CHANGES IN LIFE-HISTORY TRAITS IN THE SEA -URCHIN SPHAERECHINUS-GRANULARIS AS A RESPONSE TO ENVIRONMENTAL-STRESS

The functional deficiencies observed in several populations of the sea urchin Sphaerechinus granularis from the Bay of Brest confirm the sen sitivity of this species to environmental conditions. These abnormalit ies, though suspected for over a decade, are quantified for the first time in the present study, carried out in 1993 and 1994. It was based on the comparison of physiological (gonadal and gut indices) and demog raphic (recruitment, growth rate, maximal size and longevity) indices. The results obtained reveal that there are significant differences be tween the reference population (Goulet de Brest and Glenan Archipelago in southern Brittany) and the populations located in the centre and n orthern areas of the Bay. The sea urchins living in the vicinity of Ar morique Point, at the mouth of the river Aulne, appear to be particula rly affected, showing abnormally low levels of ingestion and gonad dev elopment, the absence of a distinct spawning and the lowest growth rat e in the Bay. The results of this demographic study confirm the result s of ecotoxicological tests simultaneously carried out (analysis of fe rtility, embryonic blocking failure and larval abnormalities in the di fferent populations). Analysis of heavy metals present within the sea urchin gonads revealed concentrations of lead, copper, iron and zinc t hat are 2 to 5 times those observed for the other populations. At Armo rique Point, the functional deficiencies observed are discussed in rel ation to metal accumulation, and notably local iron contamination.