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Dynamics of dissolved organic car‐bon lability in a eutrophic lake
Author(s) -
Søndergaard Morten,
Hansen Benni,
Markager Stiig
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.1.0046
Subject(s) - dissolved organic carbon , eutrophication , lability , substrate (aquarium) , plankton , zooplankton , environmental chemistry , biomass (ecology) , chemistry , phytoplankton , bacterial growth , bloom , carbon cycle , grazing , environmental science , darkness , algae , ecology , biology , bacteria , botany , nutrient , biochemistry , genetics , ecosystem
The concentration of labile dissolved organic C ([DOC L ]) and the plankton community structure were measured weekly during a diatom spring bloom and the subsequent clear‐water phase in a eutrophic, temperate lake. The DOC L concentration was assessed by a bacterial regrowth method based on direct measurements of the increase in bacterial biomass and its respiratory demand. [DOC] ranged from 560 to 1,130 µ g C liter −1 and accounted for only 5–9% of total DOC. DOC L oscillated around 800 µ g C liter −1 , and the amplitude over 7‐d periods was within ± 16% of the in situ bacterial carbon demand. One period (3 weeks) with consistently increasing [DOC L ] took place concomitant with the increase in macrozooplankton and bacterial biomass. Thus, DOC L was positively related to decreases in chlorophyll and zooplankton grazing. The increase in DOC L was followed by 3 weeks with decreasing concentrations, when the relationship between DOC L and bacterial production was negative. This pattern gives support to the hypothesis that grazing is a quantitatively important process in the flow of carbon to bacteria. The variations of DOC L were analyzed with a model describing interactions among substrate, bacteria, and grazing. Short‐term (days) oscillations probably result from pulses of substrate production that are followed within a few days by bacterial uptake, and long‐term (weeks) variations are explained by a variable bacterial substrate affinity ( K m ).