Missing the full story: First estimates of carbon deposition rates for the European flat oyster, Ostrea edulis

Globally, momentum to restore damaged habitats has been increasing. For example, the number of European shellfish restoration projects has quadrupled in the past 3 years. In line with the increasing focus on both restoration and climate change mitigation efforts, this study highlights how these two practices can complement each other. This experimental study quantifies the active and passive sediment deposition associated with the European flat oyster (Ostrea edulis) and the organic and inorganic carbon fractions of the deposits. Treatments included 'dead', 'live', and control to account for (i) passive deposition, (ii) biodeposition and passive deposition, and (iii) background deposition respectively. By utilizing these data, the expected carbon deposition associated with a restored flat oyster bed was investigated. The experiment was conducted ex situ, with natural seawater input. Covariate data on temperature, suspended particulate influx, salinity, and oxygen availability were recorded. Enhanced sedimentation (2.9 times) and organic carbon deposition (three times) were observed in the presence of living oysters, compared with the control. The shell structure of the oysters had no influence on passive sedimentation in this study. By developing a full understanding of the ecosystem services (functioning, supporting, regulating, and cultural) provided by a habitat, it becomes possible to quantify overall ecosystem function. This evidence is key in advising policymakers, restoration funders, and marine spatial planners on the connection between keystone species restoration, ecosystem service restoration, and conservation management. The enhancement of benthopelagic coupling by the European flat oyster, evidenced here for the first time, is contextualized from the perspective of quantification of ecosystem service provision for both restoration practices and blue carbon store management. The data produced in this study are discussed comparatively with work that has focused on other species from both Europe and the USA.