Common Sea Fans (<em>Gorgonia ventilina</em>) are one of several species of sea fans found in southeast Florida. Sea fans are also classified as soft corals or gorgonians.

Common Sea Fans (Gorgonia ventilina) are one of several species of sea fans found in southeast Florida. Sea fans are also classified as soft corals or gorgonians.

Photo: Chantal Collier

Juvenile bluehead wrasses swim along the reef in Palm Beach.

Juvenile bluehead wrasses swim along the reef in Palm Beach.

Photo: Joe Marino

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Southeast Florida Reef News

Current Status of Coral Bleaching and Disease On Southeast Florida Coral Reefs

Kristi Kerrigan, Reef Resilience Coordinator

Pseudodiploria strigosa (Symmetrical Brain Coral) observed with coral disease off of Jupiter in May 2016. Photo: Ana Zangroniz
Pseudodiploria strigosa (Symmetrical Brain Coral) observed with coral disease off of Jupiter in May 2016. Photo: Ana Zangroniz

The Florida Reef Tract has experienced widespread coral bleaching during the summer and fall months since 2014. In addition to bleaching, an unprecedented coral disease outbreak continues to spread throughout the four-county region. The Coral Reef Conservation Program (CRCP), the Florida Reef Resilience Program (FRRP) and many other partners have conducted a significant response effort to understand the prevalence and potential contributing factors of these two threats.

Coral bleaching is a stress response that happens when the coral animal expels its symbiotic algae, zooxanthellae, which is their primary source of food and energy. Bleached corals are still living but are less likely to reproduce and are more susceptible to disease, predation and mortality. If stressful conditions subside within a certain time period, the corals can regain their zooxanthellae and survive the bleaching event; however, if stressors are severe or persist, bleaching can lead to coral death.

Large-scale coral bleaching events are driven by extremes in sea temperatures (warm or cold) and are intensified by sunlight stress during days with calm weather and clear skies. Coral bleaching is most likely to occur during the later summer months and into the fall when water temperatures are the warmest. According to the National Oceanic and Atmospheric Administration (NOAA), the southeast Florida region is currently experiencing its third consecutive bleaching event, which has been triggered by the abnormally warm waters associated with El Nino. Unfortunately, the time between these bleaching events are not long enough for the corals to recover, which has led to a significant loss in coral cover during the past two years.

CRCP monitors coral bleaching events through various efforts. The Southeast Florida Action Network (SEAFAN) BleachWatch program tracks weather, sea surface temperatures and reef condition through citizen-driven field observations. Given the heat of the summer, sea surface temperatures have started rising and CRCP has started receiving bleaching reports from trained observers. In addition, FRRP’s Disturbance Response Monitoring (DRM) surveys help to document both bleaching and disease at sites throughout the Florida Reef Tract. DRM summer results classified the 2015 bleaching event as “moderate to severe” and the winter post-bleaching surveys as “moderate”. 

Extreme water temperatures during the past two years have weakened the corals and left them more susceptible to disease. CRCP staff first observed coral disease at sites in Miami-Dade County in April 2015 as the corals were recovering from a severe bleaching event from the previous summer. Since then, reports have come in from sites as far north as Palm Beach County. Unlike bleaching, coral disease destroys the coral tissue and leaves behind the bare coral skeleton. “White Plague” is a predominant coral disease being observed, however, several diseases have been impacting multiple species of coral, including some listed as “threatened” under the Endangered Species Act.

The origin of coral diseases, which can be viral or bacterial, is difficult to determine and not clearly understood. However, CRCP has contracted researchers from NOVA Southeastern University to help explain the causes of this outbreak by obtaining datasets and information from diverse sources before and during the bleaching event. Additionally, CRCP staff will work with partners to continue to conduct FRRP DRM surveys in order to characterize the prevalence of this outbreak and understand potential contributory environmental factors.



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