The release of marine debris into the oceans and seas is a global issue of growing concern. These materials are harmful to marine environments and can also transport non-native species to novel habitats. Non-native species floating on marine litter is one of the lesser known impacts associated with marine debris....
Over recent decades, the marine ecosystems of Prince William Sound (PWS), Alaska have experienced the concurrent effects of a major anthropogenic disturbance, the 1989 Exxon Valdez oil spill (EVOS), and a dynamic atmospheric-oceanic environment. Studies of top marine consumers can provide insights into processes of ecosystem change. Using data collected...
To begin to understand freshwater seasonal floodplain fish communities in the context of human alteration of the physical system, species introductions and wetland restoration efforts, I studied fish assemblages in fifteen seasonal floodplain wetlands within four geographic regions (coastal, upper Columbia River estuary, Puget Sound and eastern Oregon/Washington) in the...
The species compositions and densities of the littoral and pelagic zooplankton
assemblages in Crater Lake were compared. The littoral and pelagic zooplankton
assemblages of most lakes are typically different due to different habitat conditions in the
two zones. The littoral zone of Crater Lake lacks many of the habitat characteristics,...
The National Park Service initiated a backcountry campsite restoration project
in 1987 to restore native vegetation on severely degraded campsites in three subalpine
lake basins in Yosemite National Park. Restoration treatments included soil
scarification, transplanting, manual seeding and site protection. Eight of the treated
campsites were monitored in 1990 to...
Differences in the chemical composition of calcified structures can be used to reveal natal origins, connectivity, metapopulation structure, and reconstruct the environmental history or movement patterns of many marine organisms. Sharks, skates, and rays (elasmobranchs) lack the calcified structures, known as otoliths, that are typically used for geochemical studies of...
I compare the seasonal abundance variation, population dynamics, fecundity, egg hatching mechanism and success, and apostome ciliate parasites of the euphausiids Euphausia pac?fica and Thysanoessa spinfera from the Oregon coast, USA. Community structure and nearshore distributions were examined from bi-weekly oceanographic surveys (1970-1972). This region has a strong cross-shelf change...
This thesis provides the first general description of the natural variation in age
structure, growth rates, and survival in headwater populations of coastal cutthroat
trout Oncorhynchus clarkii clarkii from western Oregon, and a subsequent
synthesis of these life-history characteristics across the range of the subspecies.
Age, growth, and survival were...
I used current water management practices in central and eastern Oregon and Washington as natural experiments to quantify the effects of irrigation water withdrawals on macroinvertebrate community structure and life history strategies. Reduced discharge had direct (e.g. decreased velocity and wetted habitat) and indirect (e.g. increased conductivity and temperature) effects...
Changes in ocean conditions influenced by climatic fluctuations have lead to changes in individual species distributions, which alter the diversity, communities and species interactions across marine ecosystems worldwide. Assessing the species composition and identifying regions and habitats that can safeguard the persistence of biota are critically important. In this dissertation,...