Effects of seagrass restoration on coastal fish abundance and diversity.

Restoration is accelerating to reverse global declines of key habitats and recover lost ecosystem functions, particularly in coastal ecosystems. However, there is high uncertainty about the long-term capacity of restored ecosystems to provide habitat and increase biodiversity, and the degree to which these ecosystem services are mediated by spatial and temporal environmental variability. We addressed these gaps by sampling fishes biannually for 5-7 years (2012-2018) at 16 sites inside and outside of a rapidly-expanding restored seagrass meadow in coastal Virginia, USA. Despite substantial among-year variation in abundance and species composition, seine catches in restored seagrass beds were consistently more numerous (6.4× more fish, P < 0.001) and speciose (2.6× greater species richness, P < 0.001; 3.1× greater Hill-Shannon diversity, P = 0.03) than adjacent unvegetated areas, with larger catches particularly during summer (vs. autumn, P < 0.01). Structural equation modeling revealed that depth and water residence time interacted to control seagrass presence, leading to higher fish abundance and richness in shallow, well-flushed areas that supported seagrass. Together, our results indicate that seagrass restoration yields large and consistent benefits for many coastal fishes, but that restoration and its benefits are sensitive to the dynamic seascapes within which it is established. Consideration of how seascape-scale environmental variability impacts both the success of habitat restoration as well as subsequent ecosystem function will improve restoration outcomes and the provisioning of ecosystem services. This article is protected by copyright. All rights reserved.