title: Shifts in coral reef biogeochemistry and resulting acidification linked to offshore productivity.
abstract: Oceanic uptake of anthropogenic carbon dioxide (CO2) has acidified open-ocean surface waters by 0.1 pH units since preindustrial times. Despite unequivocal evidence of ocean acidification (OA) via open-ocean measurements for the past several decades, it has yet to be documented in near-shore and coral reef environments. A lack of long-term measurements from these environments restricts our understanding of the natural variability and controls of seawater CO2-carbonate chemistry and biogeochemistry, which is essential to make accurate predictions on the effects of future OA on coral reefs. Here, in a 5-y study of the Bermuda coral reef, we show evidence that variations in reef biogeochemical processes drive interannual changes in seawater pH and Ωaragonite that are partly controlled by offshore processes. Rapid acidification events driven by shifts toward increasing net calcification and net heterotrophy were observed during the summers of 2010 and 2011, with the frequency and extent of such events corresponding to increased offshore productivity. These events also coincided with a negative winter North Atlantic Oscillation (NAO) index, which historically has been associated with extensive offshore mixing and greater primary productivity at the Bermuda Atlantic Time-series Study (BATS) site. Our results reveal that coral reefs undergo natural interannual events of rapid acidification due to shifts in reef biogeochemical processes that may be linked to offshore productivity and ultimately controlled by larger-scale climatic and oceanographic processes.
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093-0244;
authors.forename: Kiley L
authors.initials: KL
authors.lastname: Yeakel
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093-0244; Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda; aandersson@ucsd.edu.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Andersson
authors.affiliation: Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda; Department of Ocean and Earth Sciences, National Oceanography Center, University of Southampton, Southampton SO14 3ZH, United Kingdom.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Bates
authors.affiliation: Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda;
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Noyes
authors.affiliation: Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda;
authors.forename: Andrew
authors.initials: A
authors.lastname: Collins
authors.affiliation: Bermuda Institute of Ocean Sciences, St. George's GE01, Bermuda;
authors.forename: Rebecca
authors.initials: R
authors.lastname: Garley
mesh_terms: D001669:Biochemical Phenomena; D002245:Carbon Dioxide / Q000032:analysis; D002980:Climate; D057894:Coral Reefs; D006863:Hydrogen-Ion Concentration
chemical_list: D002245:Carbon Dioxide
keywords: NAO; biogeochemistry; calcification; coral reef; ocean acidification