N PS ARCHIVE 1967 WELCH, R. A STUDY OF THE STRATIFICATION OF PHYTOPLANKTON AT SELECTED LOCATIONS IN MONTEREY BAY, CALIFORNIA ROBERT HORTON WELCH ^jj-s-ar This document has been approved for public release art sale; its distribution js unlimited , A STUDY OF THE STRATIFICATION OF PHYTOPLANKTON AT SELECTED LOCATIONS IN MONTEREY BAY, CALIFORNIA by Robert Horton Welch Lieutenant, United States Navy B.S., East Tennessee State University, 1960 Submitted In partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY from the NAVAL POSTGRADUATE SCHOOL June 1967 ABSTRACT Relationships between genera of phytoplankton present and the parameters of oceanographic regime and nutrient supply have been given. The research was made at three selected off-shore stations in Monterey Bay, California. Sampling and analysis procedures are described. Results of nutrient anE^fris^^B-ude reactive phosphate and silicate. A temperature and salinity profile is described for each station. Phytoplankton analysis lists five genera of dino- flagellates and sixteen genera of diatoms. The research extended for a six month period beginning in November, 1966, and was concluded in April, 1967. LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIF. 93940 TABLE OF CONTENTS Page No. List of Tables 5 List of Figures 7 Acknowledgement 8 Introduction 9 Procedure 10 Oceanographic Pattern 15 Temperature, Salinity, and Climatic Analysis 18 Nutrients 28 Phosphorus 28 Silicon 40 Phytoplankton 45 Sampling Procedure 45 Generic Analysis 47 Conclusions 64 Bibliography 67 Distribution List 68 LIST OF TABLES Page no. Table I Synoptic data for each station. 14 LIST OF FIGURES Page No. Figure 1 Chart of Monterey Bay 11 Figure 2 Temperature and Salinity, Station 1 19 Figure 3 Temperature and Salinity, Station 2 20 Figure 4 Temperature and Salinity, Station 3 21 Figure 5 Bathythermographs, Station 1 23 Figure 6 Bathythermographs, Station 2 24 Figure 7a Bathythermographs, Station 3 25 Figure 7b Bathythermographs, Station 3 26 Figure 8 Phosphate and Silicate, Station 1 30 Figure 9 Phosphate and Silicate, Station 2 31 Figure 10 Phosphate and Silicate, Station 3 32 Figure 11 Volume Phytoplankton ml/liter, Station 1 37 Figure 12 Volume Phytoplankton ml/liter, Station 2 38 Figure 13 Volume Phytoplankton ml/liter, Station 3 39 Figure 14a Percent of total Phytoplankton of each Genus, Station 1 48 Figure 14b Percent of total Phytoplankton of each Genus, Station 1 49 Figure 15a Percent of total Phytoplankton of each Genus, Station 2 50 Figure 15b Percent of total Phytoplankton of each Genus, Station 2 51 Figure 16a Percent of total Phytoplankton of each Genus, Station 3 52 Figure 16b Percent of total Phytoplankton of each Genus, Station 3 53 ACKNOWLEDGEMENT Appreciation is given to the Chemistry Department for the use of their equipment during nutrient analyses, and especially to Professor Charles Rowell for his time and help. I wish to thank my wife for her help both scientifically and secretarial. INTRODUCTION While it is often difficult to accumulate sufficient raw data to justify conclusions on an oceanographic topic, the present work represents an effort to extend the knowledge of one small area of the sea so that hypotheses may be extrapolated for the broad reaches of the sea. In searching for a research topic, the accumulation of meaningful data was a prime goal rather than the quest for a start- ling new idea or conclusion. The topic search lead to a paper pub- lished in 1961 on the marine climate and phytoplankton of Monterey Bay by Drs. R. L. Bolin and D. P. Abbott of Hopkins Marine Station, Pacific Grove, California (Bolin and Abbott, 1961). Using this paper as a guide line, it was decided that meaningful information to supplement their data could be obtained by concentrating the research area and by varying the sampling procedure somewhat. The sampling program was begun in November, 1966, early enough in the academic year to be able to collect data for a six month period. Weekly samplings were attempted thereafter until April, 1967. PROCEDURE Starting on November 9, 1966, three of the six original 'Hopkins' stations were occupied on a weekly basis for a period of six months. Rather than attempt a broad cross section of the Bay, as Bolin and Abbott did, the study centered on the first three stations located nearest the Monterey Marina. Figure 1 shows the position of the stations. Station 1 is next to buoy number 4, Station 2 is in approximately 53 fathoms of water, and Station 3 is on the edge of the Monterey Canyon. The stations were chosen because of both the nearness to the Marina and the broad range of depths that are encountered. With each cruise the stations were occupied using the most precise navigation available. This usually consisted of radar ranges and fathometer readings. Deviation from the station during the sampling was minimal and usually was restricted to + 200 yards. On station a bathythermograph cast was made to the maximum al- lowable limits, that is, either to near-bottom depth or to the oper- ational limit of the BT. At the same time a bucket sea surface temperature was read, a dry bulb air temperature was taken, and visual observations were made of wind speed and direction, sea, swell direction and height, barometer reading, descriptive sunlight, and percent cloud cover (Table 1). A Secchi disc was lowered to obtain a measure of the transparency of the water. Since the Hopkins project had included only a vertical haul from 15 meters, the depth for the present research was restricted to this layer. Before the study had commenced it was decided that stratified samples at 7.5 and 15 meters within the layer would be 10 1 \ \ 1 t / • STATION 3 / S y ' .-» / / / / / / / / / / / / I / s J • STAT / ( 1 1 1 1 / / IO>N 2 / / Id ' en , / / / / / / / / s y / / buoy Z \ STATION 1 A 121*55' FIGURE 1. Chart of Monterey Bay showing the location of the three stations. about the maximum sampling that analysis time would allow. In order to insure that the sample had come from the selected depths, a Clarke- Bumpus sampler was used. With this sampler one is able to lower the collecting net to the preselected depth, open a plate valve, sample the level, close the net and return it to the surface uncontaminated by water and organisms of other levels. To insure that the smallest possible identifiable planktonic plant was captured, a size 20 net and bucket was used. Complete flushing of the net accompanied every haul tc prevent depth to depth or station to station contamination. Since the Clarke-Bumpus sampler is outfitted with an impeller driven counter it was possible to determine the volume of sea water sampled. To make a represent- ative haul, sampling was continued for five minutes at the sample depth. A plankton sample was made at a depth of seven and one half meters. At the end of the sampling, a Nansen cast was made placing the bottles at 15 and 7.5 meters, and at the surface. Protected reversing thermometers were used on each bottle to obtain a precise temperature profile of the station at the sampling depths. After the Nansen bottles were tripped and hauled aboard, water samples were extracted in the following manner: a glass bottle was used to receive a salinity sample, and two four ounce plastic bottles were used to receive phosphate and silicate samples (these were immediately injected with about 0.5 ml of chloroform to retard bacterial growth, and then were placed in an ice bath). The second plankton sample was then taken. By reversing the course of the boat, sampling was possible - neglecting drift - over the same general area as before but at the depth of 15 meters. Both plankton samples were placed In pint jars and preserved on station with 20 ml of 40% formaldehyde. Cruise time was about five hours, depending upon weather condi- tions. Each station was occupied at about the same general time dur- ing each cruise. There are two time groups, however, the first includes the first seven cruises November through December occuring from 0800 through 1000 local time, the second group includes the remaining cruises with the time interval on station from 1000 through 1300 local time. Stations were generally occupied in the order from seaward to shore. However, climatic conditions often required a reversal of this pattern. Cruise #1 was incomplete due to foul weather and Cruise #4 has a plankton sample missing at Station 1 due to broken gear. 13 Table I. Synoptic data for each station. Water-Transparency (Tr) given in feet; sunlight (SI) given as bright (b), hazy (h), or overcast (o) ; sea condition given as calm (c), moderate (m), or rough (r) ; and time of station. uise Station 1 Station 2 Station 3 Tr SI Se Time Tr SI Se Time Tr SI Se Time 1 53 b s 0720 49 0 m 0825 45 o r 0935 2 - b s 1058 - b s 0951 - b m 0825 3 40 b s 1046 55 b s 0945 69 h s 0815 4 55 h m 1035 60 h m 0935 68 h r 0825 5 14 h 8 1032 17 h m 0924 61 h r 0803 6 21 h S 0703 20 h s 0815 49 h s 0937 7 39 b s 1045 33 b m 0943 26 b m 0815 8 31 o s 1350 32 h s 1225 50 h s 1043 9 50 h m 1312 54 b m 1155 48 b r 1032 10 60 b s 1355 70 b s 1208 82 b m 1045 11 43 b c 1340 45 b s 1235 51 b m 1105 12 19 b c 1305 12 b c 1200 36 b s 1035 13 15 o m 1345 13 b s 1245 21 b s 1118 14 18 0 m 1000 23 o r 1101 28 0 r 1211 15 29 b s 1400 37 h s 1211 46 o c 1045 16 43 b m 1412 39 b s 1205 63 b s 1050 17 43 h s 1400 37 o m 1220 47 o m 1050 18 23 o s 1255 43 o s 1140 37 o s 1035 19 16 o m 1405 33 o r 1300 31 b m 1140 20 20 o c 1320 40 o c 1215 36 o c 1053 21 16 b m 1317 25 b m 1220 12 b r 1105 22 64 h c 1305 54 h c 1205 47 b c 1047 14 OCEANOGRAPHIC PATTERN The oceanographic pattern of Monterey Bay is definitely seasonal with three distinct periods occurring during the year. Beginning sometime in November a northerly flowing current develops along the California coast which is called the Davidson Current. Reinforced by winter-time southerly winds, the current develops a net on-shore transport due to the Coriolis effect. Surface water, therefore, piles up along the coast and is continually sinking to be replaced by the shoreward flowing surface waters. As the Davidson Current continues, unstable water layers develop due to the surface water substitution and mixing occurs with the abnormally cold, previously upwelled water. This situation causes a sharp drop in the temper- ature structure of the bay. This sharp drop in temperature marks the onset of the Davidson Current Period. Due to the mixing processes, the thermal structure becomes uniform. Since the period occurs during the normal winter rainfall season surface salinities drop to low values. The lowest temperature and salinity values do not occur within the period, however, since time is required for mixing. The temperature minimum usually occurs in April while the salinity minimum at sea occurs during March. Nutrient supply in the surface layers is increased due to the vertical mixing and turbulent action caused by the storm season and the current structure close to shore. In late winter the wind shifts, causing a reversal of the Davidson Current. This occurrence is not as abrupt as the initiation of the northerly-flowing Davidson Current so that it is often diffi- cult to pinpoint the exact time of the second and longest period - 15 the Upwelling Period. By early spring the winds have shifted, coming from the northwest which reverses the surface current direc- tion. Surface waters are moved seaward, causing a divergence zone near the surface. As cold, deeper water moves toward the surface, it follows the upwelling pattern which occurs all along the coastal region. It is over the Monterey Canyon that the effects of the upwelling are first noticed in the form of cold surface temperatures. By May, the initially uniform temperature structure has been altered from both below and above. At first, the upwelling causes the total column of water to cool so that minimum surface temperatures occur in April. In May and June the surface water begins to warm due to seasonal heating; however the deeper layers continue to cool, pro- ducing a very sharp thermocline gradient at about 150 feet of 60° F/100'. As the deeper waters are upwelled, nutrients are brought from the deeper regions of nutrient abundance toward the surface. It is in this early spring period that plankton populations increase and continue to do so until late summer where they die out due to the lack of nutrients after upwelling has diminished. Accompanying the upwelling, a more saline water is brought to the surface layer so that during the early part of the upwelling period the salinity curve shows corresponding changes. As mixing occurs and upwelling diminishes in late summer, the salinity of the surface water begins to decrease. During the months of September and October, winds become variable and a period of relative calm prevails. It is during this time that the cool, saline waters of the surface become colder and begin to sink, As the surface waters sink, offshore waters move in to replace the layer. During this Oceanic Period the warmest water of the year occurs at the surface. The period is marked by clear blue oceanic water, and a relatively uniform cold water column. The surface water shows a secondary salinity maximum as the low salinity mixed waters are replaced by higher salinity oceanic water. Characteristic plankton will be the open-water species that survive on minimal nutrient or food supply. | 17 TEMPERATURE, SALINITY, AND CLIMATIC ANALYSIS All three oceanographlc periods were encountered during the period described in the research project, however, the Upwelling Period observed shows a variation from the description outlined above. The Oceanic Period was In progress when the first cruise was made on November 9. This period continued until early December when the first drop In temperatures was recorded at all three stations on December 4. The period was marked by warmer waters with Intermediate salinity values. A very definite period of nutrient minimum was noticed. Silicates reached a value of less than 0.5 micro-gram atoms per liter (/ygm at/liter) and phosphate values approached 0.1 /jgca. at/liter. The Davidson Current Period appeared somewhat late, beginning in late November or early December. In Figures 2, 3, and 4 it is seen that the surface temperature begins the first sharp decline on December 7, but the 7.5 and 15 meter level decline is two weeks earlier, occuring on November 23. These Figures also show the salinity values which give their first decline at all depths on November 30. In Figures 2 and 3, the temperature minimum occurs at all depths on January 4 with a minimum of 10.7 C occurring at Station 1 at depths of 7.5 and 15 meters. However the minimum did not occur at Station 3 until two weeks later on January 18 (see Fig- ure 4) . This is probably because the longer water column requires a longer period to cool and because of the distance from shore. From the end of each minimum, the temperature became progressively warmer until early February. This warming occurred as an abrupt change in o o O O O ■tf ro C\J «- o "* 0o 3dniVd3dH31 ooooo ooo t f) (\' ^ O -- «« o^ 3yniVd3d^3l O o en Q O O c5 if) <-> If) O O >/fc AllNHVS o m O en -r r r ** 3. 3anivy3dM3i Q o q o o ^f i«i w ^ d n r o q c\I O O O o ° •^ rO CM* ,_: d c o 00 QJ O £_ r3 CO CD C_ D -f— rt3 C_ ... QJ 4 Q. J E QJ 1— Ld cr CD -* °°/o A1INHV? the BT traces at Stations 1 and 2 on January 4 and January 11 (Figures 5 and 6). Station 3 (Figure 7a) does not show the increase until January 25. The salinity profiles (Figures 2, 3, and 4) show an increase, after an initial decrease, which continues until about January 18. This continued increase of salinity profile, rather than the expected minimum profile for the Davidson Current Period, is explained by the unusual delay in the onset of the rainy season and by the turbulent vertical mixing to lower layers during the near uniform post-Oceanic Period. As rains occurred in January, the salinity started a downward trend. The decline at the surface was abrupt, reaching a minimum of 32.72°/oo at Station 1 and 32.34°/oo at Station 2 on February 8. At 7.5 and 15 meters the decrease was more gradual at both stations; however, at the 15 meter level the minimum salinity was reached one week ahead of the upper layers, occurring on February 14. This is interpreted as a result of the diminished shoreward surface transport due to a reversal of the wind, and as a possible initiation date for upwelling. During the Davidson Current Period, mixing is evident until the first week on February 4 (Figure 7b). On this date the trend of mixing downward is reversed and an upward mixing trend is evident on February 8, which marks the onset of the Upwelling Period. The temperature decrease beginning in early February is gradual, as is expected, being only a few tenths of a degree. The salinity increase that generally accompanies upwelling is large, however, on the order of six to eight tenths parts per thousand initially. Stations 1 and 2 show a definite matching of trends at all three layers as shown 22 SO 5S 50 55 50 55 100* 1525 3t\66 1658 SrXI 1,6 I IH6 SC-X1-5* -50 55 . 'F !8? \r CM v I ' I ' I — ■ — I— o o ° o if) CO lO - i ' r i i ■ i i o o o o m oo ^ ^ cm v c o CO o £_ C o o c: n CL to O CD O or oo LlJ tr Z3 CD 30 o O O O Lf) i£> ^ ^ cm v OJ cz o Id ■♦-' to (L) O £_ o OJ 4- o -a c ft! I i OJ -♦- .c Q_ o OJ > o rs OJ cr en Ld O 31 G) r\j. in. If) 00- 00 vO. o m jw>;i|/;e lu6 rf BiVHdSOI-ld ° O C\J • O u -k. o CO o 10 o 6 in v j^;il/;euj6 ri HVOIIIS in CO c o CO GJ O V_J o rrJ OJ or Ld cr o 32 accuracy for a meaningful study. Extinction values were read at 625 mp from the Beckman DU and DK 1A Spectrophotometers. The DU Spectrophotometer requires manual control, while the DK 1A Spectro- photometer gives automatic printed values of percent transmission. Transmission values were plotted on log paper to allow for direct reading of absorbance values. Transmission extinction values were more valuable than absorption since logrithmetic plots displayed more accurate gradients of the standard curve in the low absorbance range. Shown in Figures 8, 9, and 10 are plots of the resulting curves for reactive phosphate and silicate given per depth per station. From this gross analysis one sees that the nutrient poor Oceanic Period extends well throughout November with values approaching less than 0.2 /*gm at/liter. Early in December with the onset of the Davidson Current, values of phosphates increase somewhat and then level off during late December and early January. This increase is brougtt about by the near shore position of the station and by the fact that on shore surface water carrying December runoff and river outfall are brought out in the Bay by subsurface movement. Another source for this nutrient supply is the here-to-fore nonvertically mixed subsurface waters. As the Davidson Current progresses, increased vertical mixing brings nutrients to the surface. A grad- ual decrease occurs at all stations until early February, when a small sharp increase occurs due to upwelling, and then a reduction again occurs until late March when a second upwelling maximum occurs. The pattern of Station 1 given in Figure 8 is about what one would expect for the research period. The Oceanic Period through 33 November 30 is characterized by nutrient depleted water, the slight gradual increase of the phosphate value during December, and the subsequent lowering of concentration in January. When Figure 11 is compared with Figure 8, it is evident that the small bloom of phytoplankton occurring on January 18 at 7.5 meters is responsible for the phosphate loss also occurring on that date. Contrary to the temperature-salinity curves presented earlier, there is no large increase in the phosphate concentration in early February to signal the onset of the Upwelling Period. The increases are seen only at the surface on January 18 and at 15 meters on March 1. However, when one considers that upwelling was gradual in starting and not able to reach to the shoreward stations at this early date, the curve is representative as indicated in Figure 11. Very large phyto- plankton blooms occurred on March 8 and April 1. It is shown by the plotted curves that nutrients brought to the area were minimal due to the large amount of utilization during the blooms. The profiles at Station 2 are generally the same as Station 1. When Figure 9 is placed near Figure 8, one can observe that the general low nutrient Oceanic and moderate nutrient Davidson Current Periods are similar. Here too, on January 18, a phytoplankton bloom reduced the amount of phosphate at both the 7.5 and 15 meter levels. It appears from the phosphate minimum of 0.64 /4gm at/liter on January 18 at the 15 meter level, that the bloom had originated there and had moved up to the 7.5 meter level where it was collected. The larger volume/ liter of phytoplankton that was taken at 7.5 meters supports this hypothesis. The phytoplankton apparently remained at the 7.5 meter level during the subsequent week since the 15 meter 34 level returned to the previous weeks1 concentration, but the 7.5 meter level continued to decrease in concentration due to removal by phytoplankton. The onset of the second surge of the upwelling was more evident at Station 2 than at Station 1. Figure 12 shows a very large bloom on March 22 at 7.5 meters and this corresponds rather nicely with the sharp minimum of phosphate at that level on March 22 (Figure 9). On this date the phytoplankton at 15 meters did not show such a large increase and the phosphate level at this depth correspondingly indicated a slight rise in value. On April 1 a very sharp increase in the phosphate concentration occurred at all levels due to upwelling, The next week showed a decrease of phosphate accompanying the increase of phytoplankton at those levels. Station 3 curves given in Figure 10 likewise follow the low Oceanic Period of November with increases during the Davidson Current Period due to increased seaward transport of runoff and mix- ing with the lower nutrient-rich layer. Since phosphate concentration increases with depth (Raymount, 1963), it is reasonable to assume that mixing with deeper layers further seaward will cause an increase in phosphate concentration that would place it on an equivalent level with the two more shoreward stations. Another point to consider is that the maximum concentration level during the Davidson Current Period was 1.1 ^gm at/ liter and this persisted for three or four weeks, Possibly this is the level of phosphate concentration derived from a uniformly mixed water layer, and represents the maximum resource level of nutrients within the Bay. When Figure 8 is compared with Figure 10 one sees immediately that the shoreward station acquires 35 this level at 1.0 + 0.1 /*gm at/liter more rapidly than Station 3. Probably a combination of shore influence, current concentration, vertical mixing, and sluggishness of water at Station 3 was respons- ible for the curves given for the three stations. The first sign of a possible upwelling feature was on February 15 (see Figure 10), when the phosphate concentration made its initial rise. In Figure 13, the increased concentration of phytoplankton that occurred during the following three weeks accounts for the decreased levels of phosphate found on March 15 and 25. The second surge of the upwelling on April 1 was not utilized by the phytoplank- ton population; consequently, a high phosphate level was established. The decrease that occurred on April 8 is unexplained by the curve given in Figure 13. No phytoplankton bloom occurred to reduce the phosphate level this much. There appears to be no immediate explan- ation for this inconsistency of phosphate and productivity curves. On April 15 an increase in phosphate was experienced followed by a decrease on April 22. Again, no phytoplankton bloom occurred at either level (Figure 13). The fact that the stations were occupied during periods of heavy overcast and precipitation, alternating with bright clear days, could account for near surface vertical movement of the phytoplankton. 36 1— CD O) LO r o o <9 T O O n o o o CO O O ID O O ID T O O m in UJ ce => CD O o o m 1 o o iD J«3XI[/C_01X |LU NOLVINVHdOlAHd 3 lAimOA 37 10 CM CD. CM. rr a. CM CM cm' ID co- < 2H CM. CM LO. co- rn UJ u.- m. CM CO. z < CO CM CM u O m. CM 0 > O :o>J t ♦ i o o cu 2 in j^i; e- n — >- o o ro OL x iuj 1 O O I o o ID O O to !_ CU (1) in c\j 43 to (- c: (L> r3 c Q. O E o > C\J u or => O o o 1 O o iD NOlNNVldOlAHd ILMmOA 38 I CO c o "r5 CO r3 (— CO LJ ZD L- O O ■D O o O o o O o 10 iD nn o o cn cn o o 10 J 3 1 1 1 /e0L x IUJ NOJL^NVldOlAHd BlAimOA 39 SILICON r As results show, and1 as pointed out by Bolin and Abbott (1963), most phytoplankton utilize silicon that is dissolved in the sea for body structure, primarily the cell wall. *A good index of ph 'to- plankton productivity, then, is the silicon profile of the Bay. Sampling procedures were exactly the same as for phosphorous. The samples were frozen for storage in 4 ounce plastic bottles with chloro- form added. Analysis occurred at most ten weeks after collection. Analysis followed the siliconmolybdate reduction with metol and oxalic acid as outlined in Strickland and Parsons (1965). The choice of the metol-oxalic acid reduction method was used in order to take advantage of the intense blue color that is produced. The procedure is much less sensitive than a stannous chloride reduction, but the latter requires exacting time intervals and the yellow color produced is more difficult to read on the spectrophotometer. Extinction units were read at 810 rry* on the Beckman DK 1A Record- ing Spectrophotometer. Units of percent transmission were recorded graphically when the machine was set with fixed split image and wave length. Analysis accuracy was somewhat greater than +0.25 /rfgm at/ liter using 10 cm. cells. The limit of detection of reactive sili- cate was 0.1 /tgm at/liter. Technique accuracy was considered good. A standard of fused anhydrous silicic acid and sodium carbon- ate was used. Each run of samples utilized the comparison of two separate standard curves in order to correct for any machiae or technique error. It should be pointed out that on both occasions that analyses were made, standard curves were equal, thus assuring the accuracy of the results. 40 j Dissolvable silicon is usually present in the sea as the silicate ion and appears variably in the Bay according to the oceanographic regime in process. As in the case of the nutrients, the Oceanic Period brings silicon depleted waters in from the open sea, and one would expect very minimal values. At the onset of the Davidson Current Period, the values may appear increased but will maintain a relatively low concentration during the period. During the Upwelling Period values of silicon will increase during the early months, due to the silicon rich deep waters of the Monterey Canyon, and will decrease to a summer low due to the utilization by the phytoplankton. During periods of grazing by the zooplankton, the silicon content may increase due to the rapid regeneration in the sea. This regeneration of silicon is definitely more rapid than that of other nutrients (Raymount 1963), and at times produces an irregular profile. 1 A gross analysis of Figures 8, 9, and 10 indicates the presence of all three oceanographic periods. A very low silicate concentration is observed through November at all depths and at all stations. Be- ginning in early December and continuing through January, a gradual increase to 20-30 /^gm at/ liter concentration for Station 1 and 2, and a smaller increase at Station 3 marks the Davidson Current Period. During the latter part of January and the first week of February, a decrease in concentration value is noticed at all stations due to the slackening of the current and to the utilization by the small numbers of the phytoplankton present. On February 8 the first increase in silicate is noted signalling the beginning of an Upwelling Period. As with other parameters, the silicate concentration is then decreased 41 or maintains the initial upwelling level until late March when a second and much stronger surge of upwelling is seen. Again the usual continual increase from the onset dates of early February is retarded and reversed by phytoplankton blooms occurring in early March. The small phytoplankton bloom that occurred on January 25 at Station 1 is not reflected strongly in Figure 8 in the silicate curve. Figure 11 indicates that the bloom is only measurable at the 7.5 meter level, but Figure 8 shows only a slight decrease in the silicate value on that date. The bloom that occurred on March 8 at the 7.5 meter level and to a lesser but more stable degree at 15 meters accounts for the decreased value of silicates during that time interval as shown in Figure 8. On March 25 the sudden surge downward at 15 meters corresponds to the decrease of phytoplankton at that level (Figure 11). The sudden massive increase in silicates brought on by the upwelling was the response at those levels to the continual small phytoplankton population. A second massive increase in phyto- plankton at both sampling levels accounts for the sudden drop in silicate at the 7.5 and 15 meter levels on April 15 (Figure 11). Station 2 shows the same low Oceanic Period concentration as Station 1. The trace of Figure 9 compares generally with Figure 8 throughout until the second upwelling surge. The phytoplankton bloom that occurred on January 11 at both levels (Figure 12) accounts for the lO^Ugm at/liter decrease in silicate that occurred on the same date (Figure 9). Since the bloom was not sustained, the values of silicate rose again in the next two weeks, only to decrease dur- ing the pre-upwelling period. On February 8, at all three levels 42 (Figure 9) an increase in silicate concentration was noted which signalled the upwelling onset. Again the surge was not strong enough to continue, and decreasing values were noted due to utilization by the minimal numbers of phytoplankton organisms. Figure 12 shows three bloom areas on the profile at both the 7.5 and 15 meter levels. The first, occurring on March 1, accounts for the continual decline of the silicate curve after initial upwelling. Before the upwell- ing can replace the utilized silicate totally, another stronger bloom occurs on March 15. It is after this bloom that the first large increase of silicate occurs (Figure 9). This level is maximized at the surface at 62 /igm at/liter on April 1. Subsequent losses and gains are the product of the third bloom at the station occurring on April 15. Station 3, shown in Figure 10, gave a more stable profile during both the Oceanic and Davidson Periods. No bloom occurred, (Figure 13) during January as it did at the other two stations. The upwelling of early February was noted only slightly on February 22 at 7.5 and 15 meters. This was probably due to the large dilution at the more seaward station. Responses to the second surge of the upwelling could be seen as early as March 15 at 7.5 and 15 meters (Figure 10). This ability to see the effects of upwelling was due to the fact that the phytoplankton blooms that occurred on February 22 and March 1 had died out somewhat as indicated by Figure 13. The larger, persistant bloom at 15 meters during the interval of February 22 to March 8 supports the February upwelling date. The trend of a seaward moving concentration of silicon, occurring in early January, (Figure 8) and continuing to sea to 43 terminate on February 1, (Figure 10) should be discussed. A char- acteristic of the Davidson Current Period is the shoreward movement of surface water and a subsequent piling of water along the shore. This requires a subsurface seaward movement of the near shore waters. It is entirely possible that a mass of water having a high silicon content may move seaward as a concentrated body at some subsurface depth. This seems to be shown in the silicon profile of Figures 8, 9, and 10. On January 4 at Station 1 the body moved through the 7.5 meter level with some indication of the high level of concentra- tion at the 15 meter level. At this time the concentration was 37.8/^gm at/liter at 7.5 meters and 25.5 /^gm at/liter at 15 meters. Both values were well above the mean for the period. On January 25 at Station 2 a sharp maximum of 30.2 ^gm at/liter was noted at the 15 meter level with much smaller rises at the two upper levels as shown by Figure 9. In Figure 10, the sharp maximum is noted on February 1 at 15 meters, but at this station the concentration value had increased somewhat to 42.5 /4-gm at/liter. Like the other two stations, this peak was in sharp contrast to the trend of the curve. These data showing station to station movement over a time interval may be used to support the seaward movement of nearshore waters caused by the Davidson Current. 44 PHYTOPLANKTON SAMPLING PROCEDURE One of the main objectives of this study was dividing the 15 meter layer studied by Bolin and Abbott into two layers of equal depth, and relating the genera of phytoplankton found at each stratification to the parameters studied. Due to limitations imposed by analysis time and boat scheduling, only two depths within the upper 15 meter layer were sampled; on each cruise at each of the three research stations, Clarke-Bumpus hauls were made at 7.5 and 15 meters. A net of 175 threads /inch (size 20) was used to insure the sampling of the smallest identifiable phytoplankton organisms. Use of the Clarke-Bumpus sampler was required in order to sample only the two depths of interest. In addition to providing uncontaminated, layered hauls, the Clarke-Bumpus sampler is fitted with an impeller volume counter so that by simple calculations one can obtain the approximate volume of sea water filtered. The phytoplankton hauls were preserved by the addition of formalin. Storage was in glass jars. The preserved samples were placed in graduated cylinders and allowed to settle for 12 to 24 hours. A wet volume of the plankton was then read to the nearest milliliter. The sample was then decanted to a total volume (plankton and fluid) of 100 m. This reduction of the volume to an accurate total volume was not necessary to the research project but was provided for subsequent utilization of the collected data. After agitating, a one milliliter sample was with- drawn with a Stemple pipette and placed on a rafter tray for count- ing. The sample was evenly dispersed on the counting tray and an estimation was made of the percent of the sample that was phytoplankton. 45 This percent volume was used to calculate the volume of phytoplankton per liter of sea water (Figures 11, 12 and 13). The organisms in the phytoplankton were identified to genus and counted. This numerical sum of all phytoplankton counted was used as a base in evaluating the percentage count for each genus in the total population of phytoplank- ton. The total number of phytoplankton organisms was very small during the winter months but during blooms a one milliliter sample would often contain hundreds of thousands of plants. When these extremely concentrated hauls were taken, dilutions of 10:1 and 5:1 were made for ease of counting. The whole milliliter sample was tallied regardless of total numbers present. No attempt was made to identify the organisms beyond genus. A very detailed study with identification to species would require the aid of a trained taxonomist. The Naval Postgraduate School posesses portions of each sample so that further identification or use may be made of the initial research. A discussion of the phyto- plankton in general has been given in the nutrient section. Since the research project had as a prime objective the stratification analysis of phytoplankton, a discussion of the results given by the generic identification should provide information as to the prefer- ence of the organism for the environment at each depth. 46 GENERIC ANALYSIS Several investigators have made detailed analyses of the phytoplankton present in Monterey Bay. Cupp (1943), in her manual on diatoms, references a work in 1930 by Bigelow and Leslie. From this early date comprehensive studies have been made in the gross population of the Bay. In the Hopkins paper (Bolin and Abbott, 1963), reference is made to the work done by Dr. Enrique Balech who made species identification on the Hopkins samples. The present study resulted in the counting of 21 individual genera which included 5 genera of dinoflagellates and 16 genera of diatoms. Three genera, Dinophysis, Lithodesroium,and Schroderella, were not listed in the Hopkins paper but were identified in the present study. While their presence in the previous studies may not have been large enough to report, sufficient numbers of the three genera were found during the present study to regard them as important members of the plankton community. Figures 14a and b, 15 a and b, and 16a and b show the percent of each of the genera relative to the total phytoplankton count. The accordion graphs list the genera in decending order of maximum peak attained during the research period. The dominant form during the period was the genus Chaetoceros, followed by the genus Rhizosolenia. The other genera made up from ten to sixty percent of the total count depending upon the oceanographic regime and nutrient supply. Ten of the genera normally were present only in trace amounts, CHEATOCEROS The genus Chaetoceros is generally associated with cold upwelling waters, but it is present during most of the year, even in periods of very low plankton hauls. During the early weeks of November, the 47 STATION 1 7.5 meters NOV DEC JAN FEB MAR APR SlAi ION 1 15 meters NOV DEC JAN FEB MAR APR 3 16 () JO I i» il 88 ♦ II 18 «3 ( | 15 li I B 15 U J! 3 It I] « 9 It » X T l« 41 ZB 4- II 18 25 I 8 15 HI 8 13 it « 5 ,1 It tt ■ ■ - - * • ' • ' .i .... . , , , , . , , , . 1 , . , ■ 100 FIGURE 14a. Relative abundance of genera, expressed as percent of total count. 48 STAM0N1 7.5meters STATION 1 15meters NOV DEC JAN FEB MAR APR NOV DEC JAN FEB, „ MAR APR 3 16 25 JD T 14- 21 28 * ,| (8 0 I ft 15 24 I 6 13 & 23 3 I? 13 26 8 U 23 X> T Wit ffl 4- II 18 25 I 5 0 » I 8 IS U & £ \T I) £6 THALASSIOSIRA 4 COSCINODISCUS STEPHANOPYXIS BIDDULPHIA NOC TILUCA EUCAMPIA t;-,al_assiothrix SCHRODERELLA DlNOPHYSIS LITHODESMIUM NITZCHIA ASTER ION ELLA "HALASSIONEMA COSCINOSIRA SO 50 50 50 25 i 25 25 I <5 25 i J5 ? ? 25 o I 25 I I 25 T o I 25 ? o I 25 25 A I 25 25 t 25 f O u 4 FIGURE 14b. Relative abundance of genera continued. 49 STATION 2 7.5meiers STATION 2 15 meters NOV DEC JAN FEB MAR APR NOV DEC JAN FEB MAR APR 3 U 25 30 r 14. 21 Z8 4 II 18 £5 I 8 15 Zi I 8 15 22 23 5 It 13 2< 3 II 23 30 7 I* 21 28 4 1 1 18 25 I B 13 21 I 8 1 5 il 25 5 If 13 U IOO 50 FIGURE 15a. Relative abundance of genera expressed as percent of total count. bO STATION 2 7.5meters STATION 2 15meiers NOV DEC JAN FEB MAR APR NOV DEC JAN FEB MAR APR 9 16 11 30 7 14 2i 28 * II 16 ZS I 8 IS U > B 15 «* » S « 19 « 9MO»7»*»4.lll»SI'8HBI 6 15 £i *9 5 12 19 tt . ■ , , i , , , , i , — , — t — i i — i — ■ — i — i — i — i — i — i — ■ — ■ — i — • — i — i 1 — ■ — i — i — i — ■ — i — ■ — _ SO ♦ O -♦ ^ THALASSIOS1RA I COSCINODISCUS STEPHANOPYX IS BIDDULPI-IIA NOCT ILUCA EUCAMPIA THAI ASSIOTHRIX SCHRODERELLA DINOPHYSIS •j-IQDESMIUM N ITZCHIA ASTERIONELLA THALASSIONEMA COSCINOSIRA SO so 50 — o I as Z5 o & I 25 25 + ? 25 J I -T 25 25 I o -J i 25 — o e's *|5 — o 2'5 f — o I 25 O % FIGURE 15b. Relative abundance of genera continued. 51 STATION 3 7.5meters STATION 3 15meters NOV DEC JAN FEB MAR APR NOV DEC JAN FEB MAR APR 9 16 23 JO 7 1+ 21 28 * 'i 18 11 i 8 IS It I 8 18 22 !« 6 u II » g i» 25 » ii 2i iS * M 18 25 I 6 19 S I 8 15 22 29 B 12 |J 2t ♦4HH CHAETOCEROS PERIDINIUM DHYLUM CERA7IUM 100 50 50 100 TOO SKE_- TONEMA GONIAULAX 50 SO 100 75 75 75 75 75 75 75 75 5P 50 FIGURE 16a. Relative abundance of genera expressed as percent of total count. 52 S I A t ION 3 7.5meters NOV DEC JAN FEB MAR APR STATION 3 15"meiers NOV DEC JAN FEB MAR 3 II U 30 7 I* O 9 4- II 18 *S I & 15 U I 8 IS Zl » 5 it /S « 9 It a SO 7 J* U » ♦ II 18 VS I 8 15 M I 8 15 a I) 5 12 <3 U . " » i ■ i i — i — i — i — ■ — i — I — i — i — i — ' — ' — i — ' — i — i — i — i — i — i — ■ SO ' * * * fc. A- THALASSIOSIRA COSCINODISCUS STEPHANOPYXIS B1DPULPHIA NOCTILUCA EUCAMPIA THALASSIQTHRIX SCHRODERELLA D1NOPHYSIS i THODESMIUM NiTZCHiA ASTERIONELLA HALASSIONEMA COSCINOSIRA 50 SO 50 'I I 25 zs I o I 25 O I 25 25 Z5 i5 o I 25 V ? Z5 ¥ ? 25 25 I O J. o o FIGURE 16 b. Relative abundance of genera continued. 53 genua* was foi • '.he IS meter level of Station 1. This TT&g probably beeauS'S s ! tfo>,-.- SE 11. SUPPLEMENTARY NOTES 12 SPONSORING MILITARY ACTIVITY Navy Oceanographic Office 13. ABSTRACT Relationships between genera of phytoplankton present and the parameters of oceanographic regime and nutrient supply have been given. The research was made at three selected off-shore stations in Monterey Bay, California. Sampling and analysis procedures are described. Results of nutrient analysis include reactive phosphate and silicate. A temperature and salinity profile is described for each station. Phytoplankton analysis lists five genera of dinoflagellates and sixteen genera of diatoms. The research extends for a six month period beginning in November, 1966, and concludes in April, 1967. DD FORM 1 JAN 04 1473 69 UNCTASSTFTED Security Classification UNCLASSIFIED Security Classif ication key wo R OS L I N e C Phytoplankton Monterey Bay, California Nutrients Phosphate Silicate Temperature/Salinity Oceanographic regimes f ... .*«».,., f DD ,T:„1473 'back S/N 0101-807-6821 70 UNCLASSIFIED Security Classification A- 3 I 409 lhesW394 A study of the stratification of phytopl 3 2768 001 95208 8 DUDLEY KNOX LIBRARY M ' iHJuot I I I i !mM mi monk Hi 8fl JfflfflR Ittllffl FHC M