Marine ecosystem dying a slow death

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India has been gifted with huge marine resource, aquatic biodiversity and beautiful beaches which attracts lakhs of foreign tourist every year but you would be surprised to know that our marine ecosystem across the world is dying a slow death every day.

Deteriorating climatic conditions and rising levels of air pollution, caused by human activities are posing a serious threat to the delicate marine ecosystems in the oceans around the world.

The main factor behind deteriorating condition of oceans is primarily due to a drop in dissolved oxygen level. Low level of dissolved oxygen harms fisheries, destroys biodiversity and undermines the quality of aquatic life.

What is dissolved oxygen ?

  • Dissolved oxygen refers to the level of free, non-compound oxygen present in water or other liquids. It is an important parameter in assessing water quality because of its influence on the organisms living within a body of water. Dissolved oxygen is an essential factor for the survival of aquatic life. A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality.
  • According to the study of National Academy of Sciences oxygen depletion process occurred over a relatively short period (about 150 years), but the recovery from this collapse took more than 1,000 years.

Importance of dissolved oxygen :-

  • Dissolved oxygen is necessary to all forms of acquatic life including fish, invertebrates, bacteria and plants.These organisms use oxygen in respiration, similar to organisms on land.
  • Fishes obtain oxygen for respiration through their gills, while plant life and phytoplankton require dissolved oxygen for respiration when there is no light for photosynthesis
  • Microbes such as bacteria and fungi also require dissolved oxygen. These organisms use DO to decompose organic material at the bottom of a body of water. Microbial decomposition is an important contributor to nutrient recycling

What are Dead Zones ?

  • Low oxygen zones are technically termed as dead zones as they are unable to support acquatic life. According to the study, depletion in dissolved oxygen levels has intensified over the last 40 years and currently there are more than 400 dead zones in the oceans across the world and their size is rapidly increasing .
  • The dead zone in the Arabian Sea has been growing in size, with a current area of approximately two million sq km, and it is one of the most severe zones of all the known dead zones
  • According to the National Oceanic and Atmospheric Administration, the Gulf of Mexico has the the second largest oxygen minimum zone in the world  the size of the Gulf of Mexico’s oxygen minimum zone is over 14,200 sq km, and it witnesses immense loss of aquatic life every year.

Factors resposible for acquatic massacre

  • The acquatic life is not only depleted by low level of dissolved oxygen but there are many other factors too that endanger the marine life such as ocean acidification, sea-level rise and changes in weather patterns.
  • These issues tend to aggravate the hypoxia epidemic by acting parallel to each other and increases the scale of oxygen depletion. Excessive untreated sewage from areas of high population density, fertiliser and other chemical pollutants entering the seas are some of the main contributors for rapid depletion of oxygen levels in the sea.
  • The chemical nutrient run-off from the land, especially nitrogen and phosphorous, cause eutrophication. The marine ecosystem responds to the addition of these chemical substances by increasing the photosynthesising plankton in water in the form of algal bloom.
  • The plankton die and decompose, and in the process, consumes tremendous amounts of dissolved oxygen, leading to oxygen paucity and rendering the waters unfit for life forms

Is china's enviornment so clean that it can question India's enviornment purity ?

  • China had recently put public hoardings in various cities to highlight the level of pollution in India but very recently explosion at the Port of Tianjin in China on August 12 took a toll on the marine ecosystem of china.
  • There were at least 700 tonnes of highly toxic sodium cyanide, 70 times the legal limit, stored in the warehouse. Incidents such as these show the lack of regulation on part of the Chinese Government to control the manufacturing and storage of hazardous chemicals, especially near coastal areas that are also densely populated.

Restoring acquatic life needs cutting edge effort 

  • The Government must prepare strategies that aim to safeguard marine life, and for this, an annual audit of dissolved oxygen in the sea is essential. Through this authorities can predict the formation of dead zones in the sea and formulate effective plans and policies to manage marine life,
  • The Government may also opt for the latest technology such as underwater gliders that fly from the sea surface to within about three metres of the sea floor, mapping out the distribution of dissolved oxygen from near the coast to over 80 km offshore. 
  • Other action plans can include minimising the use of fertilisers in coastal areas and maintaining vegetation at strategic locations so that the former act as chemical nutrient sinks.
  • Coastal cities and inhabited areas must also be brought under stringent effluent and sewage treatment regulations, so that effective pollution control can be established.
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