Citation:

Bradley, P., B. Jessup, S. Pittman, C. Jeffrey, J. Ault, L. Carrubba, C. Lilyestrom, R. Appeldoorn, M. Scharer, B. Walker, M. McField, Debbie Santavy, T. Smith, G. García-Moliner, S. Smith, E. Huertas, J. Gerritsen, L. Oliver, C. Horstmann, AND S. Jackson. Development of a reef fish biological condition gradient model with quantitative decision rules for the protection and restoration of coral reef ecosystems. MARINE POLLUTION BULLETIN. Elsevier Science Ltd, New York, NY, 159:111387, (2020). https://doi.org/10.1016/j.marpolbul.2020.111387

Impact/Purpose:

The biological integrity of Caribbean coral reef ecosystems is vulnerable to degradation with increasing exposure to human activities. In the U.S. Gulf of Mexico and Caribbean, over-fishing and habitat degradation, including loss of nursery areas (e.g., mangroves from shoreline development and seagrass beds from dredging) have dramatically altered fish community composition across coral reef ecosystems. Reef fish species at all trophic levels have been subjected to intense fishing pressure. Sedimentation from development along tropical shorelines and runoff from agricultural land use is widely considered to have adversely impacted fish communities, particularly through impaired feeding, poor water quality, and changes to benthic habitat. Reef fish provide valuable economic and cultural value, such as food provisioning via subsistence and commercial fishing, support of tourism and recreational activities. Given their diverse functional roles in the ecosystem, using reef fish as indicators of coral reef ecosystem condition can help managers to set targets for protection and restoration of coral reef biological integrity. The US EPA Office of Water has identified gaps in management tools for assessing the biological condition of aquatic and marine communities, especially for coral reefs in US States and Territories. One tool developed to determine the current or change in biological state is the biological condition gradient (BCG). The BCG allows scientists to interpret the biological integrity across spatial and temporal scales in streams independent of locations and assessment methods. In this study, a conceptual biological response model or BCG is applied to Caribbean coral reef fish using an assessment framework originally developed for freshwater aquatic systems. The BCG is a conceptual model that describes how the biological condition of aquatic ecosystems may incrementally change along a gradient of increasing anthropogenic stress. A coral reef BCG model for reef fish were designed by expert panels using bioassessment data and adapting the process developed for fresh water ecosystems. The Coral Reef BCG model for benthic communities uses a common scale (1-6) to translate the biological condition of reef ecosystems. The BCG model will assist decision-makers to determine the effects of land use and development on the condition of valued resources and ecosystem services for coral reef fish communities. The BCG model depicts reef conditions to inform management, development, community, science, and policy decisions impacting coral reefs. The coral reef fish BCG model will be tested for transferability to other coral reefs in the Western Atlantic, Caribbean, and Pacific Oceans where EPA regions will use them to inform biocriteria development.

Description:

Coral reef ecosystems are declining due to multiple interacting stressors. A bioassessment framework focused on stressor-response associations was developed to help organize and communicate complex ecological information to support coral reef conservation. This study applied the Biological Condition Gradient (BCG), initially developed for freshwater ecosystems, to fish assemblages of U.S. Caribbean coral reef ecosystems. The reef fish BCG describes how biological conditions changed incrementally along a gradient of increasing anthropogenic stress. Coupled with physical and chemical water quality data, the BGC forms a scientifically defensible basis to prioritize, protect and restore water bodies containing coral reefs. Through an iterative process, scientists from across the U.S. Caribbean used fishery-independent survey data and expert knowledge to develop quantitative decision rules to describe six levels of coral reef ecosystem condition. The resultant reef fish BCG provides an effective tool for identifying healthy and degraded coral reef ecosystems and has potential for global application.

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