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Mesoamerican Reef: Low Stress Leads to Resilience

Provided by Annie Reisewitz and Jessica Carilli, Scripps Institution of Oceanography, University of California, San Diego

<p>Belize from above. Photo credit: Jason Valdez</p>

Belize from above. Photo credit: Jason Valdez

Shared by Mexico, Belize, Guatemala, and Honduras, the Mesoamerican Reef spans over 1,000 km, making it the largest continuous reef in the Western Hemisphere. Portions of the Mesoamerican Reef are World Heritage sites and more than two million people in four countries benefit from the ecosystem services the reef provides, which include productive fishing grounds and the attraction of millions of tourists.12

However, agricultural runoff from more than 300,000 hectares of cropland in the region is a prime threat tothe reef’s health.3 Other local stresses to the reef include coastal development and overfishing. Two recent scientific studies have shown that these local stresses negatively impact the reef’s ability to recover from climate-related threats, such as coral bleaching.

In 1998, a mass coral bleaching caused significant coral death on the Mesoamerican Reef. A study conducted in Belize and Honduras showed that in areas with clean waters and healthy reefs, mountainous star corals (Montastraea faveolata) were able to recover and grow normally within two to three years after the bleaching. In comparison, corals living with excessive human pressures, such as pollution, coastal development, and runoff, had not recovered even eight years after the event.4

The fast-recovering corals were located far offshore, at Turneffe Atolland Cayos Cochinos.. The corals that took longer to recover were located in areas with significant land-based runoff and heavily populated and developed coastlines -- the Sapodilla Cayes in southern Belize and reefs near Utila Island in Honduras, respectively.

A related study compared a century-long record of thermal stress on the Mesoamerican Reef with a century-long record of bleaching events. Surprisingly, although temperatures in the region were much warmer in the 1950s than in recent years, no bleaching occurred during that decade—suggesting that recent mass bleaching events appear to stem from the coupling of mild warming and local stress.5

These findings suggest that by protecting reefs from local threats, bleached corals will be able to bounce back to normal growth rates more quickly after natural disturbances—and that protecting reefs from local threats will foster coral resilience in the face of rising sea temperatures.

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  1. The Nature Conservancy. Case Study: Mesoamerican Reef. Reef Resilience Toolkit (2008). 

  2. ICRAN. ICRAN-MAR Project: Terminal Report. (Mesoamerican Reef Alliance, 2007). 

  3. Burke, L. & Sugg, Z. Hydrologic Modeling of Watersheds Discharging Adjacent to the Mesoamerican Reef. (World Resources Institute, Washington, DC, 2006). 

  4. Carilli, J., Norris, R., Black, B., Walsh, S. & McField, M. Local stressors reduce coral resilience to bleaching. PLoS One 4, e6324 (2009). 

  5. Carilli, J., Norris, R. D., Black, B., Walsh, S. & McField, M. Century-scale records of coral growth rates indicate that local stressors reduce coral thermal tolerance threshold. Global Change Biology 10, 1365-2486 (2009). 

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