Coral reefs can be damaged by natural processes, such as storms, but they are increasingly at risk from human activities. Oil spills and pollutants can threaten entire reefs. Excessive nutrients from land sources, such as sewage and agricultural fertilizers, promote the growth of algae that can smother corals. Other organisms harmful to corals, such as crown-of-thorns starfish, multiply when the species that prey on them are removed.
Coral productivity is also decreased when land developments for agriculture, industry, and housing increase sediment transported from land into coastal waters as runoff. This clouds the waters and blocks light necessary for photosynthesis by algae living in corals. Corals face serious risks from various diseases. When corals are stressed, they often expel the algal symbionts that are critical to their health in a process commonly known as coral bleaching. One known cause of coral bleaching is increases in ocean temperatures, possibly due to global warming.
Scientists worldwide are working to understand the impacts of natural processes and human activities on the health and sustainability of coral reefs. The USGS is contributing to the effort to understand the biological and geological controls that affect our Nation's coral reefs. USGS coral reef research focuses on detailed mapping of reefs, the development of monitoring techniques, studying reefs' geologic growth and development, and how they are affected by water quality, fishing, and sedimentary and hydrologic processes. These efforts will help provide information that is essential if coral reefs are to be saved.
- Pacific Coral Reef Project
- Coral Reef Ecosystem Studies (CREST)
- Coral Bleaching and Disease: Effects on Threatened Corals and Reefs