M.S.

Dissolved oxygen at four times normal saturation inhibited growth and metabolism of summer planktobacteria in surface waters of alpine oligotrophic Mountain Lake (Giles County, Virginia). Data included viable colony counts, D-[U-¹⁴C]glucose incorporation into extractable lipid of colonies, and respiration-assimilation of D-[U-¹⁴C]glucose by lake water samples. Significant (P<0.05) differences were not detected in either colony counts or ¹⁴C-lipid when superoxide dismutase (30 U ml⁻¹) or catalase (130 U ml⁻¹) were added to the medium. The upper waters of Lake Hoare, Antarctica, contain dissolved oxygen at ≥42 mg liter⁻¹ (=HDO). HDO did inhibit D-[U-¹⁴C]glucose assimilation-respiration compared with normal atmospheric dissolved oxygen (=ADO) in Lake Hoare water. D-[U-¹⁴C]glucose was assimilated and respired optimally at 12°C in Lake Hoare. Colony formation was inhibited in both lakes. Colonies represented <1% of the fluorochrome-stained direct counts in Lake Hoare. Lake Hoare planktobacteria were smaller than the planktobacteria in Mountain Lake. ATP size fractionation revealed that 39% of ATP biomass was <0.5 Hm in Lake Hoare. Five microbial isolates were selected from Lake Hoare by growth under very high oxygen (=VHO, 4.6x in situ HDO, 55 lb in⁻² of added oxygen). One isolate was selected under ADO from shallow benthic mat underlying HDO waters. Isolates were examined for physiological characteristics which might enhance their survival in the HDO environment. While HDO incubation produced <36% of ADO incubated CFU, VHO was more selective producing <1%. Bacterial isolates were motile Gram negative rods, catalase and oxidase positive, differing in their growth response to temperature and nutrient concentration. One VHO isolate was a yeast. HDO reduced the maximal cell density in three isolates tested at higher nutrient concentrations, however, all three exhibited less repression as nutrients were lowered from 1000-10 mg liter⁻¹ in comparison to ADO grown controls. One isolate actually produced a cell density 3x that of the ADO control. Four of five bacterial isolates demonstrated HDO inducible superoxide dismutase (SOD). The inducible and constitutive SOD were the manganese type and had the same electrophoretic mobilities in respective isolates. All VHO isolates contained carotenoids. Pigmentation of the bacterial isolates differed due to the types and relative proportions of the constituent carotenoids. A carotenoid-negative mutant of one isolate grown under HDO exhibited a lengthened lag phase, decreased growth rate, maximal cell density and thereafter increased lysis compared to the same ADO grown strain and the carotenoid containing parent strain. The mutant and parent strain produced catalase and indistinguishable specific activities of SOD. Microorganisms in the high oxygen Lake Hoare waters may be protected from oxygen toxicity by the lake’s oligotrophic nature as well as a combination of cellular defenses. / Ph. D.

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

In-stream aquatic habitat depends on adequate levels of dissolved oxygen. Human alteration of the landscape has an extensive influence on the biogeochemical processes that drive oxygen cycling in streams. Historic datasets allow researchers to track trends in chemical parameters concomitant with urbanization, while land cover change analysis allows researchers to identify linkages between water quality trends and landscape change. Using the Seasonal Kendall's test, I examined water quality trends in oxygen demand variables during the mid-1990s to 2003, for twelve sites in the Rock Creek sub-watershed of the Tualatin River, northwest Oregon. Significant trends occurred in each parameter. Dissolved oxygen (DO (%sat)) increased at five sites. Chemical oxygen demand (COD) decreased at seven sites. Total Kjeldahl nitrogen (TKN) decreased at five sites and increased at one site. Ammonium (NH3-N) decreased at one site and increased at one site. Multiple linear regression indicates that nitrogenous oxygen demand accounts for a significant amount of variance in COD at ten of the twelve sites (adjusted R2values from 0.14 to 0.73). Aerial photo interpretation revealed significant land cover change in agricultural land cover (-8% for the entire basin area) and residential land cover (+10% for the entire basin area). Correlation results between seasonal oxygen demand data and land cover values at multiple scales indicated that: (I) forest cover negatively influences COD at the full sub-basin scale and positively influences NH3-N at local scales, (2) residential land cover positively influences DO (%sat) values at local scales, (3) agricultural land cover does not influence oxygen demand at any land cover assessment scale, ( 4) local topography negatively influences TKN and NH3-N, and (5) urban runoff management infrastructure correlates positively with COD. Study results indicate that, with the exception of forested land, local scale land cover and landscape variables dominate influence on oxygen demand in the Rock Creek basin. Since DO conditions have improved in these streams, watershed management efforts should emphasize local influences in order to continue to maintain stream health.

Water quality parameters including ammonia, nitrate+nitrite, phosphate, total suspended solids, Escherichia coli, and dissolved oxygen were statistically evaluated from sampling data collected by the Bureau of Water Quality (City of Muncie, Indiana) at five sampling locations in Delaware County over a five-year period (2002-2006). These data were also compared with water quality standards/guidelines to determine how sample values compared to acceptable levels of these parameters. Friedman's non-parametric test was used to study the differences between sites and seasons. Spearman's Rank Correlation was used to study the correlations between water quality parameters at each sampling site. Significant differences were observed for individual parameters when evaluated relative to sampling location based on pooled monthly collected data as well as data evaluated on a seasonal basis. These differences indicated the fact that different sources were responsible for observed concentrations at a particular location and that seasonal phenomenon such as precipitation, discharge and temperature also affected sample concentrations at individual sampling locations. Most notable were differences in geometric mean concentrations of ammonia, nitrate+nitrite, phosphate and E. coli upstream and downstream of the wastewater treatment plant (WWTP), with highest concentrations downstream, indicating the significant impact of the WWTP on water quality in the White River. Significant correlations observed among some study parameters suggested that sample concentrations may have been affected by similar sources. In comparison to water quality standards, concentrations of ammonia, nitrate+nitrite, phosphate, and E. coli were at unacceptable levels at most sampling locations. / Department of Natural Resources and Environmental Management