Deep Sea under Peril

R. Sabesh

Three – fourths of the earth’s surface is covered by the sea, of which only 7 – 8% is the coastal area and the rest is deep sea. Though the geographical area of deep sea is vast, our knowledge and understanding about the deep-sea environment is limited, due to inaccessibility and the requirement of very expensive and sophisticated instruments to carry out research at great depth. The vast and remote deep-sea is an attractive alternative for dumping the waste materials. To determine the impact of waste disposal on bottom-living animals, researchers in developed countries are involved in finding out the effects of dumping of waste on living resources and deep-sea biodiversity, as well as the transmission of contaminants back to the human population. But, between our limitless imaginations about the natural world and public recognition for its real value, can these invaluable resources be protected from over exploitation?

Major threats facing the deep sea

Deep-sea mining, deep sea fishing, dumping of harmful radioactive-waste and synthetic chemicals into the deep sea are some of the major threats to the ocean system. Waste materials such as sewage or sludge, mining wastes, fly ash from thermal power stations, dredged spoils from harbors and estuaries, man-made hazardous organic compounds used as pesticides, weapons, and industrial uses, as well as packaged goods may make their way to the sea floor over a period of time and cause severe ecological imbalance on the sea bed as well as in the entire marine ecosystem. Disturbances on the sea floor show vertical mixing of sediment on the sea floor, lateral migration of sediment plume, changes in geochemical and biochemical conditions as well as reduction in biomass in the benthic environment. Around 80 percent of the ocean at depths of more than 3,000 m. the sea floor may seem to be safe from the man-made disturbances that threaten the terrestrial and coastal environment.

Fig 1

Deep Sea biodiversity

The deep sea does not support many species of fish. A few marine mammals and almost no flora is found due to the lack of sunlight. Organisms in the deep sea rely primarily on organic matter falling from the top for food. Large animal remains are quickly exploited by local fauna in the deep sea. Whale carcasses may be particularly important to the deep sea because their large bodies sink fast enough across thousands of metres of water, containing fish and other planktonic scavengers, with sufficient intact tissue for seafloor-dwelling organisms to feed on. Given the potentially important role of dead whales to the deep sea, scientists fear that the booming whaling industry will seriously affect deep sea biodiversity. In whale-processing technology, the whale bones are used for various purposes like extraction of medicines, bone meal, fertilizer etc. and hence whale skeletons are no longer discarded. But, the magnitude and consequences of changes in deep sea biodiversity resulting from whaling are difficult to evaluate because of the lack of historical or even good contemporary data on most whale population sizes and distributions.

Adaptations of deep sea organisms

The physical and chemical characteristics of the deep sea environment pose a challenge to the organisms residing in this habitat, which require a wide range of adaptations. The adaptations are of two fundamental kinds: those that effect tolerance of the environment and others that establish rates of metabolic function appropriate to the deep sea. The high pressures of the deep sea are perturbing to physiological and biochemical processes of organisms. Some special proteins of deep-sea fishes have unusually rigid structures so as to withstand high pressure and low temperature. Life in the dark appears to allow a large reduction in locomotory activity and thereby, large reduction in the metabolic rate. Low concentrations of oxygen also present challenges to some deep-living animals. Fishes found in the oxygen minimum zone have elevated capacities for extracting oxygen from seawater and exhibit different patterns of gene expression for enzymes of aerobic and anaerobic metabolism

Conservation measures

National and international agencies, nongovernmental organizations and students have undertaken ocean research across the world to find solutions to the deterioration of marine ecosystem. The Indian Deep-sea Environment Experiment (INDEX) is a multi-disciplinary study to establish baseline conditions and evaluate the possible impact of deep-sea mining in the Central Indian Basin. A disturbance was simulated to study the effects of sediment re-suspension and resettlement in the benthic areas, monitoring the process of restoration and recolonisation of benthic environment and development of predictive models for environmental impact of deep seabed mining are underway. At present, ocean dumping is predominantly banned by international law. To protect the deep-sea resources, various international laws have been framed as part of United Nations Conference on Environment and Development (UNCED) in Agenda 21. The general obligation of States to protect and preserve the marine environment is codified in Article 192.

States are exhorted in accordance with the provisions of the United Nations Convention on the Law of the Sea on protection and preservation of the marine environment, commit themselves, in accordance with their policies, priorities and resources, to prevent, reduce and control degradation of the marine environment so as to maintain and improve its life support and productive capacities. The International Maritime Organisation (IMO) insists that the States commit themselves to the conservation and sustainable use of marine living resources of the seas. All our efforts to prevent the degradation of the marine environment should be a precautionary and anticipatory rather than a reactive approach.


  • Average depth of the sea is 3,800 m and the deepest trenches reach upto 11,000 m.
  • Hydrostatic pressure is very high. Pressure increases equivalent to 1 atmospheric pressure for every 10 m depth. Pressures may reach upto 1,100 atmosphere.
  • Temperatures normally range between 0 to 4°C. In the Mediterranean sea, it is -13°C at 4000m. The Red Sea’s temperature is -21.5°C at 2000 m.
  • Absolutely dark because of no sunlight. The only light generated being bioluminescence from organisms. As a result, photosynthesis is impossible and no plants exist. The deep sea animals depend on organic matter falling from the top, mainly carcasses of whales and other marine organisms for food.
  • As there is no contact with the atmosphere, the dissolved oxygen in water is very low in deep sea
  • Salinity is relatively constant at 34.8%
  • Despite all these constraints animal life still survives in deep sea

Source: Eco News, Vol 9, No 2, July to September, 2003.

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