Developing an independent measure of lake eutrophication: P, Cd & U in ostracod shells

ended

Shallow lakes provide extensive ecosystem services and are ecologically important non-marine resources, supporting a diverse flora and fauna. However, worldwide lakes are threatened by environmental degradation (e.g. nutrient pollution from agricultural fertilizers). The restoration of these environments is critical for future biodiversity, resilience to climate change, the provision of ecosystem services, and is legally binding under the EU Water Framework Directive (WFD).To meet the requirements of ‘good ecological status’, lakes must not be significantly altered from pre-defined ‘reference conditions’, which are the conditions expected in the absence of anthropogenic impacts. Due to limited long-term ecological monitoring data that covers centennial time-scales, palaeolimnology has been suggested as an alternative to define reference conditions for effective restoration. Existing approaches (e.g. diatom transfer functions) for reconstructing nutrient enrichment are, however, problematic due to their indirect approach that involves major assumptions. Multi-proxy studies attempt to disentangle drivers, but fail due to the lack of an independent measure of phosphate (P). Here, I propose a method to reconstruct eutrophication with a direct, quantifiable and independent measure of P via analysis of ostracod (small bivalved crustaceans) shell chemistry. To produce robust, quantitative palaeo-P reconstructions based on fossil ostracod shells, the research will combine laboratory, mesocosm and field experiments to establish calibrations in controlled and natural settings. I will demonstrate the quantitative reconstruction of P concentrations over the past ~200 years using well-dated lake sediment cores from sites across Europe. This project will be a significant advancement in the ability to 1) set reference condition P concentrations for shallow lake restoration targets under the WFD and 2) to predict the effects of future climate change on freshwater biodiversity.