First Advisor

Catherine de Rivera

Date of Publication

Spring 7-6-2016

Document Type


Degree Name

Master of Science (M.S.) in Environmental Science and Management


Environmental Science and Management




Fouling -- Management, Marine fouling organisms -- Control -- Pacific Coast (U.S.), Distaplia occidentalis -- Effect of predation on, Sea squirts, Nonindigenous aquatic pests, Marine biological invasions -- Oregon -- Charleston -- Case studies



Physical Description

1 online resource (viii, 110 pages)


Marine non-native species threaten economic and environmental health, making it crucial to understand factors that make them successful. Research on these species, therefore, allows for greater preparedness and informed management of biological invasions and increases understanding of elements structuring biological communities. Among the marine non-native species, and particularly the fouling community, non-native ascidians are a taxon of particular concern because they can crowd out native benthic species and smother mariculture products. This thesis addresses management for ascidians and other fouling organisms and includes research on the invasiveness of this taxon in addition to the invasibility of recipient fouling communities. On the West Coast of the U.S., limited efforts have been made to coordinate biofouling management across states, despite the myriad vectors increasing propagule pressure over time along coastal states. Building on recent state and local efforts, I developed a Pacific Regional Biofouling Plan for the states of Oregon and Washington to help start a consensus-driven process by which these states could create a forum for more comprehensive coordination efforts, following California's lead. As states address authority gaps, the biofouling management framework I've written is meant to be used to guide the conversation between managers as various stages of coastal management are realized.

To better inform the scope and efficacy of management and regulatory efforts, the study of invasions ecology asks and aims to answer questions regarding recipient community interactions and characteristics of the non-native species themselves. Studies that identify characteristics that make ascidians successful (invasiveness) and determine the influence native communities have on their success (invasibility) are important for assessing overall risk of establishment and spread from non-native ascidians. Therefore, I aimed to: 1) explore the hypothesis that fouling communities on suspended, artificial structures are more invasible than benthic habitats; and 2) identify characteristics influencing predation patterns on the native Distaplia occidentalis versus non-native ascidian species using mensurative and experimental studies in Charleston Marina, Oregon. I conducted a series of feeding assays, surveys, and a caloric content analysis. Feeding assays were conducted with a suite of predators. The flatworm predator (Eurylepta leoparda) was found to be highly selective on the native ascidian Distaplia occidentalis, and only preyed on whole colony samples. Feeding assay data suggest that test (tunic) structure or thickness may be an influential factor affecting nudibranch (Hermissenda crassicornis) predation rates on native versus non-native ascidians, with greater predation on the native ascidian species. Non-native ascidians may escape predation in floating but not benthic environments on the Oregon coast due to their palatability characteristics, likely tunic structure and low caloric content. In this case, this suite of predators may indirectly facilitate the invasion of docks but provide at least partial resistance to the invasion of natural benthic areas.

The chapters herein address gaps in management and scientific knowledge regarding non-native species of the marine fouling community. Future work enhanced by my efforts could include the development of the coastal biofouling management plan, coordinated by the Western Regional Panel on Aquatic Invasive Species Coastal Committee, and broadening the geographic and taxonomic scope of my research with a more comprehensive study of predator-prey interactions involving non-native ascidians and a diverse suite of predators. These interactions may be an important factor in explaining the success of ascidians and other fouling organisms on floating structures and lack of success on nearby benthic substrata.


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