Seagrass-pathogen interactions and the implications for seed-based restoration in Zostera marina

Extensive ecosystem restoration is occurring on land and in the ocean in response to ambitious conservation and restoration targets. Given ongoing environmental change and the recognition that local organisms may be maladapted to current and future conditions, plans to source organisms from distant locations are increasing. Because one risk of such approaches is the potential to spread disease, there is a growing need for information on pathogen distribution and abundance within and among regions. We addressed this research gap in eelgrass Zostera marina , which is the focus of extensive future seed-based restoration efforts along the Atlantic coast of the USA. Eelgrass hosts seed-based pathogens in the genera Phytophthora and Halophytophthora that can reduce seed germination and seedling health, yet little is known of pathogen prevalence across sites, or how prevalence may be impacted by common seed husbandry practices. We found considerable variation in pathogen prevalence across sites in Massachusetts, Rhode Island, and Connecticut, with no clear geographic patterns. Reduced contact of reproductive shoots via secondary containment during storage generally led to a decrease in pathogen prevalence. Similarly, seeds that were released from spathes during storage had higher prevalence than seeds sampled directly from spathes shortly after collections. Our findings highlight that pathogen spread is a potential risk during seed-based restoration efforts and that handling and storage methods can help to mediate this risk. Future work examining a broader geographic scope, along with potential environmental predictors of pathogen prevalence, is needed to inform future eelgrass restoration efforts.