Anna Krainer - Invasions Ecology Lab

Waynesburg College, Waynesburg, PA

I was a part of a group project within the marine invasions lab, working with a large, solitary, tunicate Molgula manhattensis, commonly known as the sea grape.  Molgula are cryptogenic organisms, meaning it is not clear yet whether it is invasive or native pertaining to the Chesapeake Bay.  Our project was based on the results of a past intern, Dale Booth, who suspended different sized settlement (PVC) plates from docks and expected to see the classic species area relationship curve, meaning the larger the settlement plate the more species should be found on the plate.  But because the Molgula were so dominant, the species area relationship curve was not observed at all.

This summer we set out to see if we could obtain a positive species area relationship curve by manipulating the previous experiment further.  Our experiment took place at two different marinas in Norfolk, VA, near the mouth of the Chesapeake Bay.  Our first site, the control site, contains 40 settlement plates of 4 different sizes, which will be left untouched for 8 weeks.  This site is historically known to have very low densities of Molgula, meaning the Molgula will not heavily impact the overall populations on the plates.  The second site has historically high densities of Molgula, which will greatly impact the population on the plates.  At this site there were 120 settlement plates deployed also with the same 4 different sizes. The first types of settlement plates are the “gardened” plates.  These plates will be pulled out of the water once a week, and the Molgula will be removed or “gardened” from the plate.   The second types of settlement plates are the manipulated plates, they are removed from the water in the same manner, and for the same amount of time as the gardened plates, but no Molgula are removed, this is to control for any changes due to removing the plate from the water each week.  The third types of settlement plates are control plates, which are never removed from the water for the entirety of the experiment. 

At the end of the experiment all plates from both sites will be removed and brought back to SERC to be analyzed.  We expect to observe the anticipated positive species-area relationship (the larger the plate the more species) on the gardened plates, and the control site as well because the Molgula will be absent.  On the ungardened plates we expect to see the plates dominated by Molgula with no positive species area relationship.  Hopefully the results of our experiment will shed light unto the population dynamics of the fouling community in the Chesapeake Bay.

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