Periodic Reporting for period 1 - OSTRAP (Developing an independent measure of lake eutrophication: P, Cd & U in ostracod shells)
Reporting period: 2021-09-01 to 2023-08-31
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). OSTRAP is developing a method to reconstruct eutrophication with
a direct, quantifiable and independent measure of P via analysis of ostracod (small bivalved crustaceans) shell chemistry. During OSTRAP, the potential for ostracod shell chemistry to reconstruct P concentrations over the past ~200 years using well-dated lake sediment cores and complementary eutrophication indicators has been demonstrated. This is 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.
a direct, quantifiable and independent measure of P via analysis of ostracod (small bivalved crustaceans) shell chemistry. During OSTRAP, the potential for ostracod shell chemistry to reconstruct P concentrations over the past ~200 years using well-dated lake sediment cores and complementary eutrophication indicators has been demonstrated. This is 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.
Monthly field collections show that there is a statistically significant positive relationship between soluble reactive phosphate (SRP) and the P/Ca of water. Currently, there is insufficient ostraocd data from field collections to establish a robust calibration curve, but there are indications that a relationship between the P/Ca concentration of ostracod shells and the P/Ca of water exists. Palaeo-phosphorus reconstructions have been completed for a UK site from 2008 to 1828. The reconstructions have been compared with a suite of more traditional methods. The ostracod P/Ca method shows potential to quantitively reconstruct tipping points in shallow lakes and to provide more high-resolution reconstructions than the sometimes ‘smoothed’ trends seen in other geochemical proxies (e.g. sedimentary P concentrations).
The project results will contribute towards the implementation of the EU Water Framework Directive (WFD). The WFD has required all water bodies in the EU to reach “good ecological status” or, where significant anthropogenic modification has already occurred, “good ecological potential”. To meet good ecological status, water bodies must not be significantly altered from pre-defined “reference conditions”, which are the conditions expected in the absence of anthropogenic impacts. Currently, the implementation of the WFD is limited by the absence of a robust method to reconstruct nutrient enrichment and define restoration targets. OSTRAP will provide the first direct quantitative means of palaeo-P that can be used to define realistic restoration targets. In addition to the WFD, OSTRAP will contribute as the UK seeks to establish its own alternative to the EU WFD.