Abstract
Zooplankton species diversity in the Celtic Sea in August 1982 was low; two species of copepod and two species of euphausiid accounted for 90 to 95% of the biomass sampled by a 280 μm-mesh net. Some 75% of the primary production was by phytoplankton smaller than 5 μm. The demands of both the macrozooplankton and the microzooplankton have been examined. If it is assumed that macrozooplankton cannot efficiently graze particles smaller than 5 μm, there was insufficient primary production to meet the demands of the copepods and euphausiids; however, there would have been sufficient if these animals could graze phytoplankton 5 to 1 μm. Ciliates were in competition with the macrozooplankton for phytoplankton and could not have been significant grazers of bacterial biomass. The majority of microflagellates were autotrophic; less than 10% of the population did not possess a chloroplast and were presumably heterotrophs. Bacterial production was low and was insufficient to meet the demands of the heterotrophic microflagellates, but there was sufficient production by the picophytoplankton to meet microflagellate requirements. The data do not appear to support the ideas of a significant flow of energy through the “microbial loop” in the Celtic Sea in August.
Similar content being viewed by others
Literature cited
Azam, F., T. Fenchel, J. C. Field, J. S. Gray, L. A. Meyer-Reil and F. Thingstad: The ecological role of water-column microbes in the sea. Mar. Ecol. Prog. Ser. 10, 257–263 (1983)
Azam, F. and J. A. Fuhrman: Measurement of bacterioplankton growth in the sea and its regulation by environmental conditions. In: Heterotrophic activity in the sea, pp 179–196. Ed. by J. E. Hobbie and P. J. LeB. Williams. New York: Plenum Press 1984
Bartram, W. C.: Experimental development of a model for the feeding of neritic copepods on phytoplankton. J. Plankton Res. 3, 25–51 (1980)
Conover, R. J.: Feeding interactions in the pelagic zone. Rapp. P.-v. Réun. Cons. perm. int. Explor. Mer 173, 66–76 (1978)
Conover, R. J.: Nutritional strategies for feeding on small suspended particles. In: Analysis of marine ecosystems, pp 363–395. Ed. by A. R. Longhurst. London: Academic Press 1981
Davies, J. M. and P. J. LeB. Williams: Verification of 14C and O2 derived primary organic production measurements using an enclosed ecosystem. J. Plankton Res. 6, 457–474 (1984)
Fenchel, T.: Suspension feeding in ciliated Protozoa: feeding rates and their ecological significance. Microb. Ecol. 6, 13–25 (1980)
Fenchel, T.: Ecology of heterotrophic microflagellates. II. Bioenergetics and growth. Mar. Ecol. Prog. Ser. 8, 225–231 (1982)
Fenchel, T. and B. J. Finlay: Respiration rates in heterotrophic, free-living Protozoa. Microb. Ecol. 9, 99–122 (1983)
Frost, B. W.: Effects of size and concentration of food particles on the feeding behaviour of the marine planktonic copepod Calanus pacificus. Limnol. Oceanogr. 17, 805–815 (1972)
Hardy, A. C.: The herring in relation to its animate environment. Part I. The food and feeding habits of the herring. Fishery Invest., Lond. (Ser. 2) 7, (3), 1–53 (1924)
Holligan, P. M., R. P. Harris, R. C. Newell D. S. Harbour, R. N. Head, E. A. S. Linley, M. I. Lucas, P. R. G. Tranter and C. M. Weekley: Vertical distribution and partitioning of organic carbon in mixed, frontal and stratified waters of the English Channel. Mar. Ecol. Prog. Ser. 14, 111–127 (1984a)
Holligan, P. M., P. J. LeB. Williams, D. A. Purdie and R. P. Harris: Photosynthesis, respiration and nitrogen supply of plankton population in stratified, frontal and tidally mixed shelf waters. Mar. Ecol. Prog. Ser. 17, 201–213 (1984b)
Johnson, P. W., X. Huai-shu and J. McN. Sieburth: The utilization of chroococcoid cyanobacteria by marine protozooplankters but not by calanoid copepods. Annls Inst. océanogr., Paris (N.S.) 58, 297–308 (1982)
Joint, I. R. and R. J. Morris: The role of bacteria in the turnover of organic matter in the sea. Oceanogr. mar. Biol. A. Rev. 20, 65–118 (1982)
Joint, I. R. and R. K. Pipe: An electron microscope study of a natural population of picoplankton from the Celtic Sea. Mar. Ecol. Prog. Ser. 20, 113–118 (1984)
Joint, I. R. and A. J. Pomroy: Production of picoplankton and small nanoplankton in the Celtic Sea. Mar. Biol. 77, 19–27 (1983)
Jørgensen, C. B.: Fluid mechanical aspects of suspension feeding. Mar. Ecol. Prog. Ser. 11, 89–103 (1983)
Koehl, M. A. R. and J. R. Strickler: Copepod feeding currents: food capture at low Reynolds number. Limnol. Oceanogr. 26, 1062–1073 (1981)
Lasker, R.: Feeding, growth, respiration and carbon utilization of a euphausiid crustacean. J. Fish. Res. Bd Can. 23, 1291–1317 (1966)
Marshall, S. M. and A. P. Orr: On the biology of Calanus finmarchicus IX. Feeding and digestion in the young stages. J. mar. biol. Ass. U.K. 35, 587–603 (1956)
Paffenhöffer, G.-A.: Grazing and ingestion rates of nauplii, copepodids and adults of the marine planktonic copepod Calanus helgolandicus. Mar. Biol. 11, 286–298 (1971)
Sieburth, J. McN. and P. G. Davis: The role of heterotrophic nanoplankton in the grazing and nurturing of planktonic bacteria in the Sargasso and Caribbean Seas. Annls Inst. océanogr., Paris (N.S.) 58, 285–296 (1982)
Simpson, J. H.: A boundary front in the summer regime of the Celtic Sea. Estuar. cstl mar. Sci. 4, 71–81 (1976)
Watson, S. W., T. J. Novitsky, I. C. Quinby and F. W. Valois: Determination of bacterial number and biomass in the marine environment. Appl. envirl Microbiol. 33, 940–946 (1977))
Williams, P. J. LeB.: Incorporation of microheterotrophic processes into the classical paradigm of the planktonic food web. Kieler Meeresforsch. 5, 1–28 (1981)
Williams, P. J. LeB., K. R. Heinemann, J. Marra and D. A. Purdie: Comparison of 14C and O2 measurements of phytoplankton production in oligotrophic waters. Nature, Lond. 305, 49–50 (1983)
Williams, R.: Vertical distribution of Calanus finmarchicus and C. helgolandicus in relation to the development of the seasonal thermocline in the Celtic Sea. Mar. Biol. 86, 145–149 (1985)
Williams, R., N. R. Collins and D. V. P. Conway: The double LHPR system, a high speed micro- and macroplankton sampler. Deep-Sea Res. 30, 331–342 (1983)
Williams, R. and N. Fragopoulu: Vertical distribution and nocturnal migration of Nyctiphanes couchi (Crustacea: Euphausiacea) in relation to the summer thermocline in the Celtic Sea. Mar. Biol. (In press). (1985)
Author information
Authors and Affiliations
Additional information
Communicated by J. Mauchline, Oban
Rights and permissions
About this article
Cite this article
Joint, I.R., Williams, R. Demands of the herbivore community on phytoplankton production in the Celtic Sea in August. Mar. Biol. 87, 297–306 (1985). https://doi.org/10.1007/BF00397809
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00397809