Recent changes in the management strategy of water released from Lake Pleasant into the Central Arizona Project canal have substantially reduced taste and odor complaints among water consumers. Most of the taste and odor complaints were likely caused by 2-methylisobomeol (MIB) and geosmin produced by periphytic cyanobacteria growing on canal surfaces. Most years, Lake Pleasant consists almost exclusively of water brought in via the CAP canal. The location of the inlet towers and the old Waddell dam influence sedimentation of material brought in by the CAP canal. In-coming water was found to contain large amounts of periphyton of the type commonly found growing on the sides of the CAP canal. Withdrawal of hypolimnetic water early in the spring of 1997 decreased the time that sediments were exposed to anoxic conditions, potentially decreasing the amount of nutrients released into the CAP canal and therefore available for periphytic cyanobacteria. Utilizing this management strategy since 1997 has resulted in a substantial reduction (or elimination) of consumer complaints of earthy/musty tastes and odors.

Water chemistry (carbon dioxide, pH, alkalinity, hardness, and turbidity) and physical habitat (depth, velocity and substrate) change gradually on the Little Colorado River, Arizona, downstream from Blue Springs (river kilometer 11.40 to 21.06). Fish distribution is correlated with changes in water chemistry and physical habitat. Monthly trends in water chemistry and physical habitat depended upon seasonal conditions: summer rain runoff (July and September 1992), spring runoff (April 1993), and base flow (June and July 1993).

<p> Long-term records of cyclic droughts are valuable for understanding future changes in hydrologic patterns and constraining climate models. A 3,300-year long record of &delta;¹⁸O and &delta;¹³C values from endogenic carbonate from Foy Lake, Montana is used to infer such droughts during the early Holocene. From 10.8 to 9.6 kyr BP, &delta;¹⁸O and &delta;¹³C values are low, indicating a period dominated by a cooler, less evaporative climate. Both records exhibit strong cyclicity in the ~200 yr range, which is inferred to be a solar cycle. A dramatic shift towards a warmer, drier climate occurs after 9.6 kyr BP in a step pattern, dramatic in the &delta;¹³C record. Warming occurs after the transition. Stochastic cyclicity dominates with weaker, but statistically significant, periodicities ranging from 40-70 yrs. These are believed to be an expression of the Atlantic Multidecadal Oscillation. This larger synoptic climate signal may be important to the overall Pacific Northwest climate. </p>

<p>The Pacific Coastal ecoregion contains large tracts of economically important forestlands that also serve as critical stream habitat for endangered Salmonids. Excessive fine sediment deposition in streams of this region is a major environmental concern in the region but difficult to measure directly. The use of stream invertebrates to monitor fine sediment conditions in streams requires careful consideration of several important factors that complicate their use as bioindicators including high spatial and temporal variability and covariance with other environmental variables. </p><p> To evaluate the use of stream invertebrates as bioindicators of excessive fine sediment, three hypotheses were tested. The first hypothesis was that invertebrates would be related to broad-scale climate variables (Chapter 2). The second hypothesis was that functional aspects of the invertebrate community would serve as useful indicators of excessive fine sediment condition. (Chapter 3). The third hypothesis was that invertebrates in streams with naturally high levels of sediment would be tolerant to fine sediment (&lt;2 mm, Chapter 4). Hypotheses were tested using a temporal data set at two streams in western Oregon, spatial data from 214 sites across the Oregon Coast Range, and <i> in-situ</i> experiment conducted in streams with erosive or resistant geologies. </p><p> In the temporal study, both invertebrate density and functional traits were positively related to El Ni&ntilde;o strength (R² range = 0.22&ndash;0.36, &rho; range = 0.008&ndash;0.04) and air temperature (R² range = 0.32&ndash;0.49, &rho; range = 0.002&ndash;0.01). The spatial study identified several environmental and hydrological factors that exhibited strong negative controls on both fine sediment (Mantel r range 0.14&ndash;0.25, &rho; range = 0.001&ndash;0.01) and invertebrate Scrapers (R² range = 0.11&ndash;0.14, &rho; range = 0.001&ndash;0.04). The result of the experimental study provide evidence that invertebrates in streams with erosive geologies exhibit tolerance to sediment addition when compared to invertebrates in resistant geologies (mean loss=15%, &rho; &lt;0.01) and that invertebrate grazing traits were most strongly associated with fine sediment dosing frequency (&rho; &lt;0.05). </p><p> The findings of this research demonstrate the role of geology in shaping invertebrate communities and their functional response to fine sediment addition and identify functional indicators that may be useful in different geologic settings. For environmental managers in the Pacific Coastal ecoregion, these findings are of potential value in assisting with the identification of biologically-relevant changes in stream fine sediment conditions and support efforts to balance economic needs in the region while protecting critical Salmonid habitat. </p>

<p> It is important to understand fate of nutrients like nitrogen, in streams given that anthropogenic activity, such as agriculture, have increased inputs of biologically reactive nitrogen to the environment leading to deterioration of stream health and eutrophication. Bacteria play a crucial role in the driving essential biogeochemical transformations. The purpose of this research was to improve our understanding of organic and inorganic nitrogen utilization by bacterial isolates and complex bacterial communities. Role of bacterial diversity in resource utilization is mostly neglected in biogeochemical models. Identification of bacteria based on molecular methods, like 16S rDNA sequencing, yield a wealth of information related to prokaryotic diversity and its importance in driving essential biogeochemical cycles. In this research utilization of organic and inorganic forms of nitrogen by stream heterotrophic bacterial isolates were examined. Our results reveal differences in bacterial resource utilization not as a function of the different taxa involved but of the enrichments the isolates were obtained from, as immediate environment dictate bacterial response to different nutrients and exerts a selection pressure. Carbon availability also influences nitrogen dynamics. To examine the impact of carbon on bacterial uptake of organic and inorganic nitrogen, bacterial abundance and community composition were examined in controlled, laboratory microcosms. There was a strong influence of carbon availability on bacterial nitrogen utilization, with preferential uptake of organic forms under low carbon concentrations. Carbon and nitrogen treatments likely drove changes in bacterial community composition that, in turn, affected rates of nitrogen utilization under various carbon concentrations. Metabolic functions, such as particular biogeochemical reactions are catalyzed by microbial extracellular enzymes, which are likely linked to the constituting taxa in a given microbial community. This study tracked temporal patterns of bacterial community structure and potential microbial enzyme activities in response to seasonal changes in stream organic matter pool. Differences in enzyme activities were highly correlated to nutrient (carbon and nitrogen) availability while differences in bacterial community structure were mostly driven by environmental conditions. However, the absence of link between bacterial community structure and potential enzyme activity is indicative of functional redundancy within microbial communities.</p>

For the purpose of evaluating the importance of the water column as a vector of mercury (Hg) to the biota of hydroelectric reservoirs, a comprehensive study was undertaken to provide continuous profiles of total dissolved Hg concentrations, (Hg$ sb{ tau} rbrack rm sb{D},$ in the water column and interstitial waters of natural and artificial environments. Water column samples were collected during the ice-free season (June to October), at various locations and depths within the La Grande-2 and Laforge-1 hydroelectric reservoirs, as well as in several neighbouring lakes. Close-interval sampling of porewaters in lake sediments, peat bogs, and flooded soils was accomplished via in situ dialysis. All Hg analyses were conducted in the field laboratory within 12 hours of sample collection, using cold vapour atomic fluorescence spectrometry. Water column (Hg$ sb{ tau} rbrack rm sb{D}$ are nearly constant, with an average value of 2.3 ng L$ sp{-1}.$ No significant concentration difference was noted regardless of: (1) the type of aquatic system, (2) the composition of the underlying soil, (3) the impoundment history, (4) the depth of the water column, or (5) seasonal changes. Preliminary results for porewater (Hg$ sb{ tau} rbrack rm sb{D}$ show them to be 2 to 3 times greater than those of the overlying water. In most profiles (Hg$ sb{ tau} rbrack rm sb{D}$ values do not show much variation with depth, away from the sediment-water interface. Despite the concentration differences near the interface, diffusion of Hg from the sediments to the water column is not apparent from this study, as satisfactory determinations of (Hg$ sb{ tau} rbrack rm sb{D}$ right at the interface were not possible. Biogeochemical processes acting near the interface (e.g. assimilation by periphyton, chelation by organic matter, methylation-demethylation, absorption on metal oxides) may be responsible for attenuating the release of dissolved Hg to the water column.

Thesis (Ph.D.)--Southern Illinois University at Carbondale, 2006. / (UMI)AAI3229852. Adviser: Michael T. Madigan. Source: Dissertation Abstracts International, Volume: 67-08, Section: B, page: 4240.

Thesis (Ph.D.)--Lehigh University, 2008. / Adviser: Richard P. Vinci.

Thesis (M.S.)--Lehigh University, 2010. / Adviser: Donald Morris.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6586. Adviser: Chris R. Rehmann. Includes bibliographical references (leaves 251-261) Available on microfilm from Pro Quest Information and Learning.