Do allochthonous flows explain deviations from the Redfield ratio in lakes?

Lakes or streams show strong deviations of their stoichiometry compared to the Redfield ratio measured in oceans. Allochthonous inflows of resources might contribute to those deviations directly, by changing composition of detritus in ecosystems, but also indirectly, by shaping local community dynamics and stoichiometric constrains within aquatic ecosystems. Here, we developed a stoichiometric model to understand those direct and indirect mechanisms through which allochthonous inflows affect seston stoichiometry.

Our results emphasize that increasing allochthonous inflows promotes heterotrophic functioning, and relax decomposer' carbon limitation. This release of stoichiometric constrain of decomposers (i) destabilizes the aquatic ecosystem by promoting competition between phytoplankton and decomposers, (ii) decreases the ability of the lake to regulate allochthonous flows, and (iii) push seston stoichiometry away from the Redfield ratio. Our study emphasize how the quantity and the stoichiometry of inflows shape community dynamics and the elemental constraints within the ecosystem, and open perspectives for stoichiometry at the landscape extent.