The industrialized centres along the coasts release a horde of chemical pollutants through their effluents in the streams and nalas draining in to the sea. Most dreaded are the municipal wastes, sewage sludge and dredged spill dumping, oil spills and leakages. The wastes have a wide range of hazardous elements such as petroleum hydrocarbons, chlorinated hydrocarbons and heavy metals says X.N. Verlecar and his co-workers from the National Institute of Oceanography (NIO), in one of their recent papers in the Current Science. It is interesting to note that the aquatic fauna responds to the pollutants in four ways: I) cellular; II) organism; III) population and community response. Out of these the earliest detectable changes are the cellular changes (a science called Xenobiotics) says X.N. Verlecar. The cells of an organism face the torture of pollution and show drastic chemical changes including the genetic changes as well. The genetic imprints of a species are carried by the generations. Our growth in terms of 'development' is leading to degeneration of species. A matter of concern and needs urgent attention of the society.

The problem of marine pollution is deep rooted. We have converted our rivers in to refuge carriers that carry their load to dump it in the sea and in addition we have specialized in polluting the atmosphere near the coasts via our smoke belching industries. Many times even the land is not spared and landfills are created on porous depressions and filled with solid, urban and industrial waste. Rains dissolve the toxins therein and contaminated water percolates down to aquifer to reach the sea via the subsurface route. 

Quoting earlier studies the authors inform that petroleum hydrocarbon content in Arabian Sea ranged from 1.8 to 11.1µg/l in water, 1.84 to 5.81µg/l dry weight in sediments and 0.33 to 3.67 µg/gram wet weights in fish. The coastal waters of Mumbai have a high content of mercury between 0.12 to 1.4µg/l and in sediments from 0.08 to 0.36µg/gram. The fish muscle in Thane Creek contains mercury ranging from 0.217 to 0.512µg/gram. At Karwar coast in Karnataka the mercury content is as high as 2.68 µg/l in water and 1.32 µg/gram dry weights in sediments.

While speaking at Tata Energy Research Institute, New Delhi, about marine pollution Elrich de Sa, Director, NIO presented the following compilation of type of pollutants and annual quantum of pollution of our seas within the coastal zone:

The studies carried out by NIO show that coastal pollution has global impact. The human interference has accelerated the in put of dissolved Carbon in the sea and now it is 0.4 Gigatons per year. In future perhaps this would find a way to atmosphere as carbon dioxide! All to the entire scenario is pretty grim.

The marine organisms have a major role in the human existence. They are food for the millions and also bio-regulators of the Carbon dioxide. However, a new role they have acquired is to help the scientists in determining the pollution level in water much before the instruments declare them unfit for the biota.

Aquatic environmentalists have started using 'biomarkers' to transform environmental science. Environmental biomarkers are biomolecular signatures that display a unique pattern of molecular change in an organization, such as a set of expressed proteins, and that identify an exposure or response to a specific environmental stress. 

Studies have revealed that DNA of the cells of the organisms changes as a result of xenobiotics. In this context studies carried out in developed countries have shown that a group of bivalves, Mussel show changes in the DNA immediately on exposure to pollutants in water. These biomarkers provide an early warning about the pollution in water. 

Knowing well the significance of biota of the coastal zone and also knowing that the pollution at the coasts is ever increasing, the Government Of India launched national level monitoring programmes like COMAPS (Coastal Ocean Monitoring and Prediction System) and ICMAM (Integrated Coastal Area Mapping and Management). These programmes however, could only document chemical constituents of the coastal waters and changes in the biological communities over the years. However, these programmes were of no use as far as establishing the actual damage to the cell or the genetic changes forced by the pollutants. The NIO on its own initiative carried out a biomarker study. Considering the vastness of our coasts the efforts of NIO are tiny. A data bank needs to be developed using various bivalve species along the coasts.

Bivalves like Mussels, Clams and Oysters are present all along Indian coasts. They are the most efficient and cost effective tools to measure the level of pollution. The impact of toxins on their cellular structures/colonies/species is needs to be carried out systematically urgently. These sentinels of the Indian coast could serve as the most suitable organisms for biomarker studies. The marine biologists have a lot of role to play in such studies. 

It is time to work out the extent of the damage done by anthropogenic activities on marine life. If resurrected the marine life can take care of the carbon sequestration and global warming to great extent.