Global warming and eutrophication in fresh and coastal waters may mutually reinforce the symptoms they express and thus the problems they cause.

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The distribution of diatoms with respect to salinity and ionic gradients was studied in lakes of the northern Great Plains of North America. The lakes range from freshwater to hypersaline (0.65–270 g∙L−1) and include a variety of brine types, although the majority are dominated by sulfate salts. Canonical correspondence analysis of diatoms in the surface sediments of 66 lakes and associated water chemistry data indicates that diatom distributions are highly correlated with salinity. The ordination also suggests that brine type forms a significant environmental gradient and separates taxa characteristic of bicarbonate/carbonate lakes from those of sulfate-dominated systems. The salinityoptima and tolerances of diatom species are calculated by weighted averaging regression, and these data provide a tool for the reconstruction of past salinity and the inferance of climatic change in arid and semiarid regions.

Climate change is expected to modify rainfall, temperature and catchment hydrological responses across the world, and adapting to these water-related changes is a pressing challenge. This paper reviews the impact of anthropogenic climate change on water in the UK and looks at projections of future change. The natural variability of the UK climate makes change hard to detect; only historical increases in air temperature can be attributed to anthropogenic climate forcing, but over the last 50 years more winter rainfall has been falling in intense events. Future changes in rainfall and evapotranspiration could lead to changed flow regimes and impacts on water quality, aquatic ecosystems and water availability. Summer flows may decrease on average, but floods may become larger and more frequent. River and lake water quality may decline as a result of higher water temperatures, lower river flows and increased algal blooms in summer, and because of higher flows in the winter. In communicating this important work, researchers should pay particular attention to explaining confidence and uncertainty clearly. Much of the relevant research is either global or highly localized: decision-makers would benefit from more studies that address water and climate change at a spatial and temporal scale appropriate for the decisions they make.