A5085813678- Marine and coastal ecosystems
- Isotope Analysis in Ecology
- Microbial Community Ecology and Physiology
- Wastewater Treatment and Nitrogen Removal
- Methane Hydrates and Related Phenomena
- Marine Biology and Ecology Research
- Atmospheric and Environmental Gas Dynamics
- Oceanographic and Atmospheric Processes
- Groundwater and Isotope Geochemistry
- Ocean Acidification Effects and Responses
- Geology and Paleoclimatology Research
- Nuclear Physics and Applications
- Adipose Tissue and Metabolism
- Soil and Water Nutrient Dynamics
- Arctic and Antarctic ice dynamics
- Microbial Fuel Cells and Bioremediation
- Calibration and Measurement Techniques
- Mass Spectrometry Techniques and Applications
- Underwater Vehicles and Communication Systems
- Water Quality Monitoring Technologies
- Metabolism, Diabetes, and Cancer
- Chemical Thermodynamics and Molecular Structure
- Geological and Tectonic Studies in Latin America
- Diabetes and associated disorders
- Engine and Fuel Emissions
University of South Carolina Sumter
2023-2024
University of South Carolina
2018-2024
Dartmouth College
2016-2024
University of Massachusetts Dartmouth
2014-2019
Woods Hole Oceanographic Institution
2018
University of Victoria
2010-2014
Centre Hospitalier Universitaire de Sherbrooke
2008-2010
Université de Sherbrooke
2008-2010
Université du Québec à Montréal
2009
We present a new nitrogen isotope model incorporated into the three‐dimensional ocean component of global Earth system climate designed for millennial timescale simulations. The includes prognostic tracers two stable isotopes, 14 N and 15 N, in nitrate (NO 3 − ), phytoplankton, zooplankton, detritus variables marine ecosystem model. effects algal NO uptake, fixation, water column denitrification, zooplankton excretion are considered as well removal by sedimentary denitrification. A database...
Assessment of the global budget greenhouse gas nitrous oxide ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:math> O) is limited by poor knowledge oceanic O flux to atmosphere, which magnitude, spatial distribution, and temporal variability remain highly uncertain. Here, we reconstruct climatological emissions from ocean training a supervised learning...
In addition to organotrophic denitrification, alternative pathways, such as anaerobic ammonium oxidation (anammox) or sulfide‐dependent denitrification may be important modes for the removal of fixed nitrogen (N) from lakes. We used Lake Lugano a model system with which assess possible controls on concurrence multiple suboxic N 2 production pathways in lacustrine water column. northern basin Lugano, concentration gradients dissolved inorganic toward hypolimnetic redox transition zone (RTZ)...
Abstract The ocean is an important source of nitrous oxide (N 2 O) to the atmosphere, yet factors controlling N O production and consumption in oceanic environments are still not understood nor constrained. We measured concentrations isotopomer ratios, as well , nutrient biogenic concentrations, isotopic compositions nitrate nitrite at several coastal stations during two cruises off Peru coast (~5–16°S, 75–81°W) December 2012 January 2013. varied from below equilibrium values oxygen...
Abstract Mesoscale eddies in Oxygen Minimum Zones (OMZs) have been identified as important fixed nitrogen (N) loss hotspots that may significantly impact both the global rate of N‐loss well ocean's N isotope budget. They also represent “natural tracer experiments” with intensified biogeochemical signals can be exploited to understand large‐scale processes control and associated effects ( ε ; ‰ deviation from 1 ratio reaction constants for light versus heavy isotopologues). We observed large...
Abstract The continental shelves of the Arctic Ocean and surrounding seas contain large stocks organic matter (OM) methane (CH 4 ), representing a potential ecosystem feedback to climate change not included in international agreements. We performed structured expert assessment with 25 permafrost researchers combine quantitative estimates sensitivity carbon subsea domain (i.e. unglaciated portions exposed during last glacial period). Experts estimated that contains ∼560 gigatons (GtC;...
The subtropical northeast Atlantic has previously been identified as a marine environment with an apparent imbalance between low nitrate supply to the surface and concurrent high export production. To better constrain sources fluxes of mixed layer assess potential role N 2 fixation in providing new nitrogen (N), we investigated depth distribution δ 15 18 O at six stations across Azores Front NE Atlantic. In addition, measured dissolved organic (DON) waters sinking particulate collected...
Little is known about dissolved inorganic nitrogen (DIN) transformations in hydrothermal vent (HV) fluids. Here, we present the first isotopic measurements of nitrate ( δ 15 N and 18 O) ammonium N) from three HV fields on Juan de Fuca ridge (NE‐Pacific). The dominant process that drives DIN concentration variations low‐T diffuse fluids water mass mixing below seafloor, with no effect isotope ratios. Strong inter‐site NH 4 + high‐T suggest different subsurface (N) sources (deep‐sea versus...
Abstract. O2 deficient zones (ODZs) of the world's oceans are important locations for microbial dissimilatory nitrate (NO3−) reduction and subsequent loss combined nitrogen (N) to biogenic N2 gas. ODZs generally coupled regions high productivity leading rates N-loss as found in coastal upwelling region off Peru. Stable N O isotope ratios can be used natural tracers ODZ N-cycling because distinct kinetic effects associated with microbially mediated N-cycle transformations. Here we present...
Abstract. Mesoscale eddies play a major role in controlling ocean biogeochemistry. By impacting nutrient availability and water column ventilation, they are of critical importance for oceanic primary production. In the eastern tropical South Pacific Ocean off Peru, where large persistent oxygen-deficient zone is present, mesoscale processes have been reported to occur frequently. However, investigations into their biological activity mostly based on model simulations, direct measurements...
The ocean accounts for ~20 to 30% of global nitrous oxide (N2O) emissions, with coastal upwelling systems estimated contribute disproportionately the sea-air flux this potent greenhouse gas. To resolve mechanisms and controls on N2O production in systems, we measured concentration nitrogen oxygen isotopic composition (&#948;15N-N2O &#948;18O-N2O) along a cross-shelf transect Southern Benguela Upwelling System. At shelf bottom, concentrations increased from outer towards shore (11 32...
The Arctic Ocean’s (AO) contribution to the global carbon system is changing rapidly, as it now subject extensive sea ice loss, enhanced permafrost thawing, and increased fluvial discharge due anthropogenic climate change. AO an important conduit of dense waters supporting North Atlantic Deep Water (NADW) formation, so its role in providing for storage deep ocean also Here we consider dynamics organic matter upper AO. Organic (OC), primarily introduced by marine photoautotrophs via outflow...
Abstract The physical and biogeochemical properties of the western Arctic Ocean are rapidly changing, resulting in cascading shifts to local ecosystems. nutrient‐rich Pacific water inflow through Bering Strait is modified on Chukchi East Siberian shelves by brine rejection during sea ice formation, a strong halocline (called Upper Halocline Layer (UHL)) that separates cold relatively fresh surface layer from warmer more saline (and nutrient‐poor) Atlantic‐derived below. Biogeochemical...
Abstract The oceanic nitrogen cycle is critically important for the partitioning of greenhouse gases between ocean and atmosphere. Baffin Bay connects regions that are major sources (North Atlantic) sinks Pacific western Arctic) biologically available further harbors supersaturation nitrous oxide a coincident deficit in nitrate deep basin. Isotopic tracer profiles both species presented here provide novel insights into origin cycling reactive Bay, highlighting connectivity different Arctic...
Nitrous oxide (N 2 O) is a potent greenhouse gas and ozone depleting substance, with the ocean accounting for about one third of global emissions. In marine environments, significant amount N O produced by biological processes in Oxygen Deficient Zones (ODZs). While recent technological advances are making surface concentration more available, high temporal spatial resolution water-column data relatively scarce, limiting models’ predictive capability. We present concentration, stable...
Abstract Elevated ammonium concentrations in pump‐and‐treat effluent from a volatile organic compounds–contaminated municipal aquifer originate two industrial sources: infiltration of drainage the blending operations fertilizer company (FC) located recharge area ( 500 to 700 parts per million [ppm] N and 150 300 ppm N) leakage waste water treatment ponds maintained by an adjacent chemical (CC) 50 70 N, with no ). Geochemical isotope data are used trace mechanisms for strong attenuation...
Abstract Context: Abnormal plasma nonesterified fatty acid (NEFA) metabolism may play a role in the development of type 2 diabetes. Objectives: Our objectives were to demonstrate whether there is defect insulin-mediated suppression NEFA appearance (RaNEFA) and oxidation (OxNEFA) during enhanced intravascular triacylglycerol lipolysis early natural history diabetes, if so, determine other mechanisms than reduced intracellular are involved. Design: These cross-sectional studies. Setting: The...
Abstract. Little is known about fixed nitrogen (N) transformation and elimination at diffuse hydrothermal vents where anoxic fluids are mixed with oxygenated crustal seawater prior to discharge. Oceanic N sinks that remove bio-available ultimately affect chemosynthetic primary productivity in these ecosystems. Using 15N paired isotope techniques, we determined potential rates of loss pathways (denitrification, anammox) dissimilatory nitrate reduction ammonium (DNRA) sulfidic vent discharging...
Abstract. In the current era of rapid climate change, accurate characterization climate-relevant gas dynamics – namely production, consumption, and net emissions is required for all biomes, especially those ecosystems most susceptible to impact change. Marine environments include regions that act as sources or sinks numerous climate-active trace gases including methane (CH4) nitrous oxide (N2O). The temporal spatial distributions CH4 N2O are controlled by interaction complex biogeochemical...