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Dead zone in Arabian Sea

  • Written by  Tom Hart
  • Published in Oceans
An oceanic green algal bloom An oceanic green algal bloom Shutterstock
01 Nov
2014
A growing ‘dead zone’ in the Arabian Sea has allowed low-oxygen plankton to dominate the base of the marine food chain. The ecosystem change has led scientists to warn that plankton may supplant other food sources local fish rely on

Millions of green algae living in the thick blooms of the Noctiluca scintillans have allowed it to exploit an oxygen-starved zone the size of Texas. ‘These blooms appear year after year and could be devastating to the Arabian Sea ecosystem,’ said biochemist Helga do Rosario Gomes, lead author on the study.

Researchers at Columbia University fear the new ecosystem may be without predators for the bloom. This could be bad news for fishermen in Maharashatra and Tamil Nadu, who already report declined catches over the last 20 years. Fish unable to feed on Noctiluna are dying off without a food source.

India’s boom cities could be playing a role in the problem. Mumbai’s population sends 63 tons of nitrogen and 11 tons of phosphorus into the sea each day, deoxygenating the water. ‘Rapidly growing cities don’t have the capacity to treat their sewage,’ said study co-author Joaquim Goes, a biogeochemist at Lamont-Doherty. ‘The amount of material being discharged is humongous.’

Dead zones are also on the rise globally, with 95,000 square miles affected across the world’s oceans.

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