Scientists offered a rare glimmer of hope in a recent coral reef study, which suggested that reefs in the world's warmest oceans might be protected from the deleterious affects of global warming. This potential rests on a much-debated theory that a natural "ocean thermostat" prevents sea-surface temperatures from exceeding 31 degrees Celsius. If confirmed through additional research, the study's findings could have important implications for how and where we design measures to protect reef ecosystems.
Coral Bleaching Events on the Rise Worldwide
Over the last 30 years, average ocean temperatures have increased 0.3 to 0.4 degrees Celsius. As a consequence, coral ecosystems have been dying at an alarming rate through a process known popularly as coral bleaching. Specifically, increased ocean temperatures have forced some corals to expel the colorful symbiotic algae that inhabit their tissue, causing corals to turn white and die.
Locations of Reefs Experiencing Severe Bleaching
Source: ReefBase 2008
The Warm Pool Exception
Researchers from the National Center for Atmospheric Research investigated a section of the western Pacific Ocean known as the Western Pacific Warm Pool. Between 1980 and 2005, this area experienced only four bleaching events, a far lower rate than any other reef region in the world. Similarly, its water has warmed by less than 0.1 degrees Celsius, significantly less than the global average. Scientists believe that because the Warm Pool's natural sea-surface temperatures are already close to the proposed ocean thermometer temperature of 31 degrees, it is less vulnerable to rising global temperatures. Likewise, the reefs that inhabit these waters are less likely to bleach.
Uncertainties and Other Threats
The complex processes and feedback mechanisms that regulate ocean temperatures remain poorly understood by scientists. Even if a natural ocean thermostat is currently regulating ocean temperatures, it is also possible that global warming or other human interferences could alter the natural equilibrium and raise the thermostat. Furthermore, other threats to reef ecosystems must also be addressed, including ocean acidification, pollution, and overfishing.
Top photo by yoel_tw via Flickr
RELATED LINKS:
Coral Bleaching IndexAnimations of Bleaching Events
Climate's Impact on Coral & Reef Systems
Coral Reefs: Assessing the Threat
Ocean Acidification: the Other Threat of Rising CO2 Emissions
