Factors determining the distribution of foraminiferal assemblages in Port Joinville Harbor (Ile d'Yeu, France): the influence of pollution

Port Joinville harbor is located on an island. Thus, it receives only a few freshwater inputs, contrary to most of the areas where the influence of pollution on foraminiferal assemblages has been studied. The pollution in the harbor mainly results from the boats, including cleaning, painting and outfall of oil and motor-fuel. A total of 59 sediment samples was collected at three sampling periods (November-December 1997, May 1998 and September 1998). These samplings were supplemented by the study of algal flora and macrobenthos and by the study of water circulation by means of six stations where water was collected every hour during a tide cycle. Contaminants were analyzed in the last series of 17 samples. Total assemblages were used for this study. This choice is explained and discussed. This study shows that the main factor that determines the distribution of foraminiferal species in Port Joinville harbor is the geographical position. The correlation that occurs between heavy metals and the silt and clay fraction makes it difficult to determine whether sediment characteristics or pollution have the stronger influence on foraminiferal assemblages, except in areas heavily affected by pollution. Polluted sediments, near the careening areas, are indicated by the tolerant pioneer species Cribroelphidium excavatum and Haynesina germanica. The growth of epiphytic species depends on the presence of algae and their distribution may be favored by local conditions such as the constant immersion of the supports in the wet dock. (C) 2001 Elsevier Science B.V. All rights reserved.