Fishing and pollution are chronic stressors that can prolong recovery of coral reefs and contribute to ecosystem decline. While this premise is generally accepted, management interventions are complicated because the contributions from individual stressors are difficult to distinguish. The present study examined the extent to which fishing pressure and pollution predicted progress towards the Micronesia Challenge, an international conservation strategy initiated by the political leaders of 6 nations to conserve at least 30% of marine resources by 2020. The analyses were rooted in a defined measure of coral-reef-ecosystem condition, comprised of biological metrics that described functional processes on coral reefs. We report that only 42% of the major reef habitats exceeded the ecosystem-condition threshold established by the Micronesia Challenge. Fishing pressure acting alone on outer reefs, or in combination with pollution in some lagoons, best predicted both the decline and variance in ecosystem condition. High variances among ecosystem-condition scores reflected the large gaps between the best and worst reefs, and suggested that the current scores were unlikely to remain stable through time because of low redundancy. Accounting for the presence of marine protected area (MPA) networks in statistical models did little to improve the models’ predictive capabilities, suggesting limited efficacy of MPAs when grouped together across the region. Yet, localized benefits of MPAs existed and are expected to increase over time. Sensitivity analyses suggested that (i) grazing by large herbivores, (ii) high functional diversity of herbivores, and (iii) high predator biomass were most sensitive to fishing pressure, and were required for high ecosystem-condition scores. Linking comprehensive fisheries management policies with these sensitive metrics, and targeting the management of pollution, will strengthen the Micronesia Challenge and preserve ecosystem services that coral reefs provide to societies in the face of climate change.

Despite a wealth of laboratory experiments describing seagrass growth and competitive interactions with macroalgae under varying nutrient concentrations, there is limited information available from field studies conducted in complex natural environments. We examined ecological change over time in the Saipan Lagoon, Western Pacific Ocean. Here, seagrass (Halodule uninervis) canopy cover was quantified monthly at relatively small spatial scales over a 3-year period. Where watershed size and human population were low, there was a significant relationship with seasonal environmental cycles; cooler temperatures correlated with increased drift, red algal abundance and freshwater input increased green algae. Following cyclical macroalgal overgrowth, however, seagrass again became the dominant canopy. Conversely, in the presence of high human population and urbanization, seasonal cycles were absent and a seagrass-to-macroalgal transition was evident. Adjacent to a large watershed with moderate pollution, significant ties were found between seagrass emergence and winter-time disturbance events (large swells), as detached macroalgae that formed during summer months were removed annually. In summary, seagrass systems associated with Saipan Lagoon appear to be hierarchically controlled, following: 1) disturbances, 2) land-based pollution, and 3) seasonal environmental cycles.

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