home.gif (1229 bytes)

Present state of the coastal environment in India

Elrich de Sa
National Institute of Oceanography.

A coastal zone has been variously described. One possible definition [from the US Commission on Marine Science, Engineering & Resource] is "the coastal zone represents that part of the land affected by its proximity to the sea, and that part of the ocean affected by its proximity to the land".

The definition by the Land Ocean Inter. In the Coastal Zone [LOICZ] Science plan: "the coastal zone as extending from the coastal plains to the outer edge of the continental shelves, approximately matching the region that has been alternately flooded and exposed during the region that has been alternately flooded and exposed during the sea-level fluctuations of the late Quaternary period". This second definition is of the coastal domain from 200m above to 200m below sea levels which:

The coastal domain from 200 m above to 200m below sea level:

sqb.gif (46 bytes)Occupies 18% of the surface of the globe
sqb.gif (46 bytes)Is the area where around a quarter of global primary productivity occurs
sqb.gif (46 bytes)Where around 60% of the human population lives
sqb.gif (46 bytes)Where two thirds of the world cities with population of over 1.6 million people are located
sqb.gif (46 bytes)Supplies approximately 90% of world fish catch

The coastal ocean accounts for:

sqb.gif (46 bytes)8% of the ocean surface
sqb.gif (46 bytes)< 0.5% of the ocean volume
sqb.gif (46 bytes)Around 14% of global ocean production
sqb.gif (46 bytes)Up to 50% of global oceanic denitrification
sqb.gif (46 bytes)80% of the global organic matter burial
sqb.gif (46 bytes)90% of the global sedimentary mineralisation
sqb.gif (46 bytes)75-90% of the global sink of suspended river load and its associated elements/pollutants
sqb.gif (46 bytes)In excess of 50% of present day global carbonate deposition

Most pollution in India arises from land-based sources - industrial & domestic wastes and agricultural run-off. Shipping and associated ship-building, breaking and port activities are becoming increasingly significant. The crop of recently started coastally located industries use sea-water as a resource and the coastal domain as a sink of altered sea-water [temperature and density]. These pose newer, more direct threats to sensitive eco areas.

Translating the table of cummulative discharges in the coastal seas to hot-spot locales, we have in:

A first compilation of the type and quantum of pollutants into the coastal ecosystem of India are given below:

Sr. No.

Input / pollutant

Quantum - Annual



1600 million tonnes


Industrial effluents

50 x 106 m3


Sewage - largely untreated

0.41 x 109 m3


Garbage and other solids

34 x 106 tonnes


Fertilizer - residue

5 x 106


Synthetic detergents - residue

1,30,000 tonnes


Pesticides - residue

65, 000 tonnes


Petroleum hydrocarbons (Tar balls residue)

3,500 tonnes


Mining rejects, dredged spoils & sand extractions

0.2 x 106 tonnes

Industries manufacture bulk chemicals, dyes, pharmaceuticals and phosphorus pesticides - and discharge over 200 MLD of effluents which are acidic, oxygen depleted and sediment laden. The effluents contain heavy metals, phenols, nitrogen and phosphorous. This has affected the water quality of the Narmada, Tapti and Mahi rivers.

Mumbai and around
The river Kalu, north of Mumbai, flowing through the industrial towns of Ambarnath, Ulhasnagar and Kalyan has a mercury concentration exceeding 100 ppm. Thana creek in Mumbai receives effluents of over 50 MLD where high mercury levels are present in the water, sediments and living organisms.

The Hoogly river carry effluents that have contaminated fish and shell fish with heavy metals such as Ni, Cu, Cd and Zn. The sediments near Haldia have upto 10 ug/g of pesticides. These river waters are contaminated by e-coli, shigella, salmonella and other human pathogens - indication of severe sewage contamination.

The Periyar river receives chemical industry effluents and untreated sewage. Incidents of ulsuration in shrimp and fish, and frequent fish mortality have affected traditional fishing, with no pollution abatement efforts made.

Estuarine and coastal waters are "clean", though there is high sediment load from mining activities. The Mandovi-Zuari estuaries receive over 30 MLD of partly treated domestic sewage and 15 MLD of industrial and agricultural effluents.

The data, to date, indicated that the Indian coasts have well circulated oxygenated waters, and that hot-spots remain contained within reasonable limits.

Coastal Seas and Global impacts

What are we putting in?
Man is now moving materials (nitrogen, phosphorous, wastes) into coastal spaces at rates greater than nature had been doing it. And these coastal spaces are where nutrients are recycled often (with a positive benefit for fisheries) before sequestering or export. About 0.4 Gtons/year of dissolve & partialate carbon find their way to the sea. Is this a future source of CO2 to the atmosphere? Is this balanced by the sink of CO2 formed by the increased biomass from increased N, P and wastes?

What do we need to know and do?
We need to understand the processes of carbon and nutrient cycling and the global significance of the coastal seas to the carbon cycle.

We need to be able to predict the evolution of the coastal ecosystems for different global change scenarios and the effects of these changing coastal systems on social and economic activities and how we can improvise strategies for the sustainable management of coastal resources.

What are the problems in the way?
The global impact of coastal seas is unlike systemic changes which occur throughout the earth system and are easier to comprehend for atmospheric effects because of the time scales (years to decades). Examples are the increase in atmospheric CO2 and the decrease of ozone.

The coastal seas on the other hand undergo cumulative changes which though localised have global impact. An example is the entrophication of coastal waters leading to changes in carbon flow and its sequestration and the effect on the global carbon cycle.

The other major problem is the complexity of biological systems. Even in a localised environment, the species are numerous, the numbers are large, there are different metabolic rates, life styles and life expectancies. Environmental changes will affect species differently and thus their effect on the biogeochemical cycles will alter. Biological systems have a slowness of response to chronic a low levels of external forcing, and this buffering capacity delays or in some cases masks the eco-system response.

Coastal seas - regional & local impact
There are urgent needs to be addressed at the regional and local scale. These decline in fisheries, the increasing pollution by heavy metals, PCBs & pesticides are local effects produced by anthropogenic influence. However, not enough data exists to relate these to changes in the earth system. Such effects are however keenly felt and must be dealt with scientifically to ameliorate local fallout.

Physical processes operating along Indian coasts
Only in the last decade has there been a general understanding of the large-scale dynamics of the coastal circulation in the Arabian Sea and the Bay of Bengal. The influence of basin scale currents and their influence on coastal shelf circulation is now acknowledged, even though many aspects still need study. A complete understanding of the dynamics of the estuaries is still awaited, but general features and the influence of remote forcing are acknowledged.

Large-scale currents along the outer shelf and beyond, around India, reverse seasonally with the monsoon winds. The currents forming a continuum from the northern Bay of Bengal to the northern Arabian Sea.

What influences currents on the inner shelf ? It is expected that large scale currents, tides, winds and river run off play important roles. Tides, inds in season (and sea-breezes) , and river run-off would be the major influences nearest the coast. In the few instances of direct current measurements, the cross-shore components are tidal (towards shore on flow and away on ebb). The along shore component would vary with season and location and could be due to the seasonal coastal currents.

What is clear is the beneficial effect that the tidal currents have on the coasts of India. The along shore component that can carry pollutants coastally may never be significantly strong enough to counter the dilution effects during transport.

This seems to be consistent with the COMAPS data sets which indicate that India coastal waters are clean and well oxygenated with no detectable spread of "hot-spot" influence. The large rivers on the east coast also play a role in confining along shore pollutant transport. Their large run-offs acting as barriers to close to coast transport of pollutants & sediments. The movement and spread of the fresh waters of the Ganga and Brahmaputra however still needs detailed study.

It is important to understand shelf and estuarine (of which there are a very large number of varying sizes) circulation, so that through effective modelling pertinent information is available to decision makers on movement of pollutants, sediments and offshore hazards (oil spills).

Pollution on Indian Coasts
The Arabian Sea is a major oil tankers route to South East Asia, and beyond, probably accounting for the tar like residues deposit on the nest coast of India. This chronic problem is however a seasonal feature, is largely regulated by the monsoons and associated winds.

Metals, being a conservative pollutant, needs careful monitoring since they remain indefinitely in the environment without break-down. As yet our waters are clear.

DDT which has been banned in most Western countries had been widely used in Indian agriculture. It was responsible for increase in agricultural output and eradicating of several vector borne diseases. Its high toxicity nullifies its benefits. DDT and its somers, residues of Gama BHC, Aldrine and Dieldrine have been recorded in sediments in several coastal locations. Especially high concentrations have been recorded at the river mouths of the major east coast rivers.

Sensitive environments
Indian coasts have a large variety of sensitive eco-systems. Sand dunes, coral reefs, mangroves, seagrass beds 7 wet lands are some that deserve special mention. Some of these are the spawning grounds and nurseries of a number of commercially important fishes, gastropods and crustaceans. A critical feature of these ecosystems are the variety of bioactive molecules that they host.

Recent mining of organisms from the tidal and inter-tidal zone have revealed large numbers of molecules with obvious application for human health and industrial applications. This could be the most commercially important aspect of the Coastal Zone. Molecules that show bioactivity from one ecosystem may not show the same activity, or level of activity, when mined from a different locale or different season. This feature alone should be reason enough for the protection of all such ecosystems, and not only representative isolated units in protected areas / parks.

Considering that Indian waters are of a good quality and that pollutant sources remain relatively confined, the protection of sensitive environments, with adjacent buffer zones should be promptly notified and enforced. Losses of such areas are losses to the common good and future generations.

Sand dunes seem to be ecosystems that are most often destroyed, probably because their place in the scheme of dynamic coastal morphology, is not obvious. Suffice to say that dunes are the reserves that nature stores, dissipates energy on, and moves when needed.

The modelling approach
It is the unstated goal of scientific enquiry that accurate prediction is the proof of understanding. Nature's essential processes therefore need to be modelled for the coastal seas. LOICZ proposes an hierarchy of 3 levels of models:

sqb.gif (46 bytes)process models to investigate ecosystem reaction to external forcing
sqb.gif (46 bytes)budget models to elucidate mass balances in specific geographic areas and time frames.
sqb.gif (46 bytes)system models to couple regional GCMs to bio-geo-chemical sedimentological or meteorological models

All these should, provide inputs to a future Earth System model.

As of date it needs to be appreciated, that the complexity of biological systems makes modeling difficult, and prediction of responses to changes more difficult. We cannot for instance say, if the present decline in tele-cast of biomass in the coastal seas does not feedback on global geochemical cycles, nor can we say that it does not. The fact that marine organisms occupy a true 3D world (compared to the 2D would of terrestrial organisms] compounds the modeling complexity.

Measurement and monitoring
A systematic long-term study of pollutants, in a regional context, and their effects on biota is necessary. Levels and distribution of contaminants need to be measured and monitored over long periods of time, in the water column, the sediment and the biota. Continuous information on the sources of pollution, the routes of distribution in the environment and their progress through ecosystems, is required. Similarly studies on bio-concentration, bio-accumulation and bio-magnification of pollutants are needed.

The scheme for what parameters should be measured where, when and how often, is complex. It requires careful planning to maximise the data collected per unit of cost and effort. Monitoring schemes in sentinel organisms or choice of bio-makers, have to be carefully considered to ensure the natural availability of the same species along the Indian coasts. Choice of different species for different areas has to be carefully evaluated in the lab and in-situ.

Synoptic monitoring tools of moored buoys & remote sensing by satellites and by acoustics should be used where possible. They are some of the most cost effective monitoring tools of modern technology. Quality control through validation and calibration protocols and experiments, becomes an important aspect in this context. Geographic Information System, various data bases, rapid communication of alarms are other tools for successful monitoring, along with risk analysis and disaster management plans.

The business of models - new perspective of an R&D Lab
The various hierarchy of models that the LOICZ project encourages was mentioned earlier. Here we shall discuss the challenges that must be met in integrating models form the natural sciences and those from the social sciences.

Where do the social sciences come in?
A geocentric view of global change sees humans as driving forces of global change. Examples are estimating anthropogenic production of CO2 as inputs to climate change models. An anthropocentric view of global change considers the environment as one of the drivers of social and economic change. Examples are desertification as impacting on land quality and productivity.

These two aspects are complementary halves of a feedback loop that must be constructed, analysed and understood together.

Thus the anthropocentric, systemic, social science view of global change compliments the geocentric, cumulative, natural sciences view of bio-geochemical cycling. The coastal zones are important for both.

It is sometimes suggested that models of these 2 very different sciences can be proceed in one of 2 ways. Either the output of social science models feed as inputs to bio-geochemical models of coastal change [varying scenarios and projections] ; or vice-versa.

This is untenable. The space and time scales are so different that integration of the outputs of one model type as inputs to the other model type, is impossible.

The challenge therefore is to engage both sciences simultaneously to get the scales right and to get the models right.


We began this talk with definitions and descriptions of the coastal zone, and then presented the case of India's coastal zone. Some hot spot locations were mentioned, but overall we conclude that our coastal waters are still in good condition. The activities of the Institute in the coasts, and the adoption of the LOICZ Science Plan were mentioned. A brief mention of our earth system was made, which was followed by the aspects of the global impact of the coastal seas. These were questions of what are we putting in, what do we need to know, what are the problems in the way, and the modelling approach.

The regional and local impact of the coastal seas was next discussed in terms of the physical processes operating, the pollution in our coasts and sensitive environments.

We then addressed the issues of modelling from the measurement and monitoring angle to the new perspective of an oceanographic laboratory that accepts that the state of the coastal environment has to be seen from 2 sides - the natural sciences and the social sciences.

Perhaps the Brundtland Reports sum it up best.

Sustainable development can be described as "the proper use and care of the coastal environment borrowed from future generations".

SD was defined a that which "meets the needs of the present without compromising the ability of future generations to meet their own needs".

bl.gif (534 bytes)