Microbes rule the reef. They determine both coral reef health and decline. Exploration of their diverse roles in these ecosystems has become possible only recently with the development of new research methods, such as metagenomics. Join San Diego State microbial ecologist Forest Rohwer as he builds his case for the role of microbes in the DDAMnation of coral reefs. His research expeditions to the remote Line Islands, including trips with Scripps scientists, have provided new insights into the mechanisms by which human activities can influence reef health; how we convert the essential microbial partners of a healthy coral reef ecosystem into coral killers.