A Resident Fish Guild as a Higher Trophic Level Indicator of Oyster Reef Restoration Success

Eastern oysters (Crassostrea virginica) are critical foundation species in estuarine waters, but due to a combination of natural and anthropogenic pressures, oyster abundance has declined. Restoring oyster reefs and monitoring restoration success often focuses on oyster metrics, but relatively infrequently, responses of higher trophic level species and the production of related ecosystem services are accounted for. To address this, we compare the response of a resident reef fish guild (gobies, blennies, toadfish) to standard metrics of oyster restoration success. Using lift nets and seines, natural and restored reefs were monitored over a two-year period within Mosquito Lagoon, Florida, USA. Standard metrics are indicative of restoration success; live oyster density and reef thickness increased in restored reefs after 12 and 24 months. Combined, live oyster density and reef thickness were the best predictors of annual resident reef fish abundance compared to water quality metrics. These results suggest that the benefits of restoring oyster reef habitat are conferred to broader components of the food web, with benefits accruing to reef resident fishes that are a key trophic linkage between lower trophic level foundation species and higher trophic level predators inhabiting coastal ecosystems.

Response of eelgrass (Zostera marina) to an adjacent Olympia oyster restoration project

Recent restoration efforts for the native Olympia oyster, Ostrea lurida, are commonly motivated by potential return of oyster-associated ecosystem services, including increased water filtration. The potential impact of such restoration on another species of ecological concern, eelgrass, Zostera marina, is unclear, but has been hypothesized to be positive if oyster filter feeding increases light penetration to eelgrass. For two years after construction of an oyster restoration project, we assessed the response of adjacent eelgrass (impact) compared to control and reference eelgrass beds by monitoring changes in light intensity, eelgrass shoot density, biomass, leaf morphometrics, and epiphyte load. We observed lower light intensity consistently over time, including prior to restoration, near the constructed oyster bed relative to the control and one of the reference locations. We also observed minor variations between control and impact eelgrass morphology and density. However, the changes observed were not outside the range of natural variation expected in this system, based upon comparisons to reference eelgrass beds, nor were they detrimental. This limited impact to eelgrass may be due in part to the incorporation of a buffer distance between the restored oyster bed and the existing eelgrass bed, which may have dampened both positive and negative impacts. These findings provide evidence that Olympia oyster restoration and eelgrass conservation goals can be compatible and occur simultaneously.

Farming and Restoring Oysters to Combat Climate Change

To confront the myriad challenges posed by climate change, we present oysters as a nature-based solution with an abundance of environmental benefits and economic stimulus to coastal communities. We encourage the Biden administration to support international efforts to restore oyster reefs by presenting an “Oyster Restoration Initiative” to the World Economic Forum, mirroring recent actions on trees. On the domestic front, several legislative actions can be taken to sustain the current trajectory of restoration efforts. These efforts can be pursued in tandem, but we recommend that policy actions focus on expanding low carbon, oyster-based restorative aquaculture programs. This can revolutionize U.S. food production while reducing pollution from other forms of agriculture.

Conservation of Marine Foundation Species: Learning from Native Oyster Restoration from California to British Columbia

Marine foundation species are critical to the structure and resilience of coastal ecosystems and provide key ecosystem services. Since many have suffered severe population declines, restoration of foundation species has been undertaken worldwide. The Olympia oyster (Ostrea lurida) is a foundation species, and the restoration of depleted populations is a priority for maintaining ecosystem function of estuaries along the west coast of North America. Here, we synthesize all native oyster restoration projects conducted from California, USA, to British Columbia, Canada, and analyze project goals, methods, and outcomes. Currently, restoration projects are spread unevenly across the species’ range, driven by locally varying goals and implemented with contrasting approaches. We highlight the value of regional strategic planning and decision support tools to evaluate project design and methods for restoration, including the selection of substrates and the targeted use of aquaculture. We recommend future investment in larger projects, which our analysis found were more cost-effective, but which have been relatively rare for this species. We also recommend that funders support monitoring over broader temporal and spatial scales than in the past to better characterize long-term effects of restoration on oyster populations and the services they provide beyond the project footprint. We found that most projects successfully supported native oysters and engaged local communities, and recommend similar efforts to continue to enhance understanding of Olympia oysters, which remain unfamiliar to many coastal residents. We believe that the results of this synthesis are broadly applicable to marine foundation species generally, and can inform restoration and conservation efforts worldwide.