Environmental effects of a herring mass mortality in northern Norway. Impact on and recovery of rockyshore and soft-bottom biotas

Abstract

Abstract In October 1984 a school of herring died in the small shallow bay of Alterosen, Lofoten, northern Norway. During the decay of the fish, subtidal sediments turned black from sulphides while fats and oils floated ashore covering seaweeds and rocks. In the subtidal the soft-bottom macrofauna was killed. Recovery took more than three years, following typical successional patterns. The polychaetes Capitella capitata and Scolelepis fuliginosa had high abundances during 1985 and 1986. Intertidal damage was limited. In the rocky shore the key algal species, Ascophyllum nodosum, tolerated the pollution, but encrusting algae and sponges, and epiphytes were locally affected. Intertidal sediment fauna was only affected during autumn 1984. The different impact and recovery of the intertidal and subtidal communities was found to be in marked contrast to other cases of long-term organic pollution. The results are discussed in view of various effects of stress and disturbance on communities.