Panaji(Goa): Indian scientists will be looking at rivers flowing through Bangladesh to collect data and study the "dead zones" in Bay of Bengal where oxygen level is nearly zero.
Goa-based National Institute of Oceanography (NIO) and Dhaka University have signed a Memorandum of Understanding on ocean studies, which also includes sampling of water from rivers in Bangladesh that eventually flow into the Bay of Bengal.
"In the Bay of Bengal, we have thick oxygen-minimum levels between 150 to 600 metres. These are the areas where oxygen is nearly zero," NIO Director Dr SWA Naqvi told.
The increasing run-off of nitrogen from agricultural fields in Bangladesh into the rivers which eventually meet the Bay of Bengal results in depletion of oxygen in the ocean, he said.
"What we think is that since these fertilisers are being continuously added to the system, there may be further depletion of oxygen. It will have an impact on environment as well as the ecology. That is why, we are interested in looking at the fate of nitrogen," he said.
"We are interested in looking at fluxes of nitrogen from rivers into Bay of Bengal as the biggest of these rivers flow through Bangladesh," the director said. Sampling of water will help "to quantify how much nitrogen is washed in the water", he said.
"We are looking at cycling of nitrogen in aquatic system, both freshwater as well as ocean. Nitrogen that runs in the water through fertiliser produces algae. There are harmful algal blooms which are formed. The excess nitrogen stimulates growth of algae, and when algae die they deplete oxygen in the water column," he explained.
"There are more than 600 sites in the world where coastal water has lost oxygen," added Naqvi. In South Asia, we are consuming huge amounts of fertiliser to boost agricultural production. "Most of these fertilisers are not utilised by plants and they get washed off... They run off in rivers and groundwater. It is an important issue from the environmental and human point of view," he said.
"High nitrate concentration in drinking water is not advisable as it poses health hazards and causes blue baby syndrome," he added.
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