Thresholds and drivers of coral calcification responses to climate change

Abstract

Increased temperature and CO levels are considered key drivers of coral reef degradation. However, individual assessments of ecological responses (calcification) to these stressors are often contradicting. To detect underlying drivers of heterogeneity in coral calcification responses, we developed a procedure for the inclusion of stress-effect relationships in ecological meta-analyses. We applied this technique to a dataset of 294 empirical observations from 62 peer-reviewed publications testing individual and combined effects of elevated temperature and pCO on coral calcification. Our results show an additive interaction between warming and acidification, which reduces coral calcification by 20% when pCO levels exceed 700 ppm and temperature increases by 3°C. However, stress levels varied among studies and significantly affected outcomes, with unaffected calcification rates under moderate stresses (pCO ≤ 700 ppm, ΔT < 3°C). Future coral reef carbon budgets will therefore depend on the magnitude of pCO and temperature elevations and, thus, anthropogenic CO emissions. Accounting for stress-effect relationships enabled us to identify additional drivers of heterogeneity including coral taxa, life stage, habitat, food availability, climate, and season. These differences can aid reef management identifying refuges and conservation priorities, but without a global effort to reduce CO emissions, coral capacity to build reefs will be at risk.

Impacts of Ocean Warming on Coralline Algal Calcification: Meta-Analysis, Knowledge Gaps, and Key Recommendations for Future Research

“…The current "worsecase" representative concentration pathways (RCP 8.5) are predicted to result in mean increases in surface seawaters by 2.73 • C by the year 2100 . This indicates coralline algal calcification may be relatively robust to ocean warming compared to other taxa, such as corals (Kornder et al, 2018). The comparatively greater decline in calcification in response to decreasing temperatures seems superficially surprising.…”

“…This type of approach is appropriate for assessments of short-term physiological responses of intertidal organisms to rapid changes in temperature during different tidal periods for example, but is less representative to predictions of how subtidal organisms will fare under ocean warming, or even their responses to marine heatwaves in many instances (i.e., 5 days). Much of the research on coral responses to warming follow stricter protocols where experimental organisms are slowly acclimated to elevated temperatures over periods of weeks (see Kornder et al, 2018), rather than placing the organisms instantly into such treatments, as many of the coralline algal experiments did. Although one study we examined used biologically relevant time-scales (5 years) (Rodríguez-Prieto, 2016), no study to date has assessed responses beyond the F1 generation, which is more ecologically relevant for many coralline species that possess short generation times.…”

Environmental and physiochemical controls on coral calcification along a latitudinal temperature gradient in Western Australia

“…OA can result in morphological deformities in juvenile corals (Cohen, McCorkle, de Putron, Gaetani, & Rose, ; Foster, Falter, McCulloch, & Clode, ) and a reduction in coral calcification rates for some adult corals (e.g., Crook, Cohen, Rebolledo‐Vieyra, Hernandez, & Paytan, ; Jokiel et al, ; Marubini et al, ; Marubini, Ferrier‐Pagès, & Cuif, ; Mollica et al, ), although this is not always the case (e.g., Comeau et al, ; Comeau, Cornwall, DeCarlo, Krieger, & McCulloch, ; Jury, Whitehead, & Szmant, ; Schoepf et al, ). Variation in the responses of coral calcification to OA can be explained by differences in species, life stage, food availability, growth form (e.g., Albright & Langdon, ; Cohen & Holcomb, ; Kornder, Riegl, & Figueiredo, ), and bio‐calcification mechanisms (e.g., Comeau et al, ; DeCarlo, Comeau, Cornwall, & McCulloch, ; Georgiou et al, ; Schoepf, Jury, Toonen, & McCulloch, ).…”

High temperature inhibits cnidarian-dinoflagellate symbiosis establishment through nitric oxide signaling

“…Coral reefs are facing extinction due to an increasing number of mass bleaching events caused by the warming of the oceans due to climate change [44,45]. However, climate change also has negative consequences for other fundamental aspects of coral biology such as sexual reproduction, symbiosis establishment, calcification and susceptibility to disease [23,[46][47][48][49]. Thus, it is imperative to better understand not only the symbiosis disruption, but also the underlying mechanisms and effects of environmental stress in other essential biological processes of corals to protect these critically important ecosystems.…”