Systematic Evidence Maps Relating Water Quality Thresholds to Coral Reef Health
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Water quality stressors such as nutrients, sediments, temperature, dissolved oxygen, metals and others are known to have deleterious effects on a variety of individual and population scale coral reef endpoints. U.S. coral reef jurisdictions have promulgated a variety of water quality standards for these and other water quality stressors; however, most of these standards are not crafted specifically for coral reef endpoints, as data gaps remain in understanding which stressor levels are protective of which types of coral reef endpoints. To facilitate management of the impacts of water quality on coral reef ecosystems, this project develops a methodical compilation of the existing body of information relating water quality measurements to coral reef ecosystem condition. The information is presented as a systematic evidence map, which is a summary of the kind of scientific findings available to answer a defined set of policy or management questions. The goal of this systematic map is to comprehensively organize the available literature on a specific set of select water quality and coral reef metrics and build out an evidence base of data availability and type. The evidence base is guided by a conceptual model identifying causal relationships between water quality stressors and coral reef endpoints, in the context of other stressors, location differences, climate interactions, and land management choices. The compiled and screened evidence base is then mapped to the conceptual model to understand: which causal relationships have a lot versus a little evidence; type and strength of existing evidence; magnitude and consistency of links reported under what conditions; synergies of multiple stressors or conditions; and areas with information gaps. Study titles and abstracts are reviewed for relevance and to extract initial information on a suite of water quality factors affecting coral reef endpoints at the qualitative level, to get a sense of how much and what kind of literature exists for each of the water quality stressors of import in the coral reef conceptual model. Results could be used to rank stressors, understand the interactions among stressors, and inform the circumstances under which location affects stressors. This evidence mapping approach helps clarify the types of decisions that need to be made by jurisdictions to develop coral reef-specific water quality standards or other types of water quality management methods.