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Seagrass is an important marine habitat that provides benefits to society in the form of ecosystem services. Services include the provision of food via fisheries, the regulation of water quality and the ability to sequester and store carbon. In the UK, seagrass beds are in decline, increasing the risk of ecosystem service loss. Current efforts to protect, restore and create seagrass habitat, beyond spatial management measures, rely on grant funding and donations. Emerging carbon, biodiversity and wider ecosystem service markets offering potential revenue sources could facilitate the enhancement of seagrass habitat at scale. Participation in ecosystem service markets, requires that projects deliver on the ecosystem service benefits defined. As the benefits will have been paid for, there are risks associated with not delivering on ecosystem service benefits. It is important that the risk is clearly defined. In this study we further the marine natural capital and risk register approach and apply the method to a case study area to support the development of sustainable funding options for seagrass habitat enhancement in Plymouth Sound, UK. Habitat Suitability modelling is also used to map potential areas for seagrass habitat enhancement. We find that, in the Plymouth Sound area, the risk of loss of ecosystem services for subtidal seagrass habitats is, at present, high. This is primarily linked to the declining extent and condition of subtidal seagrass assets. Under current governance, all of Plymouth Sound's subtidal seagrass are within a Marine Protected Area, though this conservation designation does not guarantee that the seagrass bed is protected from damaging activity. Under current environmental conditions there is opportunity for widespread seagrass restoration and creation. Risk to seagrass beds and any future private funding could be reduced by governance actions that enable effective direct protection of the seagrass assets and mitigate harmful pressures (e.g., reduction of water pollution). Emerging financial 'products' from seagrass ecosystem services that can support restoration and creation, require a high degree of integrity. The natural capital asset and risk register framework can provide information to underpin product development. With the development of revenue streams from ecosystem services there is a need for more intentional governance and site-based monitoring of these habitats as natural capital assets. Further research is needed to define any social or economic outcomes. Synthesis and Application: By assessing the risk to the status of seagrass assets through this approach, it is possible to determine the complementary governance actions needed to underpin investment in seagrass habitat enhancement. The methods are transferable to other locations where data exists to define the asset status. These specific findings are relevant nationally where similar vectors of risk (pressures) are identified. [ABSTRACT FROM AUTHOR]

UK recreational boating infrastructure in UK ports and harbors consistently coincides with Marine Protected Area designation. Under UK Marine Protected Area designations, vulnerable seabed habitats such as seagrass beds require protection and/or restoration. Mooring and anchoring activity has coincided with increasing concerns over the conservation status of the climate-buffering properties of seagrass beds in the literature and from empirical studies. Up until this study, there has yet to be a significant UK based trial of a number of modified moorings to see their impact on the reduction in pressure on vulnerable benthic habitats. In May 2019, we installed and tested five Advanced Mooring Systems (AMS) in Cawsand Bay, Plymouth Sound, UK. A further 10 such devices were installed in 2021 after the COVID 19 pandemic. The original five devices tested were 'Stirling' systems, whereby the rode is raised above the seabed by use of several submerged floats set at 1.5–2 m intervals along the chain, leading to a top mark that secures the vessel. Each AMS were attached to the seabed using helical screwpiles by commercial divers using a waterproof hydraulic wrench. The devices have held securely since May 2019, and monitoring of seagrass around these five moorings has occurred regularly (at approximately 6 monthly intervals) between May 2019 and May 2023. No seeding or transplantation to prime seagrass recovery has taken place around the base of the moorings during this period. Nevertheless, during the sixth dive survey in May 2023, 4 years after installation, a 212% increase in seagrass density was recorded within the zone previously abraded by the moorings and riser chains. Blade length of the longest seagrass shoots has also increased over the test period. Semi-structured interviews were held with participants in the trial from boat users, NGOs and government agencies to ascertain attitudes and responses to seagrass conservation and the use of AMS. Interaction with stakeholders are important to securing positive community buy-in to such interventions. We recommend that for small sailing craft and powerboats these systems provide a fit-for-purpose engineering and ecological solution to support the restoration of seagrass beds, but that such initiatives must be accompanied by significant understanding and interaction with local stakeholders. [ABSTRACT FROM AUTHOR]