Adapting to the Heat

Worldwide, global warming is causing the disappearance of coral reefs. A laboratory located on Ofu Island in American Samoa studies the effect of climate change on the long-term survival of reef-building coral.

In a deceptively simple setup, small pieces of coral were taken from the nearby lagoon, and transplanted into one of two water tanks. One, the control tank, was kept at the same temperature as the lagoon. In contrast, the water within the experimental tank was warmed by two degrees Celsius. After being allowed to acclimatize, the number of living coral pieces in the two tanks was compared. The mortality rate in the control tank was negligible, but two thirds of the coral died in the warm tank.

What attributes did the survivors have that enabled them to tolerate the hotter water? Part of the answer lies in the algae that live inside the coral polyps, as some strains seem to be hardier than others and better able to handle the heat. However, this is only part of the answer, and more research is needed to determine whether, in 50 -100 years, coral reefs resemble the cool tank or the hot.

See the start of this research at "Bringing the lab to the reef".