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Full-Text Articles in Physical Sciences and Mathematics

Levels Of Autotrophy And Heterotrophy In Mesophotic Corals Near The End Photic Zone, Amy Carmignani, Veronica Z. Radice, Kathryn M. Mcmahon, Alex I. Holman, Karen Miller, Kliti Grice, Zoe Richards Jan 2023

Levels Of Autotrophy And Heterotrophy In Mesophotic Corals Near The End Photic Zone, Amy Carmignani, Veronica Z. Radice, Kathryn M. Mcmahon, Alex I. Holman, Karen Miller, Kliti Grice, Zoe Richards

Biological Sciences Faculty Publications

Mesophotic corals live at ~30-150 m depth and can sustain metabolic processes under light-limited conditions by enhancing autotrophy through specialized photoadaptations or increasing heterotrophic nutrient acquisition. These acclimatory processes are often species-specific, however mesophotic ecosystems are largely unexplored and acclimation limits for most species are unknown. This study examined mesophotic coral ecosystems using a remotely operated vehicle (Ashmore Reef, Western Australia at 40–75m depth) to investigate the trophic ecology of five species of scleractinian coral (from genera Leptoseris, Pachyseris, and Craterastrea) using stable isotope analyses (δ13C and δ15N) of host and symbiont tissues …


Nitrite Cycling In The Primary Nitrite Maxima Of The Eastern Tropical North Pacific, Nicole M. Travis, Colette L. Kelly, Margaret R. Mulholland, Karen L. Casciotti Jan 2023

Nitrite Cycling In The Primary Nitrite Maxima Of The Eastern Tropical North Pacific, Nicole M. Travis, Colette L. Kelly, Margaret R. Mulholland, Karen L. Casciotti

OES Faculty Publications

The primary nitrite maximum (PNM) is a ubiquitous feature of the upper ocean, where nitrite accumulates in a sharp peak at the base of the euphotic zone. This feature is situated where many chemical and hydrographic properties have strong gradients and the activities of several microbial processes overlap. Near the PNM, four major microbial processes are active in nitrite cycling: ammonia oxidation, nitrite oxidation, nitrate reduction and nitrite uptake. The first two processes are mediated by the nitrifying archaeal/bacterial community, while the second two processes are primarily conducted by phytoplankton. The overlapping spatial habitats and substrate requirements for these microbes …


Initial Estuarine Response To Inorganic Nutrient Inputs From A Legacy Mining Facility Adjacent To Tampa Bay, Florida, Marcus W. Beck, Andrew Altieri, Christine Angelini, Maya C. Burke, Jing Chen, Diana W. Chin, Jayne Gardiner, Chuanmin Hu, Katherine A. Hubbard, Yonggang Liu, Cary Lopez, Miles Medina, Elise Morrison, Edward J. Phlips, Gary E. Raulerson, Sheila Scolaro, Edward T. Sherwood, David Tomasko, Robert H. Weisberg, Joseph Whalen May 2022

Initial Estuarine Response To Inorganic Nutrient Inputs From A Legacy Mining Facility Adjacent To Tampa Bay, Florida, Marcus W. Beck, Andrew Altieri, Christine Angelini, Maya C. Burke, Jing Chen, Diana W. Chin, Jayne Gardiner, Chuanmin Hu, Katherine A. Hubbard, Yonggang Liu, Cary Lopez, Miles Medina, Elise Morrison, Edward J. Phlips, Gary E. Raulerson, Sheila Scolaro, Edward T. Sherwood, David Tomasko, Robert H. Weisberg, Joseph Whalen

Marine Science Faculty Publications

Legacy mining facilities pose significant risks to aquatic resources. From March 30th to April 9th, 2021, 814 million liters of phosphate mining wastewater and marine dredge water from the Piney Point facility were released into lower Tampa Bay (Florida, USA). This resulted in an estimated addition of 186 metric tons of total nitrogen, exceeding typical annual external nitrogen load estimates to lower Tampa Bay in a matter of days. An initial phytoplankton bloom (non-harmful diatoms) was first observed in April. Filamentous cyanobacteria blooms (Dapis spp.) peaked in June, followed by a bloom of the red tide organism Karenia brevis …


Connecticut Embayment Characteristics 2022, Jamie M.P. Vaudrey, James E. O'Donnell Mar 2022

Connecticut Embayment Characteristics 2022, Jamie M.P. Vaudrey, James E. O'Donnell

Department of Marine Sciences

Data on Connecticut embayment characteristics. This Excel file is the centerpiece for capturing embayment characteristics as presented in RESPEC (2022), developed specifically for this project. Some parameters such as watershed size, embayment size, and tidal range were pulled from other sources described in Appendix A of RESPEC (2022), but much of the data and indicators in the Excel file were developed for this project. Each parameter included in the spreadsheet is fully defined in Appendix A of RESPEC (2022). All data available in the spreadsheet are provided by embayment in Appendix C of RESPEC (2022), including the results of bathymetric …


Coastal Upwelling Enhances Abundance Of A Symbiotic Diazotroph (Ucyn-A) And Its Haptophyte Host In The Arctic Ocean, Corday R. Selden, Sveinn V. Einarsson, Kate E. Lowry, Katherine E. Crider, Robert S. Pickart, Peigen Lin, Carin J. Ashjian, P. Dreux Chappell Jan 2022

Coastal Upwelling Enhances Abundance Of A Symbiotic Diazotroph (Ucyn-A) And Its Haptophyte Host In The Arctic Ocean, Corday R. Selden, Sveinn V. Einarsson, Kate E. Lowry, Katherine E. Crider, Robert S. Pickart, Peigen Lin, Carin J. Ashjian, P. Dreux Chappell

OES Faculty Publications

The apparently obligate symbiosis between the diazotroph Candidatus Atelocyanobacterium thalassa (UCYN-A) and its haptophyte host, Braarudosphaera bigelowii, has recently been found to fix dinitrogen (N2) in polar waters at rates (per cell) comparable to those observed in the tropical/subtropical oligotrophic ocean basins. This study presents the novel observation that this symbiosis increased in abundance during a wind-driven upwelling event along the Alaskan Beaufort shelfbreak. As upwelling relaxed, the relative abundance of B. bigelowii among eukaryotic phytoplankton increased most significantly in waters over the upper slope. As the host’s nitrogen demands are believed to be supplied primarily by UCYN-A, …


Stable Isotopes Used To Infer Trophic Position Of Green Turtles (Chelonia Mydas) From Dry Tortugas National Park, Gulf Of Mexico, United States, David C. Roche, Michael S. Cherkiss, Brian J. Smith, Derek A. Burkholder, Kristen M. Hart Sep 2021

Stable Isotopes Used To Infer Trophic Position Of Green Turtles (Chelonia Mydas) From Dry Tortugas National Park, Gulf Of Mexico, United States, David C. Roche, Michael S. Cherkiss, Brian J. Smith, Derek A. Burkholder, Kristen M. Hart

Marine & Environmental Sciences Faculty Articles

Evaluating resource use patterns for imperiled species is critical for understanding what supports their populations. Here we established stable isotope (δ13C, δ15N) values for the endangered green sea turtle (Chelonia mydas) population found within the boundaries of Dry Tortugas National Park (DRTO), south Florida, USA. There is little gene flow between turtles sampled at DRTO and in other rookeries in Florida, underscoring the need to study this distinct population. Between 2008 and 2015 we collected multiple sample types (skin [homogenized epidermis/dermis], whole blood, red blood cells, plasma, carapace) from 151 unique green turtles, including …


Elevated Atmospheric Co2 Concentration Triggers Redistribution Of Nitrogen To Promote Tillering In Rice, Juan Zhou, Yingbo Gao, Junpeng Wang, Chang Liu, Zi Wang, Minjia Lv, Xiaoxiang Zhang, Yong Zhou, Guichun Dong, Yulong Wang, Jianye Huang, Dafeng Hui, Zefeng Yang, Youli Yao May 2021

Elevated Atmospheric Co2 Concentration Triggers Redistribution Of Nitrogen To Promote Tillering In Rice, Juan Zhou, Yingbo Gao, Junpeng Wang, Chang Liu, Zi Wang, Minjia Lv, Xiaoxiang Zhang, Yong Zhou, Guichun Dong, Yulong Wang, Jianye Huang, Dafeng Hui, Zefeng Yang, Youli Yao

Biology Faculty Research

Elevated atmospheric CO2 concentration (eCO2) often reduces nitrogen (N) content in rice plants and stimulates tillering. However, there is a general consensus that reduced N would constrain rice tillering. To resolve this contradiction, we investigated N distribution and transcriptomic changes in different rice plant organs after subjecting them to eCO2 and different N application rates. Our results showed that eCO2 significantly promoted rice tillers (by 0.6, 1.1, 1.7, and 2.1 tillers/plant at 0, 75, 150, and 225 kg N ha−1 N application rates, respectively) and more tillers were produced under higher N application rates, …


Estimating The Denitrification Rate In Hood Canal Using Water Circulation, Spencer Johnson Apr 2021

Estimating The Denitrification Rate In Hood Canal Using Water Circulation, Spencer Johnson

WWU Honors College Senior Projects

Hood Canal is a long, fjordal estuarine inlet. Because of a sill near its mouth, Hood Canal experiences regular low oxygen in its bottom water; recently, dissolved oxygen has been even lower than usual, leading to fish kills and other ecosystem damage. Anthropogenic nutrients, particularly nitrogen, may be the cause, so it is important to quantify the components of the nitrogen cycle, like denitrification. To my knowledge, there is only one estimate of denitrification from Hood Canal in the literature. This study sought to supplement that data with an independent estimate of denitrification using water circulation along with N2 concentrations …


Evaluation Of Nitrogen And Phosphorus Removal From A Denitrifyingwoodchip Bioreactor Treatment System Receiving Silage Bunker Runoff, Jillian C. Sarazen, Joshua W. Faulkner, Stephanie E. Hurley Jul 2020

Evaluation Of Nitrogen And Phosphorus Removal From A Denitrifyingwoodchip Bioreactor Treatment System Receiving Silage Bunker Runoff, Jillian C. Sarazen, Joshua W. Faulkner, Stephanie E. Hurley

College of Agriculture and Life Sciences Faculty Publications

Leachate and storm-driven runoff from silage storage bunkers can degrade receiving water bodies if left untreated. This study evaluated a novel treatment system consisting of three treatment tanks with a moving-bed biofilm reactor and paired side-by-side denitrifying woodchip bioreactors for the ability to reduce influent nutrient mass loads. Flow-based samples were taken at four locations throughout the system, at the inflow to the first tank, outflow from the tanks prior to entering the woodchip bioreactors, and from the outflows of both bioreactors. Samples were analyzed for concentrations of nitrogen (N) and phosphorus (P) species. Inflow concentrations were reduced from the …


Size And Density Of Upside-Down Jellyfish, Cassiopea Sp., And Their Impact On Benthic Fluxes In A Caribbean Lagoon, Chester B. Zarnoch, Noshin Hossain, Erika Fusco, Mary Alldred, Timothy J. Hoellein, Sophia Perdikaris Jan 2020

Size And Density Of Upside-Down Jellyfish, Cassiopea Sp., And Their Impact On Benthic Fluxes In A Caribbean Lagoon, Chester B. Zarnoch, Noshin Hossain, Erika Fusco, Mary Alldred, Timothy J. Hoellein, Sophia Perdikaris

School of Global Integrative Studies: Faculty Publications

Anthropogenic disturbances may be increasing jellyfish populations globally. Epibenthic jellyfish are ideal organisms for studying this phenomenon due to their sessile lifestyle, broad geographic distribution, and prevalence in near-shore coastal environments. There are few studies, however, that have documented epibenthic jellyfish abundance and measured their impact on ecological processes in tropical ecosystems. In this study, the density and size of the upside-down jellyfish (Cassiopea spp.) were measured in Codrington Lagoon, Barbuda. A sediment core incubation study, with and without Cassiopea, also was performed to determine their impact on benthic oxygen and nutrient fluxes. Densities of Cassiopea were 24–168 …


Benchmarking On-Farm Maize Nitrogen Balance In The Western U.S. Corn Belt, Fatima Amor Tenorio Dec 2019

Benchmarking On-Farm Maize Nitrogen Balance In The Western U.S. Corn Belt, Fatima Amor Tenorio

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

A nitrogen (N) balance, calculated as the difference between N inputs and grain-N removal, provides an estimate of the potential N losses. We used N balance with other N-related metrics (partial factor productivity for N inputs, and yield-scaled N balance), to benchmark maize yields in relation with N input use in the US Corn Belt. We first used experimental data on grain-N concentration (GNC) to assess variation in this parameter due to biophysical and management factors. Subsequently, we used N balance and N-related metrics to benchmark yields in relation with N inputs in irrigated and rainfed fields in Nebraska using …


Experimental Nitrogen Addition Alters Structure And Function Of A Boreal Bog: Critical Load And Thresholds Revealed, R. Kelman Wieder, Dale H. Vitt, Melanie A. Vile, Jeremy A. Graham, Jeremy A. Hartsock, Hope Fillingim, Et Al. Aug 2019

Experimental Nitrogen Addition Alters Structure And Function Of A Boreal Bog: Critical Load And Thresholds Revealed, R. Kelman Wieder, Dale H. Vitt, Melanie A. Vile, Jeremy A. Graham, Jeremy A. Hartsock, Hope Fillingim, Et Al.

Michigan Tech Publications

Bogs and fens cover 6% and 21%, respectively, of the 140,329 km2 Oil Sands Administrative Area in northern Alberta. Development of the oil sands has led to increasing atmospheric N deposition, with values as high as 17 kg N.ha-1yr-1; regional background deposition is N.ha-1yr-1. Bogs, being ombrotrophic, may be especially susceptible to increasing N deposition. To examine responses to N deposition, over five years, we experimentally applied N (as NH4NO3) to a bog near Mariana Lake, Alberta, unaffected by oil sands activities, at …


A Multidecade Experiment Shows That Fertilization By Salmon Carcasses Enhanced Tree Growth In The Riparian Zone, Thomas P. Quinn, Helfield M. James, Catherine S. Austin, Rachel A. Hovel, Andrew Godard Bunn Nov 2018

A Multidecade Experiment Shows That Fertilization By Salmon Carcasses Enhanced Tree Growth In The Riparian Zone, Thomas P. Quinn, Helfield M. James, Catherine S. Austin, Rachel A. Hovel, Andrew Godard Bunn

Environmental Sciences Faculty and Staff Publications

As they return to spawn and die in their natal streams, anadromous, semelparous fishes such as Pacific salmon import marine‐derived nutrients to otherwise nutrient‐poor freshwater and riparian ecosystems. Diverse organisms exploit this resource, and previous studies have indicated that riparian tree growth may be enhanced by such marine‐derived nutrients. However, these studies were largely inferential and did not account for all factors affecting tree growth. As an experimental test of the contribution of carcasses to tree growth, for 20 yr, we systematically deposited all sockeye salmon (Oncorhynchus nerka) carcasses (217,055 individual salmon) in the riparian zone on one …


Harvesting Invasive Plants To Reduce Nutrient Loads And Produce Bioenergy: An Assessment Of Great Lakes Coastal Wetlands, Brendan D. Carson, Shane C. Lishawa, Nancy C. Tuchman, Andrew M. Monks, Beth A. Lawrence, Dennis A. Albert Jun 2018

Harvesting Invasive Plants To Reduce Nutrient Loads And Produce Bioenergy: An Assessment Of Great Lakes Coastal Wetlands, Brendan D. Carson, Shane C. Lishawa, Nancy C. Tuchman, Andrew M. Monks, Beth A. Lawrence, Dennis A. Albert

School of Environmental Sustainability: Faculty Publications and Other Works

In Laurentian Great Lakes coastal wetlands (GLCWs), dominant emergent invasive plants are expanding their ranges and compromising the unique habitat and ecosystem service values that these ecosystems provide. Herbiciding and burning to control invasive plants have not been effective in part because neither strategy addresses the most common root cause of invasion, nutrient enrichment. Mechanical harvesting is an alternative approach that removes tissue‐bound phosphorus and nitrogen and can increase wetland plant diversity and aquatic connectivity between wetland and lacustrine systems. In this study, we used data from three years of Great Lakes‐wide wetland plant surveys, published literature, and bioenergy analyses …


Assessing Phytoplankton Nutritional Status And Potential Impact Of Wet Deposition In Seasonally Oligotrophic Waters Of The Mid-Atlantic Bight, P. N. Sedwick, P. W. Bernhardt, M. R. Mulholland, R. G. Najjar, L. M. Blumen, B. M. Sohst, C. Sookhdeo, Brittany Widner Apr 2018

Assessing Phytoplankton Nutritional Status And Potential Impact Of Wet Deposition In Seasonally Oligotrophic Waters Of The Mid-Atlantic Bight, P. N. Sedwick, P. W. Bernhardt, M. R. Mulholland, R. G. Najjar, L. M. Blumen, B. M. Sohst, C. Sookhdeo, Brittany Widner

OES Faculty Publications

To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern Mid-Atlantic Bight, and the potential for rain to stimulate primary production in this region during summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbon-13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth …


Blooms Of Dinoflagellate Mixotrophs In A Lower Chesapeake Bay Tributary: Carbon And Nitrogen Uptake Over Diurnal, Seasonal, And Interannual Timescales, Margaret R. Mulholland, Ryan Morse, Todd Egerton, Peter W. Bernhardt, K. C. Filippino Jan 2018

Blooms Of Dinoflagellate Mixotrophs In A Lower Chesapeake Bay Tributary: Carbon And Nitrogen Uptake Over Diurnal, Seasonal, And Interannual Timescales, Margaret R. Mulholland, Ryan Morse, Todd Egerton, Peter W. Bernhardt, K. C. Filippino

OES Faculty Publications

A multi-year study was conducted in the eutrophic Lafayette River, a sub-tributary of the lower Chesapeake Bay during which uptake of inorganic and organic nitrogen (N) and C compounds was measured during multiple seasons and years when different dinoflagellate species were dominant. Seasonal dinoflagellate blooms included a variety of mixotrophic dinoflagellates including Heterocapsa triquetra in the late winter, Prorocentrum minimum in the spring, Akashiwo sanguinea in the early summer, and Scrippsiella trochoidea and Cochlodinium polykrikoides in late summer and fall. Results showed that no single N source fueled algal growth, rather rates of N and C uptake varied on seasonal …


N2o Emissions From California Farmlands: A Review, Elizabeth Verhoeven, Engil Isadora Pujol Pereira, Charlotte Decock, Gina Garland, Taryn Kennedy, Emma Suddick, William Horwath, Johan Six Sep 2017

N2o Emissions From California Farmlands: A Review, Elizabeth Verhoeven, Engil Isadora Pujol Pereira, Charlotte Decock, Gina Garland, Taryn Kennedy, Emma Suddick, William Horwath, Johan Six

School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

Of the greenhouse gases emitted from cropland, nitrous oxide (N2O) has the highest global warming potential. The state of California acknowledges that agriculture both contributes to and is affected by climate change, and in 2016 it adopted legislation to help growers reduce emissions of greenhouse gases, explicitly including N2O. Nitrous oxide emissions can vary widely due to environmental and agronomic factors with most emission estimates coming from temperate grain systems. There is, however, a dearth of emission estimates from perennial and vegetable cropping systems commonly found in California's Mediterranean climate. Therefore, emission factors (EFs) specific to California conditions are needed …


Nutrient Addition Shifts Plant Community Composition Towards Earlier Flowering Species In Some Prairie Ecoregions In The U.S. Central Plains, Lori Biederman, Brent Mortensen, Philip Fay, Nicole Hagenah, Johannes Knops, Kimberly La Pierre, Ramesh Laungani, Eric Lind, Rebecca L. Mcculley, Sally Power, Eric Seabloom, Pedro Tognetti May 2017

Nutrient Addition Shifts Plant Community Composition Towards Earlier Flowering Species In Some Prairie Ecoregions In The U.S. Central Plains, Lori Biederman, Brent Mortensen, Philip Fay, Nicole Hagenah, Johannes Knops, Kimberly La Pierre, Ramesh Laungani, Eric Lind, Rebecca L. Mcculley, Sally Power, Eric Seabloom, Pedro Tognetti

Plant and Soil Sciences Faculty Publications

The distribution of flowering across the growing season is governed by each species’ evolutionary history and climatic variability. However, global change factors, such as eutrophication and invasion, can alter plant community composition and thus change the distribution of flowering across the growing season. We examined three ecoregions (tall-, mixed, and short-grass prairie) across the U.S. Central Plains to determine how nutrient (nitrogen (N), phosphorus, and potassium (+micronutrient)) addition alters the temporal patterns of plant flowering traits. We calculated total community flowering potential (FP) by distributing peak-season plant cover values across the growing season, allocating each species’ cover to only those …


Expansion Of The Manage Database With Forest And Drainage Studies, Daren R. Harmel, Laura E. Christianson, Matthew W. Mcbroom, Douglas R. Smith, Kori D. Higgs Jan 2016

Expansion Of The Manage Database With Forest And Drainage Studies, Daren R. Harmel, Laura E. Christianson, Matthew W. Mcbroom, Douglas R. Smith, Kori D. Higgs

Faculty Publications

The “Measured Annual Nutrient loads from AGricultural Environments” (MANAGE) database was published in 2006 to expand an early 1980s compilation of nutrient export (load) data from cultivated and pasture/range land at the field or farm scale. Then in 2008, MANAGE was updated with 15 additional studies, and nitrogen (N) and phosphorus (P) concentrations in runoff were added. Since then, MANAGE has undergone significant expansion adding N and P water quality along with relevant management and site characteristic data from: (1) 30 runoff studies from forested land uses, (2) 91 drainage water quality studies from drained land, and (3) 12 additional …


Modeled Inflow Validation & Nutrient Loading Estimation In Two Subwatersheds Of The Lower Laguna Madre, Hudson R. Deyoe, Warren Pulich, Nelun Fernando Jan 2016

Modeled Inflow Validation & Nutrient Loading Estimation In Two Subwatersheds Of The Lower Laguna Madre, Hudson R. Deyoe, Warren Pulich, Nelun Fernando

Biology Faculty Publications and Presentations

University of Texas Rio Grande Valley will characterize nutrient loading rates into the Lower Laguna Madre for subwatersheds by monitoring stream flow and water quality (particularly total nitrogen and phosphorus). This information will be used to evaluate Texas Rainfall-Runoff model performance in estimating ungaged inflows and to establish a relationship between ungaged inflows and nutrient loading regimes to the Lower Laguna Madre. View on Map


Reductions Of Wheat Yield And Yield Components And Nitrogen Loss Following Frozen Soil Nitrogen Applications, Carrie Ann Knott, Edwin L. Ritchey, Lloyd W. Murdock Jan 2015

Reductions Of Wheat Yield And Yield Components And Nitrogen Loss Following Frozen Soil Nitrogen Applications, Carrie Ann Knott, Edwin L. Ritchey, Lloyd W. Murdock

Plant and Soil Sciences Research Report

Most wheat producers in Kentucky apply nitrogen (N) as a split application. The first N increment is applied when wheat plants begin actively growing (green-up) in late winter, which is typically in mid- February between growth stages Feekes 2 to 3. The second N increment typically occurs in March when wheat is between Feekes 5 to 6. Many producers in Kentucky, especially Western Kentucky, have become accustomed to beginning first N applications in late January when the ground is frozen and the wheat is still dormant. This practice allows them to apply N to large acreages of wheat while avoiding …


Combined Effects Of Phosphorus Nutrition And Elevated Carbon Dioxide Concentration On Chlorophyll Fluorescence, Photosynthesis, And Nutrient Efficiency Of Cotton, Shardendu K. Singh, Vangimalla R. Reddy Jan 2014

Combined Effects Of Phosphorus Nutrition And Elevated Carbon Dioxide Concentration On Chlorophyll Fluorescence, Photosynthesis, And Nutrient Efficiency Of Cotton, Shardendu K. Singh, Vangimalla R. Reddy

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

To examine the combined effects of phosphorus (P) nutrition and CO2 on photosynthesis, chlorophyll fluorescence (CF), and nutrient utilization and uptake, two controlled-environment experiments were conducted using 0.01, 0.05 and 0.20 mM external phosphate each at ambient and elevated CO2 (aCO2: 400 and eCO2: 800 mmol mol–1, respectively). The CF parameters were affected more by P nutrition than by CO2 treatment. Photoinhibition of photosystem II (PSII) was due to increased minimal CF (Fo') and decreased maximal CF (Fm'), and efficiency of energy harvesting (Fv'/Fm'). In addition, reduced electron transport rate (ETR), the quantum yield of PSII (FPSII) and CO2 assimilation …


Phytoplankton And Nutrient Dynamics In A Tidally Dominated Eutrophic Estuary: Daily Variability And Controls On Bloom Formation, Ryan E. Morse, Margaret R. Mulholland, Todd A. Egerton, Harold G. Marshall Jan 2014

Phytoplankton And Nutrient Dynamics In A Tidally Dominated Eutrophic Estuary: Daily Variability And Controls On Bloom Formation, Ryan E. Morse, Margaret R. Mulholland, Todd A. Egerton, Harold G. Marshall

OES Faculty Publications

To better understand nutrient dynamics and factors that promote the initiation of algal blooms, the Lafayette River, a tidal subestuary of Chesapeake Bay that experiences seasonal algal blooms, was sampled daily for a period of 54 d in the fall of 2005. Three phytoplankton blooms (chl a concentrations exceeding twice the average of monthly measurements from 2000 to 2009) occurred during this period: a mixed bloom of Akashiwo sanguinea and Gymnodinium sp., a monospecific Skeletonema costatum bloom, and a monospecific Gymnodinium sp. bloom. Over the sampling period, nutrient concentrations increased following precipitation events and were elevated between bloom periods but …


Decomposition And Nutrient Release Of Different Cover Crops In Organic Farm Systems, Jianru Shi Jun 2013

Decomposition And Nutrient Release Of Different Cover Crops In Organic Farm Systems, Jianru Shi

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

Cover crops act as green manure adding organic matter to agricultural-soils. For legume green manures to be an effective nitrogen (N) source for organic farming systems, their N release must be in synchrony with crop N demand. The objectives of this study were 1) determine the decomposition rates of three common cover crops (white clover, (Trifolium repens,L ) red clover (Trifolium pratense L.) and soybean (Glycine max L) in order to determine when most N was released and its synchrony with subsequent corn crop uptake; 2) we focused on the effect of cover crops on soil …


Uncoupling Between Dinitrogen Fixation And Primary Productivity In The Eastern Mediterranean Sea, Eyal Rahav, Barak Herut, Noga Stambler, Edo Bar-Zeev, Margaret R. Mulholland Mar 2013

Uncoupling Between Dinitrogen Fixation And Primary Productivity In The Eastern Mediterranean Sea, Eyal Rahav, Barak Herut, Noga Stambler, Edo Bar-Zeev, Margaret R. Mulholland

OES Faculty Publications

In the nitrogen (N)-impoverished photic zones of many oceanic regions, prokaryotic organisms fixing atmospheric dinitrogen (N2; diazotrophs) supply an essential source of new nitrogen and fuel primary production. We measured dinitrogen fixation and primary productivity (PP) during the thermally stratified summer period in different water regimes of the oligotrophic eastern Mediterranean Sea, including the Cyprus Eddy and the Rhodes Gyre. Low N2 fixation rates were measured (0.8-3.2μmol N m-2 d-1) excluding 10-fold higher rates in the Rhodes Gyre and Cyprus Eddy (~20μmol N m-2 d-1). The corresponding PP increased from east to west (200-2500μmol …


Using Stable Isotope Analysis Of Zooplankton To Document Trophic And Biogeochemical Changes In The San Francisco Estuary, Steven C. Westbrook, Julien Moderan Jan 2013

Using Stable Isotope Analysis Of Zooplankton To Document Trophic And Biogeochemical Changes In The San Francisco Estuary, Steven C. Westbrook, Julien Moderan

STAR Program Research Presentations

Zooplankton represent a vital link between phytoplankton and fish, like the endangered Delta Smelt. Human interferences (nitrates from waste water, flow alteration, invasive species introduction…) have altered the structure of the San Francisco Estuary (SFE) ecosystem. We use stable isotope analysis to improve our knowledge of the planktonic food web in the SFE and gain insights into its evolution over the past decades. We use the ratios of certain isotopes (Nitrogen, Carbon, Sulfur, etc.) in different species of zooplankton to tell us what it is feeding on as well as the trophic level it feeds in. My research focused on …


Cyanobacteria Dominance In The Oligohaline Waters Of Back Bay, Virginia, Harold G. Marshall Jan 2012

Cyanobacteria Dominance In The Oligohaline Waters Of Back Bay, Virginia, Harold G. Marshall

Biological Sciences Faculty Publications

Back Bay and its flora have historically been influenced by the interaction of freshwater flow in combination with frequent intrusion of saline water into its basin. These events have resulted in a dynamic environmental setting influencing the abundance and composition of its phytoplankton community. Dominating these oligohaline waters is a diverse representation and high abundance of freshwater filamentous and colonial cyanobacteria. These include the nonheterocystous Planktolyngbya contorta, Planktolyngbya limnetica, and Pseudanabaena limnetica, taxa implicated as bloom producers in Bay waters with N:P molar ratios ranging from 23:1 to 74:1.


Evaluation Of Algorithm Thresholds For Crop Canopy Sensor-Based In-Season Nitrogen Application In Corn, Brian T. Krienke Jul 2011

Evaluation Of Algorithm Thresholds For Crop Canopy Sensor-Based In-Season Nitrogen Application In Corn, Brian T. Krienke

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Nitrogen fertilizer is frequently the most limiting nutrient in corn production. Typically most nitrogen is applied before planting. Since nitrogen can leave the soil system fairly easily, the result can be an inefficient use of nitrogen fertilizer. Previous research has shown increased efficiency with no reduction in yield by applying nitrogen later in the season when the crop is actively growing, with rates regulated spatially through the use of active crop canopy sensors. This study evaluated the potential for N cutoff thresholds using a sufficiency index as the threshold value for areas with poor stand or an unrecoverable N deficiency. …


Effects Of Species, Water, And Nitrogen On Competition Among Three Prairie Grasses, Jerry L. Weatherford, Randall W. Myster Jun 2011

Effects Of Species, Water, And Nitrogen On Competition Among Three Prairie Grasses, Jerry L. Weatherford, Randall W. Myster

The Prairie Naturalist

We conducted an experiment to investigate effects of species, water (W), and nitrogen (N) on competition among little bluestem (Schizachyrium scoparium), sideoats grama (Bouteloua curtipendula), and indiangrass (Sorghastrum nutans). All biomass parameters and the root:shoot ratio of little bluestem were reduced by the presence off 1 of 2 other species, and its shoot biomass and total biomass were both increased by addition of N. Root and shoot biomass of sideoats grama were reduced by the presence of indiangrass and its total biomass was reduced by the presence of itself, whereas its shoot biomass was increased by addition of W at …


Fertilizer And Stormwater Runoff Outreach Program In Newcastle, Nh, David Anderson Dec 2010

Fertilizer And Stormwater Runoff Outreach Program In Newcastle, Nh, David Anderson

PREP Reports & Publications

The New Hampshire Coastal Protection Partnership (NH Coast) implemented a year long pilot public education and outreach program in the Town of New Castle aimed at reducing nitrogen pollution from lawn fertilizers and promoting rain gardens as a solution to storm water runoff and nonpoint source pollution. A total of 77 landowners representing 138 acres of land pledged to either not use lawn fertilizers or use only low phosphorus, slow release nitrogen brands. The program also resulted in the installation of New Castle’s first demonstration rain garden.