Abstract. The paper deals with the standing stock of macrobenthic infauna and associated environmental factors influencing the benthic community in the shelf region of the northwest Indian coast. The data were collected onboard FORV Sagar Sampada during the winter monsoon (January-February, 2003) to understand the community structure and the factors influencing the benthic distribution. The environmental parameters, sediment characteristics and macrobenthic infauna were collected at 26 stations distributed in the depths between 30 and 200 m extending from Mormugao to Porbander. Total benthic abundance was high in lower depths (50-75m), and low values noticed at 30 m depth contour was peculiar. Polychaetes were the dominant group and were more abundant in shallow and middle depths with moderate organic matter, clay and relatively high dissolved oxygen. On the other hand crustaceans and molluscs were more abundant in deeper areas having sandy sediment and low temperature. High richness and diversity of whole benthic groups observed in deeper depths counter balanced the opposite trend shown by polychaete species. Generally benthos preferred medium grain sized texture with low organic matter and high organic matter had an adverse effect especially on filter feeders. Deposit feeding polychaetes dominated in shallow depths while carnivore species in the middle depths.Ecologically, benthos were controlled by a combination of factors such as temperature, salinity, dissolved oxygen, sand and organic matter and no single factor could be considered as an ecological master factor.
This paper focuses on the partitioning of trace metals in five selected coral species from Lakshadweep Archipelago, which remains as one of the least studied areas in the Indian Ocean. Based on the morphological features, selected coral species are classified as massive (Porites andrewsi), ramose or branching (Lobophyllia corymbosa, Acropora formosa and Psammocora contigua) and foliaceous (Montipora digitata). Relating trace metal concentrations with morphological features in skeleton, highest concentrations of all the trace metals (except Zn) were reported for the ramose type corals. In tissue, all the metals (essential as well as non essential) showed highest concentrations within the branching type corals. Irrespective of their growth characteristics/pattern, all species except P. contigua displayed higher concentrations of Pb, Ni, Mn and Cd within their skeleton compared to tissue which may exemplify a regulatory mechanism to avoid the build up of the concentrations of these metals in their bio-part, strikingly toxic metals like Cd and Pb. The concentrations of trace metals in the skeleton and tissues of these coral species were subjected to 3 way ANOVA based on non standardized original data and the results showed significant differences between metals and between species leading to high skeleton/ tissue - species interaction as well as skeleton/tissue - metal interaction. The significant values of student's t calculated are depicted in the form of Trellis diagrams.
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