VALIDATION OF THE ASTEROID ASTERIAS-RUBENS (ECHINODERMATA) AS A BIOINDICATOR OF SPATIAL AND TEMPORAL TRENDS OF PB, CD, AND ZN CONTAMINATIONIN THE FIELD

The aim of the present study was to assess the value of Asterias ruben s as a bioindicator of metal contamination in the field. Spatial gradi ents of Pb, Cd, and Zn contamination were identified along Sorfjord, a nd metal concentrations were consistently higher (1.7-8.3 times) in th e body compartments of large asteroids sampled close to the smelters t han in those sampled further away. Cd and Pb concentrations in the pyl oric caeca varied along the fjord according to a decreasing sigmoidal relationship, while Cd and Pb concentrations in the body wall and the skeleton varied according to a decreasing exponential relationship. Th is suggests that the bioavailability of these metals has decreased ove r the last few years at the head of the fjord, which agrees generally with water chemistry data available from the State Pollution Monitorin g Programme (Norway). The decrease in metal bioavailability could be a direct consequence of the 1992 remedial action taken in the fjord to reduce heavy metal release from the contaminated sediments. Lead conce ntrations in the skeletons of large asteroids (12-24 cm; 154 +/- 63 mu g Pb g(-1) dry wt) were eight rimes higher than those in the skeleton s of juvenile individuals (0.5-4 cm; 19 +/- 8 mu g Pb g(-1) dry wt) in the population located at the head of the fjord Asteroids of 12-14 cm length were likely to be 4-7 y old (i.e. born before the remedial act ion) while small asteroids were born after the remedial action. Accord ing to comparisons with allometric relationships in an uncontaminated population and experimental exposures, results indicate that the half- life of Pb in the skeleton is long (i.e. several years) while the half -life of Cd and Zn is much shorter (i.e. several weeks for Cd, and sho rt but not precisely known for Zn). A smaller size and unusual reducti on of the skeleton of adult individuals at the head of the fjord were observed and may result from the effects of heavy metal pollution. A c omparison between possible sources of contamination in the fiord (meta ls in water, food, and sediments) indicates that sediment-associated m etals are likely to be an important source of contamination in this en vironment due to the microphagic activity of asteroids. (C) 1998 Elsev ier Science Ltd. All rights reserved.