A Greenpeace diver takes measures of corals. Greenpeace is helping to gather evidence of baseline conditions of coral on the Alacranes Reef in the Gulf of Mexico. According to Hector Reyes Bonilla, Mexican scientist, the data collected will help in future studies of the impacts of climate change and ocean acidification on coral ecosystems, including bleaching of corals. Bleaching happens when symbiotic algae living inside the corals are expelled into the sea. This is thought to be caused by elevated sea surface temperatures.