Sensitivity of Calcification to Thermal Stress Varies among Genera of Massive Reef-Building Corals

Reductions in calcification in reef-building corals occur when thermal conditions are suboptimal, but it is unclear how they vary between genera in response to the same thermal stress event. Using densitometry techniques, we investigate reductions in the calcification rate of massive Porites spp. from the Great Barrier Reef (GBR), and P. astreoides, Montastraea faveolata, and M. franksi from the Mesoamerican Barrier Reef (MBR), and correlate them to thermal stress associated with ocean warming. Results show that Porites spp. are more sensitive to increasing temperature than Montastraea, with calcification rates decreasing by 0.40 g cm−2 year−1 in Porites spp. and 0.12 g cm−2 year−1 in Montastraea spp. for each 1°C increase. Under similar warming trends, the predicted calcification rates at 2100 are close to zero in Porites spp. and reduced by 40% in Montastraea spp. However, these predictions do not account for ocean acidification. Although yearly mean aragonite saturation (Ωar) at MBR sites has recently decreased, only P. astreoides at Chinchorro showed a reduction in calcification. In corals at the other sites calcification did not change, indicating there was no widespread effect of Ωar changes on coral calcification rate in the MBR. Even in the absence of ocean acidification, differential reductions in calcification between Porites spp. and Montastraea spp. associated with warming might be expected to have significant ecological repercussions. For instance, Porites spp. invest increased calcification in extension, and under warming scenarios it may reduce their ability to compete for space. As a consequence, shifts in taxonomic composition would be expected in Indo-Pacific reefs with uncertain repercussions for biodiversity. By contrast, Montastraea spp. use their increased calcification resources to construct denser skeletons. Reductions in calcification would therefore make them more susceptible to both physical and biological breakdown, seriously affecting ecosystem function in Atlantic reefs

Avoiding Coral Reef Functional Collapse Requires Local and Global Action

oral reefs face multiple anthropogenic threats, from pollution and overfishing to the dual effects of greenhouse gas emissions: rising sea temperature and ocean acidification [1]. While the abundance of coral has declined in recent decades [2, 3], the implications for humanity are difficult to quantify because they depend on ecosystem function rather than the corals themselves. Most reef functions and ecosystem services are founded on the ability of reefs to maintain their three-dimensional structure through net carbonate accumulation [4]. Coral growth only constitutes part of a reef's carbonate budget; bioerosion processes are influential in determining the balance between net structural growth and disintegration [5, 6]. Here, we combine ecological models with carbonate budgets and drive the dynamics of Caribbean reefs with the latest generation of climate models. Budget reconstructions using documented ecological perturbations drive shallow (6-10 m) Caribbean forereefs toward an increasingly fragile carbonate balance. We then projected carbonate budgets toward 2080 and contrasted the benefits of local conservation and global action on climate change. Local management of fisheries (specifically, no-take marine reserves) and the watershed can delay reef loss by at least a decade under "business-as-usual" rises in greenhouse gas emissions. However, local action must be combined with a low-carbon economy to prevent degradation of reef structures and associated ecosystem services

Spatial and temporal patterns in the coral assemblage at Clipperton Atoll: a sentinel reef in the Eastern Tropical Pacific

Este artículo contiene 11 páginas, 5 figuras, 1 tabla.Isolated coral reef habitats are unique systems to study the natural dynamics of coral traits and their natural acclimatization, adaptation, and recovery from globalscale stressors such as thermally induced bleaching events. This study evaluates the spatial and temporal changes in coral community attributes (diversity, live cover, and coral assemblage structure) over 14 years (2005–2019) at Clipperton, an extremely remote Eastern Tropical Pacific (ETP) atoll. The atoll exhibited overall high coral cover (~ 50–60%) dominated by massive species (Porites spp.), yet we observed large variation (44–56%) in coral community attributes among survey years (2005, 2016, 2019) with depth explaining most of the variation. Live coral cover increased in 2019 after a severe thermal stress event (El Niño, 2015– 2016) and many tropical cyclones, which also caused a shift in assemblage structure from branching Pocillopora to massive Porites in the shallower reef zones, resulting in a less well-defined depth gradient. These changes in coral assemblage structure may have long-term effects on the configuration of the physical reef framework of the well-conserved coral reef ecosystems at Clipperton and consequently may alter the ecological functionality of one of the most important biogeographic stepping stones in the central Pacific and ETP regions.The present work was supported by Consejo Nacional de Ciencia y Tecnología (CONACYT) postdoctoral fellowship (CVU 410380) to JJATL. We thank the government of France, The Embassy of France in Mexico, Ministère Des Outre-Mer, the Mexican government, Centro de Investigación de la Isla Observatorio del Medio Ambiente (CRIOBE USR3278 EPHE-CNRS-UPVD), Instituto Nacional de Pesca y Acuacultura (INAPESCA), and the oceanographic research vessel Jorge Carranza Fraser from INAPESCA and also thank the Haut Commissariat de la République en Polynésie française for permission to perform this research at Clipperton Atoll (CITES permit no. FR1998700218-E).Peer reviewe