A survey of the literature reveals little information concerning the aquatic fungi associated with submerged wood debris. During the past fifteen years several mycologists have studied such lignicolous fungi, but their efforts have been confined almost entirely to marine and brackish waters. It was thought that a study of similar organisms from fresh water would make a significant addition to our knowledge of aquatic fungi. This study involves the collection, identification, and description of freshwater lignicolous fungi from the area about Blacksburg, Virginia. To collect the fungi, sterilized panels of pine and poplar were submerged at six aquatic sites £or fifteen days or more. After submergence the wood was incubated in sterile moisture chambers and then examined with a dissecting microscope. Specimens of fungi found on the wood-surface were mounted and studied under high power. All of the collections are described in this paper, including those that could not be identified. Generic description have been adapted. Descriptions of species have been adapted and modified from the literature when they have seemed adequate, otherwise they are the author's own. Reproductive structures are illustrated. A key to the identified fungi is provided. The following fungi were identified and described: Dematiaceae - Alternaria sp., Bisporomyces chlamydosporis, Cacumisporium sp., Dictyosporium elegans, Dictyosporium sp., Gonytrichum macrocladum, Humicola sp., Leptographium sp., Monotospora megalospora, Piricauda sp., Septonema hormiscium, S. secedens, Sporidesmium caespitulosum, S. anglicum, Sporoschisma saccardoi, Trichocladium opacum; Moniliaceae - Arthrobotrys sp., Clathrosphaerina zalewski, Fusarium solani, Helicomyces roseus, Hobsonia mirabilis, Verticillium sp.; Tuberculariaceae - Bactrodesmium arnaudii; Sphaeropsidales - Aposphaeria agminalis, Asteromella sp., Coniothyrium sp., Stagonospora sp. (1), Stagonospora sp. (2); Actinomycetes - Nocardia sp.; Pyrenomycetes - Nectria sp. Two unidentified Dematiaceae and ten unidentified Pyrenomycetes were also collected and described. A comparison of the results of this study with the results of other investigations on aquatic fungi indicates the existence of a distinct aquatic mycoflora associated with wood. Aquatic Hyphomycetes have been extensively collected by other workers from submerged leaves and from pond and stream scum. None of the species, not even the genera, of those collections have been found in the present survey. No lignicolous Phycomycetes were found in the present survey, although aquatic Phycomycetes are known to grow on a vast array of substrates. The fresh-water population of lignicolous fungi may be fairly distinct from that of salt water. A survey of marine fungi reveals only five fungi - Alternaria sp., Dietyosporium elegans, Humicola sp., Trichocladium sp., Coniothyrium sp., Nectria sp. - that can be considered closely related to fungi found in the present study. This study provides some insight into the ecology of the fresh-water lignicolous fungi, although the study itself has beer, primarily taxonomic. Perhaps the most important problem now is to determine the actual habitat of these fungi. Research so far indicates only that they grow on wood and that their spores are carried in the water. Another problem is to investigate the nutrition of these organisms, to determine if they digest lignin and if they are unique in this regard. / Doctor of Philosophy

Architecture can amplify aspects of life. The proposal in this thesis is to present the nature of competitive swimming through four specifically defined architectural moments. The vehicle for the thesis is a natatorium with four specifically designed architectural apertures that present the extraordinary motion of the swimmer, especially to the younger general public. The focus will be on the motion of swimming below and above the surface of the water. Below the water surface, the approaching swimmer and the moment of the turn will be framed. Above the water surface, two apertures penetrate the roof above the pool. One directs sightlines to moment of a race's start, while the other seeks to emphasize the linearity of swimming. / Master of Architecture

A preliminary survey of caves located in the limestone belt of the Appalachian Valley of Virginia, has revealed the presence of numerous soil and water inhabiting species of aquatic Phycomycetes. A review of the literature indicates a paucity of information dealing with these organisms. The caves sampled and the methods used in this investigation are briefly described. From nineteen caves 162 soil and water samples were collected from which 33 isolates have been obtained. In addition a number of monocentric chytrids were observed, but have not been further identified. Each species isolated has been studied and described under unifungal cultural conditions. The occurrence and distribution of each species is cited and any variations in morphology or development are discussed. Questions dealing with the taxonomy and nomenclature are considered in each case. The cavernicolous environment may be regarded as a new station for each species reported herein. Three species of Pythium, P. afertile, P. irregulare, and P. nagaii, are reported for the first time as saprophytic inhabitants of the soil. / Master of Science

Population biology and acid tolerance of the crayfish Cambarus bartonii bartonii (Fabricius) from southern Appalachian Mountain streams were investigated. Field studies were conducted primarily from May through October, 1985 at Coweeta Hydrologic Laboratory (U. S. Forest Service Southeastern Experimental Station) in Otto, North Carolina, to describe selected population parameters and life history events for this species in two first-order streams. Laboratory experiments were conducted using crayfish from Coweeta and from Craig Creek (Jefferson National Forest, Montgomery County, Virginia) to determine median lethal concentrations (LC₅₀) for sulfuric acid exposure, and to investigate physiological effects, influence of ambient water temperature, and effects of episodic acid events on molting. Population estimates of crayfish ranged from 210 to 683 crayfish in 20 to 25m study sections (≃9.2 to 29.8 per m²) of Ball Creek and Pinnacle Branch. Mean catch per baited funnel trap and mean catch per hour of hand collecting were determined in three study sections of each stream in May and September to obtain relative abundance estimates and compare capture methods. Each method selected for different segments (size classes) of the population. Sex ratios were balanced (1:1) over the whole sampling season, but differed significantly from 1:1 in some months, probably due to reproductive activity. Sexually mature males and females (form I males, females with full cement glands) were observed in all months sampled. Acute (96h) laboratory lethality tests yielded LC₅₀ values for pH's of 2.43, 2.56, 2.85 and 2.43 for Coweeta intermolt adults (25.3 to 43.2mm carapace length, CL), late juveniles (11.5 to 19.9mm CL), early juveniles (3.9 to 12.8mm CL) and Craig Creek intermolt adults (23.0 to 41.3mm CL), respectively. Decreased water temperature resulted in increased acid tolerance of intermolt adults (LC₅₀ = pH 2.33), and increased survival time during severe acid exposure. Acid exposure of intermolt adults in relatively soft water affected internal ion regulation, causing decreased hemolymph [Na⁺] and increased [Ca⁺⁺]; no Ca⁺⁺ mobilization (loss) from carapaces was observed. Preliminary work showed that extreme acidification had visible adverse effects on molting adults, causing failure of exoskeletons to become rigid. Episodic acid events at Coweeta do not appear to be a direct mortality problem to C. b. bartonii at this time. However, this does not preclude the possibility of future problems, particularly sublethal effects to reproductive activity or early life history stages, if increasing acidification and gradual loss of soil buffering capacity of watersheds persists. / M.S.

Drift was measured monthly at four sites on a southern Appalachian stream in order to examine spatial and temporal patterns along elevational and stream size gradients. Measurements consisted of four, one-hour samples corresponding to dawn, mid-day, dusk, and mid-night monthly for 14 months. On average, only 10% of the drifting insects were terrestrial, but terrestrial inputs became numerically important during summer and fall. There were no significant differences among sites in aquatic insect drift density, although taxa richness and total drift (#/sec) increased significantly downstream. None of the sites exhibited a consistent diel pattern. But, all of the lower three sites exhibited decreased drift density during the day. <i>Baetis</i>, the dominant aquatic taxon in the drift, exhibited a typical alterans patterns at UBC, LBC, and CC. Aquatic insect drift density was highest in summer when flows were lowest, while total drift (#/s) was highest in late spring and winter. FPOM and mean daily water temperature accounted for 64% of the variation in total aquatic insect drift density and 60% of <i>Baetis</i> drift density, suggesting both passive and active components in drift. Both variables were also highly correlated with drift density. Taxonomic composition of drift differed from that of the benthos, indicating drift was not simply random, but that taxa vary in the propensity to drift. Overall, this study found more evidence of temporal (diel and seasonal) drift patterns than spatial (along the gradient). / Master of Science

Three nontaxonomic indices; ATP/Chlorophyll <u>a</u>(ATP/Chla), ATP/ADP, and Chlorophyll <u>a</u>/Pheopigment (Chla/Pheo) were compared to the taxonomic measures of species diversity (d) and species richness as indicators of stress in aquatic environments. Field and laboratory microcosm responses of indigenous microbial communities exposed to municipal sewage treatment plant (STP) effluent were monitored. The STP effluent produced increased adenylate concentrations, ATP/ADP and ATP/Chla ratios, and decreased Chla, Chla/Pheo, d, and species richness relative to upstream reference communities. Nontaxonomic responses were consistent in four separate field tests. Significant differences in responses were discernible in 3 d when communities were transferred from reference to polluted sites. Chla/Pheo decreased more rapidly than other measurements. The predictive capability of laboratory flow through microcosm tests was examined by simultaneously transferring communities from upstream reference sites to downstream field sites and to various dilutions of field effluent in the laboratory. / Master of Science

Food habits, net-spinning activity, energetics, and mercury accumulation in Hydrospsyche morosa were examined over a one year period on the South River in central Virginia. Feeding nets were observed as early as April and were widespread by May. Nets were virtually absent from late November through March. Gut content analysis revealed seasonal patterns in the consumption of various food items. From April through October, when feeding nets were widespread, detritus formed the bulk of the diet in terms of both numbers of particles and volume occupied. From November through March however, the algal component dominated in terms of numbers of particles although the detritus component still occupied a greater volume. Ivlev's preference index was employed and indicated that the seasonal differences in the relative amount of the three food types were not simply a matter of changing seston concentrations, but rather suggested a shift from a filter-feeding mode of feeding in the summer months to grazing on diatoms in the winter. H. morosa was bivoltine on the South River. The estimate of secondary production for the summer cohort was 3,246 mg AFDW/m²/yr, while the estimate for the winter cohort was 2,145 mg AFDW/m²/yr. The secondary production also was estimated for each season based on food habits to determine the impact of the observed seasonal switch in feeding habits on production and egestion rates. During the summer, the detritus component contributed most to production averaging about 50 percent. Animal and algal material contributed 30 and 20 percent, respectively. During the winter, algal material contributed most to the production, averaging just over 62 percent. Detritus also contributed during the winter averaging over 30 percent. Monthly rates of production and egestion were between 3 and 3.5 times faster during the summer. The concentrations of total mercury in seston, periphyton, and in the body tissue of H. morosa were analyzed each month. Mercury concentrations were between four and six times higher in the seston than in the periphyton. The concentration of mercury in the body tissue of H. morasa ranged from 0.14 ppm in March to over 1.20 ppm in July. Differences in Mercury concentration in the insects between seasons were significant. Regression analysis revealed a significant relationship between Hg concentration in the insects and the relative amount of detritus found in the guts. / Master of Science

The genus Phytophthora includes many agriculturally and ecologically important plant pathogens. Characterization of new Phytophthora species is the first and a most critical step to understanding their biology, ecology and economic importance. Six novel Phytophthora species recovered from irrigation systems at ornamental plant nurseries in Mississippi and Virginia were described based on morphological, physiological and molecular characters: 1. Phytophthora mississippiae sp. nov. produces a mix of non-papillate and semi-papillate sporangia, and catenulate hyphal swellings. It is a heterothallic species. All examined isolates of P. mississippiae are A1. When paired with A2 mating type testers, P. mississippiae produces ornamented oogonia and amphigynous antheridia. It is phylogenetically grouped in Phytophthora subclade 6b based on sequences of the rRNA internal transcribed spacer (ITS) region and the mitochondrially encoded cytochrome c oxidase 1 (cox 1) gene. 2. Phytophthora hydrogena sp. nov. is heterothallic. It produces non-caducous and non-papillate sporangia. It is characterized by frequently producing widening at the pedicel tip of sporangiophores or tapered sporangial based toward the point of attachment. This species is phylogenetically placed in a high-temperature tolerant cluster in Phytophthora clade 9. All members in this cluster grow well at 35 C. 3. Phytophthora virginiana sp. nov. is a self-sterile species. All examined isolates are silent A1. It produces non-caducous and non-papillate sporangia and is also placed in the high-temperature tolerant cluster in clade 9. Morphologically, it is characterized by producing abundant thin-walled, lateral chlamydospores in carrot agar and clarified V8 juice agar. 4. Phytophthora macilentosa sp. nov. is a heterothallic species. Only A1 isolates have been found. It produces characteristic elongated, non-papillate sporangia. It is also a member of the high-temperature cluster in clade 9. 5. Phytophthora stricta sp. nov. is a heterothallic species. It produces unique non-papillate and slightly caducous sporangia with one to three constrictions on its sporangiophore. Phylogenetically, P. stricta represents a new ITS clade within the genus. 6. Phytophthora Xstagnum nothosp. nov. is a novel hybrid species with P. taxon PgChlamydo as its paternal parent and a P. mississippiae-like species as its maternal parent. This new hybrid produces intercalary chlamydospores and catenulate hyphal swellings, which are morphological characters of P. taxon. PgChlamydo and P. mississippiae, respectively. It also produces both smooth-walled and ornamented oogonia, which may be indicative of oogonial characters of its paternal and maternal parents, respectively. By incorporating new Phytophthora species, clusters and clades, phylogenies including approximately 128 Phytophthora taxa were constructed based on sequences of five genetic markers. Among the selected genetic markers, the beta-tubulin (B-tub) gene provided the highest phylogenetic resolution. General phylogenetic structure of the B-tub phylogeny was similar to that in previous multi-locus phylogenies, except that P. cinnamomi, P. parvispora, P. quercina, P. stricta, and a provisional species, P. sp. e1, were not clustered in any of the 10 known Phytophthora clades and represented new clades. The B-tub phylogeny was also used to study the correlations between phylogeny and morphological characteristics including sporangial papillation, caducity, homothallism, and antheridial configuration, as well as maximum growth temperature. The results indicated that the character of sporangial papillation was mostly consistent among species within individual subclades. Maximum growth temperature was also generally correlated with phylogenetic positions. Consistency in caducity, homothallism or antheridial configuration was not found. A new multi-locus phylogeny based on sequences of 11 genetic markers of more than 146 Phytophthora species was proposed to validate new clades and clusters, as well as investigate detailed phylogenetic relations among species in this quickly expanding, taxonomically complex group of plant pathogens. / Ph. D.

In the southeastern United States, ephemeral wetlands in pine flatwoods provide important habitat for amphibians and aquatic invertebrates, but extensive deforestation has destroyed or isolated many wetlands and fire suppression has altered vegetation in others. My goals were to identify how wetland hydroperiods have changed through time and to examine the effects of long-term fire suppression on aquatic communities, including Reticulated Flatwoods Salamanders (Ambystoma bishopi) and Ornate Chorus Frogs (Pseudacris ornata). Chapter 1 used a modeling approach to relate wetland hydroperiods to current climate conditions and to hindcast historic conditions. Over the past 118 years, hydroperiods were often unfavorable for A. bishopi reproduction, and in recent years hydroperiods were shortened by persistent drought. Chapters 2 and 3 focused on identifying the effects of shifting from an open, grass dominated wetland to a wetland with high canopy cover and little herbaceous vegetation. In Chapter 2, I quantified amphibian and invertebrate communities in several wetlands. A. bishopi and P. ornata tended to occupy wetlands with lower canopy cover and higher herbaceous vegetation cover. Aquatic invertebrate abundance was generally higher in wetlands with lower shrub density and lower canopy cover. In Chapter 3, I examined how a reduction in herbaceous vegetation affected tadpoles when a predatory crayfish was present using two experiments. Crayfish were effective predators of both species across all vegetation treatments and often caused nonlethal tail injury. My results suggest that managers should focus on ensuring that wetland basins regularly burn, and wetlands with longer hydroperiods should be a management priority. / Master of Science

<p dir="ltr">Aquatic ecosystems and their inhabitants are no strangers to stressors. Natural stressors like disease, competition, and predation have a near constant presence in these environments and are often accompanied by human-induced stressors like climate change and chemical contaminants. Chemical contaminants like pesticides are often found in aquatic systems located near agriculture and can have detrimental effects on wildlife. Although natural stressors and pesticides often occur at the same time, their combined interactions still require further investigation to understand, as some pesticides, like fungicides, are frequently under researched. Additionally, fungicides also are lacking in research pertaining to combined chemical stressors. Studying the interactive effects of combined stressors, whether natural or human-induced, is crucial for applying laboratory findings to natural environments.</p><p dir="ltr">Here, I conducted an outdoor mesocosm experiment and multiple laboratory experiments to broadly assess the interactive effects of the fungicide chlorothalonil. More specifically, I explored 1) the interactive effects of the herbicide atrazine and chlorothalonil on an aquatic community, 2) the interaction between chlorothalonil and predator-induced stress of three tadpole species, and 3) the impacts of chlorothalonil on amphibian predator-prey dynamics using tadpoles and larval salamanders. First, to test my hypothesis that atrazine and chlorothalonil will have combined interactions that negatively impact an aquatic community, I conducted a mesocosm experiment where I exposed an aquatic community to atrazine, chlorothalonil, and the combination of the two pesticides. I found that the two pesticides do hold the potential to interact in certain cases, but their main effects alone are often just as damaging, especially for chlorothalonil where an environmentally relevant concentration caused near total morality for bullfrog tadpoles.</p><p dir="ltr">Next, I conducted a laboratory experiment with tadpoles and caged predators exposed to a sublethal concentration of chlorothalonil to test my hypothesis that the combination of predator-induced stress and chlorothalonil will decrease tadpole survival and alter tadpole behavior. I found that chlorothalonil alters tadpole behavior by significantly reducing activity levels in all three study species. However, no evidence was found for the interaction of the two stressors decreasing survival.</p><p dir="ltr">Lastly, to test my hypothesis that the toxicity of chlorothalonil will reduce tadpole behavioral responses and thereby increase their predation risk, I conducted a laboratory experiment with free-swimming tadpoles as prey and larval tiger salamanders as predators, exposed to different combinations of chlorothalonil exposure for the prey or predator. I found no meaningful differences in survival curves for the different combinations of prey and predator, but leopard frog tadpole final survival was lower in the higher chlorothalonil dose treatment due to predation.</p><p dir="ltr">Overall, these studies have assisted in filling research gaps on fungicides and their impact on predator-prey dynamics and aquatic communities. This work provided insights into the direct impacts of the herbicide atrazine and the fungicide chlorothalonil on aquatic species, and their potential to interact with natural stressors, emphasizing the need to protect natural ecosystems from chemical stressors.</p>