Structure and functions of Polychaetofauna living in Mytilus galloprovincialis assemblages in Thermaikos Gulf (north Aegean Sea)

The purpose of this study is to examine the Polychaetes populations of the mussel Mytilus galloprovincialis Lamarck 1819 assemblage in Thessaloniki Ba y (Perea, Neoi Epivates, Agia Triada) in space and time. Forty-eight Polych aetes species, which belong to 16 families, were identified among 10 593 in dividuals. The different distribution in space and time can be attributed t o the life cycles of the Polychaetes, and also to the various biotic intera ctions. In general, the abundance follows the succession of the seasons, wi th some deviations though. Thus, the samples can be divided into two major groups, the winter and summer samples. The structure of the feeding guilds of the Polycheates population was also investigated and 9 different feeding guilds were identified. The microphagous, sedentary Polychaetes were the d ominant guild, whilst the carnivores were the most abundant among the macro phagous. No major differences were observed, as regards the composition of the feeding guilds. The study of the structure of the polychaetofauna showe d similar diversity with that of other Mediterranean regions. This fact imp lies that the polychaetofauna of the M. galloprovincialis assemblages in th e Mediterranean Sea has a stable structure and shows a certain resemblance. Furthermore, the polychaetofauna includes species known as capable of livi ng in polluted water as well as others that are more sensitive in such cond itions. Therefore, the biomonitoring of the examined regions proves to be e ssential for obtaining valuable information about the state of their waters . (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SA S.