Publications

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2015
Yeakel, KL, Andersson AJ, Bates NR, Noyes TJ, Collins A, Garley R.  2015.  Shifts in coral reef biogeochemistry and resulting acidification linked to offshore productivity. Proceedings of the National Academy of Sciences of the United States of America. 112:14512-14517.   10.1073/pnas.1507021112   AbstractWebsite

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 Omega(aragonite) 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.

2011
Zablocki, JA, Andersson AJ, Bates NR.  2011.  Diel Aquatic CO(2) System Dynamics of a Bermudian Mangrove Environment. Aquatic Geochemistry. 17:841-859.   10.1007/s10498-011-9142-3   AbstractWebsite

Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO(2)) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway (Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature, and salinity. Diel pCO(2) variability was interpolated across hourly wind speed measurements to determine variability in daily CO(2) fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO(2) exchange for these two coastal ecosystems at 59.8 +/- 17.3 in Mangrove Bay and 5.5 +/- 1.3 mmol m(-2) d(-1) in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO(2) flux in adjacent coastal environments. In addition, observation of large diel variability in CO(2) system parameters (e.g., mean pCO(2): 390-2,841 mu atm; mean pH(T): 8.05-7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates.