DeCarlo, T. M., Cohen, A. L., Barkley, H. C., Cobban, Q., Young, C., Shamberger, K. E., Brainard, R. E., Golbuu, Y.

Coral macrobioerosion is accelerated by ocean acidification and nutrients

2014

Woods Hole Oceanographic Institution; Falmouth Academy; NOAA, Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division; Palau International Coral Reef Center

Geology

43

1

7-10

"Coral reefs exist in a delicate balance between calcium carbonate (CaCO3) production and CaCO3 loss. Ocean acidification (OA), the CO2-driven decline in seawater pH and CaCO3 saturation state (Omega), threatens to tip this balance by decreasing calcification and increasing erosion and dissolution. While multiple CO2 manipulation experiments show coral calcification declines under OA, the sensitivity of bioerosion to OA is less well understood. Previous work suggests that coral and coral-reef bioerosion increase with decreasing seawater Omega. However, in the surface ocean, Omega and nutrient concentrations often covary, making their relative influence difficult to resolve. Here, we exploit unique natural gradients in Omega and nutrients across the Pacific basin to quantify the impact of these factors, together and independently, on macrobioerosion rates of coral skeletons. Using an automated program to quantify macrobioerosion in three-dimensional computerized tomography (CT) scans of coral cores, we show that macrobioerosion rates of live Porites colonies in both low-nutrient (oligotrophic) and high-nutrient (greater than1 micron nitrate) waters increase significantly as Omega decreases. However, the sensitivity of macrobioerosion to Omega is ten times greater under high-nutrient conditions. Our results demonstrate that OA (decreased Omega) alone can increase coral macrobioerosion rates, but the interaction of OA with local stressors exacerbates its impact, accelerating a shift toward net CaCO3 removal from coral reefs."

National Coral Reef Monitoring Plan (NCRMP); climatic monitoring

FY2010 20498, Ocean Acidification - Calcification Rates of Corals and Crustose Coraline Algae in the Pacific Islands; FY2011 ID 20498/655/20663, C205 Ocean Acidification - Calcification Rates of Corals and Crustose Coraline Algae in the Pacific Islands; FY2012 ID 409, Ocean Acidification - Quantification of Calcification and Accretion Rates of Corals and Crustose Coralline Algae across the Pacific Islands; FY2010 CRCP Project 985 Product 974; Project Title: Ocean Acidification - Calcification Rates of Corals and Crustose Coraline Algae in the Pacific Islands; Principal Investigator: Rusty Brainard; and FY2013 CRCP Project ID 743; Project Title: National Coral Reef Monitoring Plan (NCRMP) Implementation (Climatic Monitoring); Principal Investigator: Jessica Morgan