ECOLOGY OF POLYCHAETES OF THE HELGOLAND ROCKY INTER-TIDAL

The ecology and distribution of the polychaetes inhabiting the rocky interidal zone of the island of Helgoland (German Bight, North Sea) were studied at five ecologically different stations. Scolelepis squamata, Microphthalmus sczelkowii and Ophryotrocha gracilis were the only typical intertidal polychaetes observed. Of the 53 polychaete species documented, eight were recorded for the first time in the German Bight. Two species and one subspecies had not been described previously. The following invironmental variables were measured and, where possible, related to the occurrence of the polychaetes: pH, redox potential, O2 diffusion rate, temperature, salinity, particle-size distribution, and amount of organic particles. In the investigation area the number of species and their frequency maxima increase horizontally from east to west. This appears to be due to the increasing diversity of microhabitats in the substratum, as well as to conditions of O2 supply or H2S presence. Vertically, the number of species increases with water depth. The potential effects of temperature and salinity on the distribution patterns are discussed. © 1979 Biologischen Anstalt Helgoland.