Tuesday, 1 February 2011

One Health in the News-Changing climate of the earth's oceans


GLOBAL WARMING EFFECTS ON SEA LIFE

Caribbean corals have suffered massive die-offs in recent decades, linked to diseases that thrive in warmer waters, according to the Proceedings of the National Academy of Sciences journal study, led by Laith Yakob of the University of Queensland and Peter Mumby of the University of Exeter. "The strong link between infectious disease outbreaks and rising sea temperature has inevitably led to projections of increased epizootics in the future," says the study.
In the 2010-2040 period, coral reefs are expected to become highly susceptible to more frequent bleaching events. The IPCC sees this as the greatest threat to the world's reef systems.

Coral bleaching is whitening due to stress-induced expulsion or death of their symbiotic protozoa, zooxanthellae, or due to the loss of pigmentation within the protozoa.The corals that form the structure of the great reef ecosystems of tropical seas depend upon a symbiotic relationship with unicellular flagellate protozoa, called zooxanthellae, that are photosynthetic and live within their tissues. Under stress, corals may expel their zooxanthellae, which leads to a lighter or completely white appearance, hence the term "bleached". Once bleaching begins, it tends to continue even without continuing stress. If the coral colony survives the stress period, zooxanthellae often require weeks to months to return to normal density.
Thailand closing dive sites in order to allow coral to ‘recover’
The Marine and Coastal Resources Department is pressing ahead with a plan to close 10 popular diving sites in five provinces to limit the impact of tourism on severely damaged coral. The sites attract about one million tourists a year, and could be closed for up to 14 months. But diving operators say tourism is but one cause of the bleaching phenomemon, and if the diving sites are closed for as long as proposed, taxpayer help may be needed to keep some companies alive.
"Diving companies are being singled out for blame, when the main cause is a warming of sea temperatures," said one disgruntled company head. Some coral reefs may need several years to recover, not just a matter of months, they say.
Veteran marine biologist Thorn Thanrongnawasawat said closing the coral reefs will give the coral time to recover, but more permanent solutions are still needed.

Mercury cycling:
An international research team working with National Institute of Standards and Technology (NIST) scientists at the Hollings Marine Laboratory (HML) in Charleston, S.C., has suggested for the first time that mercury cycling in the flora and fauna of the Arctic may be linked to the amount of ice cover present.