Status and Trends of Caribbean Coral Reefs: 1970-2012, Executive Summary

Since the early 1980s Caribbean coral reefs have suffered massive losses of corals. Impacts from human population growth, overfishing, coastal pollution, global warming and invasive species have resulted in decrease of coral populations, increases of seaweeds, outbreaks of coral bleaching and disease, and failure of corals to recover from natural disturbances. This study analyses the status and trends of reef communities throughout the wider Caribbean. Metadata on the nature of the reef environment, depth and history of human population growth, fishing, hurricanes, coral bleaching and disease was compiled and analyzed. In some cases, biological information for coral and macroalgal cover, abundance of grazing sea urchin Diadema antillarum, and biomass of fishes such as grazing parrotfish was also obtained. Results imply that the three best predictors of the decline in Caribbean coral cover over the past 30 or more years are: (a) outbreaks of Acropora and Diadema diseases (1970s and early 1980s); (b) overpopulation, including increase in tourism; and (c) overfishing of herbivores, particularly parrotfish. Coastal pollution is also significant and increasingly warming seas is also a threat but so far, extreme heating events have had only localized effects.

In summary, the degradation of Caribbean reefs has occurred in three distinct phases: (1) Massive losses of Acropora (mid-1970s to early 1980s) due to White Band Disease; (2) Increase in macroalgal cover and decrease in coral cover following the mass mortality of Diadema (1983) and (3) Continuation of the patterns established in Phase 2 worsened by more overfishing, coastal pollution, tourism, and extreme warming events. Four major recommendations for management emerge from this report:

  1. Adopt conservation and fisheries management strategies to restore parrotfish populations;
  2. Simplify and standardize monitoring of Caribbean reefs and make the results available on an annual basis;
  3. Foster communication and exchange of information;
  4. Develop and implement adaptive legislation and regulations to ensure that threats to coral reefs are systematically addressed.

Author: Jackson, J.B.C.
Year: 2014
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Global Coral Reef Monitoring Network, IUCN, Gland, Switzerland.

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Chronic Nutrient Enrichment Increases Prevalence and Severity of Coral Disease and Bleaching

After exposing test plots in the Florida Keys, USA to increased nutrients (at levels equivalent to nutrient input from onshore sources), researchers found that increased nutrient levels led to increased prevalence and severity of coral diseases and coral bleaching. However, one year after nutrient enrichment stopped, there were no differences in bleaching or disease, indicating that coastal nutrients are increasing prevalence of bleaching and disease. Local scale nutrient input may worsen the effects of global stressors, so limiting nutrient input may be an important management tool for reducing threats to corals. This study is the first to show that nutrients can cause an increase of prevalence of disease or bleaching in the field. 

Vega Thurber, R.L., D.E. Burkepile, C. Fuchs, A.A. Shantz, R. McMinds, and J.R. Zaneveld
Year: 2013
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Global Change Biology 20(2): 544–554. doi:10.1111/gcb.12450

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A Framework for Responding to Coral Disease Outbreaks that Facilitates Adaptive Management

In this study, investigators develop and present a framework for responding to coral disease outbreaks with implications for reef ecosystem health. The framework contains four components, including an early warning system, a tiered impact assessment program, scaled management actions, and a communication plan.

A combination of predictive tools with in situ observations of areas at risk for disease outbreak constitute the early warning system, while reports of increasing disease prevalence triggers a tiered response of assessment, research, or management actions. Response to the disease outbreak risk is scaled based on the severity and spatial extent of impacts incurred by a disease outbreak to coral species.

Additionally, the study reviews potential management actions to mitigate coral disease impacts and facilitate recovery of the reef ecosystem, and considers coral disease-specific strategies as well as strategies already used in reef resilience.

Author: Beeden R., J.A. Maynard, P.A. Marshall, S.F. Heron, and B.L. Willis
Year: 2012
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Environmental Management 49:1–13. doi:10.1007/s00267-011-9770-9

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