Coral reefs cover many square miles of the earth’s ocean floor. But in recent decades, the reefs have been showing worldwide declines in health and productivity. Increasing sea water temperature, combined with human pollution and population growth in coastal zones threaten to further weaken this fragile ecosystem.
Scientists at EPA’s Gulf Ecology Division (GED) have developed new, rapid underwater techniques for assessing the health and condition of coral reefs. The techniques combine two traditional approaches for measuring stony corals, the hard corals that are building blocks of the reef. These methods are being used to determine what factors are causing the coral population to dwindle and the appropriate action to take to protect this important natural resource. Stony corals form the structural foundation of the reef. They are colonies of small animals, called polyps that grow and use energy from symbiotic algae to build a hard calcium carbonate (limestone) skeleton. As the coral colonies grow, so do their skeletons, which form the hard structure of the reef. It is this hard structure that provides vital shoreline protection and habitat for abundant and diverse marine life.
The coral reef assessment project is only part of a comprehensive coral research effort at GED. Innovative laboratory exposure systems are also used to investigate the responses of stony corals and their symbiotic algae to a variety of stresses. One of the greatest stresses to coral reefs is sediment that escapes downstream from land development and collects in the coastal zone. This sediment not only blocks sunlight from the photosynthetic algae that corals rely on, but forms a layer over the coral polyps that interferes with feeding and metabolism.
Nutrients, pesticides, bacteria and viruses released into rivers and streams can also reach coral reefs and have damaging effects. Research at GED is directly aimed at defining the limits of pollution that stony corals can withstand. The information can then be incorporated into the water quality standards in jurisdictions such as the Virgin Islands. It is a primary responsibility of the U.S. EPA to assist states, tribes and territories in providing clean, clear water for human use and biological integrity.
Becky Hemmer is a marine biologist within EPA’s Gulf Ecology Division at the National Health and Environmental Effects Research Laboratory.