Spatial and temporal variability of pelagic and benthic organic matter composition in lake

As part of the QUALILAC project (Influence of the watershed on the functioning of lakes: importance of nutritional quality for couplings between benthic and pelagic environments), monitoring of the origin, quantity and quality of organic matter (OM) available at the water column and benthic level was carried out on Remoray, Bonlieu, Retournemer and Longemer lakes at 2 or 3 points in their deep zone (monthly monitoring for the water column, quarterly monitoring in sediment traps at the benthic level).
The origin of the MO is evaluated using C/N ratios and the isotopic signature of the carbon (δ13C). The amount of MO is estimated by measuring the organic carbon content. Finally, the quality of the OM is estimated using C/N/P ratios and the content of polyunsaturated fatty acids.
Measurements of pH, temperature, dissolved oxygen concentration were also taken monthly along the water column in the deep zone of each lake.
This work should allow us to see if there is seasonal variability in the composition of OM at the water column and sediment level, and to see to what extent the quality of OM at the sediment level is influenced by the quality of the OM in the water column.
We will also be able to evaluate the relevance of the use of certain sedimentary markers (e.g., carbon isotopic signature) in studying the current and past functioning of lakes.