A supplement to the amphipod (Crustacea) species inventory of Helgoland (German Bight, North Sea): indication of rapid recent change

Abstract

The surroundings of the rocky island of Helgoland (German Bight, south-western North Sea) are one of the best-studied sites in European seas with species occurrence data available for nearly 150 years. As the area is strongly affected by global change (e.g. increase in mean sea surface temperature at Helgoland by 1.67°C since 1962), ecosystem structure and function are expected to change more than those of average marine systems. The paper presents a supplement to the local amphipod species inventory (5 nautical miles around the island). At least seven species of this ecologically important taxon seem to have newly established themselves at Helgoland since the late 1980s: Ampelisca typica, Amphilochus brunneus, Caprella mutica, Cheirocratus assimilis, Monocorophium acherusicum, Orchestia mediterranea and Orchomenella crenata. Most of them are not only new for the Helgoland area, but also for the German Bight; and two species (Amphilochus brunneus and Orchomenella crenata) are even new to the North Sea as a whole. Out of the seven new species, one (Caprella mutica) is a neozoon from the north-western Pacific. The other six species show clear warm water affinities (oceanic–Lusitanian species) which suggest a recent range expansion in the context of climate warming. The establishment of an increasing number of species formerly probably absent from the area does not seem to be compensated by losses of species, so that local species diversity is expected to increase.