Community structure and spatial variations in the benthic crustaceans of the western Arabian Gulf

The taxonomic composition of benthic crustaceans was studied in the Saudi Arabian waters of the Arabian Gulf. One hundred and thirty-four species from twenty-eight diverse taxa were found, comprising 60 species of amphipods, 37 species of cumaceans, 14 species of ostracods, and 23 species from the remaining 20 taxa (‘others’). Amphipods were the dominant taxa, constituting 44% of the total density and 41% of the total crustacean species. The number of species (S:32 ±1 m^-2 nearshore and 28 ±1 m^-2 offshore), density (N:1568 ±508 ind. m^-2 nearshore and 552 ±53 ind. m^-2 offshore), and the Shannon-Weiner diversity, H’ (log2) (4 ±0.08 nearshore and 3.96 ±0.09 offshore) of crustaceans decreased with increased depth, though statistically not significantly. However, these community parameters were higher in the central region (S: 35 ±1, density, N: 1631 ±684 ind. m^-2, H’ (log2): 4.13 ±0.08) than the other two regions (S: 28 ±1 - northern and 26 ±2 - southern region, N: 809 ±163 ind. m^-2 - southern and 676 ±145 ind. m^-2 - northern, and H’ (log2): 4.02 ±0.09 - northern and 3.74 ±0.13 - southern). Permutational Multivariate Analysis of Variance (PERMANOVA) showed a significant difference in density (F = 10.1, P<0.05) in relation to depth. There were also significant regional variations in the number of species (F = 7.61, P<0.05) and diversity (F = 3.84, P<0.05) in relation to depth. The Canonical Correspondence Analysis (CCA) revealed that the main environmental factors influencing the distribution of benthic crustacean species were water depth, dissolved oxygen, salinity, sand, sediment Total Organic Carbon (TOC), and sediment Total Petroleum Hydrocarbons (TPH).