Coral Reef NOAA
May 28, 2016  

Addressing Key Threats

To make the most of limited resources and to reverse the decline in coral reef health, the NOAA Coral Reef Conservation Program, together with other government agencies and non-governmental organizations, are focusing their efforts to address the top three recognized global threats to coral reef ecosystems: climate change impacts, fishing impacts, and impacts from land-based sources of pollution.

Resistant and Resilient Reefs

Of interest in the conservation of coral reefs is the idea of resistant and resilient reefs. Reef resistance is the measure of how well a reef is able to tolerate a disturbance, such as rising temperature, before the disturbance negatively affects the reef with a response, such as bleaching. Reef resilience is a measure of the ability of a reef to recover from a disturbance (i.e. the ability of a reef to recover from a coral bleaching event).

Scientists have discovered that some clades of zooxanthellae are more able to resist bleaching. One of these, called 'clade D,' is particularly resistant to bleaching and enables the coral host to avoid the bleaching stress response so that its host coral either does not bleach or does not bleach as severely as other corals exposed to the same light stressors.

There is growing interest among coral researchers and reef managers in the implications this has for reefs' resistance to and resilience from bleaching events in the face of a warming climate. For example, there is ongoing research to test out the possibility of transferring heat-resistant zooxanthellae to corals that normally host other zooxanthellae species, in order to protect corals from bleaching. If successful, this research could pave the way for 'seeding' reefs at risk of bleaching with heat-resistant zooxanthellae. There has also been a great deal of discussion within the scientific community about the potential benefit of protecting resistant and resilient reefs at a higher priority than other reefs. These topics are the focus of current research and debate.

Addressing Climate Change Impacts

Climate change impacts threaten coral reef ecosystems by increasing ocean temperatures, storm activity, ocean acidification, and sea-level rise. These physical ocean changes lead to coral bleaching and diseases. Increasing atmospheric carbon dioxide has already begun to reduces calcification Increasing atmospheric carbon dioxide reduces calcification rates in reef-building and reef-associated organisms by altering sea water chemistry through decreases in pH (ocean acidification). In the long term, failure to address the impacts of rising temperatures and ocean acidification could make many other management efforts futile.

Reducing greenhouse gases (primarily carbon dioxide) will be required to avoid irreversible climate-change effects. While regulating emissions falls outside of the NOAA's mandate, NOAA has a clear role to monitor climate change and ocean acidification, project their impacts on ecological and human systems, and develop ways to address these impacts that support local, national, and international policy. Unfortunately, we can expect at least another 1°C/1.8°F temperature rise within this century from the greenhouse gases already released. Therefore it is essential that we not only reduce emissions, but take urgent actions to reduce the impact of elevated greenhouse gases on coral reef ecosystems.

Addressing Fishing Impacts

Fishing impacts in coral reef areas, when ecologically unsustainable, has lead to the depletion of key functional fish species in many locations, with cascading impacts on coral reef ecosystems.

Specific impacts of fishing on reefs generally include one or more of the following:

  • direct overexploitation of fish, invertebrates, and algae for food and the aquarium trade;
  • removal of a species or group of species impacting multiple trophic levels;
  • bycatch and mortality of non-target species; and
  • physical impacts to reef environments associated with fishing techniques, fishing gear, and anchoring of fishing vessels.

Appropriate management actions can reverse these impacts. For instance, 'no-take' areas in the Florida Keys and marine preserves in Guam have resulted in increased numbers and size of economically and ecologically important reef fish. Management actions focused on key coral reef species, such as the Fish Replenishment Areas in West Hawai`i, have also demonstrated success in protecting reproductive stock and maintaining the fishery for important aquarium trade species. Minimizing negative fishing impacts throughout coral reef ecosystems is critical to revitalizing and protecting coral reef resources for current and future generations. [a]

Addressing Impacts from Land-Based Pollution

Watershed management activities addressing land-based sources of pollution in the Coral Program's priority areas

The suite of problems facing coral reef ecosystems from land-based sources of pollution is broad and includes sediment, nutrients, and other pollutants, originating from a variety of land-based activities, that are transported in surface waters, runoff, groundwater seepage, and atmospheric deposition into coastal waters. These pollutants can cause disease and death in sensitive coral species, disrupt critical ecosystem functions, cause changes in the structure and dynamics of the food chain, and impede coral growth, reproduction, and settlement of coral larvae.

NOAA's Coral Reef Conservation Program and other coral conservation entities seek to control land-based sources of pollution through collaborative approaches and a variety of funded projects. Controlling land-based sources of pollution through watershed management takes a concerted effort by all stakeholder parties including local, state, federal and non-governmental organizations. It requires planning, prioritizing and implementing a multitude of best management practices throughout watersheds to achieve healthy water quality. Practices might include voluntary or regulatory activities on agricultural, public, private, urban or protected lands. Waste management, through septic systems or waste water treatment plants, is integral to water quality protection. Protection of significant portions of the natural watershed landscape, through easements, trusts, or reserves, is the single most important aspect of managing the watershed for water quality and ultimately coral reef protection.