TY - JOUR

T1 - Pelagic food web processes in an oligotrophic lake

AU - Søndergaard, Morten

AU - Riemann, Bo

AU - Jensen, Lars Møller

AU - Jørgensen, Niels O.G.

AU - Bjørnsen, Peter K.

AU - Olesen, Michael

AU - Larsen, Jens B.

AU - Geertz-Hensen, Ole

AU - Hansen, Jan

AU - Christoffersen, Kirsten

AU - Jespersen, Anne Mette

AU - Andersen, Flemming

AU - Bosselmann, Suzanne

PY - 1988/7

Y1 - 1988/7

N2 - Major pelagic carbon pathways, including primary production, release of extracellular products (EOC), bacterial production and zooplankton grazing were measured in oligotrophic Lake Almind (Denmark) and in enclosures (7 m3) subjected to artificial eutrophication. Simultaneous measurements at three days interval of carbon exchange rates and pools allowed the construction of carbon flow scenarios over a nineteen day experimental period. The flow of organic carbon was dominated by phytoplankton EOC release, which amounted from 44 to 58% of the net fixation of inorganic carbon. Gross bacterial production accounted for 33 to 75% of the primary production. The lower values of EOC release (44%) and bacterial production (33%) were found in the enclosures with added nutrients. The release of recently fixed photosynthetic products was the most important source of organic carbon to the bacterioplankton. Uptake of dissolved free amino acids was responsible for 52 to 62% of the gross bacterial production. Thus, amino acids constituted a significant proportion of the EOC. Zooplankton (< 50 μm) grazing on algae and bacteria accounted only for a minor proportion of the particulate production in May. Circumstantial evidence is presented that suggests the chrysophycean alga Dinobryon was the most important bacterial remover. The results clearly demonstrated EOC release and bacterial metabolism to be key processes in pelagic carbon cycling in this oligotrophic lake.

AB - Major pelagic carbon pathways, including primary production, release of extracellular products (EOC), bacterial production and zooplankton grazing were measured in oligotrophic Lake Almind (Denmark) and in enclosures (7 m3) subjected to artificial eutrophication. Simultaneous measurements at three days interval of carbon exchange rates and pools allowed the construction of carbon flow scenarios over a nineteen day experimental period. The flow of organic carbon was dominated by phytoplankton EOC release, which amounted from 44 to 58% of the net fixation of inorganic carbon. Gross bacterial production accounted for 33 to 75% of the primary production. The lower values of EOC release (44%) and bacterial production (33%) were found in the enclosures with added nutrients. The release of recently fixed photosynthetic products was the most important source of organic carbon to the bacterioplankton. Uptake of dissolved free amino acids was responsible for 52 to 62% of the gross bacterial production. Thus, amino acids constituted a significant proportion of the EOC. Zooplankton (< 50 μm) grazing on algae and bacteria accounted only for a minor proportion of the particulate production in May. Circumstantial evidence is presented that suggests the chrysophycean alga Dinobryon was the most important bacterial remover. The results clearly demonstrated EOC release and bacterial metabolism to be key processes in pelagic carbon cycling in this oligotrophic lake.

KW - bacterial production

KW - extracellular release

KW - pelagic carbon budgets

KW - primary production

UR - http://www.scopus.com/inward/record.url?scp=0007908962&partnerID=8YFLogxK

U2 - 10.1007/BF00005945

DO - 10.1007/BF00005945

M3 - Journal article

AN - SCOPUS:0007908962

VL - 164

SP - 271

EP - 286

JO - Journal of Aquatic Ecosystem Health

JF - Journal of Aquatic Ecosystem Health

SN - 0018-8158

IS - 3

ER -