April 2003
Regional warming-induced species shift in NW Mediterranean marine caves The north-western Mediterranean Sea has a high biodiversity reflecting a mixture of temperate and subtropical species. But this basin already shows signs of large-scale warming. Marine cave communities with endemic and specialised species are particularly at risk since they are naturally fragmented and more sensitive to perturbations.In the April issue of Ecology Letters, Chevaldonn� and Lejeusne found the first convincing illustration that climate change is directly affecting marine organisms. They monitored two species of endemic cave mysids (small shrimp-like crustaceans) near Marseille, France, and demonstrated that they have different tolerances to temperature. During recent episodes of unusually warm weather, populations of the cold-loving species were replaced by congeners of warmer affinities. However, the geographical context of the Mediterranean makes it impossible for such "cold-water" species already trapped in the northernmost, coldest parts of this sea to migrate northward. A significant component of the Mediterranean biodiversity is clearly already under the threat of global warming. | |