Environmental Drivers of the Coral Reef Accretion-Erosion Balance in Present and Future Ocean Conditions

Ph.D. University of Hawaii at Manoa 2015.Includes bibliographical references.Worldwide, declines in coral cover and shifts in coral reef community composition have raised concerns about whether reef accretion will continue to exceed reef erosion. Reef persistence is influenced by global and local anthropogenic factors, such as ocean warming, acidification, eutrophication, and overfishing, as well as natural environmental variability. Predicting reef response to environmental stress requires an understanding of both natural and anthropogenic environmental drivers of reef accretion and erosion, and how these drivers interact at different spatiotemporal scales. In Chapters 2 and 3, I measured the variation in accretion, erosion, and net change rates along a natural gradient to determine the dominant environmental drivers of accretion-erosion rates at small spatial scales (tens of meters). In Chapter 4, I expanded the geographic range to 1000s of kilometers, measuring variation in accretion and erosion rates, as well as bioeroder community composition, across the Hawaiian Archipelago. In Chapter 5, I used a controlled mesocosm experiment to directly examine the effects of global anthropogenic drivers (i.e., temperature and ocean acidification) on the coral reef accretion-erosion balance. The results of my dissertation research highlight the significance of spatial scale in understanding reef dynamics and the differential responses of reef accretion and erosion to environmental drivers, which will change our predictions of net coral reef response to future environmental change. Further, my results suggest that increases in reef erosion, combined with expected decreases in calcification, could accelerate the shift of coral reefs to an erosiondominated system in a high CO2 world