Biogeochemistry Commons^™

Interactions Of Zooplankton And Phytoplankton With Cyanobacteria, Rebecca Alexander

School of Natural Resources: Dissertations, Theses, and Student Research

Cyanobacteria are a major concern in Nebraska reservoirs and are capable of producing toxins that can cause skin irritations and gastrointestinal problems, as well as affect the nervous system. It is important to determine the mechanisms that can cause cyanobacteria blooms due to the effect they can have on human health. The interaction of zooplankton and other phytoplankton groups with cyanobacteria is important because there is a biological component in surface waters that should be taken into consideration along with the physical and chemical parameters that have been noted to promote cyanobacteria. For example, zooplankton have the ability to alter …

Water And Energy Balance Response Of A Riparian Wetland To The Removal Of Phragmites Australis, Phillip Mykleby

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Vegetation and climate both play integral roles in water availability, particularly for arid to semi-arid regions. Changes in these variables can lead to extreme shortages in water for regions that rely on water for crop irrigation (i.e., the Great Plains). The objective of this study is to evaluate the impacts of vegetation on water availability in the Republican River basin in central Nebraska. Decreases in streamflow have been observed in the river basin for many years and, as a result, an invasive riparian plant species (Phragmites australis) is being removed in an effort to reduce evapotranspiration and reclaim …

Landscape-Level Controls On Dissolved Carbon Flux From Diverse Catchments Of The Circumboreal, Suzanne E. Tank, Karen E. Frey, Robert G. Striegl, Peter A. Raymond, Robert M. Holmes, James W. Mcclelland, Bruce J. Peterson

Geography

While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO2, a substantial fraction of riverine bicarbonate (HCO3-) flux represents a CO2 sink, as a result of weathering processes that sequester CO2 as HCO 3-. We explored landscape-level controls on DOC and HCO3- flux in subcatchments of the boreal, with a specific focus on the effect of permafrost on riverine dissolved C flux. To do this, we undertook a multivariate analysis that partitioned the variance attributable to known, key regulators of dissolved C flux (runoff, lithology, and vegetation) prior to examining the effect of permafrost, …

Quantification Of Nitrate Sources And Sinks Using A Water Quality Network In Morro Bay Estuary, California, Johanna Nadia Jean Weston

Master's Theses

Using an instrumented water quality network in Morro Bay Estuary, California from 2007 to 2010 (15 min sampling frequency), this study addressed the two objectives of constructing a nitrate budget and assessing the influence of sampling frequency on water quality parameters. These two objectives led to the submission of an original report of research (Appendix A) and a note (Appendix B) to peer-reviewed journals.

The first objective was to characterize the high spatial and temporal variation in physical parameters and nitrate concentrations and to construct a nitrate budget quantifying sources and sinks of nitrate from the ocean, streams, and groundwater, …

Relationships Between Snow Pack, Soil Moisture, And Forest Greenness: Implications For Smap, Jordan Anderson, Noah Molotch, Bin Guan

STAR Program Research Presentations

Snowpack in the arid/semi-arid western United States is a critical element of the hydrologic cycle as water is stored in the winter and released in the spring and summer. The warmer seasons rely heavily on this water source for various purposes including economic (farming), environmental and recreational demands. Moderate Imaging Spectroradiometer (MODIS) sensors were used in this project to measure seasonal variability in global vegetation phenology and productivity. MODIS data was used to calculate Normalized Difference Vegetation Index (NDVI) to estimate net primary production of subalpine forests in the Sierra Nevada mountain range. Preliminary results indicate that variability in forest …

Spatial Patterns Of Drought Triggers And Indicators, Joseph P. Robine

Department of Environmental Studies: Undergraduate Student Theses

Drought is a reoccurring phenomenon with widespread economic, social, and environmental impacts. Unlike other disasters, a drought cannot be easily detected. In addition, droughts are widespread and develop slowly over time making it difficult to detect its onset and monitor its severity and impacts. To assist in monitoring the severity and spatial extent of droughts, drought managers frequently use indicators and triggers. Drought indicators are meteorological or hydrological variables or indices that quantify or describe the level of drought severity. A drought trigger is a value of an indicator that initiates management and response actions. Despite the clear importance of …

Geochemical Controls On Mercury Methylation In Backwaters Of A Gulf Coastal Plain River System, Implications For Water Column Processes, Liam N. Schenk

Graduate Theses and Dissertations

The abundance and distribution of mercury and methyl mercury were investigated at three sites in the lower Ouachita River in the summer of 2010 in an effort to provide the first characterization of the extent of mercury contamination in this river system, and to investigate the potential for mercury methylation in the water column of backwaters off of the main channel. Results showed that filtered methyl mercury was positively correlated to dissolved organic carbon (r2=0.76) for water samples taken from the bottom 1 ft of the water column at three sites, suggesting the importance of dissolved organic carbon in mercury …

Iron Oxide And Calcite Associated With Leptothrix Sp. Biofilms Within An Estavelle In The Upper Floridan Aquifer, Lee J. Florea, Chasity L. Stinson, Josh Brewer, Rick Fowler, B Joe Kearns, Anthony M. Greco

International Journal of Speleology

In Thornton’s Cave, an estavelle in west-central Florida, SEM, EDS, and XRD data reveal biofilms that are predominantly comprised of FeOOH-encrusted hollow sheaths that are overgrown and intercalated with calcite. Fragments of this crystalline biofilm adhere to the walls and ceiling as water levels vary within the cave. Those on the wall have a ‘cornflake’ appearance and those affixed to the ceiling hang as fibrous membranes. PCR of DNA in the active biofilm, combined with morphologic data from the tubes in SEM micrographs, point to Leptothrix sp., a common Fe-oxidizing bacteria, as the primary organism in the biofilm. Recent discoveries …

Phosphorus Export From A Restored Wetland Ecosystem In Response To Natural And Experimental Hydrologic Fluctuations, Marcelo Ardón, Shaena Montanari, Jennifer L. Morse, Martin W. Doyle, Emily S. Bernhardt

Environmental Science and Management Faculty Publications and Presentations

Wetland restoration is a commonly used approach to reduce nutrient loading to freshwater and coastal ecosystems, with many wetland restoration efforts occurring in former agricultural fields. Restored wetlands are expected to be effective at retaining or removing both nitrogen and phosphorus (P), yet restoring wetland hydrology to former agricultural fields can lead to the release of legacy fertilizer P. Here, we examined P cycling and export following rewetting of the Timberlake Restoration Project, a 440 ha restored riverine wetland complex in the coastal plain of North Carolina. We also compared P cycling within the restored wetland to two minimally disturbed …

Evolution Of The Cretaceous Calcareous Nanofossil Genus Eiffellithus And Its Biostratigraphic Significance, Jamie L. Shamrock, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

The calcareous nanofossil genus Eiffellithus is an important taxon of mid- to Upper Cretaceous marine sediments in biostratigraphy and paleoceanography. The definition of species within Eiffellithus have been both broadly interpreted and variably applied by nanofossil workers. This is particularly true for the Eiffellithus eximius plexus. While the taxonomy of mid-Cretaceous Eiffellithus species has recently been well-defined, the remaining 35 m.y. history of the genus has not been closely examined. Our investigation of Cenomanian to Maastrichtian sediments from the Western Interior Seaway, Gulf of Mexico, and Western Atlantic gives rise to six new species of Eiffellithus that can be reliably …

A Watershed-Based Classification System For Lakes In Agriculturally-Dominated Ecosystems: A Case Study Of Nebraska Reservoirs, Henry N. N. Bulley

Department of Geography: Dissertations, Theses, and Student Research

In recent decades substantial progress has been made in improving the quality of surface waters in the United States (Hawkins et al., 2000; EPA, 2000; EPA, 2001); nevertheless, much work remains to be done in assessing the state of impairment of lake waters. Impairment implies that the existing water quality of a lake, as measured by selected criteria (e.g., nitrogen, phosphorus, chlorophyll-a, Secchi depth), exceeds a threshold value or standard that presumably reflects optimal attainable lake water quality conditions (or "reference" conditions) (Hughes, 1995; EPA, 2000; EPA, 2001). Such impaired waters are not suitable for designated uses such as drinking, …

Sources And Cycling Of Carbonyl Sulfide In The Sargasso Sea, Gregory A. Cutter, Lynda S. Cutter, Katherine C. Filippino

OES Faculty Publications

The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters of the Sargasso Sea. In August 1999, surface OCS concentrations averaged 8.6 pmol L^-1, showed minor diel variations, and varied little with depth. An OCS precursor, total dissolved organic sulfur (DOS), was lowest at the surface (40 nmol L^-1) and increased with depth. The photoproduction rate of OCS from in situ incubations averaged 9.6 pmol L^-1 h^-1, whereas dark production was 7.0 pmol L^-1 h^-1. Apparent quantum yields were 10^-5-10^-7 from 313-436 …

Uptake Of Dissolved Organic Selenides By Marine Phytoplankton, Stephen B. Baines, Nicholas S. Fisher, Martina A. Doblin, Gregory A. Cutter

OES Faculty Publications

Se is present in multiple oxidation states in nature, each of which has unique chemical and biological reactivities. As a consequence, the rate of Se incorporation into food webs or its role as either a limiting nutrient or a toxic substance is a function of complex biogeochemistry. In particular, little is understood about the accumulation of dissolved organic selenides by phyto- or bacterioplankton. We assessed the bioavailability of dissolved organic selenides to marine and estuarine phytoplankton by presenting various algal species with filtered lysates of the diatom, Thalassiosira pseudonana, grown on media amended with radiolabeled selenite (⁷⁵Se[IV]). …

Constructed Wetland Design Criteria : A Study Of Their Role In Contaminant Removal From Urban Stormwater Runoff, A. J. Braid

Theses : Honours

This study was conducted to review effective design criteria for constructed wetlaads treating urban stormwater and to assess the design features of local constructed wetlands in relation to the theoretically ideal design features. The study was generated out of Water Authority of Western Australia (WAWA) concern that existing inconsistent design criteria may result in constructed wetlands not meeting contaminant removal objectives. Three components to the study involved: design criteria compiled from a critical review of relevant literature, field assessment of selected sites with significant differences in design, and a design critique of those sites based on the compiled design criteria. …

The Marine Biogeochemistry Of Selenium: A Re-Evaluation, Gregory A. Cutter, Kenneth W. Bruland

OES Faculty Publications

Vertical and horizontal profiles from the North and South Pacific Oceans demonstrate the existence of three species of dissolved selenium: selenite, selenate, and organic selenide (operationally defined). In surface waters, organic selenide makes up about 80% of the total dissolved selenium, selenite concentrations are uniformly low, and selenate concentrations rise with increased vertical mixing. The organic selenide maximum (thought to consist of seleno-amino acids in peptides) coincides with the maxima of primary productivity, pigments, bioluminescence, and dissolved free amino acids. Deep ocean waters are enriched in selenite and selenate, while organic selenide is nondetectable. In suboxic waters of the tropical …