Conserving our Corals

February 2010
By:
Andrew Baker, Ph.D., Assistant Professor, University of Miami Rosenstiel School of Marine and Atmospheric Science
This is the second of three essays on coral reefs and climate change.

Coral reefs are some of the most important and productive places for life on Earth.

By some estimates, coral reefs contribute about $300 billion to the worldwide economy each year, providing resources for everything from tourism to medicinal products. Reefs also provide our shorelines with protection during hurricanes and strong winds, and they serve as nursery grounds for juvenile fish and other animals caught for humans to eat. But with the effects of both man-made and natural factors, corals are facing a dangerous future with much warmer and more acidic oceans than we have today.

Recent studies show that corals today are not as healthy or as abundant as they were just 30 years ago. Existing in both hard and soft forms, corals live within a very narrow temperature range and depend on tiny algal partners called "zooxanthellae" to help them absorb sunlight in shallow waters. The algae live inside the transparent tissue of the coral and help give them their brilliant colors and a steady source of energy from photosynthesis. This symbiotic relationship allows corals to build their limestone skeletons over time. 

These partner algae are the key ingredients to a balanced and healthy life as a coral, but they are also very sensitive to changes in the surrounding environment. I have spent much of my career looking at how climate change is impacting corals and studying how some corals are managing to adapt to these significant environmental changes. 

Slight changes create big problems

Even a slight change in the surrounding environment - either in ocean temperature, available light or ocean acidity - can cause widespread coral 'bleaching", in which the colorful algae are lost, leaving the transparent coral tissue and white limestone skeleton behind. If corals are not able to replenish their algal partners quickly - within a few weeks - corals begin to die. Even if they do not die, bleached corals are weakened and are more vulnerable to diseases, pollution and damage from human contact. 

But some species of coral are hardier than others, which I think may be partly due to their ability to contain certain types of partner algae that are more resistant to higher temperatures. Over the last 14 years, I have studied corals in some 25 countries in 4 different continents to understand how these special algae are distributed. We keep thousands frozen samples of coral DNA in my lab. My team and I are busy running experiments in order to pinpoint the specific genetic and physiological keys to their amazing adaptation over time. We grow different species of coral in the lab, and are trying to find ways to inoculate corals with heat-tolerant algae to help them deal with climate change and bleaching events in the future. .In this way I hope we can give corals a fighting chance of surviving the warmer and more acidic oceans of the future. 

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