First Advisor

Mark D. Sytsma

Term of Graduation

Winter 2021

Date of Publication


Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Earth, Environment, & Society


Earth, Environment, & Society




Discharge of ballast water -- Environmental aspects, Nonindigenous pests -- United States, Biological invasions -- United States, International trade -- Environmental aspects, Shipping -- United States, Introduced organisms -- Control, Ballast water -- Management



Physical Description

1 online resource (ix, 171 pages)


Globalization has escalated transfers of nonindigenous species (NIS) across natural dispersal barriers. The resulting biological invasions have become a leading global mechanism of ecological change. NIS are often transported between coastal marine ecosystems in the ballast water of commercial ships, and patterns of NIS introduction and establishment can be linked to global trade dynamics. Here I examined drivers of trade and ballast water across spatial and temporal extents of invasion. The analyses incorporated a variety of datasets on trade, industries, and ship behavior to identify fluctuations in globally transported commodities that lead to changes in maritime shipping patterns and frequency. Importantly, I estimated quantitative relationships between trade exports and ballast water imports. Changes in the number and proportion of vessel arrivals that discharged ballast water, and the frequency of discharge, drove fluxes in ballast water volume. In San Francisco Bay, California, the annual tonnage of the top 11 export commodities by vessel type predicted total bay-wide overseas ballast water discharge (R2 = 0.92), largely driven by exports of dry bulk goods to Asia and petroleum to western Central America. Across the West, Gulf, and East Coasts of the United States, a four-fold increase in exports of petroleum, coal, and liquefied natural gas explained a more than three-fold increase in ballast water delivery by vessel type (R= 0.97), linking the coastal US with trade partners in Asia, Europe, and North and South America. In coastal Alaska, the annual number of tank and bulk vessels that discharged ballast water predicted annual statewide ballast water volume by each vessel type (R2 = 0.70, R2 = 0.94, respectively), driven by oil exports to the US West Coast and mining and timber exports to Asia. These relationships clarify the influence of trade on ballast water and invasion dynamics to support hindcasts and forecasts of NIS introductions. Additionally, I created an adaptable risk-based screening protocol of ballast water delivery. An application of this tool to a dataset of vessel arrivals on the Oregon coast and lower Columbia River identified high priority vessels for inspection within the range of resources available to managers. This study as a whole is a step forward in understanding invasion patterns, NIS risk to coastal ecosystems, and the sustainability of current drivers of global maritime shipping.


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