Previous work found significant differences in growth rates of native mussels at locations downstream from the regulated Walter’s Dam and the out-of-service, free-flowing Davy Crockett Dam. The purpose of this study is to investigate differences within the macroinvertebrate communities related to factors driving the differences in mussel growth between rivers. Macroinvertebrate samples were collected following the Tennessee Department of Environment and Conservation protocol for SQKICK collection and analyzed using the Tennessee Macroinvertebrate Index (TMI). There were no significant differences in TMI scores between the downstream sites of the rivers, but there were significant increases in chlorophylla, dissolved oxygen, and specific conductance downstream compared to upstream in both rivers. This suggests that these indices are suitable to identify pollution changes, but potentially not the productivity differences that impacted mussel growth.

The cycling of nutrients is a fundamental process in streams and rivers, and scientists are increasingly recognizing the importance of animal communities to nutrient dynamics in these ecosystems. Despite growing evidence that animal excretion (i.e. urine) can supply limiting nutrients to primary producers in small streams, the importance of excretion is uncertain in large rivers. Accordingly, I used three estimation approaches based on past and new excretion rate data to determine nitrogen (N) and phosphorus (P) excretion inputs from insect communities in four large rivers (discharge > 10 cubic meters per second) in North America, and I compared these rates to both the total demand for nutrients by primary producers and background nutrient levels. Additionally, I compared the ratio of excreted nutrients (N:P) to water nutrient limitation (N-limitation or P-limitation) to understand whether excretion by insects could serve as a potential source of limited nutrients to free-floating primary producers in large river ecosystems. Across all three estimation approaches, total insect community N excretion rates ranged from 18.9 to 1070.1 μg N m-2 hr-1, while community P excretion rates ranged from 16.3 to 378.7 μg P m-2 hr-1. Across all rivers and estimation approaches, community N and P excretion was equal to 0.7 to 32.4% and 0.1 to 6.0% of total N and P demand, respectively. Additionally, excreted N and P was equivalent to 0.5 to 62.3% and 0.2 to 5.5% of background N and P levels, respectively. Excreted N:P ratios suggested that excretion may serve as an important pathway in the alleviation of nutrient limitation for some primary producers in large rivers, although additional research will be required. Compared to smaller stream ecosystems, in which animal excretion can supply >50% of total N demand, and also match > 100% of background N levels, insect excretion appears to play a smaller role in nutrient dynamics of large rivers, although excretion may contribute significantly in rivers with high animal biomass and low background nutrient levels, as for N in the North Platte River in this study.

Criteria used to characterize lotic salmonid habitat are often based on observed correlations between physical habitat characteristics and salmonid abundances. A focus on physical habitat features ignores other habitat components, such as an adequate supply of food that set the physiological limitations on salmonid growth and survival. This study outlines the development of a habitat assessment approach that focuses on how invertebrate food availability interacts with stream temperatures to determine salmonid growth potentials. Abundances of benthic and drifting invertebrate communities, stream temperatures, and juvenile steelhead trout (Onchorhynchus mykiss gairdneri) summer growth rates and abundances were measured within 10 distinct stream segments in central Oregon. Stream temperatures and growth rates were used as inputs for bioenergetics model simulations to produce estimates of O. mykiss summer consumption rates. Measures of invertebrates providing the best description of food availability were chosen based on their ability to explain observed variation in salmonid consumption. Much of the variation in O. mykiss consumption estimates was explained by measurements of total drift biomass along a type II predator response curve. A random effects analysis of variance (ANOVA) was used to partition variation in invertebrate abundances across spatial and temporal scales. Quantification of variation at multiple scales allowed identification of a relevant spatial scale at which to assess macroinvertebrates relevant to salmonid populations, and compare the precision associated with measures of benthic and drifting invertebrate abundances. Results suggested that spatial variation in drifting and benthic invertebrate abundances are greatest at the scale of streams. Total drift biomass and total benthic biomass were more precise at the stream and stream reach scale than drift and benthic density. The information provided by this study will be used to guide the development of sampling approaches that describe invertebrates in a manner more directly related to salmonid production.

No description available.

No description available.

No description available.

The structure and function of stream ecosystems may be strongly influenced by land-use practices within watersheds. The magnitude of land-use impacts may depend upon the spatial arrangement of development in watersheds. This study examines the relationship between land-cover patterns and stream structure and function in 9 southern Appalachian headwater basins. Using a GIS/remote sensing approach, land-cover patterns were quantified at several spatial scales, including the entire watershed, riparian corridor, and riparian sub-corridors extending upstream in 200 m increments for 2 km. In-stream physico-chemical variables were related to land-cover patterns at different spatial scales. Dissolved constituents (e.g., TIN, alkalinity) were frequently related to physical features or land-cover patterns at the watershed scale. Conversely, mean substrate particle size and stream temperature were most strongly related to land-use practices at the entire riparian corridor scale. Finally, maximum stream temperature was best explained from land-cover patterns at the 200 m sub-corridor scale. The relationship between land-cover patterns and benthic macroinvertebrate communities is examined in Chapter 1. Macroinvertebrate assemblage structure was quantified using the slope of rank-abundance plots, and further described using standard diversity and evenness indices. Macroinvertebrate taxa richness ranged from 24 to 54 among sites, and the analysis of rank-abundance curves defined three distinct groups with high, medium, and low diversity. In general, other macroinvertebrate indices were in accord with rank-abundance groups, with richness and evenness decreasing among sites with maximum stream temperature. Macroinvertebrate indices were most strongly related to land cover patterns evaluated at the 200 m sub-corridor scale, suggesting local, streamside development effectively alters assemblage structure. The relationship between land-cover patterns and leaf breakdown is examined in Chapter 2. Breakdown rate for American sycamore (Plantanus occidentalis) leaf packs varied significantly among sites (k = 0.0051 to 0.0180 d-1), but fell within the range reported in the literature for sycamore. Leaf breakdown rate increased among sites with shredder density and biomass. Further, breakdown rate and shredder density and biomass were positively related to mean substrate particle size. Though several instream variables were related to watershed-scale features, leaf breakdown rate was not related to land cover at the watershed scale. Leaf breakdown rate was inversely related to % non-forest within riparian sub-corridors of approximately 1 km. Results suggest that the distribution of shredders is critical to leaf processing in these streams. In some streams, increased sediment inputs as a result of agricultural activity or residential development in riparian corridors may limit the distribution of shredders and thus influence leaf breakdown rates. Alternatively, near stream development may reduce the quantity and/or quality of allochthonous inputs to streams, and thus indirectly influence the distribution of shredders. / Master of Science

Litter decomposition is a poorly understood function of constructed and natural forested wetlands. This study compared rates of litter mass loss, changes in litter morphology, and associated macroinvertebrate populations in constructed and natural non-tidal wetlands. Two sets of wetlands (constructed vs. natural) were studied in eastern Virginia; a 9 year-old riparian set near Fort Lee, (FL), and a 2 year-old wet flat set in Charles City County, (CC). Mixed deciduous forest litter collected from the FL natural wetland decayed more rapidly in the created wetlands than the adjacent forested wetlands. Mixed emergent marsh litter collected from the FL created wetland exhibited a similar relationship, although marsh litter decomposed slower than forest litter. Litter area and weight loss followed a similar pattern, although area loss lagged behind weight loss, consistent with an initial leaching phase of decomposition. Both the FL and CC created wetlands exhibited faster litter decomposition than their adjacent forested wetland, however, the FL created wetland had a lower weight:area ratio and higher detritivore abundance than the adjacent forested wetland, while the reverse was true for the CC wetland pair. These relationships suggest macroinvertebrates played an important role in decomposition in the FL created wetland, while other factors were more significant at CC. Faster decomposition in the created wetlands may be of concern for long-term soil organic matter accumulation, or conversely, may indicate quick recovery of the litter decomposition function. Overall, these findings point out the difficulties involved in using certain functional indicators to compare very young and mature systems. / Master of Science

The importance of streamside management zones (SMZ) in minimizing the impact of non-point source pollution from silvicultural operations is recognized by the forestry Best Management Practices of most states. However, research concerning the SMZ width and harvesting intensity required to maintain water quality and biotic communities is limited. The goal of this study is to evaluate the efficacy of different SMZ widths and forest harvesting intensities within SMZs, in maintaining the water quality and biotic communities of 22 headwater streams located in the mountains of East-central West Virginia. Streams were organized in four blocks and randomly assigned one of six silvicultural treatments involving variation of SMZ width and harvesting intensity within the SMZ; 30.5 m SMZ with no residual harvest, 30.5 m SMZ with 50% residual harvest, 15.3 m SMZ with no residual harvest, 15.3 m SMZ with a 50% residual harvest, 4.5 m SMZ and control (no harvest within the watershed). Stream water chemistry parameters (in particular, NO3, NH4, Ca, Mg, conductivity and total dissolved solids) as well as aquatic macroinvertebrate communities were monitored from June 2003 through March 2005. Average nitrate concentration in streams harvested with a 4.5 m SMZ was more than 4 times as high as that of control streams. Average summer and fall stream temperatures were inversely related to SMZ width. Mean values for a number of macroinvertebrate community metrics were indicative of poorer water quality in streams harvested with a 4.5 m SMZ. During this short-term study SMZs of at least 15.3 m appeared to be sufficient to maintain water quality. However, harvesting was restricted to one side of the stream and logging induced stream disturbances were observed even with SMZs of 30.5 m. For these reasons SMZs of at least 30.5 m are recommended as a cautionary measure to minimize the potential for impacts to biotic communities. In addition, residual harvest of up to 50% of the basal area within the SMZ did not appear to impact water quality during the temporal scope of the study. / Master of Science

Although sediment is a natural component of stream ecosystems, excess sediment presents a threat to natural freshwater ecosystems. Sediment management is complicated because sediment can be dissolved in the water column, suspended as particles in the water column, or rest on the bottom of the stream bed, and can move between these forms (e.g. bedded sediment can be resuspended). Each form of sediment affects aquatic life in a specific way. To manage stream sediment in a way that protects aquatic life, we need to understand the ways different forms of sediment affect living things, and we need to be able to predict how sediment changes form under different stream conditions (for example, during high water events). To improve our understanding of these things, the studies in this dissertation set out to: (1) identify how often sediment is specifically mentioned as the primary pollutant “stressor” of the benthic macroinvertebrate community (primarily aquatic insects); (2) determine which forms of sediment have the largest negative impacts on aquatic insects in Virginia and what levels of sediment may cause harm; and (3) measure the changes of sediment between suspended and bedded forms in a small stream to provide information needed to restore the health of stream ecosystems. An inventory of published US Clean Water Act Total Maximum Daily Load (TMDL) reports, which states write to identify their impaired waters and their plans to improve those waters, revealed that sediment is an important stressor in over 70% of waters that have altered aquatic insect communities. If the language used to describe how waters are evaluated and what is causing the impairments were standardized among states, data collected under the Clean Water Act could be more broadly used to help understand water quality issues and ways to address them. Analysis of 10 years of Virginia Department of Environmental Quality sediment and aquatic insect community data collected within 5 ecoregions of the state indicates that a combination of 9 sediment parameters reflecting dissolved, suspended, and bedded forms explains between 20.2% and 76.4% of the variability in the health of the aquatic insect community within these regions. Embeddedness, which measures how much larger particles such as gravel and cobble are buried by finer particles like sand; and conductivity, which is a measure of dissolved salts in the water column, both have substantial impacts on the aquatic insect community. Sensitivity thresholds for embeddedness and conductivity indicate the levels of these parameters above which 5% of insect families are absent from a stream; therefore, these levels are considered protective of 95% of the insect community. Thresholds for embeddedness are 68% for the 5 combined ecoregions, 65% for the Mountain bioregion (comprised of Central Appalachian, Ridge and Valley, and Blue Ridge ecoregions), and 88% for the Piedmont bioregion (comprised of Northern Piedmont and Piedmont ecoregions). Thresholds for conductivity are 366 µS/cm for combined ecoregions, 391 µS/cm for the Mountain bioregion, and 136 µS/cm for the Piedmont bioregion. These thresholds can be used by water quality professionals to identify waters with sediment impairments and can be used to help identify appropriate stream restoration goals. A study of sediment movement within the channel of a small stream indicated average transport speeds of ~ 0.21 m/s during floods with peak flows of ~ 55 L/s. The use of rare earth elements (REE) to trace sediment particles revealed individual particle transport distances ranging from 0 m to >850 m. Deposition on a unit area basis was greater in the stream channel than on the floodplain, and the movement of sediment from the stream bed to the water column and back again during sequential floods was evident. Approximately 80% of the tracer was deposited within the first 66 m of the reach. This information can aid the development of models that predict the impact of stream restoration practices on in-stream habitat and improve predictions on the time it will take between the initiation of stream restoration projects and when we see improvements in the biological community. / PHD