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Oxygen Isotopic Composition Of Nitrate Produced By Freshwater Nitrification, Danielle Boshers

Master's Theses

Identifying sources of nitrate (NO₃^-) in the environment is important to elucidate causes of water quality impairment and eutrophication. Measurements of naturally occurring stable isotope ratios of nitrogen (¹⁵N/¹⁴N) and oxygen (¹⁸O/¹⁶O) in NO₃^-, can be used to determine the sources, dispersal, and fate of natural and contaminant NO₃^- in aquatic environments. To this end, it is necessary to know how NO₃^- isotopologues are modified by biological reactions, as heavy and light isotopes have different reaction rates. One important microbial reaction that …

Urea As An Effective Nitrogen Source For Cyanobacteria, Kevin J. Erratt

Electronic Thesis and Dissertation Repository

Urea use has grown substantially in the past half-century, with urea now accounting for > 50% of nitrogen fertilizer applications worldwide. The shift from inorganic nitrogen fertilizers to urea-based sources has coincided with the reappearance of cyanobacteria blooms in freshwaters. Here, we examined urea as a nitrogen source for three bloom-forming cyanobacteria species. We found that (1) urea was consumed more rapidly relative to inorganic nitrogen substrates, suggesting that cyanobacteria exhibit a preference for urea; (2) urea was consumed in excess of cellular requirements; and (3) urea may offer cyanobacteria a competitive edge over eukaryotic algae by enhancing light absorption capabilities. …

Reevaluating The Occurrence And Phylogeny Of The Pigtoe Unionid Mussels Fusconaia Askewi, Fusconaia Lananensis, Fusconaia Flava, And Pleurobema Riddelli In Texas, Charles J. Pratt

Biology Theses

The recent development of DNA-based species classification methods has led to the revision of many morphology-based species designations as genetic data has provided new information for species delineation. Analysis of standardized DNA ‘barcoding’ gene regions has proven particularly effective in resolving the taxonomic status of taxa that display phenotypic and habitat overlap.

Freshwater Unionid and Margaritiferid mussels comprise one of the most diverse aquatic taxa in North America, but are also among the most threatened, with over 70% of the approximately 300 native species considered at-risk or in decline. Although mussels face extensive threats from anthropogenic activity, conservation efforts have …

Sea Lamprey (Petromyzon Marinus) As A Functional Link Between Marine And Freshwater Ecosystems, Daniel M. Weaver

Electronic Theses and Dissertations

Anadromous sea lamprey Petromyzon marinus are native to Atlantic coastal systems and serve as a functional link between marine and freshwater ecosystems. Sea lamprey spend 1–2 years in the ocean parasitizing marine vertebrates before migrating into freshwaters during the spring to spawn. There they construct nests, spawn, then die shortly afterwards. Larvae hatch, bury into fine sediments and reside in streams for generally 6–8 years, but up to 14. Larvae then undergo metamorphosis, a non-feeding period characterized by a series of physical and physiological changes. The juveniles (macropthalmia) then migrate to the ocean to begin the parasitic juvenile phase.

Historically, …

Fish Populations In A Changing World, Christine Booker

Honors Theses

Freshwater ecosystems in North America face many threats including habitat degradation, fragmentation, and hydrological changes to the river system. This is especially obvious in Southern Appalachia region, which is a hotspot for freshwater biodiversity. Large inputs of sediment from coal mining and nutrients from agriculture degrade water quality. Dams and other stream modifications have led to changes in the habitat and hinder migration. Numerous native and endemic species have small isolated populations that are threatened by extinction. Recovery rates of species depend on numerous factors, including abiotic and biotic ecosystem factors and the natural history of the species. Species like …

Phylogenetic Studies Of The Madagascan Freshwater Crabs (Potamoidea, Potamonautidae, Deckeniinae), Rainee Stevens

All NMU Master's Theses

Relationships within the Madagascan freshwater crab fauna were examined based on unstudied specimens from all parts of Madagascar. This study allowed the examination of the validity of existing genera and species, and identified potential new taxa. The new specimens provided phylogenetic and evolutionary data, as well as new insights into the distribution patterns of the Malagasy freshwater crab fauna. In addition, the large number of new localities from previously unsurveyed areas of Madagascar allowed the construction of updated distribution maps.

The present analysis included 62 unidentified specimens plus 13 identified species of Malagasy freshwater crab taxa that had already been …

Biodiversity Monitoring Using Environmental Dna: Can It Detect All Fish Species In A Waterbody And Is It Cost Effective For Routine Monitoring?, Lia Smith

Theses: Doctorates and Masters

The challenges associated with environmental monitoring such as the impact on the environment and the financial costs are problems we face when trying to conserve freshwater systems around the world. The need for precise and accurate results that are cost effective is important so that we can achieve our conservation goals.

The overall aim of this study was to explore Next-Generation - metabarcoding for the detection of feral and native freshwater fish species based on the DNA shed by individual organisms into the water column. Cytochrome c oxidase I (COI) primers were developed for this study using DNA from six …