Coral reefs and changing seawater carbonate chemistry

Kleypas, Joan A.; Langdon, Chris

doi:10.1029/61ce06

Cited by 151 publications

(73 citation statements)

References 101 publications

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“…Ocean acidification (OA) that reduces the pH and thus the abundance of CO −2 3 ions in seawater is known to disrupt the skeletogenesis process of marine calcifying organisms, including corals with a variety of mechanisms identified as potential triggering agents (reviewed by Kleypas and Langdon, 2006). The new biomineralisation model may contribute additional insight into these mechanisms, most specifically in the area of coral energetics and the proposed link to skeletal extension rates.…”

Section: Ocean Acidificationmentioning

confidence: 99%

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

Wooldridge

2013

Biogeosciences

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That corals skeletons are built of aragonite crystals with taxonomy-linked ultrastructure has been well understood since the 19th century. Yet, the way by which corals control this crystallization process remains an unsolved question. Here, I outline a new conceptual model of coral biomineralisation that endeavours to relate known skeletal features with homeostatic functions beyond traditional growth (structural) determinants. In particular, I propose that the dominant physiological driver of skeletal extension is night-time hypoxia, which is exacerbated by the respiratory oxygen demands of the coral's algal symbionts (= zooxanthellae). The model thus provides a new narrative to explain the high growth rate of symbiotic corals, by equating skeletal deposition with the "work-rate" of the coral host needed to maintain a stable and beneficial symbiosis. In this way, coral skeletons are interpreted as a continuous (long-run) recording unit of the stability and functioning of the coral–algae endosymbiosis. After providing supportive evidence for the model across multiple scales of observation, I use coral core data from the Great Barrier Reef (Australia) to highlight the disturbed nature of the symbiosis in recent decades, but suggest that its onset is consistent with a trajectory that has been followed since at least the start of the 1900s. In concluding, I outline how the proposed capacity of cnidarians (which includes modern reef corals) to overcome the metabolic limitation of hypoxia via skeletogenesis also provides a new hypothesis to explain the sudden appearance in the fossil record of calcified skeletons at the Precambrian–Cambrian transition – and the ensuing rapid appearance of most major animal phyla

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Section: Ocean Acidificationmentioning

confidence: 99%

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

Wooldridge

2013

Biogeosciences

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“…Although the negative effects of OA on production of CaCO 3 (calcification) by corals are widely documented (Gattuso et al, 1998;Kleypas and Langdon, 2006;Hoegh-Guldberg et al, 2007;Ries et al, 2009;Pandolfi et al, 2011;Dove et al, 2013), its impact on biologically induced carbonate dissolution and mechanical destruction have been understudied (Zundelevich et al, 2007;Fang et al, 2013a;Wisshak et al, 2014;Enochs et al, 2015;Schönberg et al, 2017) and has so far not been quantified in combination with eutrophication.…”

Section: Introductionmentioning

confidence: 99%

Combined Effects of Experimental Acidification and Eutrophication on Reef Sponge Bioerosion Rates

et al. 2017

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Health of tropical coral reefs depends largely on the balance between constructive (calcification and cementation) and destructive forces (mechanical-chemical degradation). Gradual increase in dissolved CO 2 and the resulting decrease in carbonate ion concentration ("ocean acidification") in ocean surface water may tip the balance toward net mass loss for many reefs. Enhanced nutrients and organic loading in surface waters ("eutrophication"), may increase the susceptibility of coral reef and near shore environments to ocean acidification. The impacts of these processes on coral calcification have been repeatedly reported, however the synergetic effects on bioerosion rates by sponges are poorly studied. Erosion by excavating sponges is achieved by a combination of chemical dissolution and mechanical chip removal. In this study, Cliona caribbaea, a photosymbiont-bearing excavating sponge widely distributed in Caribbean reef habitats, was exposed to a range of CO 2 concentrations, as well as different eutrophication levels. Total bioerosion rates, estimated from changes in buoyant weights over 1 week, increased significantly with pCO 2 but not with eutrophication. Observed chemical bioerosion rates were positively affected by both pCO 2 and eutrophication but no interaction was revealed. Net photosynthetic activity was enhanced with rising pCO 2 but not with increasing eutrophication levels. These results indicate that an increase in organic matter and nutrient renders sponge bioerosion less dependent on autotrophic products. At low and ambient pCO 2 , day-time chemical rates were ∼50% higher than those observed at night-time. A switch was observed in bioerosion under higher pCO 2 levels, with night-time chemical bioerosion rates becoming comparable or even higher than day-time rates. We suggest that the difference in rates between day and night at low and ambient pCO 2 indicates that the benefit of acquired energy from photosynthetic activity surpasses the positive effect of increased pCO 2 levels at night due to holobiont respiration. This implies that excavation must cost cellular energy, by processes, such as ATP usage for active Ca 2+ and/or active proton pumping. Additionally, competition for dissolved inorganic carbon species may occur between bioerosion and photosynthetic activity by the symbionts. Either way, the observed changing role of symbionts in bioerosion can be attributed to enhanced photosynthetic activity at high pCO 2 levels.

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“…Yet there may be winners and losers among individual species with different responses to declining pH, resulting in not only biodiversity declines (Fabricius et al 2011) but likely also hard-topredict changes in species interactions (Kroeker et al 2011). Laboratory studies demonstrate that coral calcification rates for certain species may decrease as much as 20-54% at atmospheric P CO 2 levels of 56.7 Pa (or 560 matm; Leclercq et al 2002;Langdon et al 2003), but some models predict even more drastic decline of up to 85% (Kleypas and Langdon 2006).…”

mentioning

confidence: 99%

High‐resolution carbon budgets on a Palau back‐reef modulated by interactions between hydrodynamics and reef metabolism

Teneva

Dunbar

Mucciarone

et al. 2013

Limnology & Oceanography

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Diel trends in carbon chemistry and hydrodynamic regimes were measured on a coral-dominated back-reef community in the Republic of Palau, western Pacific. Observed diel ranges over 5 d were pH 7.92-8.09, partial pressure of carbon dioxide 33.4-52.7 Pa, measured total alkalinity 2080-2272 mmol kg 21 , total dissolved inorganic carbon 1763-1939 mmol kg 21 , aragonite saturation state 2.84-3.98, and calcite saturation state 4.44-5.67. The combination of reef metabolism and hydrodynamic regimes drives this variability. We report net community calcification (NCC) and net community production (NCP) rates of 220.4 (6 7.8) to 41.2 (6 37.7) mmol CaCO 3 m 22 h 21 and 77.3 (6 95) to 64 (6 22) mmol C m 22 h 21 , respectively. Using a control volume approach, we show that NCC and NCP rate estimates are quite sensitive to the effective control volume dimensions. At this site, tracking vertical mixing of water masses within the control volume shows that active water mixing is often confined to a region 2-3 m above the corals. Vertical carbon mass fluxes into and out of the benthic environment were unexpectedly large for the slow current flow rates observed, suggesting that coral morphology or reef rugosity may affect mass transport of carbon and nutrients. The ranges of NCC and NCP values highlight the need for additional field work on various reefs to tune and optimize the control volume approach to achieve its full potential for reef metabolism monitoring.

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Coral reefs and changing seawater carbonate chemistry

Cited by 151 publications

References 101 publications

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

Combined Effects of Experimental Acidification and Eutrophication on Reef Sponge Bioerosion Rates

High‐resolution carbon budgets on a Palau back‐reef modulated by interactions between hydrodynamics and reef metabolism

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