Effects of Diversity and Disease on Seagrass and Oyster Restoration

There is a science-practice gap in restoration (Hughes et al. 2018): relatively few published restoration studies include the term biodiversity and even fewer restorations consider diversity in the design stages, despite the prevalence of biodiversity-ecosystem function studies demonstrating a relationship between a metric of diversity (e.g., species, genetic, etc.) and ecosystem function. Thus, there is potential for restoration efforts that account for biodiversity to enhance overall success, while also starting to bridge this science-practice gap by providing a real-world, large-scale study of biodiversity-ecosystem function relationships. We are addressing this question by conducting a series of restorations in two coastal ecosystems, seagrass beds and oyster reefs, with funding from NSF CAREER and in partnership with MA Division of Marine Fisheries (seagrass restoration), and RI Department of Environmental Management and The Nature Conservancy (oyster restoration). The goal of both projects is to assess how intraspecific diversity affects restoration success by manipulating a component of diversity that is realistic and accessible for restoration practitioners – source diversity, i.e., one source population or hatchery line vs multiple source populations or hatchery lines.

In addition to monitoring restoration success in terms of transplant survival, growth, and recruitment across diversity treatments, we are also testing how source identity and diversity affect disease prevalence and intensity. In eelgrass beds (Zostera marina), wasting disease (caused by the pathogen Labyrinthula zosterae) has resulted in large-scale collapse of populations along the Atlantic Coast of the United States in the past. On oyster reefs (Crassostrea virginica), a variety of micro- and macro-parasites simultaneously plague their hosts, resulting in diseases such as Dermo, MSX, and SSO, and affecting condition index and predation vulnerability through effects on investment in growth and reproduction vs shell repair and altered shell strength, in addition to effects on overall host health. Understanding how host diversity may affect disease resistance and tolerance, in addition to restoration success, in these similar yet distinct systems provides valuable information for both research scientists and restoration practitioners, with the ultimate goal of starting to bridge the science-practice gap and increase communication between research scientists and local practitioners to inform and improve future restoration efforts.