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1. Symbiont community diversity is more variable in corals that respond poorly to stress

   https://doi.org/10.1111/gcb.14999  

   Howe‐Kerr, Lauren I. ; Bachelot, Benedicte ; Wright, Rachel M. ; Kenkel, Carly D. ; Bay, Line K. ; Correa, Adrienne M. S. ( February 2020 , Global Change Biology)

   Coral reefs are declining globally as climate change and local water quality press environmental conditions beyond the physiological tolerances of holobionts—the collective of the host and its microbial symbionts. To assess the relationship between symbiont composition and holobiont stress tolerance, community diversity metrics were quantified for dinoflagellate endosymbionts (Family: Symbiodiniaceae) from eightAcropora milleporagenets that thrived under or responded poorly to various stressors. These eight selected genets represent the upper and lower tails of the response distribution of 40 coral genets that were exposed to four stress treatments (and control conditions) in a 10‐day experiment. Specifically, four ‘best performer’ coral genets were analyzed at the end of the experiment because they survived high temperature, highpCO₂, bacterial exposure, or combined stressors, whereas four ‘worst performer’ genets were characterized because they experienced substantial mortality under these stressors. At the end of the experiment, seven of eight coral genets mainly hostedCladocopiumsymbionts, whereas the eighth genet was dominated by bothCladocopiumandDurusdiniumsymbionts. Symbiodiniaceae alpha and beta diversity were higher in worst performing genets than in best performing genets. Symbiont communities in worst performers also differed more after stress exposure relative to their controls (based on normalized proportional differences in beta diversity), than did best performers. A generalized joint attribute model estimated the influence of host genet and treatment on Symbiodiniaceae community composition and identified strong associations among particular symbionts and host genet performance, as well as weaker associations with treatment. Although dominant symbiont physiology and function contribute to host performance, these findings emphasize the importance of symbiont community diversity and stochasticity as components of host performance. Our findings also suggest that symbiont community diversity metrics may function as indicators of resilience and have potential applications in diverse disciplines from climate change adaptation to agriculture and medicine.

    

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2. Place‐based management can reduce human impacts on coral reefs in a changing climate

   https://doi.org/10.1002/eap.1891  

   Delevaux, Jade M. S. ; Stamoulis, Kostantinos A. ; Whittier, Robert ; Jupiter, Stacy D. ; Bremer, Leah L. ; Friedlander, Alan ; Kurashima, Natalie ; Giddens, Jonatha ; Winter, Kawika B. ; Blaich‐Vaughan, Mehana ; et al ( April 2019 , Ecological Applications)

   Declining natural resources have contributed to a cultural renaissance across the Pacific that seeks to revive customary ridge‐to‐reef management approaches to protect freshwater and restore abundant coral reef fisheries. We applied a linked land–sea modeling framework based on remote sensing and empirical data, which couples groundwater nutrient export and coral reef models at fine spatial resolution. This spatially explicit (60 × 60 m) framework simultaneously tracks changes in multiple benthic and fish indicators as a function of community‐led marine closures, land‐use and climate change scenarios. We applied this framework in Hā‘ena and Ka‘ūpūlehu, located at opposite ends of the Hawaiian Archipelago to investigate the effects of coastal development and marine closures on coral reefs in the face of climate change. Our results indicated that projected coastal development and bleaching can result in a significant decrease in benthic habitat quality and community‐led marine closures can result in a significant increase in fish biomass. In general, Ka‘ūpūlehu is more vulnerable to land‐based nutrients and coral bleaching than Hā‘ena due to high coral cover and limited dilution and mixing from low rainfall and wave power, except for the shallow and wave‐sheltered back‐reef areas of Hā‘ena, which support high coral cover and act as nursery habitat for fishes. By coupling spatially explicit land–sea models with scenario planning, we identified priority areas on land where upgrading cesspools can reduce human impacts on coral reefs in the face of projected climate change impacts.

    

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3. Historical ecology identifies long‐term rewilding strategy for conserving M editerranean mountain forests in south I taly

   https://doi.org/10.1002/eap.2758  

   Palli, Jordan ; Mensing, Scott A. ; Schoolman, Edward M. ; Solano, Francesco ; Piovesan, Gianluca ( December 2022 , Ecological Applications)

   In the context of global decline in old‐growth forest, historical ecology is a valuable tool to derive insights into vegetation legacies and dynamics and develop new conservation and restoration strategies. In this cross‐disciplinary study, we integrate palynology (Lago del Pesce record), history, dendrochronology, and historical and contemporary land cover maps to assess drivers of vegetation change over the last millennium in a Mediterranean mountain forest (Pollino National Park, southern Italy) and discuss implications in conservation ecology. The study site hosts a remnant beech–fir (Fagus sylvatica–Abies alba) mixed forest, a priority habitat for biodiversity conservation in Europe. In the 10th century, the pollen record showed an open environment that was quickly colonized by silver fir when sociopolitical instabilities reduced anthropogenic pressures in mountain forests. The highest forest cover and biomass was reached between the 14th and the 17th centuries following land abandonment due to recurring plague pandemics. This rewilding process is also reflected in the recruitment history of Bosnian pine (Pinus heldreichii) in the subalpine elevation belt. Our results show that human impacts have been one of the main drivers of silver fir population contraction in the last centuries in the Mediterranean, and that the removal of direct human pressure led to ecosystem renovation. Since 1910, the Rubbio State Forest has locally protected and restored the mixed beech–fir forest. The institutions in 1972 for the Rubbio Natural Reserve and in 1993 for Pollino National Park have guaranteed the survival of the silver fir population, demonstrating the effectiveness of targeted conservation and restoration policies despite a warming climate. Monitoring silver fir populations can measure the effectiveness of conservation measures. In the last decades, the abandonment of rural environments (rewilding) along the mountains of southern Italy has reduced the pressure on ecosystems, thus boosting forest expansion. However, after four decades of natural regeneration and increasing biomass, pollen influx and forest composition are still far from the natural attributes of the medieval forest ecosystem. We conclude that long‐term forest planning encouraging limited direct human disturbance will lead toward rewilding and renovation of carbon‐rich and highly biodiverse Mediterranean old‐growth forests, which will be more resistant and resilient to future climate change.

    

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4. Physiological acclimatization in Hawaiian corals following a 22-month shift in baseline seawater temperature and pH

   https://doi.org/10.1038/s41598-022-06896-z  

   McLachlan, Rowan H. ; Price, James T. ; Muñoz-Garcia, Agustí ; Weisleder, Noah L. ; Levas, Stephen J. ; Jury, Christopher P. ; Toonen, Robert J. ; Grottoli, Andréa G. ( March 2022 , Scientific Reports)

   Climate change poses a major threat to coral reefs. We conducted an outdoor 22-month experiment to investigate if coral could not just survive, but also physiologically cope, with chronic ocean warming and acidification conditions expected later this century under the Paris Climate Agreement. We recorded survivorship and measured eleven phenotypic traits to evaluate the holobiont responses of Hawaiian coral: color, Symbiodiniaceae density, calcification, photosynthesis, respiration, total organic carbon flux, carbon budget, biomass, lipids, protein, and maximumArtemiacapture rate. Survivorship was lowest inMontipora capitataand only some survivors were able to meet metabolic demand and physiologically cope with future ocean conditions. MostM. capitatasurvivors bleached through loss of chlorophyll pigments and simultaneously experienced increased respiration rates and negative carbon budgets due to a 236% increase in total organic carbon losses under combined future ocean conditions.Porites compressaandPorites lobatahad the highest survivorship and coped well under future ocean conditions with positive calcification and increased biomass, maintenance of lipids, and the capacity to exceed their metabolic demand through photosynthesis and heterotrophy. Thus, our findings show that significant biological diversity within resilient corals likePorites, and some genotypes of sensitive species, will persist this century provided atmospheric carbon dioxide levels are controlled. SincePoritescorals are ubiquitous throughout the world’s oceans and often major reef builders, the persistence of this resilient genus provides hope for future reef ecosystem function globally.

    

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5. Turbid reefs moderate coral bleaching under climate‐related temperature stress

   https://doi.org/10.1111/gcb.14948  

   Sully, Shannon ; van Woesik, Robert ( January 2020 , Global Change Biology)

   Thermal‐stress events that cause coral bleaching and mortality have recently increased in frequency and severity. Yet few studies have explored conditions that moderate coral bleaching. Given that high light and high ocean temperature together cause coral bleaching, we explore whether corals at turbid localities, with reduced light, are less likely to bleach during thermal‐stress events than corals at other localities. We analyzed coral bleaching, temperature, and turbidity data from 3,694 sites worldwide with a Bayesian model and found thatK_d490, a measurement positively related to turbidity, between 0.080 and 0.127 reduced coral bleaching during thermal‐stress events. Approximately 12% of the world's reefs exist within this “moderating turbidity” range, and 30% of reefs that have moderating turbidity are in the Coral Triangle. We suggest that these turbid nearshore environments may provide some refuge through climate change, but these reefs will need high conservation status to sustain them close to dense human populations.

    

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