Disappearing Coastlines: The Effects of Dasysiphonia japonica on Mytilus edulis’ Growth, Settlement, and Survivorship.

Mytilus edulis is an ecologically and economically important species that facilitates biodiversity through both the modification and stabilization of its habitat. Unfortunately, it has been disappearing from its native range in the Gulf of Maine (GOM). Recent studies have focused on ocean acidification, warming, and predation from invasive invertebrates as the main drivers for this disappearance. While these may be important drivers, few studies have focused on algal invasive species as an impetus for M. edulis loss. Current documentation shows the presence of M. edulis in the interstitial space provided by Dasysiphonia japonica, an invasive alga that has spread throughout the GOM since 2010. Few studies have focused on the direct effects that the presence of D. japonica has on the growth rates, settlement, and survivorship of M. edulis. We conducted an in situ settlement choice experiment and a continuous growth experiment in Nahant, MA to quantify the relationship and effect D. japonica has on M. edulis growth, settlement, and survivorship. Results suggest that the relationship between D. japonica and M. edulis is a mosaic of complex and highly variable interactions. Preliminary results show that M. edulis settles within D. japonica at a higher rate than Polysiphonia lanosa, a native algal species. There is a significant interaction between time and algal species showing that M. edulis growth was slower in D. japonica, in contrast to faster growth in P. lanosa. Furthermore, M. edulis survivorship was higher across D. japonica individuals compared to P. lanosa. These results indicate that D. japonica can negatively impact M. edulis’ dispersal throughout its native range by altering growth, settlement, and survivorship. This research will provide insight into the interaction between D. japonica and M. edulis and can serve as the foundation for M. edulis conservation efforts and the understanding of D. japonica’s role in the hard substrate ecosystems of the GOM.