suggested that the sediments are moderately weathered despite the intense orographic rainfall in the source area. Variability in degree of chemical weathering is seen with the change in provenance. In general, the sediments north of Goa with a provenance of Deccan basalts show higher chemical weathering index. C org /N molar ratios (range = 6.9 and 14) are mostly between 10 and 12 which are closer to marine organic matter values. This is corroborated by marine δ 13 C values (-18.2 to-21.6‰). While, they broadly fall within the marine values, heavier values are seen in northern transects off Porbandar and Dwaraka where the sediments have a provenance different from those in the south. This could be due to a higher contribution from C-4 type vegetation in the north, consistent with heavier δ 13 C values in terrestrial plants in source regions. Comparatively heavier δ 15 N values are observed for the northern transects (north of Ratnagiri) which is supported by the intense denitrification in the northern Arabian Sea.

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.

Surficial and core samples collected from the sedimentary microenvironments of Lakshadweep Archipelago were analysed for their trace metal contents. The synoptical relations in spatial distributions with respect to environmental conditions such as pH, organic carbon and sediment texture were inter-correlated. Some of the metals exhibited good correlations with Fe/Mn, which reflect their similarity in distribution rather than anthropogenic enrichment. Inter-relating the variations in metal-pH relationships with metal-organic carbon, in general, those which exhibited positive correlations with pH, displayed negative interactions with organic carbon content and vice versa. Comparatively, higher values of Fe in the mangrove area of one of the islands highlight the possibility of precipitation of Fe as iron sulphides, which are common in mangrove ecosystem. Based on the contamination factors for Pb, Zn and Cd, as well as the geo-accumulation index of Cd, it can be generalised that some of the islands remain polluted with respect to these elements. An evaluation based on pollution load index shows that none of the islands surveyed for this study posed a serious threat in trace metal pollution. Bray Curtis similarity index was computed to find out the similarity among metals/islands, using non-transformed data of metal concentrations. Group linkage clustering technique was used for drawing dendrograms to show the similarity among them.

Pesticide residue levels in the aquatic systems are scattered and fragmentory in India. A systematic analysis of the distribution pattern of the common organochlorine pesticide Hexachlorocyclohexane (HCH) and its isomers in the waters of the tropical positive estuarine system (the Cochin Estuarine System) has been carried out for the first time. The average concentrations of HCH ranged between 0.013 and 1.125 µg 1 -1 . α-HCH was found to be at an appreciable concentrations throughout the study area and formed the highest percentage (90%) of all isomers of the HCH family

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This paper reports on the results of systematic analyses carried out to assess the distribution of dichlorodiphenyltrichloroethane (DDT) and its metabolites, o,p′‐DDT, p,p′‐DDE, and p,p′‐DDD in a tropical waterway, the Cochin Estuarine System. Six sampling stations along the system were studied. Analyses were carried out during premonsoon, monsoon, and postmonsoon seasons. ΣDDT concentrations as high as 55.422 μg L−1 were detected. The predominant DDT metabolite was found to be p,p′‐DDE. During the monsoon season, o,p′‐DDT was not detected at any of the sampling Stations. Station 1 (riverine) and station 6 (coastal zone barmouth) emerged as DDT‐free zones and the analytical results have enabled the identification of DDT “hot spots” in the estuary. © 1994 by John Wiley & Sons, Inc..

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