TY - JOUR

T1 - Qualitative importance of the microbial loop and plankton community structure in a eutropic lake during a bloom of Cyanobacteria

AU - Christoffersen, K.

PY - 1990

Y1 - 1990

N2 - Plankton community structure and m~or pools and fluxes ofcarbon were observed before and after culmination of a bloom of cyanobacteriain eutrophic Frederiksborg Slotsso, Denmark. Biomass changes ofheterotrophic nanoflagellates, ciliates, microzooplankton (50 to 140 urn),and macrozooplankton (larger than 140 Urn) were compared to phytoplanktonand bacterial production as well as micro- and macrozooplanktoningestion rates of phytoplankton and bacteria. The carbon budget was usedas a means to examine causal relationships in the plankton community.Phytoplankton biomass decreased and algae smaller than 20 um replacedAphanizornenon after the culmination of cyanobacteria. Bacterial net productionpeaked shortly after the culmination of the bloom (510 ug C liter- 1d-') and decreased thereafter to a level of approximately 124 gg C liter-'d -~. Phytoplankton extracellular release of organic carbon accounted foronly 4-9% of bacterial carbon demand. Cyclopoid copepods and smallsizedcladocerans started to grow after the culmination, but food limitationprobably controlled the biomass after the collapse of the bloom. Grazingof micro- and macrozooplankton were estimated from in situ experimentsusing labeled bacteria and algae. Macrozooplankton grazed 22% of bacterialnet production during the bloom and 86% after the bloom, while microzooplankton(nauplii, rotifers and ciliates larger than 50 Urn) ingested lowamounts of bacteria and removed 10-16% of bacterial carbon. Both macroandmicrozooplankton grazed algae smaller than 20 urn, although they didnot control algal biomass. From calculated clearance rates it was foundthat heterotrophic nanoflagellates (40--440 ml -t) grazed 3--4% of the bacterialproduction, while ciliates smaller than 50 um removed 19-39% ofbacterial production, supporting the idea that ciliates are an important linkbetween bacteria and higher trophic levels. During and after the bloom ofAphanizornenon, major fluxes of carbon between bacteria, ciliates and crustaceans were observed, and heterotrophic nanoflagellates played a minorrole in the pelagic food web

AB - Plankton community structure and m~or pools and fluxes ofcarbon were observed before and after culmination of a bloom of cyanobacteriain eutrophic Frederiksborg Slotsso, Denmark. Biomass changes ofheterotrophic nanoflagellates, ciliates, microzooplankton (50 to 140 urn),and macrozooplankton (larger than 140 Urn) were compared to phytoplanktonand bacterial production as well as micro- and macrozooplanktoningestion rates of phytoplankton and bacteria. The carbon budget was usedas a means to examine causal relationships in the plankton community.Phytoplankton biomass decreased and algae smaller than 20 um replacedAphanizornenon after the culmination of cyanobacteria. Bacterial net productionpeaked shortly after the culmination of the bloom (510 ug C liter- 1d-') and decreased thereafter to a level of approximately 124 gg C liter-'d -~. Phytoplankton extracellular release of organic carbon accounted foronly 4-9% of bacterial carbon demand. Cyclopoid copepods and smallsizedcladocerans started to grow after the culmination, but food limitationprobably controlled the biomass after the collapse of the bloom. Grazingof micro- and macrozooplankton were estimated from in situ experimentsusing labeled bacteria and algae. Macrozooplankton grazed 22% of bacterialnet production during the bloom and 86% after the bloom, while microzooplankton(nauplii, rotifers and ciliates larger than 50 Urn) ingested lowamounts of bacteria and removed 10-16% of bacterial carbon. Both macroandmicrozooplankton grazed algae smaller than 20 urn, although they didnot control algal biomass. From calculated clearance rates it was foundthat heterotrophic nanoflagellates (40--440 ml -t) grazed 3--4% of the bacterialproduction, while ciliates smaller than 50 um removed 19-39% ofbacterial production, supporting the idea that ciliates are an important linkbetween bacteria and higher trophic levels. During and after the bloom ofAphanizornenon, major fluxes of carbon between bacteria, ciliates and crustaceans were observed, and heterotrophic nanoflagellates played a minorrole in the pelagic food web

M3 - Journal article

VL - 20

SP - 253

EP - 272

JO - Microbial Ecology

JF - Microbial Ecology

SN - 0095-3628

ER -