Deliverable 3.12

Abstract: Review on processes and effects of temperature regimes in lakes and threats due to climate change on current adaptive management and restoration efforts.

Warming exacerbate some symptoms of eutrophication in both cold and warm climates. The structure and functioning of cold temperate shallow lakes are expected to become more similar to those of (sub)tropical shallow lakes, as the temperature increase will enhance the top-down controls of omnivorous and benthivorous fish as well as the nutrient cycling. We found profound changes in fish assemblage composition, size and age structure during recent decades and a shift towards higher dominance of eurythermal species and small individuals occurring in high abundance.

The shift has occurred despite an overall reduction in nutrient loading that should have benefited the fish species typically inhabiting cold-water low-nutrient lakes and larger-sized individuals. The response of fish to the warming in recent decades has been surprisingly strong, making them ideal sentinels for detecting and documenting climate-induced modifications of freshwater ecosystems.

We can expect cascading effect of the fish down through the food-web, leading to higher abundance of phytoplankton and cyanobacteria, the latter further stimulated by higher temperatures and in deep lakes more stable and longer stratification. In addition, macrophytes will be a less efficient refuge for zooplankton further reducing the grazing capacity of zooplankton on phytoplankton.

Therefore, the critical loading for good ecological status (WFD) in lakes has to be lowered in a future warmer climate. This calls for adaptation measures, which should include more sustainable agriculture, improved nutrient and soil management with less loss of nutrients to surface waters, reduced loading from point sources and, where appropriate, re-establishment of lost wetlands, riparian buffer zones and re-meandering of channelized streams.

This deliverable include four review papers/book chapters on climate effects on lakes and the needs for adaptation.

Link http://www.refresh.ucl.ac.uk/webfm_send/1790

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