Influence of desalination plant effluent on shore macroinvertebrate assemblages

Abstract

The present study was aimed to establish whether effluent from two desalination plants at different locations in Malta has an influence on biological attributes of rocky shore assemblages, and if so to determine the spatial extent of such influence, and whether the magnitude and extent of effects differs between the two plants. Samples of biota were collected from the Lower Mediolittoral Zone (LMZ) and Upper Mediolittoral Zone (UMZ) using a 20 x 20 cm quadrat, and from the Supralittoral Zone (SZ) using a 30 x 30 cm quadrat, at distances of 0 m, 15 m, 30 m, 80 m and 150 m away from the effluent outfall on either side of it. The collected biota was then sorted and identified in the laboratory. The results indicated that the influence of the desalination effluent on shore macroinvertebrate assemblages was localized at both study localities. Within the LMZ and UMZ, the influence was most evident 15 m away from the outfall, decreased beyond 30 m and was almost negligible 150 m away. In the case of the SZ, the influence was evident in the immediate vicinity of the outfall. Differences in the magnitude of the effect of effluent between the two study localities were attributed to the exposure of the shore to different flow regimes of the effluent discharge.