The Muddy Fine Sand Abra alba- Melinna palmata Community of the Bay of Morlaix Twenty Years After the Amoco Cadiz Oil Spill

摘要

The muddy fine sand Abra albaMelinna palmata com- munity from the Bay of Morlaix (western English Chan- nel) was strongly polluted by hydrocarbons from the Amoco Cadiz oil spill in April l978. Long-term changes of this community (l977--l996) showed that it was weakly affected by thc spill. This was due to the low number and low abundance of sensitive species present on the com- munity in normal conditions. Polychaetes, such as Chae- tozone setosa dominated the community, supporting high levels of organic matter. Only two opportunistic poly- chaetes Mediomastus fragilis and Tharyx marioni in- creased in abundance just after the spill. Temporal changes showed two successive periods: (i) l978--l984 with an establishment of the polychaete Lanice conchilega, and its associate fauna, then (ii) from l985 to the end of the survey in l996 with the disappearance of L. conchilega and the establishment of the polychaete Clymenura clypeata and the bivalve Thyasira flexuosa.