Citation:

Santavy, Debbie, S. Jackson, B. Jessup, C. Rogers, E. Weil, A. Szmant, D. Cuevas-Miranda, B. Walker, C. Jeffrey, D. Ballantine, W. Fisher, R. Clark, H. Ruiz-Torres, B. Todd, C. Horstmann, AND S. Raimondo. A biological condition gradient for Caribbean coral reefs: Part II. Numeric rules using sessile benthic organisms. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 135:13, (2022). https://doi.org/10.1016/j.ecolind.2022.108576

Impact/Purpose:

Problem: Increases in human population & coastal development have led to the rapid decline of the nation’s coral reefs. Increased sediment & nutrients entering coastal waters, habitat alteration & pollution have stressed reef ecosystems to an ecological tipping point where full recovery is not expected. Existing regulatory & management tools include chemical & physical criteria, but these have not been protective of coral reefs. Biological criteria reflect cumulative stressor impacts on the condition of biological communities and provide a better approach to evaluate decisions.Action: OW identified gaps in management tools for assessing aquatic resources & developed the Biological Condition Gradient (BCG) to allow interpretation of biological condition across spatial & temporal scales - independent of locations and assessment methods. Two coral reef BCG models were designed by employing professional expert panels & scientific data, using the process developed for fresh water ecosystems.Results: Coral Reef BCG numeric models for fish & benthic communities have been developed. The models use a common scale (1-6) to translate biological condition of reef ecosystems. These models will assist decision-makers to determine the effects of land use & development on the condition of valued resources & ecosystem services for coral reefs.Impact: The BCG models depict reef conditions to inform management, development, community, science, & policy decisions impacting coral reefs. The coral reef BCG models are transferable to other coral reefs in the Western Atlantic, Caribbean, and Pacific Oceans where EPA regions will use them to inform biocriteria development.    

Description:

The Biological Condition Gradient (BCG) is a conceptual model used to describe incremental changes in biological condition along a gradient of increasing anthropogenic stress. As coral reefs collapse globally, scientists and managers are focused on how to sustain the crucial structure and functions, and the benefits that healthy coral reef ecosystems provide for many economies and societies. We developed a numeric (quantitative) BGC model for the coral reefs of Puerto Rico and the US Virgin Islands to transparently facilitate ecologically meaningful management decisions regarding these fragile resources. Here, reef conditions range from natural, undisturbed conditions to severely altered or degraded conditions. Numeric decision rules were developed by an expert panel for scleractinian corals and other benthic assemblages using multiple attributes to apply in shallow-water tropical fore reefs with depths <30 m. The numeric model employed decision rules based on metrics (e.g., % live coral cover, coral species richness, pollution-sensitive coral species, unproductive and sediment substrates, % cover by Orbicella spp.) used to assess coral reef condition. Model confirmation showed the numeric BCG model predicted the panel’s median site ratings for 84% of the sites used to calibrate the model and 89% of independent validation sites. The numeric BCG model is suitable for adaptive management applications and supports bioassessment and criteria development. It is a robust assessment tool that could be used to establish ecosystem condition that would aid resource managers in evaluating and communicating current or changing conditions, protect water and habitat quality in areas of high biological integrity, or develop restoration goals with stakeholders and other public beneficiaries.

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