|
Shrinking Himalayan snow threatens Goan fish BY MELVYN MISQUITA
a few days ago. According to Dr Joaquim Goes, a senior investigator at Bigelow Laboratory for Ocean Sciences in the USA, the Indian subcontinent is already witnessing the effects of global warming within in its own backyard and the trends are particularly disturbing. On account of the shrinking Himalayan snow cover, the southwest monsoon winds are becoming stronger than ever before. While these winds help bring much needed rainfall to the Indian subcontinent, in the Arabian Sea they also help pull up nutrient-rich water from the deep to the surface, a process called upwelling. These nutrient rich waters create ideal conditions for tiny ocean plants, called phytoplankton to bloom. Phytoplankton are the base of the marine food chain. Stronger monsoon winds would thus mean more phytoplankton, which might seem like a good thing as more phytoplankton should mean more fish. But not so, according to Dr Goes and his team. Excessive phytoplankton blooms can cause oxygen depletion in the water at depth suffocating marine life. “Indeed, fishermen off the coasts of Somalia, Oman and Yemen say the number of dead fish they catch has been increasing steadily for the past five to seven years. If the trend continues, more fish will die,” says Dr Goes. However, the problem does not end there. Bringing deep water to the surface in this part of the globe could also dramatically increase global warming. Some bacteria have found a way of dealing with the low oxygen levels at the bottom of the Arabian Sea. Scientists at the National Institute of Oceanography, have shown that they do this by extracting oxygen from nitrate, which is found in the water. The process, known as 'de-nitrification', produces nitrous oxide, a powerful greenhouse gas. When de-nitrification happens at the bottom of the sea, the nitrous oxide is trapped. But when the water rises to the surface, the gas is released into the atmosphere where it acts as a greenhouse gas that is about 300 times more harmful to the environment than carbon dioxide. “If the Himalayas continue to receive less winter snow, it would make the Indian subcontinent heat up faster in summer. We could be witnessing stormier monsoons and more flooding incidents if the warming trend continues,” says Goes. “In turn, the Arabian Sea could become like a chimney for nitrous oxide. And that could mean that climate change would be much worse than is currently anticipated,” Dr Goes adds. According to the research, Dr Goes and his colleagues used data from OrbImage and NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite to show that phytoplankton concentrations in the Arabian Sea have increased by over 350 percent over the past 7 years. The Arabian Sea hosts one of the world's largest pools of oxygen-poor water at depths between 200 and 1,000 metres (656 to 3,281 feet). Since the Arabian Sea lacks an opening to the north, the deeper waters are not well ventilated. The research team funded by NASA includes another Goan Dr Helga Gomes who hails from Verna and was a student of Marina English High School. Dr Joaquim Goes is from Cortalim and studied at Our Lady of Perpetual Succour High School. They came to the USA in the fall of 1999 after working at the NIO for sometime. Details of their research -- which has evoked worldwide interest and is expected to be presented at a Congressional Testimony on Capitol Hill in Washington DC -- are available at the Bigelow Laboratory for Ocean Sciences website: http://www.bigelow.org/climatechange. [Comments on this report] Date:
Sat, 30 Apr 2005 Senhor Mesquita very interesting article of Goans contributing to preserve nature. Thanks. Agnelo Gomes Date:
Sun, 1 May 2005 Congratulations to the two Goan scientists for their works! B Colaco Date:
Sun, 1 May 2005 My reading of the original Science paper led me to the wrong conclusion, namely that the increase in phytoplankton biomass would mean more fish. Indeed, the title of the paper is quite misleading to a non-expert like me. The title is: "Warming of the Eurasian Landmass Is Making the Arabian Sea More Productive". The paper also does not explain what exactly is meant when the authors state that their findings have "immediate and important bearing on regional fisheries". This is how they end their paper: "Our findings raise the intriguing possibility that the western as well as the central regions of the Arabian Sea could witness more widespread blooms of phytoplankton if the mid-latitudinal continental warming trend and the decline in winter snow cover over the Northern Hemisphere continue. Although our findings have an immediate and important bearing on regional fisheries, the implications of a more productive Arabian Sea go far beyond that; for example, to our planet's climate. The Arabian Sea hosts a distinct, basin-wide oxygen minimum zone between 150 and 1000 m (35–37), whose presence has a substantial impact on marine elemental cycles, in particular those linked to the production of climatically relevant trace gases (37). The changing productivity of the Arabian Sea could thus have far-reaching consequences for the oxygen minimum zone, whose existence is regulated by a balance between the ventilation of intermediate depths and oxygen consumption during the oxidation of organic matter produced in the euphotic column (36, 37)." I hope Helga clarifies this issue. Cheers, To comment on this report, please Click Here to contact Melvyn Misquita. |
