Citation:

Oliver, L., Debbie Santavy, AND P. Bradley. Developing a multi-stressor gradient for coral reefs of Puerto Rico. In Proceedings, 13th International Coral Reef Symposium, Honolulu, HI, June 19 - 24, 2016. Springer, New York, NY, 245-257, (2016).

Impact/Purpose:

A multi-stressor gradient framework was developed as part of a larger effort to support biocriteria development for coral reef protection. The multi-stressor gradient relates to biological condition gradient development.

Description:

Coral reefs worldwide are threatened by multiple anthropogenic stressors, yet understanding reef responses to multiple stressor gradients is complicated by interactive stressor effects, co-occurrence of some stressors, and inconsistent data availability. Indirect protection of aquatic life under the US Clean Water Act (CWA) may occur through requirements for effluent discharge permits and provisions for setting chemical and physical criteria based on designated water body uses for humans. Biological water quality criteria or “biocriteria” established under the CWA offers a direct means to protect corals. Biocriteria are quantitative thresholds or narrative descriptions of coral reef ecosystem attributes needed to maintain biological integrity. Biocriteria development involves defining the biological community associated with a wide range of ecosystem conditions ranging from pristine, undisturbed state to severely disturbed by human activities. As part of this process for Puerto Rico, Caribbean coral reef ecosystem experts prioritized the most important anthropogenic stressors to Puerto Rico’s coral reef ecosystems as land-based sources of pollution, fishing pressure, and global climate change-related thermal anomalies. Spatial data representing these stressors were mapped, showing some areas where all three stressors were high and also areas where the magnitude of stressors contrasted. In northeast Puerto Rico, urban development around San Juan results in the island’s highest watershed development index, which co-occurs with high fishing pressure. In contrast, southwest Puerto Rico had high fishing pressure but relatively low watershed development and ocean temperatures compared to other coastal areas. Narrative descriptions for each stressor were also developed to more fully describe the gradient and incorporate stressors for which spatial data is absent or limited. For example, coastal wastewater treatment plants and industries generate effluent plumes which reduce water quality, but quantitative water quality data at relevant spatial and temporal scales is limited or unavailable. Future expert workshops will continue to refine this model by developing stressor weighting factors and by considering interactive effects. This conceptual framework will contribute to developing a multi-stressor gradient model for the coral reefs of Puerto Rico, identify data needs, stimulate addition of new spatial data, and generate testable hypotheses to calibrate the stressor-response model.

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