Costa Rica: Reef Life after Bleaching

Provided by Jorge Cortés and Héctor M. Guzmán

Caño Island Biological Reserve is located off the Pacific coast of Costa Rica, 15 km from the mainland Osa Peninsula. The reserve supports a variety of reef life, including 22 coral species.1 Cocos Island, located much farther out in the Pacific Ocean, was declared a National Park in 1978, and covers a 22-km area around the island and also supports a diversity of coral species.2 The islands’ reefshave been degraded by several El Niño–Southern Oscillation (ENSO) warming events, but have shown promising signs of recovery.

The 1982-83 ENSO caused widespread bleaching and unprecedented mass mortality across the reefs of the eastern Pacific, and the 1997-98 ENSO—considered the most severe on record-- caused coral bleaching in many regions of the world.3 Other natural disturbances, such as phytoplankton blooms, have led to coral mortality in the eastern Pacific.4 After the 1982-83 ENSO, scientists predicted that the recovery of live coral cover would take decades, and that the recovery of the reefs’ framework would take centuries. Compounding these slow recovery scenarios was the low rate of sexual reproduction in corals observed in the eastern Pacific.5

The Caño Island Biological Reserve experienced a 50-percent decline in live coral cover during the 1982-83 ENSO, and experienced another setback with the subsequent ENSO events and the severe phytoplankton bloom.1 At present, however, the reef is recovering its live coral cover, with the same coral species recolonizing the reef. The reefs of the oceanic Cocos Island National Park are recovering as well. Cocos Island’s reefs lost 90 percent of their live coral cover during the 1982-83 ENSO, and incurred smaller losses during the following events. Recovery has since been significant; live coral cover off Cocos Island has grown from around 3 percent in the 1980’s to 23 percent in 2002, with one reef above 58 percent.

Among the many reports of coral decline worldwide, the coral reefs of the Cocos Island National Park and the Caño Island Biological Reserve are showing positive signs of recovery from warming events. Working in their favor, both areas are protected and no-take zones. Cocos Island, which has a much lower human influence than Caño Island, has seen an even higher rate of recovery. This suggests that protecting reefs from localized human threats can make reefs more resilient in the face of climate change.

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  1. Guzmán, H. M. and J. Cortés. Changes in Reef Community Structure after Fifteen Years of Natural Distrurbances in the Eastern Pacific (Costa Rica). Bulletin of Marine Science 69, 133-149 (2001).
  2. Guzmán, H. M. and J.Cortés. Reef Recovery 20 Years after the 1982–1983 El Niño Massive Mortality. Marine Biology 151, 401-411 (2007).
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