High temperatures, coral bleaching and mortality reported in Bocas

October 04, 2010

High temperatures, coral bleaching and mortality reported in Bocas

A warning message was issued from Bocas del Toro on coral bleaching and invertebrate mortality this past week

A warning message was issued from Bocas del Toro on coral bleaching and invertebrate mortality this past week. Although the National Oceanic and Atmospheric Administration (NOAA) had issued a warning on above-average sea surface temperatures in the wider Caribbean region in July, there was no indication in Panama of the rising temperatures until two weeks ago.

A team of Smithsonian scientists and local dive operators first noticed the bleaching and mortality event in the surrounding waters of Istmito in Isla Colon, Bocas del Toro, showing an abnormal warming to an extreme of 32EC, as reported initially by Nancy Knowlton and colleagues. This area is located in front of STRI´s Bocas del Toro Research Station. The average during the past 10 weeks was around 30EC, with normal temperatures being 28E C. The warming event is affecting the entire coast of Panama, from Kuna-Yala, Isla Grande, Portobello and Galeta, to Bocas del Toro.

STRI’s coral reef monitoring network, implemented over a decade ago, partially funded by the Nature Conservancy and headed by Héctor M. Guzmán, confirms that temperatures started to rise in deep waters on mid-September. This network covers 33 sites on the Isthmus, with 11 sites in Bocas del Toro. The specialists confirmed that up to this morning, 90% of the Bocas floor had been checked, and that mortality was limited to the above-mentioned area and further inside Bahia Almirante. This is a very vulnerable area since water circulation is slow and temperatures tend to rise easily, maintaining elevated temperatures for days and weeks. They expect to have a complete report of the state of the coral reefs in Bocas del Toro in about two weeks.

Bleaching is the result of stress experienced by reef corals due to factors like increased water temperature, and does not necessarily mean mortality. Generally, it affects and impairs some vital activities of the organisms cycle like reproduction and growth. However, when prolonged warming, corals start to die. During this process, coral reefs release great amounts of mucous turning the waters turbid and bacteria and fungus proliferation is expected. Oxygen runs low and anoxic conditions may affect fish. Panama´s Authority for Aquatic Resources (ARAP have been monitoring the water column at different depths with STRI personnel and measuring the profile of oxygen and temperature.

The images show ocean temperatures in September 2009 and this year´s temperatures. There is an increasing intensity of orange towards red, indicating warming and regional magnitude. There was a similar event in 2005 in the wider Caribbean, including intense bleaching in Panama. However, the mortality was less that 12% in the zone and reefs have been relatively healthy. In the opinion of Guzman, it is possible that the hurricane season is enhancing the problem and creating low water circulation in the Southwestern Caribbean, thus creating a "warming pocket" in Panama and Costa Rica in the sea's western corner.


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