A survey of current trends and suggested future directions in coral transplantation for reef restoration

Extinction risk of the endemic soft coral Phyllogorgia dilatata (Esper, 1806) in a remote island of the Brazilian coast

The Brazilian endemic octocoral Phyllogorgia dilatata (elephant ear sea fan) plays a crucial ecological role in the marine ecosystems of the Brazilian coast. Our work investigates the local extinction of P. dilatata on Trindade Island, a remote oceanic island in the Southwestern Atlantic, and assesses the potential impacts of climate change on its distribution. Field surveys conducted over two years (2016-2019) revealed no live individuals of P. dilatata, with only dead peduncles remaining, marking the first observed local extinction of this species. Species distribution models (SDMs) incorporating current and historical climate data were used to estimate the species' habitat suitability and project future distribution under different climate scenarios. Results indicate that P. dilatata currently inhabits approximately 93,090 km2 of suitable area, primarily within tropical ecoregions, but faces significant habitat loss under future climate projections. By 2090-2100, models predict a 63.38 % loss of habitat under the high-emission RCP 8.5 scenario, with severe impacts on tropical regions, including Trindade Island. Environmental variables such as temperature, oxygen concentration, and salinity were identified as key drivers of the species' distribution, while non-climatic factors like seawater velocity, were also significant. The extinction on Trindade Island is attributed to a combination of historical isolation, climate change, and local anthropogenic stressors, including pollution and overfishing. The current investigation highlights the urgent need for conservation efforts, including the establishment of marine protected areas and restoration programs, to protect this vulnerable species and similar marine organisms again climate change.

Restoration cannot be scaled up globally to save reefs from loss and degradation

Coral restoration is gaining popularity as part of a continuum of approaches addressing the widespread, recurring mass mortality events of corals that-together with elevated and chronic mortality, slower growth and recruitment failure-threaten the persistence of coral reefs worldwide. However, the monetary costs associated with broad-scale coral restoration are massive, making widespread implementation challenging, especially with the lack of coordinated and ecologically informed planning. By combining a comprehensive dataset documenting the success of coral restoration with current and forecasted environmental, ecological and climate data, we highlight how such a coordinated and ecologically informed approach is not forthcoming, despite the extent of previous and ongoing efforts. We show that: (1) restoration sites tend to be disproportionally close to human settlements and therefore more vulnerable to local anthropogenic impacts; (2) the immediate outcomes of restoration do not appear to be influenced by relevant ecological and environmental predictors such as cumulative impact; and (3) most restored localities have a high and severe bleaching risk by the middle of this century, with more than half of recently restored sites already affected. Our findings highlight the need for the coral reef community to reinforce joint development of restoration guidelines that go beyond local objectives, with attention to ocean warming trends and their long-term impacts on coral resilience and restoration success.

Escaping the benthos with Coral Reef Arks: effects on coral translocation and fish biomass

Anthropogenic stressors like overfishing, land based runoff, and increasing temperatures cause the degradation of coral reefs, leading to the loss of corals and other calcifiers, increases in competitive fleshy algae, and increases in microbial pathogen abundance and hypoxia. To test the hypothesis that corals would be healthier by moving them off the benthos, a common garden experiment was conducted in which corals were translocated to midwater geodesic spheres (hereafter called Coral Reef Arks or Arks). Coral fragments translocated to the Arks survived significantly longer than equivalent coral fragments translocated to Control sites (i.e., benthos at the same depth). Over time, average living coral surface area and volume were higher on the Arks than the Control sites. The abundance and biomass of fish were also generally higher on the Arks compared to the Control sites, with more piscivorous fish on the Arks. The addition of Autonomous Reef Monitoring Structures (ARMS), which served as habitat for sessile and motile reef-associated organisms, also generally significantly increased fish associated with the Arks. Overall, the Arks increased translocated coral survivorship and growth, and exhibited knock-on effects such as higher fish abundance.

Investigating the outcomes of a threatened gorgonian in situ transplantation: Survival and microbiome diversity in Paramuricea clavata (Risso, 1827)

Gorgonian octocorals are threatened by global and local stressors that can act synergistically to affect their health. In recent years, mass mortality events triggered by marine heatwaves have caused demographic declines in Mediterranean gorgonian populations that may lead to their collapse. Potential changes in microbiome composition under stressful conditions may further increase the susceptibility of the gorgonian holobiont to disease. Given the low recovery capacity of gorgonians, restoration approaches using transplantation are becoming an increasingly attractive option to counteract their decline. Here, we compared the survival and microbiome diversity of Paramuricea clavata colonies transplanted to sites differing in depth and local environmental conditions. Gorgonians sampled at a greater depth than the transplantation site were more likely to suffer necrosis after 1 year of monitoring. Gorgonian transplantation into environments disturbed by an anthropogenic source of pollution resulted in an imbalance of the microbiome with potential consequences on the success of restoration initiatives.

Including environmental and climatic considerations for sustainable coral reef restoration

Coral reefs provide ecosystem benefits to millions of people but are threatened by rapid environmental change and ever-increasing human pressures. Restoration is becoming a priority strategy for coral reef conservation, yet implementation remains challenging and it is becoming increasingly apparent that indirect conservation and restoration approaches will not ensure the long-term sustainability of coral reefs. The important role of environmental conditions in restoration practice are currently undervalued, carrying substantial implications for restoration success. Giving paramount importance to environmental conditions, particularly during the pre-restoration planning phase, has the potential to bring about considerable improvements in coral reef restoration and innovation. This Essay argues that restoration risk may be reduced by adopting an environmentally aware perspective that gives historical, contemporary, and future context to restoration decisions. Such an approach will open up new restoration opportunities with improved sustainability that have the capacity to dynamically respond to environmental trajectories.

Shanmugaraj, Ramesh Chatragadda, M.V. Ramana Murthy. Photographic evidence of fish assemblage in artificial reef site of Palk Bay - an implication for marine resource management

In 2021, a reef restoration programme was introduced to the selected sites of Palk Bay to improve coral nurseries and assist with the establishment of artificial reefs by implementing local coral transplantation. To monitor the growth and survival of transplanted corals, numerous fish assemblages have been observed in restoration sites which are positive sign of reef recovery and also enrich marine resources in Palk Bay. Photographic evidence of the fish assemblages were collected during surveys and detailed observations have been discussed in the present paper.