Browsing by Author "Dickson, Kenneth L."
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- Changes in the invertebrate populations, fish populations, and water chemistry of a small stream above and below two impoundmentsConnor, Laurence Lee (Virginia Tech, 1977-06-15)The major impacts associated with the ponds appeared to be an alteration of energy dynamics. The alterations were seasonally dependent, and may have resulted from interception of larger particle organic matter being transported downstream and its replacement by finer organic matter. The alterations manifested themselves in changes in numbers and biomass of benthic macroinvertebrates and fish, and changes in drift patterns below the ponds. The energy dynamics alterations may have also influenced competitive interactions among benthic organisms and fish. The direct influence of physiochemical alterations appeared to be masked by energy-related alterations; however, alterations in physiochemical factors may have caused minimal changes in species composition in aquatic communities below the ponds. Material impacts in the system studied appeared to be negligible; however, Young (unpublished data) found significant impacts associated with the introduction of a floc of iron and iron bacteria below a bottom release impoundment. Material impacts may be of major importance in bottom release systems. The ponds appeared to cause a general increase in stream productivity downstream. However, increased amplitude in seasonal fluctuations of physiochemical factors combined with seasonal fluctuations in energy below the ponds appeared to produce a more fluctuating environment below the ponds leading to reduced stability in downstream communities. The impacts evidenced in this study do not appear to be as drastic as those reported in larger systems, There were no large-scale alterations in species composition or reductions in number of taxa present below the ponds. In systems containing rare species or with uniquely adapted faunas, the less stable environmental conditions, possible introduction of exotic species, and the possible disruption of competitive balance with the system may cause major impacts. These possible impacts should be dealt with in the design and planning of small pond construction.
- The development and assessment of an automated biological monitoring system using crayfish locomotor activity to detect toxic stressMaciorowski, Anthony F. (Virginia Tech, 1978-06-15)In-plant biomonitors, controlled by dedicated microcomputers, may ultimately provide detection of developing toxicity and hazardous spills in industrial effluents rapidly enough to prevent serious damage to receiving waters. A computer automated system was developed to continuously monitor spontaneous locomotor activity of eight crayfish. Electric potentials generated by muscular movements of untethered crayfish were detected by external electrodes, amplified, digitized, and analyzed by a hybrid computer network. A microcomputer evaluated the number of peaks produced in the waveforms of eight individual C. acuminatus for successive one-hour intervals. The resultant counts were directly related to locomotor activity. The effectiveness of the crayfish biomonitor in detecting simulated spills of cadmium in the laboratory was determined by 7 experiments with 56 crayfish. Results indicated that crayfish responded to 2.5 and 0.5 mg Cd⁺⁺/l with increased activity, which was detected by the crayfish biomonitor two hours after exposure. A simulated spill of 0.1 mgCd⁺⁺/l was detected by the biomonitor within 113 hours. These results support the assumption that the crayfish activity monitor may be used as a potential tool for water quality management.
- An ecosystematic study of the South River, VirginiaCairns, John Jr.; Dickson, Kenneth L. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1972)
- The effects of waste discharges from Radford Army Ammunition Plant on the biota of the New River, VirginiaCairns, John Jr.; Dickson, Kenneth L. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1973)
- The role of forest debris in a southeastern stream and the effects of its removal on trout populationsCoulston, Patrick J. (Virginia Tech, 1977-01-15)Measurements of substrate composition, cover characteristics, and trout populations and biomass were made at a total of ten sites on South Fork Mills River and one of its tributaries. Poplar Creek, in 1975 and 1976. Besides providing cover debris accumulations generally caused a reduction in stream velocity with accompanying deposition of smaller substrate types. Removal of debris caused a shift to larger substrates. A multiple regression treatment of the physical characteristics and trout populations indicated that regression models relating the presence of debris and large substrates (interpreted here as increasing water flow) to trout populations were the only ones significant at the .1 level and accounted for 58% of the variation in trout biomass. The presence of debris could account for none of the variations in trout numbers. Areas containing debris were found to contain populations made up of larger fish than areas without debris. The effects of debris removal were not clear cut, however, there was a trend towards reduced biomass but not necessarily reduced number of trout. This was probably due to decreases in cover, which made the areas less desirable for large trout, but increased flows which favored smaller trout.
- A taxonomic revision of the Nearctic specis of the genus Bezzia (Diptera: ceratopogonidae)Dow, Mark Ian (Virginia Tech, 1974-08-05)This study is intended as a collective standardization of descriptions and illustrations of the species of Bezzia in the Nearctic Region. Forty-three species are reviewed, 14 of which are new. Two species are thought to be junior synonyms. A new subgeneric name, Aspinabezzia, is proposed for the already occupied Probezzia of the authors. A key to the adults is presented. When possible, both sexes are illustrated. Including types, approximately 5,000 specimens have been examined. The specimens are both pinned and dissected, mounted on microscope slides. The specimens were borrowed largely from two collections, the U.S. National Collection and the Canadian National Collection. Type specimens were borrowed from several other collections. Numerical data is presented concerning measurements and ratios of the antenna, palp, length-width- costa-R₁-and last costal segment of the wing, tarsi, and the female spermathecae. The subgeneric groupings are discussed. Four subgenera are recognized: Pseudobezzia, Bezzia s. str., Aspinabezzia n. subgen., and Phaenobezzia.
- Water quality at five proposed industrial sites on the Roanoke and New RiversWilson, James H.; Dickson, Kenneth L. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1977)Aquatic ecological surveys were conducted at five potential industrial development sites in Virginia, four on the New River and one site on the South Fork of the Roanoke River.Eighteen physical-chemical parameters were analyzed and biological information was collected in order to determine the physical, chemical, and biological water quality. This study was designed to generate baseline information essential in assessing the environmental impacts of future development in the watershed. The results indicate that the New River and the South Fork of the Roanoke River support diverse populations of macrobenthic invertebrates and that physical and chemical water quality is high, except for increased levels of nitrate in the New River. Although both rivers have water quality that is considered good by biological and chemical standards, they both are vulnerable. If the assimilative capacity of these two rivers is to be preserved as a valuable resource, they must be used intelligently. Future industrial development shouId be managed carefuIly in these watersheds to maintain the high quality of the aquatic environment in the New River and the South Fork of the Roanoke River.