Scales of the stoneroller, Campostoma anomalum (Rafinesque), common shiner, Notropus cornutus (Mitchill), and the bluntnose minnow, Pimephales notatus (Rafinesque) were analyzed by means of atomic absorption spectrophotometry to determine levels of cadmium, calcium, copper, iron, lead, manganese, nickel and zinc. Metal concentrations were determined seasonally and relationship established between scale metal content and environmental water metal levels. Calcium, iron manganese and zinc were found in all samples analyzed. Cadmium, copper, lead and nickel were not observed in measurable quantities. Metal concentrations varied interspecifically, but most showed little fluctuation in response to increased metal content of the water. Elemental composition of the scales was found to have been selective in that zinc and manganese were more readily taken up, even when present in considerably lower concentrations in the water. The metal content of scales was found to be related to behavioral characteristics of the species and the size of the fish.

This study examined the diet composition of ninety-nine Sacramento pikeminnow (150-410 mm [5.9-16 in] fork length [FL]) collected from the upper and lower main stem of Chorro Creek, Morro Bay Watershed, California in 2006. The goal of this study was to characterize the spatial and seasonal variability in the diet of Sacramento pikeminnow within Chorro Creek and to determine what proportion of the diet is represented by rainbow trout (Oncorhynchus mykiss) and their anadromous form (steelhead). Prey was identified in 88% of the samples collected in the early season and 84% of the samples collected in the late season. Fish and/or scales were identified in 12% of the samples collected. Sacramento pikeminnow consumed a wide variety of prey; the diversity of individual diets was higher in the lower main stem than the upper. Overall, diet diversity increased with Sacramento pikeminnow length. In both the early and late season, crayfish formed the largest part of the diet of large Sacramento pikeminnow (>250 mm [9.8 in]). There was a slight increase in the proportion of fish in the diet during the late season, and tendency for cannibalism which was primarily observed in the upper main stem of Chorro Creek. In summary, the overall results of this study support the conclusion that Sacramento pikeminnow are not significant predators of O. mykiss in natural stream conditions. However, conclusions about the ability of Sacramento pikeminnow in Chorro Creek to reduce O. mykiss populations will require further information on the prey selection of Sacramento pikeminnow when juvenile O. mykiss and adult pikeminnow are abundant.

Natural lake-watershed ecosystems in Oregon compose a diverse and valuable assemblage of land and water resources. With an increasing demand on lakes for recreation, water supplies, and aesthetic values and an increase in available data on Oregon lake systems, there is a need for applicable and timely scientific water management information about lake conditions statewide. This thesis is an attempt to summarize some of the data collected on natural Oregon lake-watershed ecosystems. The purpose of the thesis is to identify the most typical natural systems out of an initial data base of twenty-four variables, measured over ninety-eight lake-watershed ecosystems. The selected variables are reduced to five common factors using principal components factor analysis. K-means cluster analysis is used to create similar groups of lake systems. These groups are compared to ecoregions in Oregon and a typical, representative lake ecosystem is identified for each group. Results show that several lake systems of the state are unique.

Forests are an important component of the global carbon (C) cycle and contribute to climate change mitigation through atmospheric C uptake and storage in biomass and soils. However, the forest C sink is susceptible to disturbance, which modifies physical and biological structure and limits spatial extent of forests. Unlike severe, stand-replacing disturbances that reset forest successional trajectories and may simplify ecosystem structure, moderate severity disturbances may instead introduce complexity in ways that sustain net primary production (NPP), leading to the phenomenon of “NPP resilience.” In this study, we examined the linkage between disturbance severity and ecosystem biological and physical structural change, and implications for NPP within an experimentally disturbed forest in northern Michigan, USA. We computed spatially resolved and spatially agnostic metrics of forest biological and physical structure before and 10 years after disturbance across a continuum of severity. We found that while biological structure did not change in response to disturbance, three of four physical structural measures increased or were unimodally related to disturbance severity. Physical structural shifts mediated by disturbance were not found to directly influence processes coupled with NPP. However, decadal changes in the spatial aggregation index of Clark and Evans, though not a function of disturbance severity, were found to predict canopy light uptake, leaf physiological variability, and relative NPP within plots. We conclude that ecosystem structural shifts across disturbance severity continua are variable and differ in their relationship to NPP resilience.

The objective of this study was to characterize water quality and hydrologic properties of urban streams in the Richmond metropolitan area. Water quality data were analyzed for six urban sites and two non-urban sites. Geomorphological surveys and conservative tracer studies were performed at four urban sites and one non-urban site to describe intra- and inter- site variability in transient storage, channel geomorphology, and related hydrologic parameters. Urban sites showed elevated concentrations of nitrogen and more variable TSS concentrations relative to reference sites. Urban channels were deeply incised with unstable banks and low sinuosity. Little Westham Creek exhibited the greatest transient storage. This site was characterized by large, deep pools and therefore it is likely that transient storage was associated with surface water storage. Transient storage was low at all other sites, particularly for the study reach at Reedy Creek, which flowed through a concrete channel. Lowest transient storage was observed at this site in spring, though higher values were measured in summer corresponding to the presence of biofilms, A lower, more naturalized section of the concrete channel was found to have greater transient storage suggesting the possibility of passive restoration of concrete channels in urban environments. This study documents variability in the structure and function of urban streams. Restoration projects should work to improve impairments that are specific to each site at both the reach and watershed scale to maximize the efficacy of restoration.

To assess how urbanization impacts stream nutrient uptake, a series of instantaneous (i.e. slug) nutrient additions were conducted in 3 urban and 3 non-urban streams during open and closed canopy conditions. Single additions of N, P, and combined additions of N and P were performed at each site. These data were used to test the hypothesis that high N:P concentrations in urban streams would result in P-limited conditions, and to assess differences in nutrient uptake kinetics (i.e., the relationship between uptake and concentration) between urban and non-urban streams. The results show that there were no consistent differences in N vs. P limitation among urban and non-urban streams suggesting that ambient N:P ratios are not useful predictors of nutrient limitation at the ecosystem scale. Areal uptake rates of N in urban streams were greater than non-urban streams coinciding with elevated N concentrations. Conversely, areal uptake rates of P were similar between urban and non-urban streams because these systems have similar ambient concentrations of P. Urban and non-urban streams demonstrated similar uptake velocity and areal uptake rate responses to increasing nutrient concentrations. However, unique to this study, urban streams had greater uptake velocities at ambient nutrient concentrations. These findings suggest that urban streams could have a greater capacity for nutrient uptake over a broad range of nutrient concentrations, but prior work indicates that this capacity may be constrained by the duration of the nutrient addition.

Invasive plants are a significant threat to native ecosystems and to biodiversity. They are often strong competitors and have multiple techniques to outcompete native plants. Thus, controlling or removing invasive plants facilitates the restoration of native ecosystems. We used GPS technology coupled with field surveying techniques adapted from the U.S. Fish and Wildlife Service to locate and identify invasive plants present within VCU’s Rice Rivers Center. We digitally overlaid a 50-meter x 50-meter grid system over the property. In each grid cell we recorded visual estimations of invasive plant coverage sorted into modified Daubenmire cover classes and used ArcGIS for mapping and analysis. Altogether, we found 25 unique invasive plant species. 93% of the grid cells contained at least one invasive species, and one grid cell contained seven unique species. The influence of anthropogenic disturbance on invasive species distribution, analyzed by using a 50-meter wide buffer zone around each disturbance (e.g., roads, buildings, etc.), showed that the presence and coverage of invasive species was greater within disturbed areas compared to intact forest. Microstegium vimineum, Lonicera japonica, and Ligustrum sinense were most common and widely distributed within terrestrial habitats, while Murdannia keisak was most widely distributed in the restored wetland. Our results for M. vimineum were compared to a similar 2004 study: this species has since spread from 40% to 76% of the grid cells. The spatial maps we have created will be a foundation for an integrated invasive species management program at the Rice Rivers Center and will assist with management, control and restoration efforts within terrestrial and aquatic ecosystems.

Bull trout are a fish species listed as threatened under the Endangered Species Act.Historically, they ranged from Northern California at the southernmost extent, into Canada at the northern most extent, and east into Nevada and Montana. Bull trout are highly migratory and require large, unfragmented habitats to persist and are thus highly susceptible to human induced land-use practices. The goal of my thesis was to obtain a better understanding of bull trout movement patterns in the Walla Walla River, Washington using complimentary techniques; Passive Integrated Transponder (PIT)technology and otolith microchemistry. PIT tags can be injected into a fish body cavity, similar to how pets are “chipped”, and as the fish swim through antennas placed in the river, their location and movements are be documented.Otolith microchemistry is a technique that is similar to analysis of tree rings. The otolith, a hard bony structure of a fish’s ear, develops over a lifetime and as the rings of the otolith are created the chemical signature in the water in which they live is recorded and can be compared to chemical makeup of water samples collected through the river system. Using these two techniques, I found that the age or size of a fish and the season are important factors to explain both a fish’s movements and where in the river a fish might be located at a given time. Knowing at what size, age and season a fish is attempting to migrate allows managers to provide the best possible river conditions (e.g., temperatures, flow) to allow for unimpeded migrations to occur and to foster conservation and recovery of bull trout populations.

Nutrient availability and herbivory can regulate primary production in ecosystems, but little is known about how, or whether, they may interact with one another. Here I investigate how nitrogen availability and insect herbivory interact to alter above- and belowground plant community biomass in an old-field ecosystem. In 2004, 36 experimental plots were established in which soil nitrogen (N) availability (at three levels) was manipulated and insect abundance (at two levels) in a completely randomized plot design. In 2009, after six years of treatment, I measured aboveground biomass and assessed root production at peak growth. Overall, I found a significant effect of soil N availability on both above- and belowground plant biomass while insects affected only aboveground biomass of subdominant plant species and coarse root production; there were no statistical interactions between N availability and insect herbivory for any response variable. Specifically, responses of aboveground and belowground community biomass to nutrients were driven by reductions in soil N, but not additions, indicating that soil N may not be primarily limiting production in this ecosystem. Insect herbivory altered the aboveground biomass of the subdominant plant species and altered allocation patterns to coarse root production belowground. Overall, the results of six years of nutrient amendments and insect removals suggest strong bottom-up influences on total plant community productivity.

Nutrient availability and herbivory can regulate primary production in ecosystems, but little is known about how, or whether, they may interact with one another. Here I investigate how nitrogen availability and insect herbivory interact to alter above- and belowground plant community biomass in an old-field ecosystem. In 2004, 36 experimental plots were established in which soil nitrogen (N) availability (at three levels) was manipulated and insect abundance (at two levels) in a completely randomized plot design. In 2009, after six years of treatment, I measured aboveground biomass and assessed root production at peak growth. Overall, I found a significant effect of soil N availability on both above- and belowground plant biomass while insects affected only aboveground biomass of subdominant plant species and coarse root production; there were no statistical interactions between N availability and insect herbivory for any response variable. Specifically, responses of aboveground and belowground community biomass to nutrients were driven by reductions in soil N, but not additions, indicating that soil N may not be primarily limiting production in this ecosystem. Insect herbivory altered the aboveground biomass of the subdominant plant species and altered allocation patterns to coarse root production belowground. Overall, the results of six years of nutrient amendments and insect removals suggest strong bottom-up influences on total plant community productivity.