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Entocytherid ostracods were collected on crayfishes inhabiting the James and York River basins of Virginia. Of the seventeen species encountered, only one (Donnaldsoncythere ardis) seems to be endemic. Ankylocythere ancyla, Dactylocythere banana, Dt. falcata, Dt. suteri, Donnaldsoncythere ardis, Dn. hiwasseensis, Dn. truncata, Entocythere sp. A, E. internotalus and Phymocythere phyma occur on the crayfishes Cambarus acuminatus, C. b. bartonii, C. longulus and Orconectes juvenilis in the streams of the Valley and Ridge Province. In the Coastal Plain where sluggish streams are encountered, Ankylocythere telmoecea and Ank. tiphophila are associated with Procambarus a. acutus. Cambarus acuminatus is also found in the Coastal Plain in moderately flowing streams and it is infested with Dactylocythere suteri and Donnaldsoncythere hiwasseensis. The primary burrowing crayfish of the Alleghany Mountains (Cambarus dubius) is host to Ascetocythere asceta and Dactylocythere chalaza whereas its ecological similar Cambarus d. diogenes of the Piedmont and Coastal Plain is the only host known with certainty for Dactylocythere jeanae, Okriocythere cheia and Ornithocythere waltonae. Ankylocythere tiphophila is associated with Fallicambarus uhleri, an inhabitant of swampy areas and marshes and may ocassionally construct simple burrows in the Coastal Plain. / Master of Science

Rivers and their surrounding riparian and subsurface ecosystems, known as river corridors, are important landscape features that provide a myriad of ecological and societal benefits. While the importance of riverine flooding has been widely acknowledged and extensively studied, very little research has been conducted on the interactions between river channels and their adjacent floodplains. The importance of this hydrologic connectivity between rivers and floodplains has been emphasized in recent decades and now ecological engineering techniques such as stream restoration are often utilized to restore connectivity between streams and their riparian ecosystems. Despite its ubiquity in practice, there are still many basic components of river-floodplain connectivity that are not well understood. Furthermore, a lack of cost-effective monitoring techniques makes sustainable management of river corridors quite challenging. Thus, the overall goals of my dissertation were: 1) develop user-friendly river corridor monitoring techniques utilizing cost-effective approaches such as time-lapse digital imagery and satellite remote sensing and 2) identify the effects of anthropogenic activities on river corridor hydrologic and biogeochemical processes that occur at varying spatial and temporal scales during flood events. These goals were addressed through five independent studies that span spatiotemporal scales. The five studies utilized a combination of novel remote sensing, hydrologic/hydraulic modeling, and high frequency spatial sampling techniques to analyze river corridor dynamics. Results highlight that digital imagery and satellite remote sensing can be effective tools for monitoring river corridors in data scare regions. Additionally, impounding streams and river corridors alters floodplain connectivity and biogeochemical processing of reactive solutes such as nitrogen and phosphorus. Findings from this work highlight the important role that spatial and temporal scale plays in river corridor dynamics. Overall, this research provides new analytical techniques and findings that can be used to effectively monitor and manage river corridors. / PHD

This Ph.D. project aims to aquire a better understanding of sedimentological and ecological processes within the immediate vicinity of Large Igneous Province (LIP) activity and of the effects that LIP volcanism may have on the environment. The Miocene Columbia River Flood Basalt Province (CRBP) comprises an up to 4500 m thick succession of basaltic lavas intercalated with fluvio-lacustrine siliciclastic and volcaniclastic sediments. Detailed field-based studies (logging of 47 interbed sites) and the generation of geochemical (XRF, SEM, and microprobe) and palynological data provide an integrative study of characterising and modeling sedimentological and ecological processes within the lava field. The generation of a sedimentary facies scheme allowed a reconstruction of the intra-lava drainage system through time. Drainage system evolution is largely controlled by CRBP volcanism which is capable of forcing fluvial systems to the margin of the lava field during the phases of high volcanic activity, while phases of waning effusion frequencies and volumes allow the fluvial environment to migrate back into the central part of the lava field. The composition of the siliciclastic sediments suggests external source areas mainly located in the Cascade Range west and north of the CRBP. High plant diversity and late successions occurred during the early stage of CRBP evolution, and were affected by the increased deposition of ash derived from Cascade Range volcanoes and the Yellowstone hot spot during the late stage of CRBP evolution. Interbed sites distal to the volcanic source are generally colonized by late-successional plants and suggest a relationship between nutrient flux, sedimentary environment and volcanism. Palaeoclimate reconstructions based on soil chemistry and floral composition suggest that climatic changes within the CRBP reflect the global trend of the Mid-Miocene Climate Optimum. The present work allows to model sedimentological and ecological processes within the CRBP and considers the various effects that volcanic activity has on the environment. The complexity and differences in the geology and igenous evolution of individual LIPs need to be considered when applying this model to other LIPs.

Atmospheric rivers (ARs) are long, narrow plumes of concentrated water vapor that are a critical factor in the transport of moisture from oceans to continents in the mid-latitudes. Much of the existing research on the impact of ARs on the United States focuses on the Pacific Coastal states and their importance as contributors to precipitation, their impact on water resources, and their role as flood producers. The objective of this study is to determine the importance of Pacific Ocean ARs penetrating further inland and affecting flooding in the state of Arizona. The following questions were addressed: (1) Are certain regions in Arizona more susceptible to AR-related flooding? (2) Do ARs produce flooding events of greater magnitude in Arizona than floods produced by other mechanisms? (3) Are there identifiable variables or conditions that influence the frequency, magnitude, and location of AR-related flooding in the state? Based on a study of selected watersheds throughout Arizona, results showed that the most active region of AR-related flooding in Arizona is associated with the abrupt increase of elevation along the Mogollon Rim of the state's Central Highlands Transition Zone physiographic region. The percentage of AR-related flooding events in this region can reach over 50% for some watersheds, such as the Verde and the Salt. The influence of ARs on flooding is weaker to the north, in the Colorado Plateau region, and to the south, where summer convective storm activity in southeastern Arizona's Basin and Range physiographic region is a more common flood producer, and where the most extreme floods are associated with late-summer tropical cyclones. When ARs did affect northern or southern Arizona, they did not have the same degree of influence on flood magnitude and frequency as in the Mogollon Rim/Central Highlands watersheds, which implies that watersheds in the Mogollon Rim/Central Highlands have characteristics that are favorable for AR-related flooding. Lastly, in addition to the importance of the Central Highlands' orography on AR flooding, another finding of this study points to the importance of the trajectory of the inland-penetrating AR as a factor. The corridor along which the AR enters the region can strongly affect which ARs will produce floods and which ARs will not, with a south/southwesterly trajectory across Baja California producing the largest percentage of AR floods in Arizona in this study.

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The physical, chemical and biological characteristics of five southern English chalk streams in neighbouring catchments were investigated seasonally over two years. At the catchment scale, the five chalk rivers had very similar physio-chemical properties. Differences between years and between seasons were much greater than those between rivers or within-river longitudinal differences. Elevated inorganic nutrient concentrations, relative to reportedly 'pristine' systems, indicated some degree of catchment water quality deterioration in all five rivers. The effect of physical habitat degradation (channel overwidening and sedimentation) on river biota was investigated at a within-river, reach scale. The increased proportion of fine sediment within the coarse gravel substratum had a marked effect on invertebrate communities. Overwidening, however, was found to have little impact over the two years. Communities showed a high degree of stability between years, and between individual catchments, reflecting the high overall biological stability of these aquifer-fed river systems. Habitat manipulation experiments at the within-reach scale demonstrated the importance of substratum characteristics to macroinvertebrate communities. Invertebrate colonisation of newly exposed substrata over time was quantitatively and qualitatively different for coarse and fine particles - a function of shifting resource utilisation and microhabitat preferences. The relatively long time taken to fully colonise new substrata demonstrated the weak ability of chalk stream invertebrate communities to respond rapidly to changes in habitat, reflecting the stable physical nature of natural chalk streams and the vulnerability of their communities to anthropogenic disturbance.