Human Impacts on Marine Biodiversity: Macrobenthos in Bahrain, Arabian Gulf

Abstract

In recent decades, biological diversity has received increased interest. However, most studies are related to terrestrial systems, and knowledge of marine biodiversity lags behind that of land systems (Ellingsen, 2002). Oceans cover about 70% of the earth, and softsediment habitats cover most of the bottom of marine environments (Snelgrove, 1998). These habitats support a diverse array of macrobenthic communities that play important roles in ecosystem processes such as recycling nutrients, detoxifying pollutants, dispersion and burial, and secondary production (Gray, 1997; Snelgrove, 1997). Additionally, these organisms provide food for humans and are considered an important source of food for fishes and birds (Snelgrove, 1999; Thrush & Dayton, 2002). Human activities are the primary cause of recent changes to marine biological diversity in coastal and subtidal areas. It is therefore important to improve our understanding of both biodiversity in marine sediments and anthropogenic impacts affecting these habitats in order to effectively incorporate conservation measures. The Arabian Gulf is a semi-enclosed sea situated in the subtropical zone and characterized by low precipitation and high aridity. It is a shallow sedimentary basin dominated by soft substrate benthos. The average depth of the Arabian Gulf is 35 m, and whole of its substrate lies within the photic zone. The Kingdom of Bahrain is an archipelago composed of 37 islands located in the Arabian Gulf between latitude 25o 32′ and 26o 20′ north and longitude 50o 20′ and 50o 50′ east (Fig. 1). The total land area of Bahrain is about 762 km2. The length of the coastlines of Bahrain is approximately 126 km and the marine area is estimated to be around 8000 km2. Despite the limited land area of Bahrain, waters around its islands support a range of coastal and marine habitats such as seagrass beds, coral reefs, mangrove swamps, offshore islands, and mud and sand flats. High levels of salinity and surface temperature are the main natural stresses in the Arabian Gulf. Salinities around Bahrain are generally high due to the effects of high temperatures associated with high evaporation rates. Salinities on the west coast are higher than those on the east coast, with average means of 50-57 psu for the west coast and 43-45 psu for the east coast (Price et al., 1985). This variation in the salinity gradients may be attributed to a complex system of water circulation around Bahrain enforced by reduced water exchange,