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Lake surfaces are warming worldwide, raising concerns about lake organism responses to thermal habitat changes. Species may cope with temperature increases by shifting their seasonality or their depth to track suitable thermal habitats, but these responses may be constrained by ecological interactions, life histories or limiting resources. Here we use 32 million temperature measurements from 139 lakes to quantify thermal habitat change (percentage of non-overlap) and assess how this change is exacerbated by potential habitat constraints. Long-term temperature change resulted in an average 6.2% non-overlap between thermal habitats in baseline (1978–1995) and recent (1996–2013) time periods, with non-overlap increasing to 19.4% on average when habitats were restricted by season and depth. Tropical lakes exhibited substantially higher thermal non-overlap compared with lakes at other latitudes. Lakes with high thermal habitat change coincided with those having numerous endemic species, suggesting that conservation actions should consider thermal habitat change to preserve lake biodiversity.

AbstractClimate change impacts include such an overwhelming number of facets that the extent of references is impossible to cover. The selection presented in this review on global warming is presumably subjective, although the author has tried to assemble relevant and/or most recent information. The references specified should be regarded as examples that direct the reader to more information on a specific subject.

Abstract:: The hypothesis that both photosynthesis and pigment pattern are more reflective of size related strategies than taxonomic composition of the assemblages was tested under natural conditions in alpine lakes during fall 1999. The small size fraction (< 10 μm) in Lake Lucerne, Mondsee and Traunsee and in an additional incubator experiment contributed 55-67 % to the total integral of chlorophyll-a and photosynthesis per m2. The photosynthetic depression induced by UV-A in Lake Lucerne, measured during the 7th GAP-workshop, markedly increased to 65 % with PAR up to 500 μmol m-2 s-1. At super-saturating light intensities near the surface, UV-A inhibition further increased marginally to 69 %. Effects of light acclimation and pigment adaptation on photosynthetic rates and efficiencies of phytoplankton indicated size related strategies that were more important than the taxonomic composition of the assemblage measured in Traunsee and Mondsee. Algal communities and small size fractions (<10 μm), that had a high maximum light utilisation coefficient (*) were adapted to low light by high ratios of chlorophyll-a to photo-protective -carotene. Algae at high solar radiation and of large size (>10 μm) were photosynthetically less efficient but high light adapted having low ratios of chlorophyll-a to -carotene. In contrast to low light adapted small cells the high light adapted large-cells increased their relative proportion of photo-protective carotenoids above saturating light levels. At light limitation in deeper water layers lipophilic accessory photo-synthetic versus photo-protective pigments increased for all fractions.

Epilithic diatom assemblages were analysed in 1988 from an artificial flood-water impoundment and the river Danube to assess water quality using the differentiating species concept. Results were consistent and in agreement with other independent chemical and biological measurement of water quality, but at times indicated more subtle changes in trophic status. We concluded that photolithoautotrophic organisms such as benthic diatoms, which react more directly to nutrient concentrations and supply, are useful indicators of trophy and pollution in both running waters and in impoundments.