Award: OCE-1041106

The skeletal growth of corals is critically important for the building and maintenance of coral reef ecosystems. Ocean acidification (OA), the lowering of ocean pH caused by rising levels of atmopsheric CO2, threatens reefs by reducing the availabilty of carbonate ions that corals need to produce their skeletons faster than they can be eroded by the sea or by boring organisms. Multiple experiments show that skeletal growth and calcification rates decline when pH declines. However in some experiments, and on some naturally more acidic reefs, growth rates are maintained under low pH and the question is why? We proposed that the energetic cost of skeletal growth increases under OA. We hypothesized that coral nutrition, whether derived by autotrophy or heterotrophy, would play a major role in modulating the coral calcification response to OA (OA). In a series of laboratory-based manipulation experiments conducted at Woods Hole Oceanographic Institution and the Bermuda Institute of Ocean Sciences (BIOS) over 3 years, we quantified coral calcification under OA combined with i) inorganic nutrient enrichment ii) heterotrophic feeding and iii) elevated light (PAR). Our results indicate that all forms of nutritional enhancement significantly modulate/weaken the impact of OA on coral calcification. Conversely, we found that spawning female corals exhibit heightened sensitivity to OA. This result is consistent with our hypothesis that depletion of coral energy reserve caused by spawning, bleaching, disease, or alteration of the reef nutritional enviroment due to global warming, will exacerbate the impact of OA on coral calcification and thus reef health. 12 peer-reviewed papers have been published and two chapters contributed to the IPCC Workshop Report on Impacts of Ocean Acidification on Marine Biology and Ecosystems.The project supported PhD thesis research of 4 graduate students in the MIT-WHOI Joint Program in Oceanography (Michael Holcomb, Elizabeth Drenkard, Hannah Barkley, Thomas DeCarlo), 3 post-doctoral researchers (Justin Ries, Neal Cantin, Katie Shamberger) and 10 undergraduate/high school interns and Summer Student Fellows. More than 35 talks and plenary lectures have been given by PIs and students/post-docs, and more than 20 abstracts published. This work was shared through multiple education and outreach events including WHOIÆs Ocean Acidification Public Event, the Cambridge Science Festival, the New England Aquarium, television (NOVA), newspaper articles (CC Times) and radio (NPRÆs The World). Our work on the naturally acidified reefs of Palau was presented at John Kerry's Our Ocean conference in Washington DC in June 2014 (http://www.state.gov/documents/organization/225857.pdf). Last Modified: 08/07/2014 Submitted by: Anne Cohen