SPATIAL AND TEMPORAL VARIATION IN HEAVY-METAL CONTAMINATION OF NEREISAND CERASTODERMA IN THE WADDEN SEA

We investigated the spatial and temporal variation of Pb, Hg and Cd co ncentrations in benthic organisms. Ragworms, (Nereis diversicolor), co mmon cockles (Cerastoderma edule) as well as some sediment samples wer e collected at six different sires within the backbarrier of the East Frisian island of Spiekeroog/Germany. The results indicated a similar microgeographic pattern in both species and point ro a higher contamin ation of Pb and Hg at the coastal fine grained sampling sites than at the other stations. Therefore the spatial variability evidently coinci ded more with the sediment composition than with spatial, relatively h omogeneous contamination of the pelitic fraction (< 20 mu m grain size ). In order to study temporal variation of Pb and Hg cont amination sa mples were collected at one site quarterly between November 1992 and N ovember 1994. Levels were relatively high in winter and low in summer. The heavy metal contamination of sediment as well as organisms were r elatively low in comparison to other studies. Furthermore, the spatial variation of heavy metal contamination in organisms was low in relati on to spatially large scaled studies.