New York: Global warming has led to expansion of low-oxygen "underwater deserts" in the tropical oceans over the past five decades, which scientists view as a potential threat to marine ecosystems.

Climate models predict that the trend will continue, potentially threatening marine ecosystems, a report published in Nature magazine said. The discovery, it said, concerns a layer of the ocean called the oxygen-minimum zone , where concentrations of dissolved oxygen are particularly low.

The new study shows that this zone has been expanding both upwards and downwards into the adjacent layers in tropical waters. Climate models, according to the report, predict that warming of the sea surface as a result of human activity will hamper the mixing of oceanic waters, preventing dissolved oxygen from mixing evenly through the water column. The new results suggest that this process has already begun.

Researchers led by Lothar Stramma of the University of Kiel, Germany, measured the oxygenation of the oceans at depths of between 300 and 700 metres during a series of observation cruises in tropical regions of the world's three main oceans, Nature reported. The scientists added their new data to previous oxygen measurements to build up a picture of the trend over the past 50 years.
Source : PTI