Coral reefs are among the most diverse and productive marine ecosystems, but are also among the most threatened by human activities. At the local scale, fishing and land-based sources of pollution can directly alter the structure of reef communities, and at the global scale, the effects of climate change and ocean acidification are expected to impose episodic and chronic stresses to even the most remote reefs. To most effectively implement ecosystem approaches to the management of coral reefs, it is critical to understand the pathway by which reef health is degraded and the functional consequences of these changes. The Pacific Islands region forms the nation's largest management area, and includes many of the most biologically diverse and pristine coral reef ecosystems. Monitoring programs within NOAA provide a time series of methodologically consistent data with which to use comparative approaches to address fundamental questions of the role of ecosystem organization and structure in maintaining ecosystem resilience. The sampling design spans across space, time and multiple gradients of anthropogenic disturbance allowing for replicated tests of the effects of local versus global stressors on the current status and recovery of these systems from human disturbances. Analysis of these data will provide an unprecedented view of how anthropogenic activities affect coral reef community structure, diversity, and dynamics in the U.S. Pacific. These will focus on coral reef community structure, diversity, and ecosystem resilience to 1) document the status and variability of U.S. Pacific coral reef community structure; 2) advance understanding of the complex dynamics controlling coral reef ecosystems; and 3) develop effective density- and diversity-based indicators of reef ecosystem health. A collaboration between Scripps Institution of Oceanography and NOAA will provide skills and resources to conduct comparative analyses and syntheses of some of the most unique, taxonomically thorough and geographically extensive data from coral reefs of the U.S. The investigators will integrate existing Pacific interdisciplinary ecosystem observations, including habitat, biological, physical, and biogeochemical data, with newly collected socioeconomic data using a tailored suite of statistical approaches.
In addition to outreach through a series of primary publications, results will have broad impacts through training of graduate and undergraduate students as well as communication with governmental, non-profit, and academic coral reef interest groups, providing specific recommendations to increase the efficacy of management policies and practices. By investigating patterns of similarity and difference among geographic regions, region-specific scientific advice will be provided to improve management efficacy at local, regional, and national levels. Results will also be directly incorporated into comprehensive Coral Reef Ecosystem Monitoring Reports for each U.S. Pacific Islands region that are aimed specifically at resource managers to facilitate implementation of ecosystem approaches in regional management plans.
The major goals of this project were to advance understanding of natural and human factors influencing coral reef ecosystems. We found consistent evidence of the strong negative influence that human populations can have on reef fish communities in the absence of effective management measures. Specifically, our analysis of 1607 diver transects from 46 reefs across the central-western Pacific Ocean shows that human populations are a strong predictor of reef shark numbers: densities of gray reef sharks (Carcharhinus amblyrhynchos), whitetip reef sharks (Triaenodon obesus), and various other sharks decreased significantly as human population increased. Reef shark densities also were positively correlated with primary productivity and minimum sea surface temperature (or reef area, which was highly correlated with temperature). A comparison of present numbers to estimated historical densities suggests that density of reef sharks has declined to 3–10% of baseline levels in these areas. Our results also indicated that overall reef fish biomass has been significantly depleted throughout the central-western Pacific Ocean, influenced by habitat complexity, oceanographic productivity, and human disturbance. The results from this research contribute to the societal understanding of human impacts on coral reefs and sharks, and highlight the need for improved management and conservation measures of these species and ecosystems.
