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Images: Coral Crusader

Hannah Barkley, a Ph.D. student in the MIT-WHOI Joint Program in Oceanography, works in WHOI scientist Anne Cohen's lab, studying the potential impacts on corals of changing ocean conditions, including warmer and more acidic seawater. (Geory Mereb, Palau International Coral Reef Center)
Researchers in Anne Cohen's lab have found and targeted certain coral reefs that thrive in places with naturally more acidic waters, including sites off the Rock Islands in Palau. These corals can provide valuable information as the rest of the ocean becomes more acidic. The ocean's pH is dropping as it absorbs excess carbon dioxide in the atmosphere, produced by fossil-fuel burning. (Hannah Barkley, Woods Hole Oceanographic Institution)
One impact of warming ocean temperatures is bleaching, a phenomenon that can kill corals. White or bleached areas of the coral indicate where symbiotic algae have departed from coral tissues. (The corals have retained the algae and their color in the brown patches.) Without the algae to make food, the corals can starve. (Hannah Barkley, Woods Hole Oceanographic Institution)
To investigate water temperatures that Palauan reefs are experiencing, Hannah Barkley and colleagues have deployed an extensive network of underwater temperature sensors around the islands’ barrier reef and several interior lagoon reefs. A black temperature sensor lies on coral reef off Palau, attached to a purple float to mark its location. (Hannah Barkley, Woods Hole Oceanographic Institution)
MIT-WHOI graduate student Hannah Barkley (left) and colleagues install equipment to measure water conditions around coral reefs in Palau. (Anne Cohen, Woods Hole Oceanographic Institution)
Just below the water off Rock Islands, the reseearchers discovered healthy coral reefs with a high diversity of species living in high temperature, low-pH seawater. They are exploring why these corals have thrived in low-pH waters. (Hannah Barkley, Woods Hole Oceanographic Institution)
Graduate student Hannah Barkley uses an underwater drill to core a sample of coral skeleton. By analyzing chemical changes in the skeletons, scientists can detect changes in water conditions and the corals' growth. The skeletons have growth rings, similar to tree rings, which scientists use to date the changes. (Anne Cohen, Woods Hole Oceanographic Institution)
The living tops of corals are brought back to a lab where they are set in containers with seawater infused with different levels of carbon dioxide to see how each level affects the corals' growth. (Hannah Barkley, Woods Hole Oceanographic Institution)
The corals are put in containers with different carbon dioxide levels. Green containers have current levels. Yellow ones have carbon dioxide levels equal to what is projected in 2050. Red containers have even higher levels of carbon dioxide. (Hannah Barkley, Woods Hole Oceanographic Institution)
Hannah Barkley and colleagues in Anne Cohen's lab at WHOI have been collaborating with researchers at the Palau International Coral Reef Center, including Geory Mereb (left), to help identify strategic Paluan reefs to designate as marine protected areas. (Pat Lohmann, Woods Hole Oceanographic Institution)
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