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Fluxes of free amino acids in three Danish lakes
Author(s) -
JøRGENSEN NIELSO. G.
Publication year - 1986
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1986.tb00969.x
Subject(s) - phytoplankton , diel vertical migration , environmental chemistry , zooplankton , eutrophication , assimilation (phonology) , dissolved organic carbon , moss , amino acid , plankton , heterotroph , chemistry , ecology , environmental science , biology , nutrient , bacteria , biochemistry , linguistics , philosophy , genetics
SUMMARY. 1. Heterotrophic assimilation rates and concentrations of dissolved free amino acids (DFAA) were followed during diel studies in the eutrophic Lake Mossø, Lake Esrom and Lake øm in spring and summer in 1982. In all three lakes, three to four fold diel variations in concentrations and assimilation rates were measured. These fluctuations appeared to be iindependent of phytoplankton and bacteria production. Pools of DFAA varied from 380 nM (Lake Mossø) to 2430 nM (Lake ørn), with serine, glycine, alanine and ornithine as dominant free amino acids. 2. When similar water samples were incubated in a natural light‐dark cycle or in total darkness, different pools of DFAA were measured in light and dark. 3. Decomposition of organic matter or zooplankton activity (rather than e.g. phytoplankton exudates) appear to be responsible for the concentration changes. 4. Observed discrepancies between simultaneous concentration changes and assimilation rates are discussed in relation to the applied tracer procedure and the concentration measurements. 5. Assimilation of DFAA sustained from 6% to 25% of the bacterial carbon requirement, corresponding to 2–12% of the phytoplankton production in the lakes.