Chemistry Commons^™

Unraveling Sources Of Cyanate In The Marine Environment: Insights From Cyanate Distributions And Production During The Photochemical Degradation Of Dissolved Organic Matter, Rui Wang, Jihua Liu, Yongle Xu, Li Liu, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

Cyanate is a nitrogen and energy source for diverse marine microorganisms, playing important roles in the nitrogen cycle. Despite the extensive research on cyanate utilization, the sources of this nitrogen compound remain largely enigmatic. To unravel the sources of cyanate, distributions and production of cyanate during photochemical degradation of natural dissolved organic matter (DOM) were investigated across various environments, including freshwater, estuarine, coastal areas in Florida, and the continental and slope regions of the North American mid-Atlantic Ocean (NATL). Cyanate production was also examined during the photochemical degradation of exudates from a typical strain of Synechococcus, an important phytoplankton …

Taxonomic And Nutrient Controls On Phytoplankton Iron Quotas In The Ocean, Benjamin S. Twining, Olga Antipova, P. Dreux Chappell, Natalie R. Cohen, Jeremy E. Jacquot, Elizabeth L. Mann, Adrian Marchetti, Daniel C. Ohnemus, Sara Rauschenberg, Alessandro Tagliabue

OES Faculty Publications

Phytoplankton iron contents (i.e., quotas) directly link biogeochemical cycles of iron and carbon and drive patterns of nutrient limitation, recycling, and export. Ocean biogeochemical models typically assume that iron quotas are either static or controlled by dissolved iron availability. We measured iron quotas in phytoplankton communities across nutrient gradients in the Pacific Ocean and found that quotas diverged significantly in taxon‐specific ways from laboratory‐derived predictions. Iron quotas varied 40‐fold across nutrient gradients, and nitrogen‐limitation allowed diatoms to accumulate fivefold more iron than co‐occurring flagellates even under low iron availability. Modeling indicates such “luxury” uptake is common in large regions of …

Microdialysis: A Method For Quantifying In Situ Nitrogen Fluxes In Soil Microsites, Srusti Maddala, Mary C. Savin, Julie A. Stenken, Lisa S. Wood

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Microdialysis, a diffusion-based sampling technique commonly used in biomedical research, has recently been recognized as a candidate for monitoring chemical changes in the rhizosphere. The information it provides about nutrient diffusion may improve nitrogen use efficiency, leading to enhanced management and success of restoration projects. The objective of this study was to determine the efficacy of microdialysis sampling to quantify the relative recoveries (RR%) of nitrate-N and ammonium-N, the two inorganic nitrogen compounds typically found in soil. The effects of microdialysis flow rate, sample medium concentration, and the presence of both analytes in solution on the relative recoveries obtained from …

Effects Of Silvopasture Establishment On Aqueous And Gaseous Soil N Losses At The University Of New Hampshire Organic Dairy Research Farm, Kathryn Ann Slebodnik

Honors Theses and Capstones

The expansion of local agriculture in the New England region is putting increased pressure on farmers to expand their arable land base. While clear-cutting is a traditional method of converting forested land to agriculture, it is known for having adverse ecological impacts. To minimize these impacts, farmers can create a silvopasture which incorporates a portion of the original forest canopy into pastures or crop fields. This study evaluates the impact of land-use changes for agriculture on soil nitrogen (N) retention. In particular, this study investigates the differences in soil N turnover, gaseous loss, and aqueous loss among an established forest, …

Evidence Of Late Quaternary Fires From Charcoal And Siliceous Aggregates In Lake Sediments In The Eastern U.S.A., Joanne P. Ballard

Doctoral Dissertations

The late-glacial transition to the Holocene, 15,000–11,600 cal yr BP, is an enigmatic period of dynamic global changes and a major extinction event in North America. Fire is an agent of disturbance that transforms the environment physically and chemically, and affects plant community composition. To improve understanding of the linkages between fire, vegetation, and climate over the late glacial and Holocene in the eastern U.S., I analyzed lake-sediment cores for charcoal and indicators of wood ash, and compared results to existing pollen records. A new microscopic charcoal record from Anderson Pond, Tennessee revealed high fire activity from 23,000–15,000 cal yr …

Carbon And Nitrogen Dynamics From Slow Pools Of Soil Organic Matter In A Temperate Forest: Pyrogenic Organic Matter And And Root Litter, Fernanda Dos Santos

Dissertations, Theses, and Capstone Projects

Soil organic matter (SOM) is the dominant reservoir of organic carbon (OC) in terrestrial ecosystems, storing approximately three times the size of the C pool in the atmosphere. In temperate forests, a major fraction of the SOM consists of slowly decaying soil organic C (SOC) pools. While slowly cycling C pools constitute a large reservoir of stable C in soils, the dominant environmental factors controlling this C pool remain unresolved. This research investigates two significant, but poorly characterized slowly decaying C pools: fine root litter (< 2mm) and thermally altered plant biomass (pyrogenic organic matter, PyOM). Specifically, I used compound-specific stable isotope analysis (¹³C and ¹⁵N) as my main methodological approach to examine the (1) …

Production Of Bioactive Secondary Metabolites By Florida Harmful Bloom Dinoflagellates Karenia Brevis And Pyrodinium Bahamense, Cheska Burleson

USF Tampa Graduate Theses and Dissertations

Despite the critical role algae serve as primary producers, increases or accumulation of certain algae may result in Harmful Algal Blooms (HABs). Algal toxins from these blooms contribute significantly to incidences of food borne illness, and evidence suggests HABs are expanding in frequency and distribution. Mitigation of these HABs without knowledge of the ecological purpose and biochemical regulation of their toxins is highly unlikely. The production, function, and potential of secondary metabolites produced by the dinoflagellates Karenia brevis and Pyrodinium bahamense, were investigated.

Brevetoxins were demonstrated by two different methods to localize within the cytosol of Karenia brevis. …

The Nature, Origin And Preservation Of Amide Organic Nitrogen In Organic Matter, Georgina Anne Mckee

Chemistry & Biochemistry Theses & Dissertations

Past studies have found much of nonliving sedimentary/aqueous nitrogen-containing organic matter (NCOM) is composed of amides, assumed to be peptides/proteins. Their lability calls into question their survival, and several hypotheses have been suggested to explain this. Using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and nuclear magnetic resonance (NMR) spectroscopy I investigated the molecular amide composition in sedimentary/aqueous systems while reassessing their preservation and formation routes.

Development of a suitable methodology is essential for successful NCOM study due to electrospray ionisation source requirements: sediment samples need to be rendered into solution. Based on NMR and FT-ICR-MS analysis, I determined …

Modeling Distinct Vertical Biogeochemical Structure Of The Black Sea: Dynamical Coupling Of The Oxic, Suboxic, And Anoxic Layers, T Oguz, Hw Ducklow, P Malanotte-Rizzoli

VIMS Articles

A one-dimensional, vertically resolved, physical-biogeochemical model is used to provide a unified representation of the dynamically coupled oxic-suboxic-anoxic system for the interior Black Sea. The model relates the annual cycle of plankton production in the form of a series of successive phytoplankton, mesozooplankton, and higher consumer blooms to organic matter generation and to the remineralization-ammonification-nitrification-dentrification chain of the nitrogen cycle as well as to anaerobic sulfide oxidation in the suboxic-anoxic interface zone. The simulations indicate that oxygen consumption during remineralixation and nitrification, together with a lack of ventilation of subsurface waters due to the presence of strong stratification, are the …

Nitrite Reactions In Soil, John Otto Reuss

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Losses of soil nitrogen that cannot be attributed to leaching or crop removal have been observed in many field experiments. Several mechanisms have been proposed to account for these losses.