Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Excess nitrogen input is deleterious to coastal waters, resulting in deterioration of the water quality, increases in harmful algal blooms and disease in commercial fish stocks. A significant portion of this nitrogen enters coastal waters through groundwater systems. Here we use isotopic and molecular biological methods to identify the populations of nitrifiers and denitrifiers, where they occur, and what levels of activity are present through the upper four meters of a coastal groundwater system. This work shows two different populations of putative ammonia-oxidizing archaea (AOA) based on the ammonia mono-oxygenase gene (amoA), one shallow population most closely related to open ocean water column-like sequences and a deeper population that is more closely related to estuarine-like AOA. Interestingly, while the surface population has a potential nitrification rates (456 pmol g-1 sediment day-) similar to marine sediments, the deeper population does not show detectable evidence of nitrification. Between these two archaeal populations resides an active population of ammonia-oxidizing bacteria with similar nitrification rates as the surface AOA population. The upper meter of the aquifer is also an active area of denitrification as evidenced by the coincident drop in nitrate concentration and increase in both 15N (up to + 20. 1%o) and 5180 (up to + 11. 7%o), characteristic of groundwater affected by denitrification. 16S rRNA gene surveys of the organisms present in the upper meter also are similar to soil/sediment type environments including many potential denitrifiers. However, nitrite reductase, nirS and nirK, genes were also recovered from the sediments with nirK dominating in the surface sediments. This contrasts with the deep salt wedge, where the microbial community 16S rRNA genes appear more closely related to marine or reducing sediment/wastewater type organisms, and nirS genes become the dominant denitrification gene. / by Daniel Richard Rogers. / Ph.D.

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Includes bibliographical references (p. 96-102)

Spatially explicit ecosystem service valuation (ESV) allows for the identification of the location and magnitude of services provided by natural ecosystems to human activities along with a measure of their significance based upon economic valuation. While ESV has been used to provide new insight into land use management, few studies have identified the connections between the values of ecosystem services and ecological sensitivity to nitrogen loading despite a growing body of ecosystem service literature. This research combines a GIS-based, value transfer approach to map ecosystem services in the Lower Yakima River Basin (LYRB), Washington, USA, along with estimates of nitrogen loading to identify how nitrogen management may affect ecosystem services in the basin. This analysis combines values of ecosystem services with estimates of nitrogen loading and identifies subwatersheds and specific parcels within a Groundwater Management Area (GWMA) most susceptible to reductions in ecosystem services due to excess nitrogen loading. Based on the benefit transfer analysis, wetlands and forested areas have disproportionately high values of ecosystem services when compared to their land area in the LYRB, while pasture and cultivated crops contribute much less to the total value of ecosystem service flows in proportion to the total area in the LYRB. Across the study area estimated nitrogen loads are strongly driven by the location of concentrated animal feeding operations (CAFOs) and cultivated crops. Areas of particularly high nitrogen loading and high ESV may highlight specific areas for achieving immediate success in increasing or maintaining ecosystem services through appropriately focused regulatory mechanisms. The land cover analysis however, completely neglects the values and importance of subsurface processes and groundwater resources in ecosystem service assessment, and therefore an econometric model is applied to estimate willingness to pay (WTP) to maintain safe nitrate levels in private wells. Through the incorporation of WTP estimates for groundwater quality, a more complete economic and ecological perspective on the effects of landscape N loading in the study site is highlighted. The results of these estimates clearly indicate that ecosystem services from groundwater should be considered to have significant value in the LYRB. Further economic valuation data on specific land cover types and the value of groundwater quality, whether from primary studies or meta-analysis, is needed to refine relative measures of ecosystem service values and more confidently describe these values in specific dollar amounts. Additionally, limits in spatial data resolution may contribute to errors in location and magnitude of ecosystem services, and is an area in need of further development. Despite these potential limitations, this analysis highlights a promising direction for combining spatially explicit ecosystem service valuation with nutrient loading data to identify the location and potential magnitude of effects on ecosystem services from management practices. / Graduation date: 2013

The increased demand for wood and fiber from a continually shrinking land base has resulted in the use of intensively managed forest plantations. The concentration of timber production on the most suitable sites allows the world's demand for forest products to be met on less land and enable native forests to be conserved. Because much of the water flowing in rivers in the U.S. originates as precipitation in forests, there is a justified concern about the impacts of forest management on water quality. Nutrient concentrations were measured in eight streams from October 2002 to September 2011 to assess nutrient response to contemporary forest practices at the Hinkle Creek Paired Watershed Study in the Oregon Cascades. This period of time included a two-year pre-treatment calibration between control and treatment watersheds, a fertilization treatment of both basins in October 2004, and a post-treatment period from 2005 to 2011. A treatment schedule comprised of two temporally explicit harvest entries was used to assess the effects of clearcutting at the non-fish-bearing headwater scale and the fish-bearing watershed scale. Stream water samples were analyzed for nitrogen, phosphorus, calcium, sodium, potassium, magnesium, sulfate, chloride, and silicon as well as specific conductance, pH, and alkalinity. Programmable water samplers were used to take water samples during fall freshets in November 2009 to assess the stream water discharge versus NO₃ + NO₂ concentration relationship. All treatment watersheds showed a statistically significant increase in NO₃ + NO₂ concentrations after clearcutting (p < 0.001). The slope of the streambed through the disturbance was a stronger predictor of the magnitude of the response than was the magnitude of disturbance. Ammonia and organic nitrogen displayed notable increases after harvest treatment, but these increases were attributed to increases in the control watersheds. Phosphorus showed a response to timber harvest in one headwater stream. The remaining nutrients showed a small decrease in the control and treatment watersheds for the period after harvest. There was some evidence to suggest that the addition of urea nitrogen to both basins may have caused an increase in in-stream biota uptake of these nutrients. The storm response results showed that NO₃ + NO₂ concentrations in stream water increase with discharge during small storms that occur after periods of negligible precipitation. Concentrations of NO₃ + NO₂ observed during the calibration period were similar to concentrations observed in an old-growth forest in the H.J. Andrews, suggesting that nutrient processing within the Hinkle Creek watershed had returned to levels that existed prior to its initial harvest sixty years ago. This finding helps to assess long-term impacts of shorter rotation timber harvest of regenerated Douglas-fir stands characteristic of industrialized timber harvest in Oregon. / Graduation date: 2012

The purpose of this study was to evaluate the level of nitrate contamination in the water in Cherry Valley. It examines the theory that human effluent is the source of the nitrate and evaluates the role of politics in the nitrate issue.

Indiana University-Purdue University Indianapolis (IUPUI) / The characterization of the nutrients nitrogen, phosphorus and carbon (NPC) export to streams during storms is an integral part of understanding processes affecting water quality. Despite the fact that excessive levels of these nutrients in the Mississippi River basin adversely affects water quality in the Gulf of Mexico, little research has been conducted on NPC dynamics during storms on larger (>20 km2) agriculturally dominated Midwestern watersheds. This project examined the storm export of nitrate, ammonium, total phosphorus, and dissolved organic carbon (DOC) in the upper Eagle Creek Watershed (UECW) (274 km2) in Central Indiana, USA. Water samples were collected during five winter and spring storms in 2007 and 2008 on the rising and falling limb of the hydrograph, in order to characterize NPC dynamics during storm events. Stream discharge and precipitation was monitored continuously, and major cations were used to examine changes in source water over the duration of the storm and assist in the determination of potential flowpaths. DOC, total P, and TKN (Total Kjeldahl Nitrogen) tended to peak with discharge, while nitrate usually exhibited a slight lag and peaked on the receding limb. Total phosphorus, NH3-, TKN, and DOC appear to be delivered to the stream primarily by overland flow. NO3--N appear to be delivered by a combination of tile drain and macropore flow. Overall UECW displayed smoother nutrient export patterns than smaller previously studied watersheds in the area suggesting that scale may influence nutrient export dynamics. Further research is underway on a 3000 km2 watershed in the area to further examine the role scale may play in nutrient export patterns.