Seasonal growth and succession of tropical and introduced phytoplankton cultured in deep sea water

Aquaculture, 14 (1978) l-12 o Elsevier Scientific Publishing

1 Company,

Amsterdam

- Printed in The Netherlands

SEASONAL GROWTH AND SUCCESSION OF TROPICAL AND INTRODUCED PMYTOPLANKTON CULTURED IN DEEP SEA WATER

YOCIE Y. BRAGA and LOUIS D. DRUEHL* Esta@o de Biologia Marinha, Arraial do Cabo (Brazil) *Present address: Department B.C. V5A lS6 (Canada) (Received

of Biological

Sciences,

Simon Fraser University,

Burnaby,

31 October 1977; revised 6 February 1978)

ABSTRACT Braga, Y.Y. and Druehl, L.D., 1978. Seasonal growth and succession of tropical and introduced phytoplankton cultured in deep sea water. Aquaculture, 14: l-12. Seasonal variation in species composition and cell production.by indigenous phytoplankton was studied in unaltered and nutrient-enriched 42 m deep sea water. Species composition changed throughout the year, but pennate diatoms remained dominant. With the exception of one instance in June 1975, maximum cell concentrations never fell below 10’ cells/litre. Introduced phytoplankton cultured in 42 m deep sea water usually obtained high cell concentrations. Phaeodactylum tricornutum inhibited the development of natural diatom populations.

INTRODUCTION

An attempt is being made to develop a mariculture system based upon relatively nutrient rich sea water pumped from 42 m depth (Moreira da Silva, 1971). This project, Projeto Cabo F’rio, is being conducted in the vicinity of Arraial do Cabo, 110 km east of Rio de Janeiro, Brazil. In this system, sea water from 42 m deep is held in large tanks located outdoors. These tanks support animals that require phytoplankton for either (1) part of their developmental cycle (shrimp), (2) throughout all their life cycle (oysters), or (3) not at all (fish). Any indigenous phytoplankton inhabiting these tanks serves either as a nutritive source, as a competitor with introduced phytoplankton, or as a fouling agent. It is therefore imperative to understand the behaviour of the phytoplankton indigenous to the deep sea water when retained in tanks. The purpose of this study was to determine which phytoplankton would dominate at different times of the year when cultured under the following conditions: (1) indigenous phytoplankton in unaltered 42 m deep sea water, (2) indigenous phytoplankton in 42 m deep sea water enriched with urea and superphosphate, and (3) 42 m sea water inoculated with either Platymonus sp.,

2

Dunaliella tertiolectu Butcher, SkeEetonema costutum (Greville) Cleve or Phaeodactylum tricornutum Bohlin. An estimate of productivity, as assessed

by particulate carbon, was extrapolated from laboratory conditions for the introduced species and from one outside tank experiment. MATERIALS AND METHODS

The sea water was pumped from 42 m depth into 1000 litre concrete tanks covered with white wooden slats (3 cm wide) which occluded approximately 30% of the incident light. Vigorous aeration was provided by perforated tygon tubing placed across the bottom of the tanks. Seawater temperatures in the tanks were monitored daily at mid-morning. Solar radiation was monitored continuously with a pyroheliometer. Nutrient concentrations were determined using the methods of Strickland and Parsons (1968). Particulate carbon analyses were made on cultures filtered through Gelman type E glass fiber filters, using a Hitachi Perkin-Elmer CNH analyzer. Duplicate cell counts were made on unconcentrated Lug01 preserved samples, using a haemocytometer. Taxonomic determinations were made using the following references: Moreira ,Filho and Kutner, 1962; Moreira Filho, 1964,1966; Macedo, 1974; Macedo et al., 1975; Valentim et al., 1975. Three of the introduced algae (Dunaliella tertiolectu, Platymonus sp. and Phaeodactylum tricornutum) were supplied by the Woods Hole Oceanographic Institute, U.S.A., and the fourth (Skeletonemu cost&urn) was supplied by the Oceanographic Institution, University of Sao Paulo, Brazil. These species were cultured in 20 litre glass carboys under the following conditions: temperature, 19-23”C, continuous illumination of 10 400 lux provided by cool white fluorescent lamps (Osram, TLW/RS), vigorous aeration, and in fortified sea water. Prior to each experiment the tanks were scrubbed and allowed to dry in the sun for at least 1 week. Two tanks were filled with 900 1 of 42 m sea water; one was filled with 900 142 m sea water, with 14 mg/l urea (NH&ONHz) and 5 mg/l superphosphate (CaJ(PO,),) added; the remaining 4 tanks were inoculated with 20 1 of either DunaZieZZa,PZutymonas, Skeletonemu or PhaeoductyEum culture in log phase of growth and the total volume brought up to 900 1 with 42 m sea water. Each day the tanks were carefully scraped and samples of sea water for cell counts taken. RESULTS

Physical and chemicaZ conditions

Temperatures of the 42 m deep sea water at the time of pumping varied from 14 to 20°C for the season of upwelling (September-February) and from 17 to 24°C for the remainder of the year (Table I). The range of average daily

1976

n.d. 158 299 341 293 458 383 644 573 386 287

2/v -12/v 5/VI -12/VI 25/VII4/VIII 11/1X -18/1X 30/X - 7/X1 25/XI - 3/XII lo/XII-17/XII 13/I -20/I 14/II -23/11 27/111 - 6/IV 22/IV - 2/v

1975

Insol. (Iy/day)

Experimental period

17 19 19 14 17 16 16 13 20 24 22

Water ternpi (“Cl

Initial temperatures and nutrient concentrations and mean daily insolation values

TABLE I

22.2 20.4 18.6 19.2 20.6 22.4 22.6 22.6 24.9 25.0 22.1

Water tempavc (“Cl 21.02 5.45 8.31 1.57 9.73 20.97 10.69 8.31 4.34 2.84 7.53

SiO,-Si 2.53 3.44 5.46 7.24 8.28 10.74 10.37 10.51 4.78 0.93 2.15

NO,-N 0.24 0.37 0.26 0.26 0.23 0.16 0.22 0.25 0.47 0.18 0.52

0.95 0.58 1.01 0.73 0.76 0.29 0.89 0.54 1.30 0.74 2.22

NH,-N

@g-at/l)

NO,-N

Initial nutrient cont.

0.78 0.64 0.63 0.93 0.82 1.00 0.93 1.10 0.81 0.40 0.61

PO,-P 4.8 6.9 10.7 8.9 11.3 11.2 12.3 10.3 8.1 4.6 8.0

N/P

of water pumped from 42 m depth, and the mean daily tank seawater temperatures

W

4

temperatures of the sea water in the tanks during the experiments was 18.6 to 25°C. Insolation values followed the austral seasons; average summer values were from 383 to 644 ly/day and winter values from 158 to 341 ly/day. Phosphate and nitrate values were highest during the season of upwelling. The N/P ratio varied from a low of 4.6 in March/April to a high of 12.3 in December (Table I). Nitrite, ammonia and silicate concentrations did not demonstrate a consistent seasonal pattern of variation. Species composition and dominance

Thirty-eight diatom species in 28 genera were noted during this study (Table II), of which 18 genera were usually numerically dominant (Fig.1). Coccolithophorids and other phytoflagellates were often present in high numbers (Table III). Under the heading “Other Forms” what were believed to be auxospores were included. In the unaltered 42 m sea water, three major groups of numerically dominant forms were observed (Fig.1). The first group (Tropidoneis, Skeletonemu, Nitzschia, Chaetoceros, and “Other Forms”) dominated throughout the year. The second group (Pseudoeunotia, Rhizosolenia, and Biddulphia) dominated during the upwelling season (September-February). The third group (Nauicula, Orthoneis, and phytoflagellates), dominated only outside of the upwelling season. The addition of nutrients or of an introduced species altered the abovedescribed pattern of dominance. Indigenous diatoms were not frequently TABLE II Diatom species observed throughout the course of study

Amphora marina(?) W. Smith A. angusta(?)Gregory Anomoeoneis serians(?)(Beb)Cleve Asterionella japonica Cleve Biddulphia sinensis(?)Grevllle Caloneis sp. Chaetoceros sp. C. didymus Ehrenberg Corethron pelagicum(?)Brun Coscinodiscus excentricus(?)Ehr. Diploneis didyma(?)(Ehr.)Cleve Endictya oceanica Ehr. Fragilaria sp. Grammatophora marina(?)(Lyng.)Kut. Gyrosigma sp. Hemiaulus sine&s Greville Lauderia borealis Grunow Leptocylindrus danicus Clev? Licmophom lyngbyei(Kut. )Grunow

Melosira suZcata(? )( Ehr. )Kut. Navicula membranacea(?)Cleve Nitzsehia closterium(Ehr.)W. Smith N. delicatula Cleve N. longissima(Bre. ex Kut.)Balfs N. panduriformis Gregory N. seriata Cleve N. sigma(Kut. )W. Smith .Orthoneis(?)sp. Pinnularia sp. Pleurosigma normanii(?)Ralfs Pseudoeunotia doliolus(Wall.)Grunow Rhizosolenia delicatula Cleve R. fragilissima Bergon Skeletonema costatum(Gre.)Cleve Synedra tabulata(?)(Ag.)Kut. Thalassionema nitzschioides Grunow ex Hustedt Thalassiosira sp. Tropidoneis lepidoptera(Greg.)Cleve

Fig.1. Seasonal phytoplankton dominance, as observed at the time of maximum diatom number, in cultures with unaltered 42 m sea water (A), nutrient-enriched 42 m sea water (B), Dunaliella added (C), Platymonaa added (D), Skeletonema added (E), and Phaeodactylum added (F). Solid black indicates that the form is among the top four most numerous forms. Where more than 4 forms are indicated, 2 or more were of equal number. “X” means observed.

6

TABLE III Maximum cell concentrations (X 10’ cells/l) and the day of occurrence and nutrient-enriched (E) 42 m sea water (A means absent) Period

May June July/August September Oct./Nov. Nov./Dee. December January February March April/May

Coccolithophorids

Phytoflagellates

U

E

U

E

2(7) I(S) A 2(7) i(7) A A A 2(S) I(7) A

5(7) l(3) 200) A 5(3) A I(5) G(7) 4(2) 3(3) A

3(7) A A A A A A A

A A A A A A A

I(S) 20(S) 23(S)

I3(3) 624(11) 174(10)

( ) in unaltered

(U)

3(S)

observed in the cultures with introduced Phaeodactylum. In the presence of Skeletonema, Caloneis, Endictya, Asterionella, Thalassionema, Fragilaria and dinoflagellates dominated. Dominant forms in the Dunaliella cultures were coccolithophorids, several of the diatoms which dominated the unaltered cultures, and Pseudoeunotiu. Dominance in the Platymonas cultures was similar to the Dunufiellu situation with the exception of the coccolithophorids, which dominated less frequently. Nuuicula, Orthoneis, Rhizosoleniu and Biddulphia (all dominants in the unaltered 42 m sea water) did not dominate in the nutrient-enriched cultures, otherwise dominance was similar to the unaltered cultures. The production of new cells by the diatoms indigenous to the contained sea water was greatest during the upwelling season (Figs 2-4). A notable exception was the high production observed during May when nitrogen and phosphorus nutrients were low but silicates high. This was the only time the unaltered and enriched tanks were essentially equal in productivity. The highest diatom level (1.7 X lo9 cells/l) was observed in the nutrient-enriched tank during January. Throughout the year the highest production by indigenous diatoms occurred in the nutrient-enriched tank, second highest in the unaltered 42 m sea water, and third highest in the tank inoculated with Skeletonemu. The other phytoplankton groups typically reached maximum cell numbers following indigenous diatom blooms; The highest levels obtained by these groups occurred during the period of no upwelling (Table III). Particulate carbon content of unaltered and nutrient-enriched tanks was determined after 0, 5 and 10 days of the April/May 1976 experiment (Table IV). Initial cell levels were high when compared with the other experi-

A

OCT,NO”

NOV/DEC

MAR/PPR

l!srcJ_ h

Fig.2. Seasonal growth curves of indigenous phytoplankton in unaltered (A) and nutrientenriched (B) 42 m sea water. Curves for the two unaltered cultures are shown separately.

mental periods. After five days, cell numbers had approximately doubled in both situations but particulate carbon had increased considerably more in the enriched tanks. By the tenth day, phytoplankton in the enriched tanks were numerically dominated by a phytoflagellate believed to be an Isochrysis

A

IA_ ::

6’

‘\,___. \ :

i

!

\

,I

4

b_ ’

8’

:

,’

.-’

/’ ,,*

:

;

: :

:

:

; : :

Fig.3. Seasonal growth curves of indigenous phytoplankton (solid line) in the presence of’ either Skeletonem (A) or Phaeoductylum (B) (broken line). species. These tanks had approximately twice the concentration of particulate carbon as the unaltered tanks. The production of new cells by the introduced species was generally highest during the season of upwelling (Figs 3 and 4). The greatest increase in

FEE

Fig.4. Seasonal growth curves of indigenous phytoplankton either Dunalieh (A) or Phtymonas (B) (broken line).

(solid line) in the presence of

cell number over the inoculated level was achieved by Phaeodactylum (7.7 X 10’ cells/l) in 4 days during NovemberDecember. On the basis of cells produced, PhaeodoctyZum had the greatest average productivity, followed in order by Platymonas, Skeletonema, and Dunaliella.

10

TABLE IV Cell concentrations (X 10’ cells/l) and particulate carbon in two unaltered and two enriched tanks during the April/May 1976 experiment Condition

Day

Diatoms

Unaltered

0 5 10

18 41 27

1 0 14

211 2450 5115

0 5 10

19 26 26

3 0 17

184 1906 3782

0 5 10

15 48 20

1 0 144

246 4898 8415

0 5 10

19 45 18

1 0 205

361 4958 9695

Enriched

Phytoflagellates

rg C/I

TABLE V Carbon concentrations and standard deviations (SD) in introduced phytoplankton cultured under culture room conditions. Determinations were made during the log phase of growth, N=5 Species

picog. C/cell

SD

Phaeodactylum tricornutum Platymonas sp. Skeletonema costatum Dunaliella tertiolecta

16.81 56.46

3.32 20.43

30.19

5.65

39.75

6.15

Conversion of cell number into particulate carbon, using values obtained during the log phase of growth under culture room conditions, alters the pattern of productivity described above (Table V). On the basis of particulate carbon production, Platymonas had the highest mean rate of production, followed in order by Phaeodactylum, Dunaliella, and Skeletonema. DISCUSSION

The sea water near Arraial do Cabo cycles through a summer season of upwelling, characterized by low temperatures and relatively high nutrients, and a winter season of no upwelling characterized by high temperatures and low nutrients. The deep seawater environment of these studies differed from tests in natural conditions in that seasonal temperature differences were lessened;

11

more solar energy was available; constant, vigorous aeration was provided; and none of the photosynthetically fixed carbon could settle out of the tanks. In situ natural phytoplankton (0 to 50 m depth) in the vicinity of Ilha Cabo Frio had a greater diatom diversity (151 spp.) and lower cell concentrations (maximum l-2 X 10’ cells/l) than were achieved in the experimental tanks (Macedo et al., 1975). Further, only 3 (Pseudoeunotiu, Rhizosolenia, Nitzschiu) of the 13 naturally dominant forms dominated the cultures. Experimental cultures were usually dominated by pennate diatoms. This same pattern was observed in a continuous flow culture, employing sewageenriched sea water (Dunstan and Menzel, 1974). The addition of nutrients or of an introduced phytoplankton species influenced the expression of dominance by the indigenous forms. This was most pronounced in the Phaeodactylum cultures, where indigenous diatoms were often absent. Goldman and Stanley (1974) observed Phaeodactylum tricornutum dominating continuous flow cultures. The greatest growth of indigenous diatoms occurred during the season of upwelling, and the greatest growth within the various situations tested occurred in the nutrient-enriched cultures (average 61 X 10’ cells/l). This was approximately twice the cell concentration noted in the unaltered 42 m sea water (average 28 X 10’ cells/l). These values compare favourably with those obtained by Dunstan and Menzel(l974) in a continuous culture system using sewage as a nutrient supplement (1 X lOa cells/l); and Cruz and Alfonso (1975) who employed closed nutrient-enriched cultures of Dunaliella (1.1 X lo6 cells/l) and Nunnochrysis (1.8 X 10’ cells/l). After 10 days, during April 1976, the cultures had increpsed by approximately 3.5 mg C/l (unaltered tanks) and 7.1 mg C/l (enriched tanks). These values greatly exceeded those found naturally (0.1-0.5 mg C/l, Parsons and Takahashi, 1973). In part, this difference reflected the closed nature of the system which did not allow for loss by settling. In partially continuous systems, lower values of particulate carbon are common. Dunstan and Menzel (1974) recorded levels of about 0.1 mg C/l using diluted sewage (indigenous diatoms, turnover rate 0.25/day); Kabanova and Borodkin (1976) recorded 0.3 mg C/l in Caribbean surface water enriched with deep water (indigenous phytoplankton, turnover rate 0.2/day); and Malone et al. (1975) recorded approximately 4.8 mg C/l in Antarctic Intermediate Water fortified with an EDTA-trace metal vitamin mix (Chaetoceros, turnover rate 0.5/day). Generally, the introduced phytoplankton grew well. However, the species were in competition with the indigenous forms and, with the exception of Phaeodactylum, they gave way to the natural populations after an early bloom.

ACKNOWLEDGEMENTS

This research was financed by F.I.N.E.P. (Brazil). We are grateful to E. Macedo for her assistance in the identifications, A. Jacob for the chemical

12

analyses, E. Rodriguez, I. Diniz and E. Vergara for field assistance, D.R. Pace for many helpful suggestions, H. Margalef and F.J.R. Taylor for reviewing parts of this study, and P.C. Moreira da Silva for his support and encouragement.

REFERENCES Cruz, S.A. and Alfonso, E., 1975. Cultivo masivo de algas planctonicas marinas mediante fertilization. Universidad de la Habana, Serie 8, Investigaciones Marinas. No.17, 25 pp. Dunstan, W.M. and Menzel, D.W., 1974. Continuous cultures of natural populations of phytoplankton in dilute, treated sewage effluent. Limnol. Oceanogr., 16: 623-632. Goldman, J.C. and Stanley, H.I., 1974. Relative growth of different species of marine algae in waste water-sea water mixtures. Mar. Biol., 28: 17-25. Kabanova, Yu.G. and Borodkin, SO., 1976. Effect of mineral nutrition on photosynthesis and production of phytoplankton (Caribbean Sea). Oceanology (U.S.S.R.), 15: 351-364. Macedo, F.E., 1974. 0 plancton na ressurg&icia de Cabo Frio (Brasil). III Primeiras observa@es sobre o microfitoplancton. Inst. Pesq. Marinha. Rio de Janeiro. Brasil. No.84, 10 pp. Macedo, F.E., Tenenbaum, D.R. and Valentin, J., 1975. 0 plancton na ressurgsncia de Cabo Frio (Brasil). VI. ComposiqZo floristica e suas varia$es de comportamento nas aquas da esta@o fixa ocbanica; Inst. Pesq. Marinha. Rio de Janeiro. Brasil No.87, 9 pp. Malone, T.C., Garside, C., Haines, K.C. and Roels, O.A., 1975. Nitrate uptake and growth of Chaetoceros sp. in large outdoor continuous cultures. Limnol. Oceanogr., 20: 9-19. Moreira Filho, H., 1964. ContribuiCZo as estudo das diatomaceas da Regizo de Cabo Frio. Bol. Univ. Parana, Bol. 14,ll pp. Moreira Filho, H., 1966. Contribui@o as estudo das Bacillariophyceae (diatomaceas) no agar-agar (gelosa) e agarofitos. Bol. Univ. Parana, Bo1.16, 55 pp. Moreira Filho, H. and Kutner, M.B., 1962. Contribui$o para o conhecimento das diatomaceas do Manguesal de Alexandra, Parana, Brasil. Bol. Univ. Parana, Bo1.14, 24 PP. Moreira da Silva, P.C., 1971. Fertilization of the sea as a by-product of an industrial utilization of deep water. In: J.D. Costlow, Jr. (Editor), Fertility of the Sea, Vol.11. Gordon and Breach Science Publishers, New York, pp.463-468. Parsons, T. and Takahashi, M., 1973. Biological Oceanographic Processes. Pergamon Press, Oxford, 186 pp. Strickland, J.D.H. and Parsons, T.R., 1968. A manual of seawater analysis. Fish. Res. Board Can. Bu11.125, 185 pp. ’ Valentim, J., Macedo, F.E., Monteiro, W.M. and Mureb, M.A., 1975. 0 plancton na ressurggncia de Cabo Frio. V. An$ilise comparativa entre duas esta&Ies da baia de Arraial do Cabo e uma esta&o fixa ocbanica. Inst. Pesq. Marinha. Rio de Janeiro. Brasil No.86, 11 PP.