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.
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 sudden and long-lived 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’ degrades and how the reef responds and changes in terms of its structure and function. Our research project investigates the effect of local human impacts and regional-scale variations in oceanography and climate on coral reef community patterns across the Pacific Ocean, specifically the U.S.-affiliated islands monitored by the Coral Reef Ecosystem Division (CRED) of the National Oceanic and Atmospheric Administration (NOAA) over the past 12 years. Our analyses focus on coral reef community structure, diversity, and ecosystem resilience with the interrelated objectives of (i) documenting the current status and variability of U.S. Pacific coral reef community structure; (ii) advancing our understanding of the complex natural and anthropogenic dynamics controlling coral reef ecosystem dynamics; and (iii) developing effective density- and diversity-based indicators of reef ecosystem health. Through the combined expertise of researchers from both Scripps Institution of Oceanography (University of California San Diego) and CRED (NOAA), we show that human activities (e.g. fishing) are indeed a major contributor to the decline of reef health across the Pacific and play a key role in dictating reef community patterns. However, we also show that natural variation still exists between reefs even in the absence of human habitation and that this is due, in part, to large gradients in oceanography (e.g. wave energy, ocean productivity) and climate (e.g. incoming irradiance). Fishing was seen to dramatically alter coral reef fish communities in three key ways: 1) reduction in overall reef fish biomass, particularly the biomass of predators (piscivores) (Mora et al. 2011, Williams et al. 2011, Richards et al. 2012), a dramatic reduction in the biomass of herbivorous fishes (Edwards et al. accepted) and a reduction in the biomass of rare (IUCN red-listed) fish species, such as the bumphead parrotfish (Bolbometopon muricatum) (Zgliczynski et al. 2013). The presence of local human impacts also had dramatic effects on coral reef benthic communities, shifting from a community dominated by calcifying (reef-building) organisms, such as hard coral and crustose coralline algae, where humans were absent, to fleshy (non-calcifying) communities, such as turf algae and fleshy seaweeds at inhabited islands. While we clearly observed strong links between coral reef community organization and human habitation, these results also motivated us to investigate the natural variation evident across our study system even in the absence of human habitation. We started by developing several novel measures with which to determine variation in environmental conditions across the islands, specifically sea-surface temperature (SST), wave energy, ocean productivity, and irradiance (Gove et al. 2013). As we suspected, considerable variation existed for each of these environmental forcings across our study system at an island-level, both in terms of the long-term average and the frequency and magnitude of unusual (anomalous) events. We found that these variations in environmental forcing were also important driving forces in structuring coral reef benthic communities, and in some cases were as important as human habitation. For example, in the absence of local human impacts, wave energy was a key structuring force, with increases in wave energy resulting in lower hard coral cover and an increase in fleshy turf algae (Williams et al. 2013). Across our entire study system (39 islands), increases in wave energy resulted in a reduction in overall coral cover, explaining why some islands, even though free from local human impact, still did not demonstrate particularly high coral cover, for example some of the remote parts of the Hawaiian Archipelago. We found the opposite relationship with ocean productivity, with more productive islands having higher overall coral cover or higher cover of crustose coralline algae where there were higher levels of irradiance. In summary, our results show that human activities dramatically alter the structure and function of coral reef communities across the U.S. Pacific, but that natural variation also exists in the absence of human habitation, due in part to regional-scale variations in environmental forcings. This finding demonstrates the need for a context-specific approach to reef management and the future stewardship of reefs.
