The vulnerability of coral reefs to climate change, eutrophication, sedimentation, and other human-related threats has created an eruption of studies focusing on the impact of human activities on coral reef health. Historically, coral reef research has focused on the corals themselves and the resource species in which they support. However, many of the less charismatic cryptofauna that live within the cracks and crevices of the reef play a vital role in the reefs ability to bounce back from acute or long lasting disturbances. Many of these cryptic organisms are bioeroders — animals and algae that naturally breakdown the calcium carbonate skeleton formed by corals. Understanding the baseline bioerosion rates on reefs and how these rates may change in the future is important because reefs will only persist if bioerosion rates are slower than coral growth, or accretion rates. Only a handful of studies have examined bioerosion rates in Hawai‘i and even fewer studies have addressed the potentially harmful relationship between climate stressors and the accretion-erosion balance. In my dissertation, I characterize how environmental variation influences the accretion-erosion balance to provide context for the effects of anthropogenic climate change. I merge high resolution environmental data with very accurate measures of bioerosion in the field to determine how natural variation shapes the accretion-erosion balance of coral reefs. To specifically address how climate stressors impact the accretion-erosion balance, I manipulate pCO2 and temperature using a mesocosm system. My specific questions are:
1) What are the baseline net erosion rates in Hawai‘i and how do these rates change across different spatial scales (from within a reef to across the entire archipelago)?
2) What are the main environmental drivers (i.e. pH, nutrients, depth, etc.) of the accretion-erosion balance of coral reefs?
3) How will the accretion erosion balance be influenced by the predicted increases in ocean acidity and sea surface temperatures?
These studies are being conducted in collaboration with the Thomas Lab (to better understand the physicochemical properties on the reef that influence the accretion-erosion balance), the Toonen Lab (to use molecular tools to describe the bioeroder community), and NOAA’s Coral Reef Ecosystem Division (to co-locate bioerosion study sites with NOAA calcification study sites). We are also using µCT, a high resolution 3D medical imaging technology, to accurately calculate bioerosion rates. These µCT scans are being conducted at the Cornell Image Multiscale CT Facility.