Research in response to Florida’s emerging coral disease

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Coral reefs are both ecologically and economically important, serving as nurseries for fisheries, protecting the coastline from storm surges, and generating income from tourism. Since 2014, a wide variety of corals have been dying from unexplained causes throughout South Florida with mortalities ranging from North Miami to the Florida Keys.

Coral mortality has since spread through the Caribbean, including Jamaica, Mexico, St. Maarten, the US Virgin Islands, and the Dominican Republic. The mortality results from loss of tissues in affected corals and has been termed stony coral tissue loss disease (SCTLD). Ongoing coral mortality is of concern in that it could eliminate the few remaining coral reefs in the region that survived earlier declines. Various reasons for the cause of SCTLD have been suggested including infectious disease, global warming, or land-based pollution, however, none has been confirmed.

In response to this emerging coral disease, the National Wildlife Health Center (NWHC) and partners are

  • providing disease investigation services to help identify the causative agent of SCTLD, 
  • providing statistical support through development of data-driven surveillance and modelling, and
  • providing decision analysis to help management agencies make timely and impactful management decisions. 

Recently, a team from the Florida Fish and Wildlife Conservation Commission, George Mason University, and the U.S. Geological Survey National Wildlife Health Center – Honolulu Field Station microscopically examined corals affected by SCTLD. Their findings show that SCTLD results from an interruption in the relationship between the zooxanthellae and coral, leading to host tissue death. It is currently unclear whether this breakdown is initiated by the zooxanthellae or coral host cells, but the investigators were unable to find any evidence that infectious agents like bacteria, fungi, or parasites were responsible. Recent diagnostic efforts indicate that a virus of zooxanthellae may be associated with SCTLD. In June-July of 2021, in collaboration with US Virgin Islands NP, USGS Wetlands & Aquatic Research Center, and Universidad de Puerto Rico, the NWHC Honolulu Field Station sampled corals from Puerto Rico and US Virgin Islands to confirm whether corals manifesting tissue loss there have SCTLD.

In August 2021, the U.S. Geological Survey National Wildlife Health Center and U.S. Geological Survey Wetland and Aquatic Research Center will begin leading a series of expert workshops to develop a rigorous framework to synthesize current knowledge available regarding the likelihood SCTLD is caused by particular etiological agent(s). The workshops will include representation of coral and disease experts from multiple agencies and institutions. The long-term goal of this research effort is to provide a framework to the coral scientific community to use to synthesize the scientific studies of SCTLD and identify the most likely etiological agent(s) to guide future research and management. 

 

two photos of same coral. Left coral mostly covered in live tissue, with dead section. Right photo: dead coral covered in algae

Depicted here are two photographs of the same coral colony of symmetrical brain coral, Pseudodiploria strigosa, that was infected by the disease in April 2015 (left photo) and completely dead by April 2016 (right photo). One of the signatures of this disease is the speed at which most corals are consumed by it; a coral can go from apparently healthy to one-hundred percent mortality in a few weeks. The photographs were taken during USGS research in Biscayne National Park by Ilsa Kuffner.