Effects Of Rising Seawater Temperature On Coral Reefs
Thomas J. Goreau, Global Coral Reef Alliance, Cambridge, MA, and Raymond L. Hayes, Howard University, Washington, DC
Abnormally high temperatures trigger physical, chemical, and biological changes in the oceans that affect coral reefs and fisheries,
both directly and indirectly. The mechanisms responsible for those changes are qualitatively reviewed in this chapter. Almost all are potentially detrimental to reef ecosystems. The most dramatic is the uncoupling of symbiosis among corals and their zooxanthellate algae, on which coral reef construction depends. This obligate symbiosis is destroyed by small increases in temperature. Additional increases threaten the viability of corals and their symbionts. Coral reef ecosystems are vulnerable to thermal stress because they live very close to their upper tolerance limit for temperature. Coral reefs throughout the world have already been exposed repeatedly to excessive temperatures starting in the 1980s. Coral mortality has ranged from mild to catastrophic. Continued climate changes, including global warming, will trigger the demise of reef-building corals, leading to the collapse of our most productive, biodiverse, and economically valuable coastal Ray Ban outlet marine ecosystem, the coral reef.
Global reef and pelagic fisheries are also vulnerable to climate change. Reef fisheries are threatened by the loss of habitat, and pelagic fisheries are vulnerable to bottom-up trophic collapse from warm surface waters that block nutrient upwelling. While declines in global fisheries is often blamed on top-down effects from over-fishing, changes in ocean circulation patterns from climate instability pose serious threats from below. Failure to recognize the impacts of these large-scale changes make conventional fisheries management strategies, based on controlling fishing efforts, increasingly irrelevant. Marine protected areas are insufficient to restore these fisheries when ray ban baratas habitats have been destroyed or the food chain has collapsed. Reduction of global greenhouse gas concentrations is the sine qua non for preservation of coral reef ecosystems and reef fisheries, and for conservation of pelagic fisheries.