☆Let us create the future with hope☆
ScienceDaily (Jan. 26, 2009) — Unchecked global warming would leave ocean dwellers gasping for breath. Dead zones are low-oxygen areas in the ocean where higher life forms such as fish, crabs and clams are not able to live. In shallow coastal regions, these zones can be caused by runoff of excess fertilizers from farming. A team of Danish researchers have now shown that unchecked global warming would lead to a dramatic expansion of low-oxygen areas zones in the global ocean by a factor of 10 or more.
Mississippi Dead Zone, off U.S. coast. Reds and oranges represent low oxygen concentrations. (Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)
Whereas some coastal dead zones could be recovered by control of fertilizer usage, expanded low-oxygen areas caused by global warming will remain for thousands of years to come, adversely affecting fisheries and ocean ecosystems far into the future.
Professor Gary Shaffer of the Niels Bohr Institute, University of Copenhagen, who is the leader of the research team at the Danish Center for Earth System Science (DCESS), explains that "such expansion would lead to increased frequency and severity of fish and shellfish mortality events, for example off the west coasts of the continents like off Oregon and Chile".
Large extinction events
Together with senior scientists Steffen Olsen oceanographer at Danish Meteorological Institute and Jens Olaf Pepke Pedersen, physicist at National Space Institute, Technical University of Denmark, Professor Shaffer has performed projections with the newly-developed DCESS Earth System Model, projections that extend 100,000 years into the future.
He adds that "if, as in many climate model simulations, the overturning circulation of the ocean would greatly weaken in response to global warming, these oxygen minimum zones would expand much more still and invade the deep ocean." Extreme events of ocean oxygen depletion leading to anoxia are thought to be prime candidates for explaining some of the large extinction events in Earth history including the largest such event at the end of the Permian 250 million years ago.
Series of changes
Furthermore, as suboxic zones expand, essential nutrients are stripped from the ocean by the process of denitrification. This in turn would shift biological production in the lighted surface layers of the ocean toward plankton species that are able to fix free dissolved nitrogen. This would then lead to large, unpredictable changes in ocean ecosystem structure and productivity, on top of other large unpredictable changes to be expected from ocean acidification, the other great oceanic consequence of high atmospheric carbon dioxide concentrations from fossil fuel burning.
Professor Shaffer warns that as a result, "the future of the ocean as a large food reserve would be more uncertain. Reduced fossil fuel emissions are needed over the next few generations to limit ongoing ocean oxygen depletion and acidification and their long-term adverse effects".
SoFi Software for Enterprise Carbon Footprint Management
Ocean Dead Zones Likely To Expand: Increasing Carbon Dioxide And Decreasing Oxygen Make It Harder For Deep-sea Animals To Breath (Apr. 18, 2009) — Low-oxygen "dead zones" in the ocean could expand significantly over the next century, according to marine chemists. These predictions are based on the fact that, as more and more carbon dioxide ... > read more
Oxygen Depletion Zones In Tropical Oceans Expanding, Maybe Due To Global Warming (May 2, 2008) — Scientists confirm computer model predictions that oxygen-depleted zones in tropical oceans are expanding, possibly because of climate change. Oceanographers have discovered that oxygen-poor regions ... > read more
'Dead Zone' Causing Wave Of Death Off Oregon Coast (Aug. 14, 2006) — The most severe low-oxygen ocean conditions ever observed on the West Coast of the United States have turned parts of the seafloor off Oregon into a carpet of dead Dungeness crabs and rotting sea ... > read more
Nitrous Oxide From Ocean Microbes Could Be Adding To Global Warming (Dec. 12, 2007) — A large amount of the greenhouse gas nitrous oxide is produced by bacteria in the oxygen poor depths of the ocean. Nitrous oxide is a powerful greenhouse gas some 300 times more so than carbon ... > read more
Ocean 'Dead Zones' Trigger Sex Changes In Fish, Posing Extinction Threat (Apr. 3, 2006) — Oxygen depletion in the world's oceans, primarily caused by agricultural run-off and pollution, could spark the development of far more male fish than female, thereby threatening some species with ... > read more
Number of stories in archives: 76,647