COS 87-9 - Invasive tunicate restructures invertebrate community on fishing grounds and a large protected area on Georges Bank

Wednesday, August 9, 2017: 10:50 AM
E143-144, Oregon Convention Center
Katherine Anne Kaplan1,2, Patrick Sullivan2 and Deborah Hart3, (1)California Fish and Wildlife, Belmont, CA, (2)Natural Resources, Cornell University, Ithaca, NY, (3)population dynamics, NOAA-Northeast Fisheries Science Cetnter, Woods Hole, MA

Marine invasive species can profoundly alter ecosystem processes by displacing native species and changing community structures. The invasive tunicate Didemnum vexillum was first found on the northern edge Georges Bank in 1998. It can form encrusting colonies on gravel substrates that are also a preferred habitat for a number of other invertebrates. In this study we used data collected via HabCam, a vessel-towed underwater imaging system, to investigate the distribution of D. vexillumand its relationship to other benthic invertebrates in a portion of Georges Bank that includes fishing grounds and an area protected from bottom fishing. This novel technology provides high resolution imaging of species distributions in areas of the benthic environment that were previously unobservable.


We found that D.vexillum density is negatively correlated with the Atlantic sea scallop (P.magellanicus), barnacles (genus Balanus), the tube anemone (genus Cerianthus), the green sea urchin (Strongylocentrotus dreobachiensis), the globular sponge of the genus Polymastia, and bryozoans, but it positively correlated with Cancer spp. Crabs, the tube forming polychaete, Filograna implexa, and Asterias spp. sea stars. The hypothesis that D.vexillum restructures the invertebrate community is supported by principal components analysis, revealing it as a primary driver of variation in the community when present. Additionally, as consistent with previous studies, there is an effect of the closed area as compared to fishing grounds on the structure of the invertebrate community and the abundance of certain species. Principal components analysis revealed that bottom-fishing also appears to weaken clustering among species in the invertebrate community as compared to the community structure in the closed area. Biodiversity in high gravel sites, as measured by the Shannon diversity index, also declined with increasing D.vexillum percent cover, while the open and closed areas were not significantly different in their level of biodiversity. Didemnum vexillum appears to be the key driver of biodiversity decline when present, rather than other processes such as direct disturbance and extraction from dredging. This research evaluates ecological responses to the presence of an invasive tunicate and suggests that this invasive species is a major force in shaping the ecological interactions in invaded areas.