Coral bleaching in Panama as sea hots up

DYING: Bleaching is one of the first signs that coral is dying

Affecting whole Caribbean region as well as sites in Costa Rica

October 2010: The western Caribbean is now afflicted with major coral bleaching, with sea temperatures anomalously high according to the The Smithsonian Tropical Research Institute.

Earlier this year the US National Oceanic and Atmospheric Administration (NOAA) announced above-average sea surface temperature in the wider Caribbean region, but there had been no clear indication of increased sea temperatures in Panam and the western Caribbean until late August / early September.

Extreme sea water temperatures

Scientists and local dive operators first noticed coral bleaching in the waters surrounding Isla Colon, in Panama's Bocas del Toro province in July. Smithsonian staff scientist Nancy Knowlton and colleagues documented an extensive bleaching event in late September. Station personnel recorded an extreme sea water temperature of 32 degrees Celsius. Normal temperatures at this time of year are closer to 28 degrees. This warming is affecting the entire Caribbean coast of Panama from Kuna-Yala to Bocas del Toro and has also been reported at sites in Costa Rica.

There is an extensive coral reef monitoring network in Panama, consisting of 33 sites along both the Pacific and Atlantic coasts of the Isthmus, with 11 sites in the Bocas del Toro area. As of Oct. 3, 95 percent of the seafloor at the Bocas del Toro sites had been checked for bleaching. Coral mortality was limited to shallow areas near Isla Colon and a semi-lagoon area in Bocas del Toro, which is considered to be particularly vulnerable as water circulation there is slow and temperatures tend to rise quickly. Researchers expect to have a complete report of the state of the coral reefs in several weeks.

Bleaching impairs vital functions such as reproduction

Coral polyps, the tiny organisms that make up a coral reef, contain photosynthetic algae called zoxanthellae. Coral bleaching occurs when corals lose their colour as a result of the loss of their algal component, which is caused by increased water temperature or other stress factors. Bleaching impairs vital functions of the coral such as reproduction and growth.

With prolonged warming, corals begin to die releasing great quantities of mucous resulting in increasingly turbid waters. Oxygen levels may fall as bacteria and fungi proliferate. Anoxic conditions affect fish and coastal productivity. STRI has monitored the water column to a depth of 20 meters at 23 sites.

Oxygen levels are dropping

‘Dissolved oxygen dropped to less than 3 milligrams per liter at ten meters and nearly zero milligrams per liter at the bottom,' said STRI technician Plinio Gondola, who recorded the measurements. It is still not clear if temperature rise is directly related to bleaching and anoxia at this site.

It is not the first time the area has experienced such warming. Similar temperature rises in 2005 caused intense bleaching in Panama, but mortality was less than 12 per cent, with reefs remaining relatively resilient.

The current problem may be being exacerbated by the hurricane season, during which low water circulation in the southwestern Caribbean creates a ‘warm pocket' of water along the coasts of Panama and Costa Rica.