Spatial and temporal assessment of metals contamination in the surface sediments of biogenic intertidal reefs of Sabellaria alveolata (Annelida: Polychaeta) from Essaouira protected coastal area (Atlantic coast of Morocco)

Abstract

In the present study, we assessed the spatial and temporal distributions of metal contents and their environmental risks in the surface sediments from Essaouira protected coastal area (Atlantic coast of Morocco). Surface sediment samples of the biogenic reefs of Sabellaria alveolata (Annelida: Polychaeta) were collected seasonally, and the fine fraction (<$63\mu m$) analysed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The sediment characteristics of this coastal zone were comparable to other Moroccan coastlines, and the sequence of metal concentrations decreased Al > Fe > Zn > Cr > Cu > Pb > Cd. Concentrations were lower than mean Earth crustal contents and world average background levels except for Cd. Spatial and temporal variations of metals were highly significant, and largely determined by geochemical background properties and inputs of terrigenous material except for Cd which was associated with upwelling phenomena. Comparison with sediment quality guidelines (SQGs) and ecotoxicological values indicated few exceedances with regard to most metals except for Cd, Cr and Cu. Consequently, the dredged sediment may be dumped at sea with little likelihood of adverse biological effects. However, some sediments had a moderately high Cd content, especially during summer and warrant more detailed assessment.