coral death

When corals are exposed to extended periods of excess heat, they are subject to bleaching, which occurs when they expel the algae that live within their structure. Bleaching can lead to coral death.

This summer, temperatures in the Florida Keys crossed the bleaching threshold in mid-June and remained above it for extended periods of time. This cumulative heat exposure leads to widespread bleaching and significant die-offs. The last major mass bleaching event in the Florida Keys occurred in 2014 and 2015.

The Coral Restoration Foundation has been receiving reports ranging from partial bleaching to mass coral mortality throughout the keys. Several coral restoration sites in the lower Keys have been totally lost already.

The National Oceanic and Atmospheric Administration and its state agency, university, and non-profit partners have initiated actions to try to save Florida’s corals.

They have halted all restoration-related planting and are evacuating some of their nursery-grown stock to climate-controlled labs. They are considering interventions such as shading coral nurseries or even high-value reef sites. They are also considering feeding nursery and wild corals until the waters cool off enough for algae to return.

Modeling indicates that there is a 70-100% chance that the extreme heat in the North Atlantic will persist through September-October. NOAA and its partners will continue to do what they can to save Florida’s Coral Reef for the marine and human communities that depend on them.

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NOAA and partners race to rescue remaining Florida corals from historic ocean heat wave

Photo, posted April 19, 2012, courtesy of U.S. Fish and Wildlife Service Southeast Region via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Coral reefs around the world have been suffering in recent years from warming ocean temperatures as well as from increasing ocean acidification. Corals are very sensitive organisms that can only tolerate relatively slight changes in their environment. Thus, the majority of reef-building corals are found in tropical and subtropical waters with favorable conditions.

New research has confirmed that drastic changes in ocean salinity from, for example, severe freshwater flooding, provoke similar stress responses in corals as the heating that has resulted in freshwater bleaching and, eventually, coral death.

The coast of northeast Queensland in Australia has experienced abnormal monsoon-related freshwater flooding that caused extreme and sudden changes in the ocean salt concentration. In places, nearshore reefs were exposed to water with only half the normal ocean salinity. The result has been a shock response in corals that prevents normal cell function. Unlike their response to heat stress, corals exposed to reduced salinity experience a complete collapse of their internal cellular protein balance.

The central Great Barrier Reef has actually been relatively free from mass thermal bleaching events this Australian summer, but many coastal reefs instead have been battling dramatic changes in water conditions as a result of massive plumes of floodwater.

The wild weather in Australia is undoubtedly associated with the changing climate and this new research shows that it is leading to yet another threat to the world’s coral reefs. With the frequency and severity of heavy rainfall and runoff events predicted to continue to increase over the next few decades, proactive measures to increase the resiliency of coral reefs are needed more than ever.

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Reduced salinity of seawater wreaks havoc on coral chemistry

Photo, posted December 12, 2010, courtesy of Gareth Williams via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Saving Florida’s Corals | Earth Wise

When corals are exposed to extended periods of excess heat, they are subject to bleaching, which occurs when they expel the algae that live within their structure. Bleaching can lead to coral death.

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Another Problem For Coral Reefs

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