Missing meadows fail to mop up microbes: Seagrass meadows, a prominent feature of most healthy coastal ecosystems, are often also associated with shallow coral reefs. Many plants have bioremediation qualities, and seagrasses, of which there are 60 or so species, produce natural biocides. Lamb et al. found that the seagrass meadows of inhabited atolls near Sulawesi, Indonesia, ameliorated seawater pollution from human-origination bacteria. This effect extended to potential pathogens of marine invertebrates and fish: Reefs fringing the seagrass meadows showed significantly less impact from coral and fish disease. Science , this issue p. 731

In 2019, the United Nations Environment Assembly requested that the United Nations Environment Programme (UNEP) and the International Coral Reef Initiative (ICRI) define best practices for coral restoration. Guidelines led by the UNEP were prepared by a team of 20 experts in coral reef management, science, and policy to catalog the best-available knowledge in the field and provide realistic recommendations for the use of restoration as a reef management strategy. Here, we provide a synthesis of these guidelines. Specifically, we present (1) a case for the value of coral reef restoration in the face of increasing frequency and intensity of disturbances associated with climate change, (2) a set of recommendations for improving the use of coral reef restoration as a reef management strategy, tailored to goals and current methods. Coral reef restoration can be a useful tool to support resilience, especially at local scales where coral recruitment is limited, and disturbances can be mitigated. While there is limited evidence of long-term, ecologically relevant success of coral reef restoration efforts, ongoing investments in research and development are likely to improve the scale, and cost-efficiency of current methods. We conclude that coral reef restoration should not be seen as a “silver bullet” to address ecological decline and should be applied appropriately, with due diligence, and in concert with other broad reef resilience management strategies.

While coral reefs in Australia have historically been a showcase of conventional management informed by research, recent declines in coral cover have triggered efforts to innovate and integrate intervention and restoration actions into management frameworks. Here we outline the multi-faceted intervention approaches that have developed in Australia since 2017, from newly implemented in-water programs, research to enhance coral resilience and investigations into socio-economic perspectives on restoration goals. We describe in-water projects using coral gardening, substrate stabilisation, coral repositioning, macro-algae removal, and larval-based restoration techniques. Three areas of research focus are also presented to illustrate the breadth of Australian research on coral restoration, (1) the transdisciplinary Reef Restoration and Adaptation Program (RRAP), one of the world’s largest research and development programs focused on coral reefs, (2) interventions to enhance coral performance under climate change, and (3) research into socio-cultural perspectives. Together, these projects and the recent research focus reflect an increasing urgency for action to confront the coral reef crisis, develop new and additional tools to manage coral reefs, and the consequent increase in funding opportunities and management appetite for implementation. The rapid progress in trialling and deploying coral restoration in Australia builds on decades of overseas experience, and advances in research and development are showing positive signs that coral restoration can be a valuable tool to improve resilience at local scales (i.e., high early survival rates across a variety of methods and coral species, strong community engagement with local stakeholders). RRAP is focused on creating interventions to help coral reefs at multiple scales, from micro scales (i.e., interventions targeting small areas within a specific reef site) to large scales (i.e., interventions targeting core ecosystem function and social-economic values at multiple select sites across the Great Barrier Reef) to resist, adapt to and recover from the impacts of climate change. None of these interventions aim to single-handedly restore the entirety of the Great Barrier Reef, nor do they negate the importance of urgent climate change mitigation action.

Coral reef restoration is a rapidly growing movement galvanized by the accelerating degradation of the world's tropical coral reefs. The need for concerted and collaborative action focused on the recovery of coral reef ecosystems coalesced in the creation of the Coral Restoration Consortium (CRC) in 2017. In March 2020, the CRC leadership team met for a biennial review of international coral reef restoration efforts and a discussion of perceived knowledge and implementation bottlenecks that may impair scalability and efficacy. Herein we present six priorities wherein the CRC will foster scientific advancement and collaboration to: (1) increase restoration efficiency, focusing on scale and cost‐effectiveness of deployment; (2) scale up larval‐based coral restoration efforts, emphasizing recruit health, growth, and survival; (3) ensure restoration of threatened coral species proceeds within a population‐genetics management context; (4) support a holistic approach to coral reef ecosystem restoration; (5) develop and promote the use of standardized terms and metrics for coral reef restoration; and (6) support coral reef restoration practitioners working in diverse geographic locations. These priorities are not exhaustive nor do we imply that accomplishing these tasks alone will be sufficient to restore coral reefs globally; rather these are topics where we feel the CRC community of practice can make timely and significant contributions to facilitate the growth of coral reef restoration as a practical conservation strategy. The goal for these collective actions is to provide tangible, local‐scale advancements in reef condition that offset declines resulting from local and global stressors including climate change.

Here we describe an efficient and effective technique for rearing sexually-derived coral propagules from spawning through larval settlement and symbiont uptake with minimal impact on natural coral populations. We sought to maximize larval survival while minimizing expense and daily husbandry maintenance by experimentally determining optimized conditions and protocols for gamete fertilization, larval cultivation, induction of larval settlement by crustose coralline algae, and inoculation of newly settled juveniles with their dinoflagellate symbiont Symbiodinium. Larval rearing densities at or below 0.2 larvae mL⁻¹ were found to maximize larval survival and settlement success in culture tanks while minimizing maintenance effort. Induction of larval settlement via the addition of a ground mixture of diverse crustose coralline algae (CCA) is recommended, given the challenging nature of in situ CCA identification and our finding that non settlement-inducing CCA assemblages do not inhibit larval settlement if suitable assemblages are present. Although order of magnitude differences in infectivity were found between common Great Barrier Reef Symbiodinium clades C and D, no significant differences in Symbiodinium uptake were observed between laboratory-cultured and wild-harvested symbionts in each case. The technique presented here for Acropora millepora can be adapted for research and restoration efforts in a wide range of broadcast spawning coral species.