Impacts of epilimnetic metazooplankton on recycling and sedimentation of carbon, nitrogen and phosphorus in a pelagic stratified ecosystem

Nutritional ressources for consumers are not always equilibrate in nature. This is particularly true for herbivorous zooplankton feeding on nutrient-deficient algae. Cladocerans for example, and particularly the species of the genus Daphnia, have large demands in phosphorus (P) while summer algal planktonic assemblages are often P-deficient. This mismatch between requirements and supplies observed for the quantitatively most important trophic relationship of a lake is not without consequences. Firstly, for the growth of zooplankton which can be reduced. Secondly, for the primary producers which have limited access to dissolved nutrients stored by the large demands of grazers. And thirdly, for the entire ecosystem, with modifications of some major biogeochemical cycles.
Our project deals with some questions brought up by this problematic :
1) what are the behavioural and physiological responses that herbivorous zooplankton may engage to decrease this mismatch between requirements and supplies and its impacts '
2) if nevertheless the consumer undergoes large imbalance, may we observe some impacts on its reproductive potential in the field '
3) what is the future of the elements which are, at the opposite, in excess in the food ' Are they confine in sedimenting particles, such as feces, or are they recycled to a dissolved form available for autotroph or heterotroph organisms '
The answers that our project aims to resolve will be coming from laboratory experiments (1 and 3), from theoretical modelisation (1), and from field observations and experimentations in the Esch-sur-Sûre reservoir (Grand-Duchy of Luxemburg) (2 and 3).