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Pages 1-16

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From page 1...
... The recent pan-tropical bleaching events showed that remote coral reefs under minimal influence from human activities bleached as severely as reefs exposed to multiple stressors such as pollution and overfishing. Reduction and mitigation of carbon emissions will be required for successful global management of marine ecosystems.
From page 2...
... The report also includes consideration of interventions that could promote persistence of coral reefs although they may not improve resilience, particularly those that reduce exposure to environmental stress, as an important part of the toolkit of responses to deteriorating environmental conditions. For each intervention, its attributes, current feasibility, potential scale, limitations, and risks are reviewed.
From page 3...
... SUMMARY OF INTERVENTIONS TO INCREASE PERSISTENCE AND RESILIENCE Genetic and Reproductive Interventions Managed selection is the detection of corals with above average stress tolerance and their use in subsequent interventions. The intervention builds on the fact that coral reefs exist along a range of environmental gradients, including temperature and other stressors, reflecting the ability of individuals to acclimate, of populations and communities to adapt via selection of resilient phenotypes, and of species to adapt to one or multiple environmental pressures.
From page 4...
... Feasibility for enhancing coral resilience will be dependent on the identification of clear gene targets hypothesized to be able to alter coral resilience through genetic changes. In addition, the long generation time of corals will significantly lengthen the time from research to deployment.
From page 5...
... However, because the majority of corals produce gametes that do not contain algal symbionts, there are also opportunities to introduce algal symbionts during early coral life stages. A potential tradeoff in selecting symbionts that are naturally more heat tolerant, such as some members of the symbiont genus Durusdinium, is that their coral hosts may grow more slowly.
From page 6...
... Antioxidants may be used to deplete the reactive oxygen species that are produced as a result of exposure of corals to high incident light levels, which are linked to degradation and loss of symbionts. Antioxidants would be applied during early and peak periods of environmental stress, and potentially even following the stress events to help coral recovery.
From page 7...
... Key knowledge gaps for managed relocation generally concern what drives species distributions, species responses to novel environmental conditions, localscale impacts of climate change, natural scales of long-distance dispersal, and the scale of local adaptation. Environmental Interventions Shading of coral reefs reduces their exposure to high solar irradiance, lowering peak sea-surface temperatures during warm summer months and reducing light stress, which is a co-factor in the coral bleaching response.
From page 8...
... A consequence of artificial upwelling is that nutrient- and CO2-enriched water can be introduced, leading to enhanced algal growth and acidification effects. The efficacy of artificial water mixing to reduce coral bleaching risks depends on the reef setting, geomorphology, flow direction, prevailing winds, and the oceanography and bathymetry of surrounding waters.
From page 9...
... Table S.1 contains a summary of the different types of coral reef interventions included in this report. Current feasibility, potential scale, limitations, and risks are estimated on the basis of current knowledge, research, or deployment, and are interrelated.
From page 10...
... TABLE S.1  Overview of Interventions Examined in This Report 10 Intervention What It Is Current Feasibility Potential Scale Limitations Risks Genetic and Reproductive Interventions Managed Creating increased In laboratory and at Local reef scale; Needs large Decrease in genetic Selection frequency of existing small local scales potentially populations variation tolerance genes transgenerational Managed Enhancing Success with some Local reef Depends on sufficient Decrease in genetic Breeding: population size by species at small scales population; population sampling variation Supportive captive rearing and potentially and recruitment Breeding release transgenerational success of released individuals Managed Introducing Demonstrated in Local reef Requires transport of Outbreeding Breeding: diversity from other laboratory for a few population; gametes or colonies depression; native Outcrossing populations through species potentially across distances and genotypes may be Between breeding transgenerational field testing across swamped Populations generations Managed Creation of novel Demonstrated in Local reef Limited ability to Outbreeding Breeding: genotypes through laboratory for a few population; create hybrids; requires depression; competition Hybridization breeding species potentially testing for fertility and with native species Between Species transgenerational fitness Gamete and Collection and Feasible at local scales Laboratory to Site-specific Limited genetic Larval Capture manipulation in the local reef scale; reproductive timing, diversity; selection for and Seeding field and laboratory potentially recruitment success can laboratory versus field and release into the transgenerational be poor success wild Coral Frozen storage of Feasibility is high for Materials can Requires excess Long-term survival Cryopreservation gametes and other sperm, and growing be transported gametes, larvae, or uncertain; genetic cells for later use and for other tissue types globally tissues variation reflects only transport current conditions
From page 11...
... Genetic Altering coral genes Technically feasible Would occur in Gene targets and Might alter wrong Manipulation: for new function for larvae laboratory; can be cellular raw material genes; unknown risks Coral self-perpetuating unidentified, long lead time to roll out to reefs Genetic Altering symbiont Not yet feasible Would occur in Technology not Might alter wrong Manipulation: genes for new laboratory; can be established; gene genes; kill target cells; Symbionts function self-perpetuating targets and cellular raw unknown risks material unidentified Physiological Interventions Pre-exposure Using stress exposure In laboratory and Local reef scale; Difficult to scale up Could be detrimental if to make colonies small-scale field trials may be temporary beyond local applied incorrectly more tolerant or transgenerational Algal Symbiont Changing algal Observed after Individual coral Difficult to scale; easier Ecological tradeoffs, Manipulation symbionts to more bleaching events; colony or large for some coral species e.g., slower growth tolerant types demonstrated in spawning events; than others laboratory unknown longevity Microbiome Maintaining/ Demonstrated in Locations on Reef-wide delivery Potential to increase Manipulation increasing abundance laboratory and reefs to reef scale; mechanisms are deleterious microbes, of the native or new nursery facilities for applied at times of lacking; lack of known decrease beneficial ones beneficial microbes limited coral species stress beneficial microbes; little understanding of direct or indirect effects Antibiotics Adding antibiotics to Used in aquaculture Laboratory, Lack of specificity to Promote antibiotic control pathogenic and demonstration in aquarium, and target pathogens limits resistance in microbes small-scale field trials colonies on reef; effectiveness deleterious microbes; requires repeated destabilization of application native beneficial microbiomes 11 continued
From page 12...
... TABLE S.1  Continued 12 Intervention What It Is Current Feasibility Potential Scale Limitations Risks Phage Therapy Adding phage Demonstrated Local reef scale; Lack of identified Undesirable gene viruses to control in laboratory potential to self- target coral pathogens transfers across pathogenic microbes experiments propagate microbial populations; impact on beneficial microbes Antioxidants Reducing cellular Demonstrated in Laboratory only; Little understanding of May affect other reef oxidative damage some laboratory requires repeated direct or indirect effects species derived from stress experiments application using chemical treatments Nutritional Using nutrients Regular use in Laboratory Poor understanding of Shifts carbon, nitrogen, Supplementation to improve fitness coral research and and aquarium; balanced coral diets; and phosphate balance and increase stress aquaculture requires repeated reef-wide delivery and may benefit coral tolerance application mechanisms are lacking competitors Coral Population and Community Interventions Managed Increasing abundance Technically feasible Regional reef scale; Uncertain maintenance Moving nontarget Relocation: of stress-tolerant with information gaps can be permanent of stress tolerance over genes; ecological Assisted Gene genes or colonies regarding successful time tradeoffs Flow within population methods range Managed Moving stress- Technically feasible Regional reef scale; Uncertain maintenance Moving nontarget Relocation: tolerant or diverse with information gaps can be permanent of stress tolerance and genes, species, and Assisted Migration genes or colonies just regarding project persistence over time microbes; ecological outside species' range design  between locations tradeoffs
From page 13...
... regimes Abiotic Ocean Reducing CO2 levels Effective in small- Sites within reefs Costly to scale up Impact of chemicals on Acidification chemically scale laboratory depending on chemical quantities environment Interventions experiments environmental setting; requires consistent input Seagrass Meadows Reducing daytime Some efficacy shown Local reefs Limited environmental Detritus; altered and Macroalgal CO2 levels in field measurements depending on settings; need to nutrient loads; Beds biologically environmental remove macroalgae competition from setting; long-term macroalgae; increased benefit CO2 at night 13
From page 14...
... However, sustaining coral reef ecosystems that will be exposed to a diversity of stressors will require multispecies approaches and consideration of the broad suite of both biological and ecological processes that underpin ecosystem resilience. Ecological Tradeoffs Interventions that target a particular resilience trait may necessitate a tradeoff.
From page 15...
... Physiological interventions affecting individual coral holobionts are generally not permanent and are unlikely to convey resilience to future generations. Managed relocation of coral individuals, if successful, has the potential to remain permanent.
From page 16...
... The task for this report is to synthesize current knowledge and lay the groundwork for informed decisions about conserving coral reefs under climate change. The remainder of the committee's task, to be documented in a subsequent report, is to provide a framework for evaluating the relative risks and benefits of implementing these interventions.


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