department of Fish and Game Fish Bulletin No. 90, 1953.

Greene, H.G. ," Geology of Southern Monterey Bay and its Relationship to the Ground Water Basin and Salt Water Intrusion , United States Department of the Interior, Geological Survey, p. 8-45, 1970.

104

Haderlie, E.C., "Marine Fouling and Boring Organisms in Monterey Harbour," The Veliger, v. 10, p. 327, 1968.

Haderlie, E.C., "Marine Fouling and Boring Organisms in Monterey Harbour—Second Year of Investigation," The Veliger, v. 12, p. 182-192, 1969.

Haderlie, E.C., "Fouling Organisms in the Harbour at Monterey, California," in Proceedings of the Second International Congress of Marine Corrosion and Fouling, Athens, p. 1-14, 19 70.

Haderlie, E.C., "Ecological Implications of Breakwater Construction in Monterey Harbour," Marine Pollution Journal , v. 2, p. 90-92, June 1971.

Jaccarini , V. and Bannister, W.H., "The Pallial Gland and Rock Boring in Lithophaga 1.," Journal of Zool- ogy, v. 154, p. 397-401, 1968. ~

Johnson, M.E. and Snook, H.J., Seashore Animals of the Pacific Coast, Macmillan Company, 19 27.

Keen, A.M., Marine Molluscan Genera of Western North America, Stanford University Press, 1963.

Light, S.F., and others, Intertidal Invertebrates of the Central California Coast, University o£ California Press, 1954.

Minter, C.S.,III, Sublittoral Ecology of the Kelp Beds

off Del Monte Beach, Monterey, California, M.S. Thesis, Naval Postgraduate School, 19 71.

Nair, N.B. and Ansell, A.D., "The Mechanism of Boring in Zirphaea crispata (L.) ," Proceedings of the Royal Society of London, Series B, v. 170, p. 155-173, 1968.

Trumbauer, D.S., A Coliform Bacteria Survey of Monterey Bay off Del Monte Beach, M.S. Thesis, Naval Postgrad- uate School, 1966.

Turner, R.D., "The Family Pholadidae in the Western

Atlantic and the Eastern Pacific Part I--Pholadinae , " Johnsonia, v. 3, p. 1-64, 17 May 1954.

Turner, R.D., "The Family Pholadidae in the Western

Atlantic and the Eastern Pacific Part II — Martesiinae, Jouannetiinae and Xylophaginae , "Johnsonia, v. 3, p. 65-160, 29 March 1955.

105

Yonge , CM., "Marine Boring Organisms," Research , v. 4, p. 162-167, April 1951.

Yonge, CM., "On the Primitive Significance of the

Byssus in the Bivalvia and its Effects in Evolution," Journal of the Marine Biology Association of the United Kingdom, v. 42, p. 113-125,1962.

106

INITIAL DISTRIBUTION LIST

No. Copies

1. Defense Documentation Center 2 Cameron Station

Alexandria, Virginia 22314

2. Library, Code 0212 2 Naval Postgraduate School

Monterey, California 93940

3. Professor E.C. Haderlie, Code 58Hc 2 Department of Oceanography

Naval Postgraduate School Monterey, California 93940

4. Assistant Professor R.S. Andrews, Code 58Ad 1 Department of Oceanography

Naval Postgraduate School Monterey, California 93940

Mr

Mr. J.C. Mellor, Code 58 Department of Oceanography Naval Postgraduate School Monterey, California 9 39 40

6. Department of Oceanography, Code 5: Naval Postgraduate School Monterey, California 93940

7. Lt. G.S. Booth, USN VF-121

NAS Miramar, California 92145

8. Oceanographer of the Navy The Madison Building

732 N. Washington Street Alexandria, Virginia 22314

9. Dr. Ned A. Ostenso Code 480D

Office of Naval Research Arlington, Virginia 22217

107

Security Classification

DOCUMENT CONTROL DATA -R&D

[Security etas si I ic etton o( title, body of attstract and indexing annotation must be entered when the overall report is classified)

1 ORIGINATING ACTIVITY (Corporate author)

Naval Postgraduate School Monterey, California 9 39 40

i.a. REPORT SECURITY CLASSIFICATION

Unclassified

26. GROUP

3 REPORT TITLE

The Ecology and Distribution of Rock-Boring Pelecypods off Del Monte Beach, Monterey, California.

4 DESCRIPTIVE NOTES ( Type ol repot t andjnchisive dales)

Master's Thesis; June 19 72

S- au THORCS) (First name, middle initial, last name)

Gregory Seeley Booth

6. REPORT DATE

June 1972

70. TOTAL NO. OF PAGES

109

7b. NO. OF REFS

26

8«. CONTRACT OR GRANT NO.

6. PROJEC T NO.

»«. ORIGINATOR'S REPORT NUMBER(S)

9b. OTHER REPORT NO(S) (Any other numbers that may be assigned this report)

10. DISTRIBUTION STATEMENT

Approved for public release; distribution unlimited.

II. SUPPLEMENTARY NOTES

12. SPONSORING MILITARY ACTIVITY

Naval Postgraduate School Monterey, California 9 39 40

13. ABSTRACT

Divers using SCUBA gear gathered and identified rock-boring pelecypods found in the subtidal outcrops of Monterey silicious shale off Del Monte Beach, Monterey, California. Underwater photo- graphs were taken of all the recognizable species present.

A species distribution and mapping survey was made along two transects, one of which would be subjected to radical ecological change after isolation from the open sea by a proposed breakwater project.

Most species found are common to both transects. Their distribution is variable and depends to a great extent on the character of the substrate, which varies from soft, carbonate- rich mudstone to chert. However, within this framework of dis- tribution dependent on substrate, there are inconsistencies which remain unresolved.

DD ,!.

NOV 68 I *"T I O

S/N 0101 -807-681 1

(PAGE 1 )

108

Security Classification

A-3M06

Security Classification

KEY WORDS

SCUBA

Pholad

Rock borers

Chert

Monterey Breakwater Study

Pelecypods

Ecology

Monterey Formation

FORM

I HOW 69

1473 (BACK)

'"< ^.101-607-6821

109

Security Classification

13 JUI

? 1 '

Li

Thesis

M

503G

B69

Booth

c.l

The ecology

and

dis-

tribution of

rock-

-bor-

ing pelecypod

s of

Del

Monte Beach,

Monterey

Cal i fornia.

thesB69

The ecology and distribution of rockbon

illlilillililliliilllillllll 3 2768 002 07292 8

DUDLEY KNOX LIBRARY