Chandrabhotla

Distribution of Meiobenthos with special reference to nematode assemblages of Continental slope Sediments, Northeast Coast of India C.Annapurna and Lilly Maria Goretti Cooper Department of Zoology, Andhra University, Visakhapatnam-530003, A.P., India A comprehensive study on the taxonomy and community structure of meiobenthic fauna at 15 locations on the Indian north east continental slope (250-1000m) representing 5 pre-fixed transects (160 to 200N) was undertaken through cruise (225) onboard FORV Sagar Sampada held in May and June, 2004. At each location (replicate) samples were collected using a Smith-McIntyre grab (0.1m2) and data on sediment texture, organic content, ambient salinity and dissolved oxygen obtained synchronously according to standard protocols. As many as 87 species that represented 4 diverse (meiofaunal) taxa namely foraminifera (5) copepoda (2) ostracoda (2) and nematoda (78) were encountered. Overall, meiofaunal (mean) abundance ranged from a mere 4 numbers at 1000m (off Barua) to a high 868 nos.10cm-² at 250m off Barua. Overall, the meiobenthic biomass (mg/ 10cm2) ranged between 0.01 at 1000 mt (off Barua), and 2.37 at 250 mt (off Barua). On the whole, nematodes constituted an overwhelming 62% of the total meiofauna in terms of numerical abundance and biomass. In the present study altogether there were 78 nematode species represented by 66 genera and 25 families. Since nematodes constituted one of the most important faunal groups in view of their numerical abundance and species richness in this study, they were examined and studied in detail and correlated with various environmental factors. Univariate indices (e.g. Margalef d & Shannon-Wiener H′) revealed high nematode diversity (d: 7.5; H’: 3.1) at 250m (Barua) than further deep (>500m). Based on Bray-Curtis similarity and multi dimensional scaling (implemented in PRIMER) it was possible to demonstrate two distinct assemblages among nematodes favoured by depth classes. Two communities could be distinguished in the north east continental slope, named after the most important (determining) species recognised through SIMPER as 1.Araeolaimus assemblage (assemblage I) and 2.Dorylaimposis punctata (assemblageII) representing 250 mt&500 m and 1000 mt depth categories respectively. Biotic and environment relationship was analysed by using BIO-ENV protocol implemented in PRIMER. The results showed that dissolved oxygen; depth, seawater temperature and organic matter (ρw ≥0.568) seemed to influence the distribution of nematode population.