The recolonization potential of Metridium senile in an area previously depopulated by oxygen deficiency

Every summer the deepest parts of the inner Flensburg fjord are subject to O 2 -deficiency lasting from a few weeks to several months. In spring, however, populations of Metridium senile can be found in these areas, in spite of the fact that frequently the local anoxic period of the previous summer has been 2-3 times longer than their anoxia LD 50 -value (3 wks).Responsible for this phenomenon is an intensive recolonization by adult Metridium during autumn and winter. This process has been investigated in an 8 months monitoring from May to December 1981. Results on the recolonization mechanism, the population structure of immigrating anemones and recolonization rate as a function of available hard substratum are presented.