Graduation Date

Spring 2024

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Dr. Sean Craig

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Claire Till

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Matthew Hurst

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Dr. Paul Bourdeau


Bryozoan, Invasive species, Larval preference, Antifouling paint, Fouling organism, Copper

Subject Categories



The bryozoan Watersipora subtorquata and its cryptic congener Watersipora ‘new species’ are now globally invasive species. Previous studies have found this species complex to have a high tolerance to copper-based antifouling paints, which represent a large portion of the mitigation effort toward preventing hull fouling by invasive invertebrates. Tolerance alone, however, is unlikely to explain the full extent of Watersipora’s massive and rapid worldwide invasion success. The aim of this research was to move beyond tolerance, and test whether larvae of Watersipora ‘new species’ exhibit a preference for copper-coated settlement surfaces in both laboratory and field settings. For the laboratory portion of my study, I collected maternal colonies from four sites along the northern California coastline, induced larval release, and gave them a settlement surface with four choices: (1) black paint (33% copper), (2) red paint (25% copper), (3) gray primer (0% copper) and (4) unpainted plastic. For the field study, I replicated these settlement surfaces underneath local docks in Humboldt Bay and recorded natural larval settlement every two weeks for roughly four months. The laboratory study found a roughly 4:1 ratio of larvae that preferred to settle on either of the two copper surfaces versus no copper or unpainted plastic. The field study found no obvious preference of larvae for copper surfaces, but the settlement that was observed on field panels may be indicative of larval success rather than larval preference. Taken together, these results suggest that copper may have played a greater role in the spread of this species than previously thought, and that Watersipora “new species” may have evolved a preference for hitchhiking on copper painted ship hulls.

Citation Style


Included in

Biology Commons


Thesis/Project Location


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