Patterns and Drivers of Eelgrass Invertebrate Diversity along the Coast of British Columbia

The grazing invertebrates that live within eelgrass meadows are a vital component of coastal ecosystems. These grazers, which feed primarily on epiphytes, connect eelgrass and top predators such as salmon, birds and otters through trophic interactions. Grazers are a diverse assemblage of invertebrates that fill different functional roles and therefore variation in their biodiversity can have dramatic effects on eelgrass community functioning. Variable biodiversity reflects a combination of movements of grazers between eelgrass meadows and other coastal marine habitats as well as local species interactions and environmental controls. Work in other regions has shown that grazer biodiversity differs greatly through space and time, however, patterns of biodiversity in BC are not well documented and the main drivers of this variation are not yet known. In this study, we compared the biodiversity of the grazing community and environmental conditions between eelgrass meadows along the BC coast, including the Salish Sea. Patterns of grazer biodiversity, and epiphyte and microbe abundances were discovered between 21 spatially separated meadows. We revealed correlations in community composition with environmental conditions and spatial attributes of the seascape. Further dispersal experiments allowed us to test the role of species movements and showed dispersal limitation on small scales. We found that functional composition of eelgrass meadows varies substantially in space and the spatial relationships between eelgrass meadows most strongly impacted the diversity and structure of the community. With these findings, we suggest that conservation efforts of eelgrass meadows in BC must consider the connectivity and spatial relationships between eelgrass meadows to preserve invertebrate diversity. This study was conducted as part of a broader, long-term monitoring program. We hope to contribute to critical baseline species data and gain greater insight into the context of our fragile eelgrass communities within the local ecology and oceanography of the BC coast