Scientific components and achievements:
Marine Microbiology
Marine microbes not only form the “unseen majority” but are also responsible for mediating various biogeochemical processes turning over elements like C, N and S.
For example in the Cochin estuary monsoonal forcing had a strong impact on autotrophic and heterotrophic shifts in the trophic status of this estuary initiated through bacterially mediated carbon flux. The estuary is also characterized by weak auto-heterotrophic coupling and high carbon flow through bacterioplankton. The change in functional diversity with salinity is evident from the shift in the substrate utilization from carbohydrates at zero salinity to carboxylic/amino acids at higher salinity (Shoji et al, 2008).
Yet another example is from microbiological studies of the Arabian Sea coastal anoxia. It has shown that the three of the four main processes of the nitrogen cycle namely ammonification, nitrification and denitrification appear to operate more in temporal and spatial proximity than hitherto appreciated. The alarming nitrous oxide input into the atmosphere could be due to high productivity driven tighter nitrification–denitrification coupling, rather than denitrification driven by extraneous nitrate alone (Krishnan et al, 2008).
Nitrifiers also partner with heterotrophic bacteria to mitigate concentration of Mn and related metals in mangrove sediments. A comparison between the Mandovi and Chapora mangrove sediments was made to assess the probable influence of iron ore mining on bacterial groups in this region. We suggest that bacterial populations in the mangrove sediments could play an important role in preventing the concentration of the metal species from accumulating (Krishnan et al, 2007)
The mangrove region fringing the Goan estuaries are also home to anaerobic bacteria especially the sulphate reducing forms. They mediate the carbon turnover through sulphur cycle. Dissimilatory sulfate reduction is carried out by a diverse group of strictly anaerobic sulfate-reducing prokaryotes (SRP) that share the ability to use sulfate as a terminal electron acceptor in the oxidation of organic matter, thus reducing sulfate stoichiometrically to sulfide. Contrary to earlier reports, we find that SRA is not totally arrested at salt saturation in the salterns of Ribander but could instead could get retarded. Further, our studies show that availability of an extraneous carbon source could serve to stimulate, and thus counter, the retardation. Our findings suggest that SRA in saturated saltpans around mangrove sediments is more carbon limited than sulfate limited. (Kerkar and Loka Bharathi, 2007). This process is known dominate anaerobic terminal oxidation of organic matter in high-sulfate systems, degrading up to 50% of the organic matter in coastal marine sediments (Jorgensen 1982).
Marine Benthos:
Benthic fauna are sediment dwelling animals of marine and estuarine environment. They not only feed on sediment bacteria and detritus but by their bioturbating activity they aid microbial processes.
Seasonal studies on Benthic flora of Paradip waters in the Bay of Bengal showed that Nephythis sps was most dominant. While coastal regions were marked by density, offshore stations were more diverse. The lower diversity at the nearshore was perhaps due to persistent dredging activities (Ingole, 2007)
These fauna respond to salinity changes in the estuaries by undergoing cyclic changes. There is a period of proliferation and rejuvenation when salinity picks up during post and pre monsoon followed by a period of death and decay due to fall in salinity during summer monsoon. There are also interannual changes attributable to anthropogenic influences like ore mining on land and sand mining in estuarine channels (Ansari et al, 2007).
Yet another anthropogenic influence is the increasing trend in oil pollution along the west coast of India. Illegal discharges from a large volume of shipping is noticeable. This could affect the fisheries as pelagic catch on west coasts accounts for 73% of the world catch. Stringent regulatory and conservatory measures are therefore need of the hour and also call for sustained studies on EIA for monitoring pollution (Ingole and Sivadas, 2007)
Nematodes could be good indicators of pollution. They are known to be the most dominant in marine benthic environment constituting 83% of meiofauna. Nine taxa were recorded in the harbour area. Of the 32 meiofaunal samples from the sub-tidal area along the south west coast of India, there was decreased diversity off Marmagoa due to harbour activities and pollution. Nematodes are taxonomically diverse with an world estimate of 50,000sps (Nananjakr and Ingole, 2007)
In an attempt to relate acoustic characterization of seafloor to benthic distribution on the western continental shelf of India it has been shown that there is a strong relationship between back scatter signal parameters, sediment grain size and benthic biomass. The positive correlation between the 210Khz back scatter signal with sediment and macrobenthos affirm the dominance of sea-water sea floor interphase scattering (Chakraborty et al, 2007)
We have also made some new records for marine water mites in our waters. The male of marine water mite, Litarachna denhami (Lohmann, 1909) are described and this is the first record of the family Pontarachnidae from Korea and India (Pesic et al , 2008).
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