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Edmunds, PJ, Comeau S, Lantz C, Andersson A, Briggs C, Cohen A, Gattuso JP, Grady JM, Gross K, Johnson M, Muller EB, Ries JB, Tambutte S, Tambutte E, Venn A, Carpenter RC.  2016.  Integrating the effects of ocean acidification across functional scales on tropical coral reefs. Bioscience. 66:350-362.   10.1093/biosci/biw023   AbstractWebsite

There are concerns about the future of coral reefs in the face of ocean acidification and warming, and although studies of these phenomena have advanced quickly, efforts have focused on pieces of the puzzle rather than integrating them to evaluate ecosystem-level effects. The field is now poised to begin this task, but there are information gaps that first must be overcome before progress can be made. Many of these gaps focus on calcification at the levels of cells, organisms, populations, communities, and ecosystem, and their closure will be made difficult by the complexity of the interdependent processes by which coral reefs respond to ocean acidification, with effects scaling from cells to ecosystems and from microns to kilometers. Existing ecological theories provide an important and largely untapped resource for overcoming these difficulties, and they offer great potential for integrating the effects of ocean acidification across scales on coral reefs.

Bates, NR, Amat A, Andersson AJ.  2010.  Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification. Biogeosciences. 7:2509-2530.   10.5194/bg-7-2509-2010   AbstractWebsite

Despite the potential impact of ocean acidification on ecosystems such as coral reefs, surprisingly, there is very limited field data on the relationships between calcification and seawater carbonate chemistry. In this study, contemporaneous in situ datasets of seawater carbonate chemistry and calcification rates from the high-latitude coral reef of Bermuda over annual timescales provide a framework for investigating the present and future potential impact of rising carbon dioxide (CO(2)) levels and ocean acidification on coral reef ecosystems in their natural environment. A strong correlation was found between the in situ rates of calcification for the major framework building coral species Diploria labyrinthiformis and the seasonal variability of [CO(3)(2-)] and aragonite saturation state Omega(aragonite), rather than other environmental factors such as light and temperature. These field observations provide sufficient data to hypothesize that there is a seasonal 'Carbonate Chemistry Coral Reef Ecosystem Feedback' (CREF hypothesis) between the primary components of the reef ecosystem (i.e., scleractinian hard corals and macroalgae) and seawater carbonate chemistry. In early summer, strong net autotrophy from benthic components of the reef system enhance [CO(3)(2-)] and Omega(aragonite) conditions, and rates of coral calcification due to the photosynthetic uptake of CO(2). In late summer, rates of coral calcification are suppressed by release of CO(2) from reef metabolism during a period of strong net heterotrophy. It is likely that this seasonal CREF mechanism is present in other tropical reefs although attenuated compared to high-latitude reefs such as Bermuda. Due to lower annual mean surface seawater [CO(3)(2-)] and Omega(aragonite) in Bermuda compared to tropical regions, we anticipate that Bermuda corals will experience seasonal periods of zero net calcification within the next decade at [CO(3)(2-)] and Omega(aragonite) thresholds of similar to 184 mu moles kg(-1) and 2.65. However, net autotrophy of the reef during winter and spring (as part of the CREF hypothesis) may delay the onset of zero NEC or decalcification going forward by enhancing [CO(3)(2-)] and Omega(aragonite). The Bermuda coral reef is one of the first responders to the negative impacts of ocean acidification, and we estimate that calcification rates for D. labyrinthiformis have declined by > 50% compared to pre-industrial times.

Jokiel, PL, Rodgers KS, Kuffner IB, Andersson AJ, Cox EF, Mackenzie FT.  2008.  Ocean acidification and calcifying reef organisms: a mesocosm investigation. Coral Reefs. 27:473-483.   10.1007/s00338-008-0380-9   AbstractWebsite

A long-term (10 months) controlled experiment was conducted to test the impact of increased partial pressure of carbon dioxide (pCO(2)) on common calcifying coral reef organisms. The experiment was conducted in replicate continuous flow coral reef mesocosms flushed with unfiltered sea water from Kaneohe Bay, Oahu, Hawaii. Mesocosms were located in full sunlight and experienced diurnal and seasonal fluctuations in temperature and sea water chemistry characteristic of the adjacent reef flat. Treatment mesocosms were manipulated to simulate an increase in pCO(2) to levels expected in this century [midday pCO(2) levels exceeding control mesocosms by 365 +/- 130 mu atm (mean +/- sd)]. Acidification had a profound impact on the development and growth of crustose coralline algae (CCA) populations. During the experiment, CCA developed 25% cover in the control mesocosms and only 4% in the acidified mesocosms, representing an 86% relative reduction. Free-living associations of CCA known as rhodoliths living in the control mesocosms grew at a rate of 0.6 g buoyant weight year(-1) while those in the acidified experimental treatment decreased in weight at a rate of 0.9 g buoyant weight year(-1), representing a 250% difference. CCA play an important role in the growth and stabilization of carbonate reefs, so future changes of this magnitude could greatly impact coral reefs throughout the world. Coral calcification decreased between 15% and 20% under acidified conditions. Linear extension decreased by 14% under acidified conditions in one experiment. Larvae of the coral Pocillopora damicornis were able to recruit under the acidified conditions. In addition, there was no significant difference in production of gametes by the coral Montipora capitata after 6 months of exposure to the treatments.