Benthic Community Recovery after Hypoxic Stress in Chinhae Bay, Korea

초록

Hypoxia and anoxia have become a major cause of benthic ecological changes. We examined the scale and intensity of disturbance, and the response of benthic community to bay hypoxia in an organically enriched environment from May 1989 to May 1990 in Chinhae Bay, Korea. These environmental disturbances resulted in abnormal dynamics of the benthic communities including complete defaunation during the summer and recolonization of the azoic areas in winter. As oxygen concentration close to the bottom progressed, the abundance and biomass of the benthic macrofauna decreased significantly in the inner bay stations. However, benthic communities were not responding rapidly to the gradual change in bottom oxygen concentration so that the azoic area due to the oxygen deficiency started to be recolonized by the pioneers first after three to four months according to the station following the hypoxic and anoxic events. The following three polychaetes, Sigambra tentaculata, Mesochaetopterus sp., Lumbrineris longifolia were most persistent under the hypoxic conditions, but the first opportunistic recolonizers after renewals of bottom water are the following three polychaetes (Paraprionospio pinnata, Sigambra tentaculata, Nectoneanthes multignatha) and two bivalves (Theora fragilis, Raetellops pulchella). As a result, oxygen deficiency event in Chinhae Bay, Korea, eventually killed most of the benthic macrofauna so that changes in abundances and species diversity of the benthic communities were very striking in the zone of oxygen deficiency.