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 po llution on foraminiferal assemblages has been studied. The pollution in the harbor mainly results from the boats, including cleaning, painting and out fall of oil and motor-fuel. A total of 59 sediment samples was collected at three sampling periods (Nov ember-December 1997, May 1998 and September 1998). These samplings were sup plemented 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 expl ained and discussed. This study shows that the main factor that determines the distribution of f oraminiferal species in Port Joinville harbor is the geographical position. The correlation that occurs between heavy metals and the silt and clay fra ction makes it difficult to determine whether sediment characteristics or p ollution have the stronger influence on foraminiferal assemblages, except i n areas heavily affected by pollution. Polluted sediments, near the careeni ng areas, are indicated by the tolerant pioneer species Cribroelphidium exc avatum and Haynesina germanica. The growth of epiphytic species depends on the presence of algae and their distribution may be favored by local condit ions such as the constant immersion of the supports in the wet dock. (C) 20 01 Elsevier Science B.V. All rights reserved.