Various pre-treatment methods and three different media were employed for the isolation of bioactive actinomycetes from mangrove sediments of Andaman and Nicobar Islands, India. Sediments from four different sites of mangrove forest were collected and pre-treated by dry heat method, and the media were supplemented with cycloheximide 80 μg/mL and nalidixic acid 75 μg/mL. The mean actinomycetes population density in sediment samples were recorded as 22 CFU-10-6 /gm in KUA medium followed by 12 CFU-10-6 /gm in AIA medium and 8 CFU-10-6 /gm in SCA medium. A total of 42 actinomycetes were isolated, and all the isolates were evaluated for their antibacterial activity against pathogenic bacteria on two different media. Among 42 isolates tested, 22 species were found to be antibacterial metabolite producer against test bacteria namely, Staphylococcus aureus, Bacillus subtilis, Salmonella typhi and Klebsiella pneumoniae. Particularly, the actinomycete strains such as A101,

The Indian Ocean earthquake of 26 December 2004 led to significant ground deformation in the Andaman and Nicobar region, accounting for ϳ800 km of the rupture. Part of this article deals with coseismic changes along these islands, observable from coastal morphology, biological indicators, and Global Positioning System (GPS) data. Our studies indicate that the islands south of 10Њ N latitude coseismically subsided by 1-1.5 m, both on their eastern and western margins, whereas those to the north showed a mixed response. The western margin of the Middle Andaman emerged by Ͼ1 m, and the eastern margin submerged by the same amount. In the North Andaman, both western and eastern margins emerged by Ͼ1 m. We also assess the pattern of long-term deformation (uplift/subsidence) and attempt to reconstruct earthquake/tsunami history, with the available data. Geological evidence for past submergence includes dead mangrove vegetation dating to 740 ‫ע‬ 100 yr B.P., near Port Blair and peat layers at 2-4 m and 10-15 m depths observed in core samples from nearby locations. Preliminary paleoseismological/tsunami evidence from the Andaman and Nicobar region and from the east coast of India, suggest at least one predecessor for the 2004 earthquake 900-1000 years ago. The history of earthquakes, although incomplete at this stage, seems to imply that the 2004-type earthquakes are infrequent and follow variable intervals.

Isotopic analysis of precipitation over the Andaman Island, Bay of Bengal was carried out for the year 2012 and 2013 in order to study the atmospheric controls on rainwater isotopic variations. The oxygen and hydrogen isotopic compositions are typical of the tropical marine sites but show significant variations depending on the ocean-atmosphere conditions; maximum depletion was observed during the tropical cyclones. The isotopic composition of rainwater seems to be controlled by the dynamical nature of the moisture rather than the individual rain events. Precipitation isotopes undergo systematic depletions in response to the organized convection occurring over a large area and are modulated by the integrated effect of convective activities. Precipitation isotopes appear to be linked with the monsoon intraseasonal variability in addition to synoptic scale fluctuations. During the early to mid monsoon the amount effect arose primarily due to rain re-evaporation but in the later phase it was driven by moisture convergence rather than evaporation. Amount effect had distinct characteristics in these two years, which appeared to be modulated by the intraseasonal variability of monsoon. It is shown that the variable nature of amount effect limits our ability to reconstruct the past-monsoon rainfall variability on annual to sub-annual time scale.

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Andaman and Nicobar Islands, the gastropod diversity is high, due to the majority of shores are rocky. The wet rocky shore promotes algal growth, which is ultimate for feeding ground for gastropod growth and development leading to more diversity. The global warming, anthropogenic activities, industrial and domestic pollution, etc., have accelerated the loss of coastal and marine biodiversity components over the last few decades which has been of great concern. However, except global warming, the other factors were of least concern with reference to Andaman and Nicobar Islands biodiversity due to a pristine environment. Therefore, exploration of biodiversity in these islands is essential to create a baseline data for record and future research. Four locations of south to north Andaman Islands which represented Carbyns Cove from south Andaman, Rangat and Mayabunder from the Middle Andaman and Diglipur from the North Andaman were selected for this study. Gastropoda species were collected for a period of one year in three prevailing seasons of Andaman and Nicobar Islands. They are South West Monsoon (SW monsoon), North East Monsoon (NE Monsoon) and Non Rainy Seasons (NR Seasons). The present study of gastropods distribution in the South, Middle and North Andaman groups of Islands suggested that there are 71 species belonging to 52 genus and 33 families. At any one of the time and any one of the locations, only one occurrence was noticed for 38 species and remaining 33 species were overlapping with respect to stations and seasons. Evaluation of the cluster suggested that Cluster A (NR season in Carbyns Cove) and Cluster B (NE and SW Monsoon in Mayabunder) as a separate entity among the 12 combinations of stations and seasons due to their species representation. It How to cite this paper: