Summer 2017, two student research fellows – one Bowdoin student, one Barnard College student – delved into figuring out what invasive green crabs (Carcinus maenas) are eating in Harpswell Sound. Pauline Unietis (’20) and Vanessa Van Deusen (Barnard ’18) set crab traps at four locations around Harpswell sound every week. Crabs caught in these traps offer several types of data: a census of how many (and what sex) crabs are moving into these locations as the season progresses, stomach contents, and tissue. After measuring and counting crabs, Pauline and Vanessa extracted DNA from stomach contents to prepare for a next generation sequencing-based metabarcoding effort to ID different kinds of algae, plants, and animals eaten by the crabs. Future efforts will include compound stable isotope analysis of the crabs’ tissue (from a leg or claw) to figure out the relative proportions of their diet items.