Open Access. Powered by Scholars. Published by Universities.®

Biogeochemistry Commons™

Open Access. Powered by Scholars. Published by Universities.®

Dissertations and Theses

Discipline
Institution
Keyword
Publication Year

Articles 1 - 12 of 12

Full-Text Articles in Biogeochemistry

Temperature And Hydrologic Context Influence Methane Variability In A Low-Salinity Marsh, Zoie Brauser Aug 2026

Temperature And Hydrologic Context Influence Methane Variability In A Low-Salinity Marsh, Zoie Brauser

Dissertations and Theses

Coastal wetlands are biogeochemical hotspots that capture and transform carbon and nutrients. Wetland restoration is increasingly used as a climate mitigation strategy because of wetlands' capacity to sequester large amounts of carbon. However, low-salinity tidal marshes exhibit high variability in methane (CH4) emissions, which could partially offset carbon sequestration under certain conditions. Understanding the drivers of CH4 variability is crucial for restoration and conservation work. This project uses an observational research approach to assess the relationships between environmental factors and carbon dioxide (CO2) and CH4 soil gas fluxes in a restored low-salinity tidal marsh …


Understanding The Impacts Of Freshwater Fluxes On The Biogeochemistry Of The Coastal Arctic: A Case Study Of Prudhoe Bay, Francesca Lingo Jan 2023

Understanding The Impacts Of Freshwater Fluxes On The Biogeochemistry Of The Coastal Arctic: A Case Study Of Prudhoe Bay, Francesca Lingo

Dissertations and Theses

The Arctic region, undergoing significant environmental changes due to rapid warming, faces alterations in air temperatures, melting permafrost, declining sea ice, and changes in riverine inputs. These shifts have profound implications for Arctic coastal ecology and biogeochemical cycles. This study, focusing on Alaska's North Slope, explores the influence of freshwater fluxes on water optical properties, vital for accurate satellite remote sensing interpretations. Our approach combined field measurements, existing data, and satellite remote sensing retrievals to identify biogeochemical gradients and their seasonal and interannual variations. A novel finding was the unique CDOM composition in Prudhoe Bay, characterized by a lower molecular …


Fine Characterization Of Leafing Phenology In The Brazilian Atlantic Forest By Optical And Microwave Remote Sensing, James B. Bell Jan 2023

Fine Characterization Of Leafing Phenology In The Brazilian Atlantic Forest By Optical And Microwave Remote Sensing, James B. Bell

Dissertations and Theses

Tropical forests provide important ecosystem functions in the global biosphere, but they remain among the most poorly understood elements of land surface models, especially with regard to their seasonal dynamics. For instance, in seasonally dry forests, the pattern of the annual green-up in their canopies closely follows annual patterns of rainfall. The same, however, does not occur in wet forest canopies which are dominated by evergreen trees. In the latter, water is not scarce enough to limit leaf photosynthetic function. Canopy leafing phenology in these forests is therefore poorly characterized by optical remote sensing methods which are not sensitive to …


Shallow Water Coral Distribution And Its Response To Climate Change, Amaury De Jesus Jan 2023

Shallow Water Coral Distribution And Its Response To Climate Change, Amaury De Jesus

Dissertations and Theses

Shallow water corals are one of the main reef-building organisms that secrete carbonates as their skeletons, and therefore, are one of the major sinks of CO2 in the ocean. These reef builders are also very crucial to marine environments and human society. As the global energy demand continues rising, fossil fuel burning increases at a faster pace despite the increase in energy supply using clean and renewable energy. The increase of CO2 in the atmosphere has been shown to exacerbate global warming and may cause ocean acidification, threatening the habitat of shallow-water corals. Many recent observations show alarming signs of …


Inverse Modeling Of Atmospheric Ch4 And Δ13C-Ch4 Measurements From Surface Observation Sites To Understand Trends In Global Methane Emissions Over More Than Three Decades, Sayantani Karmakar Jan 2022

Inverse Modeling Of Atmospheric Ch4 And Δ13C-Ch4 Measurements From Surface Observation Sites To Understand Trends In Global Methane Emissions Over More Than Three Decades, Sayantani Karmakar

Dissertations and Theses

Methane (CH4) is the second most important greenhouse gas with a radiative forcing of 0.97 W/m2 including both direct and indirect effects and a global warming potential of 28 over a 100-year time horizon. Unlike CO2 whose rate of growth in the atmosphere has remained positive and increased in recent decades, the behavior of atmospheric methane is considerably more complex and is much less understood on account of the spatiotemporal variability of its emissions which include biogenic (e.g., wetlands, ruminants, rice agriculture), thermogenic (fossil fuels), and pyrogenic (i.e., biomass burning) sources. After sustained growth during most …


Long Term Nutrient And Chlorophyll A Dynamics Across Long Island Sound And Impacts On Dissolved Oxygen Conditions Within The Western Sound (1991-2019), Sherry Perreira Jan 2021

Long Term Nutrient And Chlorophyll A Dynamics Across Long Island Sound And Impacts On Dissolved Oxygen Conditions Within The Western Sound (1991-2019), Sherry Perreira

Dissertations and Theses

Nitrogen overload, eutrophication, and hypoxia have been challenging and persistent water quality problems in Long Island Sound (LIS) over the past decades with major impacts on commercial industries, ecology, and recreational activities in the region. Recognizing these problems, the EPA enforced three phases of the Clean Water Act (CWA) to reduce nitrogen loads in an effort to improve this important estuary. This study examines how nitrogen (NH3, NOx & TDN), chlorophyll a (CHLA), and dissolved oxygen (DO) concentrations changed in LIS over the past 30 years, in response to water quality regulations as well as changes in …


Ecosystem Health In Guánica Bay And La Parguera, Puerto Rico: Remote Sensing Of Ocean Color And Metal Analysis Of Coral Tissue And Surficial Sediments, Jahnelle Howe Jan 2020

Ecosystem Health In Guánica Bay And La Parguera, Puerto Rico: Remote Sensing Of Ocean Color And Metal Analysis Of Coral Tissue And Surficial Sediments, Jahnelle Howe

Dissertations and Theses

Guánica Bay is an estuary located in southwest Puerto Rico, with a coral reef ecosystem at its periphery. This ecosystem is affected by sediments, nutrients, and contaminants from the watershed through the Bay and into the offshore water. This project evaluates Guánica Bay and La Parguera coastal areas through remote sensing and chemical analysis to assess coastal ecosystem health. The concentration of metals in two coral species and their associated surface sediments was were analyzed by X-ray fluorescence (XRF) and Direct Mercury Analyzer (DMA- 80). Ocean color remote sensing was used to estimate nutrient inputs and phytoplankton biomass through chlorophyll- …


Microbial Degradability Of Terrigenous, Marsh-Exported, And Estuarine Colored Dissolved Organic Matter In Long Island Sound, John R. Supino Jan 2020

Microbial Degradability Of Terrigenous, Marsh-Exported, And Estuarine Colored Dissolved Organic Matter In Long Island Sound, John R. Supino

Dissertations and Theses

The Long Island Sound is one of the world's most urbanized estuaries, polluted from excess nutrients which impact the quality of water through increased biological productivity. Dissolved organic matter (DOM) is a sensitive indicator of anthropogenic pollution and nutrient enrichment in coastal waters as well as an important part of the carbon cycle and serves as a primary food source for aquatic food webs. Additionally, the colored portion of DOM (CDOM) impacts coastal optical properties, ocean color, and light attenuation. High levels of CDOM have been shown to inhibit the growth of phytoplankton and limit photosynthesis, damaging the food chain …


Scenes From The Swale: Investigating Spatial And Temporal Dimensions Of Nitrogen Cycling In Urban Stormwater Bioretention Facilities, Erin Nicole Looper Jun 2019

Scenes From The Swale: Investigating Spatial And Temporal Dimensions Of Nitrogen Cycling In Urban Stormwater Bioretention Facilities, Erin Nicole Looper

Dissertations and Theses

Urban development is transforming landscapes at unprecedented rates. Human activities and landscape modifications associated with urbanization extensively increase hydrologic demands and modify natural hydrologic systems; consequently, population growth occurring in urban areas increases pressure on water resources. Urban aquatic ecosystems are vulnerable to impacts associated with increased connectivity with urban surfaces and hydrologic changes that initiate long-term changes in receiving waterbodies. Nitrogen (N) loading from urban and suburban catchments to receiving surface waters can lead to impairment of aquatic ecosystems and is a concern in many cities with water quality issues. To improve urban water quality, cities are increasingly adopting …


Marsh-Exported Dissolved Organic Matter Fate In Estuaries, Laura Ann Logozzo Jan 2017

Marsh-Exported Dissolved Organic Matter Fate In Estuaries, Laura Ann Logozzo

Dissertations and Theses

Dissolved organic matter (DOM) is a significant driver of estuarine productivity and nutrient cycling. The colored component of DOM, chromophoric dissolved organic matter (CDOM), impacts coastal optical properties, ocean color, and light attenuation. While marshes are largely considered sinks for carbon due to their high productivity and low soil carbon degradation rates, laterally they are sources of carbon as optically and chemically distinct DOM to surrounding aquatic ecosystems; these inputs are often essential in sustaining a net heterotrophic system. However, the photoreactivity and bioavailability of marsh-exported DOM is largely uncategorized, thus making it difficult to quantify its impacts on estuarine …


Temporal Variability Of Fluorescent Dissolved Organic Matter At A Brackish, Tidal Marsh-Estuary Interface, Alana B. Menendez Jan 2017

Temporal Variability Of Fluorescent Dissolved Organic Matter At A Brackish, Tidal Marsh-Estuary Interface, Alana B. Menendez

Dissertations and Theses

Marshes are both terrestrial and aqueous, sitting as an intermediate between land and water. Studies over constrained numbers of tidal cycles have demonstrated that these marshes are net exporters of dissolved organic carbon (DOC) to adjoining estuaries, however, there is need for continuous monitoring to better understand the temporal variability of this flux: tidally, seasonally, and during episodic rain events. Through use of a YSI EXO2 sonde, an in situ optical sensor at the interface of the brackish, tidal Kirkpatrick Marsh and Rhode River sub-estuary in Edgewater, Maryland (located on the northwestern shore of the Chesapeake Bay), we were able …


Indicators Of Nutrient Limited Plankton Growth In Lakes Near Mount Saint Helens, Washington, Kurt Davis Carpenter Dec 1994

Indicators Of Nutrient Limited Plankton Growth In Lakes Near Mount Saint Helens, Washington, Kurt Davis Carpenter

Dissertations and Theses

Several lakes located in the blast zone of the 1980 eruption of Mount St. Helens were studied to determine if the plankton in the lakes were limited in their growth by nitrogen or phosphorus availability. Long term nutrient enrichment experiments were performed on lake water from five lakes and measures of chlorophyll-a, carbon fixation, and nutrient uptake were used to evaluate the extent of limitation. Nutrient concentrations, ratios, and uptake from 14 lakes provided additional evidence for limitation by nitrogen and/or phosphorus. The physical, chemical, and biological characteristics of the lakes were also examined to monitor the return of these …