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Macrobenthic faunal composition was studied at six different depth ranges (30-50, 51-75, 76-100, 101-150, 151-175 and >176 m) in five transects (off Karaikkal, Parangipettai, Cuddalore- SIPCOT, Cheyyur and Chennai) in the continental shelf of southeast coast of India. Eleven diverse taxa were found, comprising 113 species of polychaetes, 14 species of bivalves, 10 species of amphipods and 'others' (five tanaids, five crabs, four isopods, three echinoderms, two shrimps, two cnidarians, two fishes and one cephalochordate). Polychaetes were the dominant taxa, constituting 88.5% of the total abundance and 30.7% of the total biomass. The number of species (seven per 0.2 m2 at >176 m depth range in Chennai to 46 per 0.2 m2 at 30-50 m in Cheyyur), abundance (216 per 0.2 m2 at >176 m in Karaikkal to 353 per 0.2 m2 at 30-50 m in Cheyyur) and biomass (0.09 g per 0.2 m2 at 151-175 m in Karaikkal and 4.6 g per 0.2 m2 at 30-50 m in Cheyyur) of macrobenthos decreased with increase in depth. DO decreased gradually from 30 m depth; beyond 150 m, the decrease was pronounced due to the presence of the oxygen minimum zone. Using the distance based linear model ( DISTLM), it was found that the environmental variables explained about 73.3% of the total variability in macrofaunal distribution. The heavy metals cobalt and mercury, as well as water pressure (proxy for depth), showed a significant relationship with macrofauna, explaining respectively 9, 7.3 and 7% of the total variability. The contribution of other variables was smaller. [ABSTRACT FROM AUTHOR]

This study compares the feeding guild composition of macrobenthic (infaunal) polychaetes from two different transects (Cheyyur and Singarayakonda) situated in the continental shelf region of southeast coast of India. The polychaetes collected from these transects were identified using standard manuals [Fauvel P. 1953. The fauna of India including Pakistan, Ceylon, Burma and Malaya: Annelida, Polychaeta. Allahabad: The Indian Press Ltd; 507 p.; Day JH. 1967. A monograph of the polychaeta of southern Africa. London: British Museum (Natural History Museum) Publication; 878 p.]. The total number of species recorded from the study area was 75 belonging to 54 genera and 29 families. These species were categorized into various feeding types following Fauchald and Jumars [Fauchald K, Jumars PA. 1979. The diet of worms: a study of polychaete feeding guilds.Oceanography and Marine Biology: Annual Review17: 193–284] and confirmed after examination of mouthparts. Among these, 34 species (45.3%) were found to be surface deposit feeders, 25 species (33.3%) carnivores, 8 species (10.7%) subsurface deposit feeders, 5 species (6.7%) filter feeders and 3 species (4%) were omnivores. A total of 1330 polychaetes were collected, with 65% representing surface deposit feeders, 31% carnivores, 3% filter feeders and less than 1% were subsurface deposit feeders and omnivores. The sediment was sandy in Cheyyur and silty overall in Singarayakonda. Although the surface deposit feeders were dominant [72.97% with higher Margalef richness (d) value of 2.27 ± 1.56 and Simpson richness (1 −  λ′) value of 0.72 ± 0.36] in Cheyyur, carnivores were dominant (48.36% with higher richness values ofd– 1.52 ± 0.82 and 1 −  λ′ – 0.80 ± 0.11) in Singarayakonda transect. The distance-based linear model showed the influence of median particle diameter (explained 24.7% of total variability), depth (19.1%) and total organic carbon (16.2%) on the distribution of feeding guild composition of polychaetes, indicating that the co-variables strongly differentiate the feeding guild composition of polychaetes in the two transects. [ABSTRACT FROM AUTHOR]

The Gulf of Aqaba (hereafter 'the Gulf') is a narrow, semi-enclosed, warm, high saline, and oligotrophic water body. This baseline study provides the first quantitative data on deep-sea (207–1281 m depth) benthos of the Gulf. Fifty-five benthic species (predominantly polychaetes) with a density of 160–670 ind. m−2, species richness of 11–25, and Shannon-Wiener diversity (H′) of 3.14–4.17 bits. ind.−1 were recorded from nine stations. The density and H′ of benthos of the Gulf are comparable with those of the Red Sea, while both are lower than those reported from the Arabian Sea and the Mediterranean Sea. The good-high ecological status of benthic communities indicates the absence of major stress in the deep-sea habitats of the Gulf. As large-scale urbanization is proposed in the Saudi coastal areas of the Gulf, this study is expected to provide a baseline dataset for future environmental impact assessments. • Deep-sea benthic community is composed mainly by polychaete species. • Density and diversity are comparable to those of the northern Red Sea. • Density is lower than that reported from the Arabian Sea and Mediterranean Sea. • Deep-sea benthic communities have good-high ecological status. • Factors affecting the benthos are organic matter and hydrographical parameters. [ABSTRACT FROM AUTHOR]