Why are Tropical Reefs Growing Faster in Cooler Waters?

The growth and survival of coral species that thrived in warm seas have been hampered for thousands of years by the chilly waters in tropical upwelling zones. Corals living in cooler waters are now forming reefs quicker than adjacent corals living in warmer waters, according to new research from Florida Tech.

Researchers used ecological studies of coral reefs off the coast of Panama to demonstrate that reefs exposed to strong upwelling events-when deep, cold water rises to the surface-are constructing the reef structure more quickly than reefs that do not benefit from the stress-relieving effects of cool waters.

Rodriguez-Ruano and associates quantified the beneficial and detrimental processes that occur naturally on reefs to calculate a reef's growth potential. The fundamental constituents of the reef are the robust calcium carbonate (limestone) skeletons that corals leave behind as they develop. Rodriguez-Ruano stated, "we employed biological surveys to determine the number of constructing and eroding creatures on a reef."

To determine whether a reef is producing enough calcium carbonate to continue developing over time or if more calcium carbonate is being withdrawn than what is being generated, we assessed how much is being produced and how much is being lost within a year.

If global greenhouse gas emissions are reduced by 50% by 2080, reefs in regions of high upwelling may be growing quickly enough to keep up with the rising sea level. However, other regions need help to keep up with the current rates of sea-level rise and run the risk of being overtaken by deeper waters.

Study's Conclusion

These findings are encouraging since they show that certain reefs can still stave off the consequences of climate change, according to Aronson. Cooling from upwelling will only last for a while if we don't reduce carbon emissions, so we should keep sight of the reality that temperatures are rising quickly.

He concluded that "if we want to protect reefs that have a fighting chance and stop the bleeding of the ones that are already being eroded, we need to strengthen our efforts at carbon control."