Impact of land-derived organic matter on the allochthony, metabolism and health of crustacean zooplankton communities in boreal freshwaters

Rising surface water concentrations of brown-pigmented dissolved organic matter (DOM) is a current aspect of environmental change. The physical and chemical causes and consequences of water browning are relatively well known, but the ecological impact, e.g., on zooplankton and fish, has been less studied. This project aims at determining the impact of land-derived DOM on the performance of crustacean zooplankton – an organism group that represents a critical food web component which provides the basis for fish production in open water systems. Based on multiple isotope ratios, the degree to which terrestrial organic matter is incorporated into zooplankton biomass will be assessed along a freshwater gradient from clear-water to brown-water systems. Enzymatic assays will be used to indirectly assess the production and respiration of the zooplankton. It is expected that increases in DOM are linked to increases in zooplankton allochthony, but to decreases in health parameters such as growth efficiency (production relative to respiration) and apparent absolute production rates. The project will perform some of the first attempts ever conducted to assess the health and allochthony of crustacean zooplankton along gradients of increasing DOM.