Environmental factors affecting benthic infaunal communities of the Western Arabian gulf

Abstract Species composition and abundances of benthic organisms > 0·5 mm in size were determined in seagrass and sand/silt substrata along the Saudi Arabian Gulf coastline. Synoptic measurements were made of environmental and pollution-related parameters. Numbers of species and individuals were significantly greater in seagrass than in sand/silt substrata, indicating that the finer grained sediments of the seagrass areas support more diverse and abundant benthic communities. In both seagrass and sand/silt, abundances of species and individuals decrease significantly with increasing salinity, resulting in substantially reduced benthic communities in the Gulf of Salwah at the southern extent of the western Gulf where salinities average up to 56·5%o. In contrast, biomass of the total benthos in the sand/silt substratum increases significantly with salinity. All pollution-related parameters tested indicated relatively low concentrations in sediments. The only significant relationship found with the benthos was an increase in numbers of individuals with sediment petroleum hydrocarbons, resulting in significantly lower species diversities in areas of higher sediment petroleum. The most abundant organism in the area increases significantly with sediment petroleum hydrocarbons within the relatively low concentrations that occur, indicating that this species is primarily responsible for the observed relationship between petroleum hydrocarbons, numbers of individuals and species diversity.