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Local Management Actions Can Increase Coral Resilience to Thermally-Induced Bleaching

Abstract: Recent large-scale analyses suggest that local management actions may not protect coral reefs from climate change, yet most local threat-reduction strategies have not been tested experimentally. We show that removing coral predators is a common local action used by managers across the world, and that removing the corallivorous snail Coralliophila abbreviata from Caribbean brain corals (Pseudodiploria and Diploriaspecies) before a major warming event increased coral resilience by reducing bleaching severity (resistance) and post-bleaching tissue mortality (recovery). Our results highlight the need for increased evaluation and identification of local interventions that improve coral reef resilience.

Authors: E. C. Shaver, D. E. Burkepile, B. R. Silliman

Year: 2018

View the article here, or request a copy from lizcshaver@gmail.com

Nature Ecology & Evolution 2: doi.org/10.1038/s41559-018-0589-0

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Host and Symbionts in Pocillopora damicornis Larvae Display Different Transcriptomic Responses to Ocean Acidification and Warming

Abstract: As global ocean change progresses, reef-building corals and their early life history stages will rely on physiological plasticity to tolerate new environmental conditions. Larvae from brooding coral species contain algal symbionts upon release, which assist with the energy requirements of dispersal and metamorphosis. Global ocean change threatens the success of larval dispersal and settlement by challenging the performance of the larvae and of the symbiosis. In this study, larvae of the reef-building coral Pocillopora damicornis were exposed to elevated pCO2 and temperature to examine the performance of the coral and its symbionts in situ and better understand the mechanisms of physiological plasticity and stress tolerance in response to multiple stressors. We generated a de novo holobiont transcriptome containing coral host and algal symbiont transcripts and bioinformatically filtered the assembly into host and symbiont components for downstream analyses. Seventeen coral genes were differentially expressed in response to the combined effects of pCO2 and temperature. In the symbiont, 89 genes were differentially expressed in response to pCO2. Our results indicate that many of the whole-organism (holobiont) responses previously observed for P. damicornis larvae in scenarios of ocean acidification and warming may reflect the physiological capacity of larvae to cope with the environmental changes without expressing additional protective mechanisms. At the holobiont level, the results suggest that the responses of symbionts to future ocean conditions could play a large role in shaping success of coral larval stages.

Authors: E. B. Rivest, M. W. Kelly, M. B. DeBiasse, G. E. Hofmann

 

Year: 2018

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Frontiers in Marine Science 5: doi.org/10.3389/fmars.2018.00186

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Loss of coral reef growth capacity to track future increases in sea level

Abstract: Sea-level rise (SLR) is predicted to elevate water depths above coral reefs and to increase coastal wave exposure as ecological degradation limits vertical reef growth, but projections lack data on interactions between local rates of reef growth and sea level rise. Here we calculate the vertical growth potential of more than 200 tropical western Atlantic and Indian Ocean reefs, and compare these against recent and projected rates of SLR under different Representative Concentration Pathway (RCP) scenarios. Although many reefs retain accretion rates close to recent SLR trends, few will have the capacity to track SLR projections under RCP4.5 scenarios without sustained ecological recovery, and under RCP8.5 scenarios most reefs are predicted to experience mean water depth increases of more than 0.5 m by 2100. Coral cover strongly predicts reef capacity to track SLR, but threshold cover levels that will be necessary to prevent submergence are well above those observed on most reefs. Urgent action is thus needed to mitigate climate, sea-level and future ecological changes in order to limit the magnitude of future reef submergence.

Authors: C. T. Perry, L. Alvarez-Filip, N. A. Graham, P. J. Mumby, S. K. Wilson, P. S. Kench, D. P. Manzello, K. M. Morgan, A. B. A. Slangen, D. P. Thomson, F. Januchowski-Hartley, S. G. Smithers, R. S. Steneck, R. Carlton, E. N. Edinger, I. C. Enochs, N. Estrada-Saldivar, M. D. E. Haywood, G. Kolodziej, G. N. Murphy, E. Perez-Cervantes, A. Suchley, L. Valentino, R. Boenish, M. Wilson, C. Macdonald

Year: 2018
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Nature 558: doi.org/10.1038/s41586-018-0194-z

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A Framework for Identifying and Characterising Coral Reef “Oases” Against a Backdrop of Degradation

Abstract:

  1. Human activities have led to widespread ecological decline; however, the severity of degradation is spatially heterogeneous due to some locations resisting, escaping, or rebounding from disturbances.
  2. We developed a framework for identifying oases within coral reef regions using long‐term monitoring data. We calculated standardised estimates of coral cover (z‐scores) to distinguish sites that deviated positively from regional means. We also used the coefficient of variation (CV) of coral cover to quantify how oases varied temporally, and to distinguish among types of oases. We estimated “coral calcification capacity” (CCC), a measure of the coral community’s ability to produce calcium carbonate structures and tested for an association between this metric and z‐scores of coral cover.
  3. We illustrated our z‐score approach within a modelling framework by extracting z‐scores and CVs from simulated data based on four generalized trajectories of coral cover. We then applied the approach to time‐series data from long‐term reef monitoring programmes in four focal regions in the Pacific (the main Hawaiian Islands and Mo’orea, French Polynesia) and western Atlantic (the Florida Keys and St. John, US Virgin Islands). Among the 123 sites analysed, 38 had positive z‐scores for median coral cover and were categorised as oases.
  4. Synthesis and applications. Our framework provides ecosystem managers with a valuable tool for conservation by identifying “oases” within degraded areas. By evaluating trajectories of change in state (e.g., coral cover) among oases, our approach may help in identifying the mechanisms responsible for spatial variability in ecosystem condition. Increased mechanistic understanding can guide whether management of a particular location should emphasise protection, mitigation or restoration. Analysis of the empirical data suggest that the majority of our coral reef oases originated by either escaping or resisting disturbances, although some sites showed a high capacity for recovery, while others were candidates for restoration. Finally, our measure of reef condition (i.e., median z‐scores of coral cover) correlated positively with coral calcification capacity suggesting that our approach identified oases that are also exceptional for one critical component of ecological function.

Authors: J. R. Guest, P. J. Edmunds, R. D. Gates, I. D. Kuffner, A. J. Andersson, B. B. Barnes, I. Chollett, T. A. Courtney, R. Elahi, E. A. Lenz, S. Mitarai, P. J. Mumby, H. R. Nelson, B. A. Parker, H. M. Putnam, C. S. Rogers, L. T. Toth

Year: 2018
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Journal of Applied Ecology pg. 1-11: doi.org/10.1111/1365-2664.13179 

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Spatial and Temporal Patterns of Mass Bleaching of Corals in the Anthropocene

Abstract: Tropical reef systems are transitioning to a new era in which the interval between recurrent bouts of coral bleaching is too short for a full recovery of mature assemblages. We analyzed bleaching records at 100 globally distributed reef locations from 1980 to 2016. The median return time between pairs of severe bleaching events has diminished steadily since 1980 and is now only 6 years. As global warming has progressed, tropical sea surface temperatures are warmer now during current La Niña conditions than they were during El Niño events three decades ago. Consequently, as we transition to the Anthropocene, coral bleaching is occurring more frequently in all El Niño–Southern Oscillation phases, increasing the likelihood of annual bleaching in the coming decades.

Authors: Hughes, T. P. , K. D. Anderson, S. R. Connolly, S. F. Heron, J. T. Kerry, J. M. Lough, A. H. Baird, J. K. Baum, M. L. Berumen, T. C., Bridge, D. C. Claar, C. M. Eakin, J. P. Gilmour, N. A. J. Graham, H. Harrison, J. A. Hobbs, A. S. Hoey, M. Hoogenboom, R. J. Lowe, M. T. McCulloch, J. M. Pandolfi, M. Pratchett, V. Schoepf, G. Torda, S. K. Wilson

Year: 2018
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Science 359: doi.org/10.1126/science.aan8048

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Interspecific Hybridization May Provide Novel Opportunities for Coral Reef Restoration

Abstract: Climate change and other anthropogenic disturbances have created an era characterized by the inability of most ecosystems to maintain their original, pristine states, the Anthropocene. Investigating new and innovative strategies that may facilitate ecosystem restoration is thus becoming increasingly important, particularly for coral reefs around the globe which are deteriorating at an alarming rate. The Great Barrier Reef (GBR) lost half its coral cover between 1985 and 2012, and experienced back-to-back heat-induced mass bleaching events and high coral mortality in 2016 and 2017. Here we investigate the efficacy of interspecific hybridization as a tool to develop coral stock with enhanced climate resilience. We crossed two Acropora species pairs from the GBR and examined several phenotypic traits over 28 weeks of exposure to ambient and elevated temperature and pCO2. While elevated temperature and pCO2 conditions negatively affected size and survival of both purebreds and hybrids, higher survival and larger recruit size were observed in some of the hybrid offspring groups under both ambient and elevated conditions. Further, interspecific hybrids had high fertilization rates, normal embryonic development, and similar Symbiodinium uptake and photochemical efficiency as purebred offspring. While the fitness of these hybrids in the field and their reproductive and backcrossing potential remain to be investigated, current findings provide proof-of-concept that interspecific hybridization may produce genotypes with enhanced climate resilience, and has the potential to increase the success of coral reef restoration initiatives.

Authors: Chan, W. Y., L. M. Peplow, P. Menéndez, A. A. Hoffmann, and M. J. H. van Oppen
Year: 2018
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Frontiers in Marine Science 5: doi.org/10.3389/fmars.2018.00160

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Raising the Voices of Pacific Island Women to Inform Climate Adaptation Policies

A new paper highlights the critical role that Pacific Island women are playing in climate adaptation and provides guidance for governments, NGOs, and development agencies on how to incorporate the needs and perspectives of women in climate policies and projects. Based on qualitative data from Pacific women leaders in conservation, development, and climate adaptation policies, key priorities to support climate adaptation include: (1) increased recognition for the importance of traditional knowledge; (2) greater support for local women’s groups, including strategic planning and training to access climate finance mechanisms; and (3) climate policies that consider alternative metrics for women’s empowerment and inclusion, formalize women’s land rights, and provide land for climate refugees. The authors emphasize the need for research, programs, and policies that recognize the importance of traditional knowledge in climate adaptation strategies. Bringing women and vulnerable groups into climate adaptation decision-making is critical to support sustainable and resilient communities and to avoid exacerbating existing gender-inequalities.

Author: Mcleod, E., S. Arora-Jonsson, YJ. Masuda, M. Bruton-Adams, C.O. Emaurois, B. Gorong, Berna C.J. Hudlow, R. James, H. Kuhlken, B. Masike-Liri, E. Musrasrik-Carl, A. Otzelberger, K. Relang, B.M. Reyuw, B.  Sigrah, C. Stinnett, J. Tellei, and L. Whitford
Year: 2018
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Marine Policy 93: 10.1016/j.marpol.2018.03.011.

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Climate Change Promotes Parasitism In a Coral Symbiosis

Abstract: Coastal oceans are increasingly eutrophic, warm and acidic through the addition of anthropogenic nitrogen and carbon, respectively. Among the most sensitive taxa to these changes are scleractinian corals, which engineer the most biodiverse ecosystems on Earth. Corals’ sensitivity is a consequence of their evolutionary investment in symbiosis with the dinoflagellate alga, Symbiodinium. Together, the coral holobiont has dominated oligotrophic tropical marine habitats. However, warming destabilizes this association and reduces coral fitness. It has been theorized that, when reefs become warm and eutrophic, mutualistic Symbiodinium sequester more resources for their own growth, thus parasitizing their hosts of nutrition. Here, we tested the hypothesis that sub-bleaching temperature and excess nitrogen promotes symbiont parasitism by measuring respiration (costs) and the assimilation and translocation of both carbon (energy) and nitrogen (growth; both benefits) within Orbicella faveolata hosting one of two Symbiodiniumphylotypes using a dual stable isotope tracer incubation at ambient (26 °C) and sub-bleaching (31 °C) temperatures under elevated nitrate. Warming to 31 °C reduced holobiont net primary productivity (NPP) by 60% due to increased respiration which decreased host %carbon by 15% with no apparent cost to the symbiont. Concurrently, Symbiodinium carbon and nitrogen assimilation increased by 14 and 32%, respectively while increasing their mitotic index by 15%, whereas hosts did not gain a proportional increase in translocated photosynthates. We conclude that the disparity in benefits and costs to both partners is evidence of symbiont parasitism in the coral symbiosis and has major implications for the resilience of coral reefs under threat of global change.

Author: Baker, D. M., C.J. Freeman, J.C. Wong, M.L. Fogel, N. Knowlton
Year: 2018
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Email for the full article: resilience@tnc.org
The ISME Journal. doi:10.1038/s41396-018-0046-8

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Effects of thermal stress and nitrate enrichment on the larval performance of two Caribbean reef corals

Abstract: The effects of multiple stressors on the early life stages of reef-building corals are poorly understood. Elevated temperature is the main physiological driver of mass coral bleaching events, but increasing evidence suggests that other stressors, including elevated dissolved inorganic nitrogen (DIN), may exacerbate the negative effects of thermal stress. To test this hypothesis, we investigated the performance of larvae of Orbicella faveolata and Porites astreoides, two important Caribbean reef coral species with contrasting reproductive and algal transmission modes, under increased temperature and/or elevated DIN. We used a fluorescence-based microplate respirometer to measure the oxygen consumption of coral larvae from both species, and also assessed the effects of these stressors on P. astreoides larval settlement and mortality. Overall, we found that (1) larvae increased their respiration in response to different factors (O. faveolata in response to elevated temperature and P. astreoides in response to elevated nitrate) and (2) P. astreoides larvae showed a significant increase in settlement as a result of elevated nitrate, but higher mortality under elevated temperature. This study shows how microplate respirometry can be successfully used to assess changes in respiration of coral larvae, and our findings suggest that the effects of thermal stress and nitrate enrichment in coral larvae may be species specific and are neither additive nor synergistic for O. faveolata or P. astreoides. These findings may have important consequences for the recruitment and community reassembly of corals to nutrient-polluted reefs that have been impacted by climate change.

Author: Serrano, X. M., M.W.Miller, J.C. Hendee, B.A. Jensen, J.Z. Gapayao, C. Pasparakis, A.C Baker
Year: 2017
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Email for the full article: resilience@tnc.org
Coral Reefs 37(1). doi:10.1007/s00338-017-1645-y

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