Thesis (Ph. D.)--Virginia Polytechnic Institute, 1966. / Vita. Abstract. Includes bibliographical references (leaves 80-86). Also available via the Internet.

1, Eighteen species of aquatic Hyphomycetes are recorded from South Africa for the first time. All except two of these can be assigned to described species. The other two are new species of Articulospora and Anguillospora and are described in this thesis. Three unidentified spore types, an "Articulospora" type and "Anguillospora" type and a Y-shaped spore are also described. 2. Spore development in ten species is described. 3. A key to the fungi described in this thesis is given. 4. General notes on the ecology of these fungi and a table recording the fungi found in the Eastern Cape Province of South Africa, their distribution within the localities and the nature of the material on which they are growing are given. 5. The gross characteristics of plate cultures of six species, five growing on malt agar, Czapek agar, plain agar and maize agar and one on malt agar only are described. 6. Growth of four species in liquid culture using the Czapek-Dox medium is reported. 7. The results of an investigation into the effect of variations in temperature and medium on the growth of plate cultures of five species are analysed, discussed and conclusions are drawn. 8. Growth of certain isolates of four species on twigs is described.

Freshwater fungi are vital to the aquatic food web, essential for nutrient cycling, energy flow, and ecosystem regulation. Their distribution is particularly contingent upon agricultural runoff, which can carry agrochemicals capable of influencing the freshwater mycobiota and potentially impacting the ecosystem services which they provide. While such impacts are well documented for freshwater bacterial communities, fungal communities are critically understudied. Here, we address this research gap by assessing the impact of anthropological and environmental perturbations on the freshwater mycobiota in the agriculturally dominated South Nation River basin in Eastern Ontario, Canada. We undertook biweekly water sampling from 2016-2021, complemented by rich ancillary data including water properties, hydrology, weather conditions, and fungal ITS2 metabarcoding. Our study yielded 6,571 Operational Taxonomic Units from 503 water samples, spanning 15 fungal phyla, dominated by Ascomycota, Basidiomycota, and Chytridiomycota. Agricultural land use decreased the mycobiota alpha diversity and distinct fungal communities were observed at agricultural ditch and mixed-use sites compared to the forested site. Notably, river discharge emerged as a predominant influencer of both alpha and beta diversity, likely transporting fungi via precipitation, especially from plant-rich catchment basins. Intriguingly, environmental data only explained a fraction of fungal community variation, underscoring the significance of unmeasured factors such as fungicide application, alongside stochastic community assembly processes. This work highlights the complex interplay of factors influencing the freshwater fungal community in agriculturally impacted watersheds and shows the need for further investigation for a more comprehensive understanding of the freshwater fungal ecology.

M.S.

This study was undertaken to investigate the mineral nutrition of aquatic Hyphomycetes by determining the mineral requirements of several species. On the basis of rapidity and renroducibility of growth, four species were selected, These were Heliscus lugdunensis Webster (Nectria lugdunensis webster), Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni), Clavariopsis aquatica DeWildeman, and Lunulospora curvula Ingold. These were grown in liquid culture on a rotary shaker at constant temperature. The containers and other equipment were cleaned by acid washing. When necessary to establish a nutritional reguirement for an element, the nutrient salts were purified by the phosphate adsorption and dithizone methods. In addition to nutrient salts and purified water, the media contained only glucose. Since all the species except Clavariopsis aquatica DeWildeman grew well for many transfers and approximately two years on this completely defined medium, without vitamins or amino acids being provided, it is concluded that they do not require these nutrients. Whether an element was required, and in what concentration, was decided on the basis of the amounts of growth obtained with various concentrations of the element in the initial media. Growth was measured as the dry weight of the mycelium from 100 ml of medium and the values from four replicates were averaged. Phosphorus, calcium, nitrogen, zinc, iron, magnesium, and sulfur requirements were demonstrated for all four species. Efforts to demonstrate requirements for potassium were unsuccessful. Manganese toxicity was demonstrated for Clavariopsis aquatica DeWildeman and a manganese requirement was suggested for Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni). The results suggested a molybdenum requirement for Heliscus lugdunensis Webster (Neetria lugdunensis Webster) and Lunulospora curvula Ingold, a boron requirement for H. lugdunensis and toxicity for C. aquatica, and a copper requirement for F. penicillioides. Approximately 0.50, 0.25, 0.50-1.00, and 0,.05-0.10 milli-moles per liter of phosphate were required to obtain maximum dry weight yields of Heliscus lugdunensis Webster (Nectria lugdunensis Webster), Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni), Clavariopsis aguatica DeWildeman, and Lunulospora curvula Ingold respectively. Calcium concentrations of 7.5, 50, 7.5, and 25 milli-moles per liter supported maximum growth of these species in the same order. All four were able to utilize ammonium nitrogen, nitrate nitrogen, or ammonium nitrate to produce about the same amounts of growth. C. aquatica was apparently able to use nitrate nitrogen only in the presence of an unidentified nutrient and this is interpreted as indicating a role for that nutrient in the nitrate metabolism of this species. Fifteen milli-equivalents per liter of ammonium nitrate, ammonium, or nitrate nitrogen was adequate to obtain maximum dry weight yields of H. lugdunensis. Five milli-equivalents per liter of ammonium nitrate, 15 of ammonium, and 35 of nitrate nitrogen supported maximum growth of F. penicillioides. As little as 5 milli-equivalents per liter of ammonium nitrate or ammonium nitrogen was optimal for C. aguatica and 5 milli-equivalents per liter of any of the three nitrogen sources was optimal for L. curvula. The optimal nitrate concentration for C. aquatica was not determined. There is an obvious advantage to a single medium on which a great number and wide variety of species may be grown. The author is of the opinion that a far greater advantage lies in the use of a completely defined medium on which one or more organisms may be reproducibly grown, Such media are suggested and their employment is strongly urged. Only in this manner can considerable morphological and physiological variations be avoided. / Ph. D.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

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

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

Fungal communities of aquatic ecosystems are understudied, leaving major gaps in estimating global fungal biodiversity. In particular, little is known regarding the distinctiveness of (1) aquatic endophytes vs. those in terrestrial plants, and (2) waterborne fungi vs. those inhabiting aquatic plants or sediments. I assessed the diversity, composition, host affiliations, and geographic structure of culturable endophytes associated with aquatic angiosperms in reservoirs in northern Arizona, and their distinctiveness relative to waterborne- and sediment fungi. Endophytes were low in abundance yet extremely diverse. Communities differed significantly in composition among reservoirs and tissues. Aquatic endophytes were largely distinct from those in terrestrial plants, and from those in water and sediment, but did not demonstrate host specificity. This work reveals the uncommon diversity and distinctiveness of endophytes in aquatic plants, and provides a first quantitative estimation of endophytic associations in diverse, ecologically important, and economically relevant aquatic plants.

No description available.