Global warming benefits small fish

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One unintended consequence of global warming is a shrinking in size of the aquatic organisms, according to research published in a recent issue of the Proceedings of the National Academy of Sciences.

The study by French and German scientists Martin Daufresne, Kathrin Lengfellner and Ulrich Sommer examined the effects of elevated global temperatures on freshwater fishes in large French rivers, fishes in the North Sea, and herring and sprat in the Baltic Sea (by analysing sampling and fisheries data over a period of 14 to 31 years).

They also studied the effects of elevated temperatures on bacteria and plankton in temperature-controlled mecocosms.

The authors found a correlation between increasing global temperatures and decreasing body size in the aquatic organisms studied.

They surmise that there are three possible mechanisms at work to account for this phenomenon: (1) small-sized species become more abundant within the community; (2) the average size within any given species decreases and (3) sexual maturity is achieved with a smaller body size.

Although studies have shown that increased global temperatures have led to a shift of species ranges toward higher altitudes and latitudes and seasonal shifts in life-cycle events, this is the first study to suggest a reduction in body size to be a universal ecological response to global warming.

For more information, see the paper: Daufresne, M, K Lengfellner and U Sommer (2009) Global warming benefits the small in aquatic ecosystems. Proceedings of the National Academy of Sciences 106, pp. 12788"12793.