Effect of brine discharge from Al-Dur RO desalination plant on the infauna species composition in the east coast of Bahrain

Abstract

The GCC countries have been experiencing an accelerated socio-economic development process since 1970s, resulting in rapid demographic and urbanization growth and associated with rapidly increasing municipal water demands. To meet these demands’ quantity and quality, the GCC countries resorted to desalination. Currently, the GCC countries collectively possess the largest desalination capacity in the world (~45%), and based on the current urbanization trends, it is expected that current rates in desalination capacity growth will continue in the future. However, desalination has a number of environmental externalities on the marine, and their severity will depend on various factors (i.e., site-specific). As a pre-requisite for designing and implementing programs to minimize these environmental externalities, the impact of desalination has to be investigated and character-ized. The study objective is to investigate the impacts of Al-Dur RO desalination plant on the coastal infauna benthic species composition on the east coast of Bahrain. The in situ measurements over high and low tide cycles in winter and summer were conducted at 42 selected locations for surface and bottom waters. Sediment samples were collected from 10 locations selected at different distances from the discharge outlet. The species composition of infauna was investigated using the univariate analysis (number of species and individuals, species richness, evenness index and diversity index). The results showed an extreme elevation in temperature (>38°C) and hypersaline waters (>55‰) at locations nearby the discharge outlet, and also at bottom waters of depths more than 3 m during the high and low tide cycles in both seasons with exceptional levels in summer. Four main groups of benthic infauna identified are represented by polychaetes (12 taxa), bivalves (4 taxa), Gastropoda (2 taxa) and Amphipoda (3 taxa) including 256 specimens. The univariate analysis indicated spatial variations in infauna species composition where the lower diversity indices were found at locations close to the discharge outlet and at station 5 at which noticeable vertical differences were observed indicating exceptional elevation of temperature and hypersaline waters at bottom layer. However, the highest species diversity indices characterized the most offshore stations. Polychaetes are consid-ered as the most useful bio-indicators to reveal any contamination from desalination brine discharge, due to their sensitivity and their capability to adopt to any environmental alteration.