No description available.

No description available.

No description available.

Stream fish assemblages exist within stream networks defined by the size and proximity of connected streams (i.e., stream network topology). The spatial position of sites within stream networks may therefore regulate opportunities for fish dispersal to access distant resources or colonize "new" habitats. Such inter-stream dispersal dynamics will influence local fish assemblage structure and the vulnerability of local assemblages to anthropogenic stressors. In this dissertation, I explored the effects of stream network topology on fish assemblage structure in the mid-Atlantic highlands, USA and tested the hypothesis that dispersal would affect the sensitivity of fish-based environmental quality assessments (i.e., bioassessments). In chapter 1, I evaluated the effects of stream networks by comparing fish assemblages between sites with and without large downstream confluences (>3rd order) in western Virginia, USA (i.e., mainstem tributaries and headwater tributaries, respectively). I found that local species richness was higher in mainstem tributaries than headwater tributaries and that these effects could not be explained by variation in local environmental habitat conditions. In chapter 2, I developed and applied a continuous model of stream network topology to explore the effects of downstream size and proximity on local fish assemblage structure within the mid-Atlantic highlands. I found that fish assemblage structure (i.e., Bray-Curtis distances in species abundance) was significantly related to variation in stream network topology up to approximately 9 fluvial km from sites. Chapters 3 and 4 explored the implications of inter-stream dispersal for fish bioassessments. In Chapter 3, I identified 10 fish metrics that corresponded predictably to environmental stressors in the mid-Atlantic highlands. However, headwater tributary assemblages showed stronger relations to local environmental quality than mainstem tributaries, consistent with the hypothesis of riverine dispersal. In Chapter 4, I compared the effects of stream network topology on fish and benthic macroinvertebrate assemblages. Fish metrics were influenced by the size and proximity of connected streams but benthic macroinvertebrate metrics were not. This finding suggests that stream fishes may complement benthic macroinvertebrate bioassessments by indicating environmental conditions at larger spatial grains. / Ph. D.

Effluent samples for a treated textile waste water and treated domestic sewage waste water and water and sediment samples for an 8.2 km region of Ash Camp Creek near Keysville, Virginia, were collected in June, 1977. Effluent and stream water samples were analyzed for various water quality parameters and for suspended, dissolved, and total zinc. Sediment samples were analyzed for zinc and percent loss on ignition. The treated textile waste water was the major source of zinc to the stream. The effluent and stream water samples exhibited a marked partitioning of zinc among the dissolved and suspended fractions of the water column. The ratios of mean dissolved to mean suspended zinc ranged from about 0.76 to about 1.40. The ratios of mean dissolved to total zinc and mean suspended to total zinc ranged from about 0.42 to 0.62 and from about 0.38 to 0.57, respectively. Anomalously high zinc concentrations were found in the sediments 0.80 m downstream from the point of discharge of the treated textile wastewater and appeared to be caused by sedimentation of suspended zinc induced by a reduction in stream velocity. The domestic discharge together with flow from a small unnamed tributary had a moderating effect on the water quality of the stream functioning to dilute stream pollutant load. Sulfide precipitation appeared to be an important mechanism by which zinc was concentrated in the sediments 40 m below the domestic sewage discharge. Zinc concentrations declined further downstream likely as a result of such factors as dilution, sedimentation, and sorption by inorganic sediment particles. / Master of Science

Forested mountain watersheds provide essential resources and services (e.g., water supply) to downstream ecosystems and human communities. Fast-growing mountainside residential development not only modifies the terrestrial system but also aquatic systems by changing the nutrient input from the terrestrial to aquatic. However, the impacts of mountainside residential development on stream ecosystems are complex because interactions between in- stream process and hillslope soils control in-stream nutrient dynamics, and it is difficult to experimentally study these interactions at broad spatial scales. In my dissertation research, I first developed models for leaf decomposition in a forested headwater stream by synthesizing several important ecological concepts, including ecological stoichiometry, microbial nutrient mining, and microbe-substrate interaction. I then extended the single stream model to a stream network model and further linked the stream network model with a terrestrial model that simulates nutrient processes and hydrology in hillslope soils. With this complete modeling framework, I conducted a global sensitivity analysis to evaluate the importance of terrestrial nutrient input versus in-stream processes in modifying nitrogen export. I also conducted a simulation to investigate the impacts of housing density, buffer zone protection, and stream travel distance from the residential development to the catchment outlet on nitrogen export at the local and regional scale. The model for leaf decomposition performed better for predicting detritus decay and nutrient patterns when microbial groups were divided into immobilizers and miners and when leaf quality was included as a variable. The importance of terrestrial nutrient input versus in-stream nutrient processes greatly depended on the level of terrestrial nutrient input. When terrestrial nitrate input was low, nitrogen export was more sensitive to in-stream net microbial nitrogen flux (mineralization - immobilization) than nitrate input. However, when terrestrial nitrate input was high, nitrate input was more important than in-stream net nitrogen flux. Greater impacts, i.e., higher nitrogen export at the local scale or greater change in nitrogen export at the regional scale, were associated with higher residential density, a lack of buffer zone protection, and shorter stream travel distance from the residential development to the catchment outlet. Although subject to model assumptions and further validation through field experiments, this research provides a general modeling framework for in-stream processes and aquatic-terrestrial linkages and expands an understanding of interactions between terrestrial and in-stream nitrogen dynamics and the impacts of mountainside development on stream ecosystems, identifies directions for further research, and provides insights for land and river management in mountainous areas. / Ph. D.

This study investigated the diet and growth of a leaf-eating caddisfly, Pycnopsyche, in streams draining a >60 year-old reference forest and a 16-year-old c1earcut (disturbed) forest at Coweeta Hydrologic Laboratory in southwestern North Carolina. The objective was to examine whether Pycnopsyche larvae grew better on fast-decaying leaf types more prevalent in the disturbed streams (e.g., black birch) because leaf-eating insects (shredders) in a previous study were more productive in these streams despite having less food available. Larvae consumed mostly unidentified plant material in streams of both forest types over three seasons (fall, winter, and spring) which suggested larvae did not consume higher quality foods (e.g., algae) in disturbed streams. When fed 2-mo "conditioned" black birch and white oak leaves, lab experiment larvae grew significantly faster on birch leaves. However, when larvae were fed the same leaf types after 3 mo of conditioning, larvae grew significantly faster on oak leaves. A field growth experiment conducted for 42 d using leaf diets representative of both forest types and conditioned for 2 mo found Pycnopsyche grew better on the diet representative of the reference forest. found Pycnopsyche grew better on the diet representative of the reference forest. / Master of Science

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen viewed (4/7/2008). Includes bibliographical references (leaves 49-56).

A comparative study was made of environmental variables and the density, biomass, diversity, and species composition of macroinvertebrates in areas downstream from a dam with a hypolimnetic release (Hungry Horse Dam on the Flathead River) and a dam with a selective withdrawal system (Libby Dam on the Kootenai River). A major objective of this study was to examine the response of macroinvertebrate communities to defined environmental gradients in temperature, flow, substrate, and food-related variables (periphyton, particulate organic carbon in the seston). In addition, the effects of experimental manipulations in discharge on macroinvertebrate drift and stranding were assessed, and the effects of temperature on the growth rates and emergence of five species of insects were measured.

Doctor of Philosophy / Department of Biology / Keith B. Gido / Many native freshwater animals are imperiled as a result of habitat alteration, species introductions and climate-moderated changes in disturbance regimes. Native conservation and nonnative species management could benefit from greater understanding of critical factors promoting or inhibiting native and nonnative success in the absence of human-caused ecosystem change. The objectives of this dissertation were to (1) explain spatiotemporal patterns of native and nonnative success, (2) describe native and nonnative response to uncharacteristic wildfire disturbance, and (3) test the hypothesis that wildfire disturbance has differential effects on native and nonnative species. This research was conducted across six sites in three reaches (tributary, canyon, and valley) of the unfragmented and largely-unmodified upper Gila River Basin of southwestern New Mexico. Secondary production was measured to quantify success of native and nonnative fishes prior to wildfires during 2008-2011. Native fish production was greater than nonnatives across a range of environmental conditions, although nonnative fish, tadpole, and crayfish production could approach or exceed that of native macroinvertebrates and fishes in canyon habitats, a warmwater tributary, or in valley sites, respectively. The second objective was accomplished by measuring biomass changes of a warmwater native and nonnative community during 2010-2013 before and after consecutive, uncharacteristic wildfires. Several native insect and fish taxa decreased after both wildfires, whereas nonnative decreases were most pronounced for salmonids and more limited for other taxa. Finally, effects of uncharacteristic wildfires followed by extreme flooding on metapopulations of native and nonnative fishes were contrasted during 2008-2013. Wildfire and flood disturbances increased extinction probabilities of all native fishes while leaving many nonnative fishes unaffected. These findings revealed a swinging pendulum of native and nonnative success, wherein wildfire disturbance resulted in a pendulum swing in favor of nonnatives. Ensuring the pendulum swings back in favor of natives will be facilitated by management activities that decrease wildfire size and intensity and maintain inherent ecosystem resilience.