Long-term variation of benthic infauna has been studied in two stations in La Coruña Bay, NW Spain, during a 12-year period (1982 to 1993). One of the stations is located in muddy, hypoxic sediments of the harbour area, where harbour dredging was carried out in 1982. Following a relatively quick recovery after dredging operations, the infaunal community did not vary much with time, in spite of frequent sediment disturbances. The bivalve Thyasira flexuosa and opportunistic polychaetes are the dominant organisms. The high stability of this community is related to the dominance of opportunists having short life-cycles, and thus well adapted to environmental disturbances. The other station is located in a relatively clean fine sand area of the bay, and the community is dominated by species having longer life-cycles, such as Tellina fabula and Paradoneis armata. This community shows a wider temporal variation, both seasonally and interanually. Species composition remained very stable through time in both stations, although the relative dominance of the main species may change. The Aegean Sea oil-spill (3 December 1992) has affected the communities during the last phase of the study, causing a decrease of amphipods and some bivalves and a dramatic increase of opportunistic polychaetes.

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