Diseased Coral

Many have now heard that 2010 was either the warmest year on record or tied with 2005 (New York Times).  

Was 2010 the Warmest Year in Ecologically Significant Habitats?

March 3, 2011

Diseased Coral

Many have now heard that 2010 was either the warmest year on record or tied with 2005 (New York Times).

Drew HarvellDrew Harvell, CCSF Associate Director - Environment

I don’t want to argue the case, because what is more relevant than the mean global temperature is how hot it got in ecologically sensitive habitats. In my earlier CNN OP Ed, I drew attention to the developing over-warming in the Caribbean this past fall. By the end of the event (early November), temperatures in the south eastern Caribbean from Tobago to Curacao were the warmest on record (Figure 1).

Overall, heat stress for the basin exceeded 2005 making it another disastrously warm year in the Caribbean. The photos in my Op Ed were taken by my colleague, Ernesto Weil at his lab in Puerto Rico. Many Puerto Rico corals died in the 2005 bleaching event and we were very concerned about a repeat in 2010. In mid October, during the peak of the warming, the weather was over-cast and stormy in Puerto Rico. By the time the sun returned, the hot temperature anomaly had slid to the south east Caribbean. Although Puerto Rico’s reefs did experience an extensive bleaching event and some corals were still bleached when I dove there last week, it was not as lethal as initially feared.  Basically, the vagaries of weather (a rain storm) offset the lethal climate effect in one region (Puerto Rico) during the critical time. We did take samples in October to measure the immunity of the corals to disease and whether their beneficial surface bacteria shifted during the event. This will enable us to learn more about the vulnerability of coral reefs during these warm temperature anomalies.

Temperature map of the CaribbeanFigure 1

The most severe impacts of this year’s bleaching event occurred in the South east—in Curacao, Grenada and the reefs of Los Roques. We received reports of widespread bleaching and do not know yet the extent of the mortality following that event. This picture of Ernesto Weil’s shows what these reefs looks like this week (Feb 4) nearly 4 months after the event—still lots of bleached corals and ones that have developed a killing disease (Fig 2).

Similarly, the arctic experienced the warmest temperatures in history this past year, perhaps the warmest in 2000 years (New York Times). Climate scientists are in agreement that these kind of events will increase in frequency. It is not an exaggeration to say we are facing an ecological disaster on Caribbean coral reefs—live coral cover can plummet by half with each extreme warming event like in 2005 and in 2010 and we are now at a low of about 20% live coral cover on many Caribbean reefs. Improved local management for water quality and to reduce over-fishing can help, but ultimately the recommendation of 350.org to reduce greenhouse gas emissions immediately and below our present levels that exceed 390 parts per million of carbon dioxide is required.

Bleached CoralFigure 2

Photo credits: Caribbean heat stress courtesy of Mark Eakin, NOAA Coral Reef Watch;
Bleached, diseased coral from Curacao courtesy of Ernesto Weil