Warning bells: Pollution turns sea acidic, threatens fish, corals

There is a new threat to the country’s coastal waters, already struggling to cope with pollution from heightened industrial activity. The increasing amounts of carbondioxide getting dissolved in the water is acidifying it that could destroy corals reefs and reduce fish population, warn oceanographers. While most of the carbondioxide released annually by the consumption of fossil fuels such as coal, oil, and natural gas contributes to global warming, about onethird gets dissolved in the oceans, causing the more serious problem of acidification, said former Zoological Survey of India director K Venkataraman.

Organisms such as corals and calcifying planktons, key to the ocean’s ecosystem with their ability to grow shells, will be unable to perform their ‘magic’ in waters with acidic content, a situation that could prove hazardous in the long run, Venkatraman said. Similarly, marshlands, mangroves and seagrass, termed ‘blue carbon’ for their effective high rates of annual carbon sequestration, will not be able to store carbon for longer periods of time because of such waters, he added.

During the process of photosynthesis, they absorb a lot of carbondioxide that becomes part of their biomass and helps reduce the amount of the gas in the atmosphere. And, when these ecosystems die they sink under the bottom of the ocean along with the biomass, he said.

Another problem, National Centre for Sustainable Coastal Management director R Ramesh said, was untreated raw sewage draining into the ocean. This is mainly composed of nitrogen and ammonia that cause microbial degradation, leading to reduction in oxygen levels in the sea water making it acidic. Increased acidification, a few studies have shown, has led to incomeplete shell growth and malformed shell plates in forminifere, a species of coral. Acidification, some experts predict, could alter coral reefs in Lakshadweep, Gulf of Mannar and Andaman and Nicobar islands. Increase in carbondioxide in the ocean waters will decrease the pH (negative form of hydrogen concentration) and make water more corrosive, causing shells to dissolve, Venkataraman said.

Sensing the danger, the Union ministry of environment, forests and climate change has brought out a policy on controlling ‘Eutrophication and Ocean Acidification’, Ramesh said. This envisages reducing nutrient loading in to coastal waters through control of chemical fertilizers run-off from agriculture as well as discharge of untreated raw sewage containing a high concentration of nutrients. It also plans to encourage research in multiple ecosystems to better understand the link among temperature, salinity and nutrients. There was a proposal to improve the capacity of governments to monitor and design policies to reduce nutrients flowing into the coastal waters from agriculture and nonagriculture sources, he added.

P. Oppili, The Times of India, 21 April 2016. Article.


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