Coral bleaching

Corals are made up of many animals called coral polyps, which receive ninety percent of their food and energy through photosynthesis from microscopic algae living within them called zooxanthellae. These algae have a symbiotic relationship with coral, both relying on each other to survive. The zooxanthellae give corals their characteristic colorful appearance. However, when placed under stress coral expel their zooxanthellae, exposing their white tissue and skeletons, and losing their main food source. This is called coral bleaching and has been occurring in increasing severity in the last twenty years. Mass bleaching events have been increasingly observed where a wide range of species bleach over a large area of reef. These mass bleaching events have been correlated to rising sea surface temperatures that cause the coral thermal stress. A rise in temperature of only one to two degrees Celsius can trigger bleaching events, and when long term averages are raised, mass bleaching is more likely to occur. This can cause eventual mortality if environmental stressors are not resolved quickly enough to give corals a chance to recover. Disease is the second part of the two-part threat causing coral casualties in the tropical Atlantic and wider Caribbean region. Beginning in the 1970s, disease has been observed at staggering levels worldwide and is the result of a bacteria, virus, fungus, or abnormal growth. In the Florida Reef Tract, this can present as black band disease, stony soral tissue loss disease, or tumors. It is identified by a change in tissue color or structure and causes tissue loss and eventual mortality. BleachWatch is a program designed to detect and monitor coral bleaching events and disease outbreaks in the Florida Reef Tract and serve as an early warning system for bleaching events. Southeast Florida Action Network (SEAFAN) in conjunction with the Florida Department of Environmental Protection developed the SEAFAN BleachWatch program in 2013 as a compliment to the Florida Keys BleachWatch program managed by Mote Marine Laboratory and the Florida Keys National Marine Sanctuary. The northernmost one-third of the Florida Reef Tract is in the SEAFAN BleachWatch program’s jurisdiction, beginning at the end of Biscayne National Park, and ending at the Hobe Sound National Wildlife Refuge. BleachWatch consists of a combination of oceanographic data and field observations recorded by an Observer Network made up of trained volunteers and scientists that are used to generate a Current Conditions Report monthly, weekly, or bi-weekly, depending on conditions. The National Oceanic and Atmospheric Administration’s Coral Reef Watch is used to predict likelihood of future bleaching events and alerts are sent out to the Observer Network if a risk of bleaching is deemed. Participants then complete and submit data sheets to be used in the next Current Conditions Report. In 2019, three such reports were generated in July, September, and October. Sea surface temperatures remained consistently above monthly averages in two-thirds of the reports, and bleaching and disease were consistently reported, especially in Broward County. However, participation was low, with only nineteen data sheets being submitted over the entire annual period. More participation and submitted data sheets are greatly needed for more accurate results and better analysis. Still, the program has helped to improve scientific understanding regarding the timing, distribution, and severity of disease and bleaching in southeast Florida. It also gives citizen scientists the chance to be involved in collecting data to enable the restoration of their local reefs and enables assessment of the health of the Florida Reef Tract while providing an outlook for potential future events. Current Condition Reports aid in making responsible management decisions by the Florida Department of Environmental Protection and the Florida Keys National Marine Sanctuary regarding Florida’s beautiful and invaluable coral reef ecosystems.