Julia Blum - Crab Lab

Tufts University, Boston, MA

As a Crab Lab intern, my responsibilities were threefold:  I had to (1) work on my project, (2) help out with my mentor's projects, and (3) help out with ongoing lab activities.

My project was a study on the effect of Molgula manhattensis, a solitary ascidian that is a possible invader in Chesapeake Bay, on the Chesapeake Bay fouling community, as well as a study of the effect of predator exclusion on populations of Molgula.  (The title of my final presentation was "Interactive Effects of an Invasive Species and Epifaunal Predators in the Fouling Community").  Following a full-factorial, replicated experimental design, I placed 24 fouling plates in the York River for 1 month.  These plates were divided among 6 treatments based on 2 factors, Initial Molgula Presence and Predator Exclusion.  The Initial Molgula Presence factor had 3 levels: Molgula Present (plates with adult Molgula glued on), Molgula Absent (blank plates), and Structural Mimic of Molgula Present (plates with fake grapes glued on).  The Predator Exclusion factor had 2 levels: Predators

Excluded (plate enclosed in cage) and Predators Not Excluded (plate not enclosed in cage).  My 6 treatments were all the possible combinations of these factors, i.e. Caged Molgula Present, Uncaged Molgula Present, Caged Molgula Absent, Uncaged Molgula Absent, Caged Mimic Present, Uncaged Mimic Present.  After the 1 month experimental period was over, I retrieved the plates and brought them back alive to SERC for analysis.  Using a 50-point grid, I recorded the primarily and secondarily settling species at each point.  I analyzed percent cover data and species richness across treatments.  I found that caging allowed Molgula to dominate the community on my plates and that when it was dominant Molgula decreased overall species richness by decreasing the amount of secondary settlement.

My research mentor, Libby Jewett, was a University of Maryland graduate student studying the effect of decreased dissolved oxygen on the Chesapeake Bay fouling community.  Helping her involved traveling with her to the Virginia Institute of Marine Science (Gloucester Point, VA) several times during the summer to perform the manipulations involved in her experiments. I learned a lot about field work in the process of making these trips, as well as having lots of chances to discuss my project with Libby (VIMS is 3 and a half hours away from SERC!).

The Crab Lab has a number of ongoing projects surveying the population and community structure of the Rhode River that I also participated in these included monthly trawling, weekly work at the fish weir, and seining and tethering (of crabs and fish) throughout the summer.  I also helped out post-docs in the lab with their field research when they needed an extra hand.  These activities taught me many practical skills (seining, tethering, trawling, fish and crab identification and handling) as well as being a good chance to go muck around in rivers in the summer.

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