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Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Mr Mulholland, Da Bronk, Dg Capone
Dinitrogen Fixation And Release Of Ammonium And Dissolved Organic Nitrogen By Trichodesmium Ims101, Mr Mulholland, Da Bronk, Dg Capone
VIMS Articles
Two methods used to measure dinitrogen (N-2) fixation (acetylene reduction and N-15(2) uptake) often result in different N-2 fixation rates. Part of the discrepancy may arise from the observation that Trichodesmium can release a fraction of their recently fixed N-2 as dissolved organic nitrogen (DON) and/or ammonium (NH4+). To resolve outstanding issues regarding N-2 fixation and the production of dissolved combined nitrogen (N) by Trichodesmium, we conducted a comprehensive analysis of N-2 fixation and the production of DON and NH4+ in cultures of Trichodesmium IMS101. We performed N-15(2) uptake experiments in parallel with acetylene (C2H2) reduction assays, and measured production …
Temporal Variability Of Delta C-14, Delta C-13, And C/N In Sinking Particulate Organic Matter At A Deep Time Series Station In The Northeast Pacific Ocean, J Hwang, Erm Druffel, S Griffin, Kl Smith, Rj Baldwin, Je Bauer
Temporal Variability Of Delta C-14, Delta C-13, And C/N In Sinking Particulate Organic Matter At A Deep Time Series Station In The Northeast Pacific Ocean, J Hwang, Erm Druffel, S Griffin, Kl Smith, Rj Baldwin, Je Bauer
VIMS Articles
A 6-year time series of Delta(14) C, delta(13) C, and C/N measurements in deep sinking particulate organic matter ( POM) is presented for an abyssal site, Station M in the northeast Pacific Ocean. The Delta(14)C values revealed that sinking POM at 3450 m depth ( 650 m above bottom) contained old carbon despite its presumed short transit time in the water column. The isotopic and chemical properties of the sinking POM varied with time and appear to be controlled by more than one major process. In 1993, 1994, and late 1996, isotopic signatures and C/N molar ratios indicate negligible or …
Bacterial Utilization Of Transient Plankton-Derived Dissolved Organic Carbon And Nitrogen Inputs In Surface Ocean Waters, J Cherrier, Je Bauer
Bacterial Utilization Of Transient Plankton-Derived Dissolved Organic Carbon And Nitrogen Inputs In Surface Ocean Waters, J Cherrier, Je Bauer
VIMS Articles
The majority of bacterial growth and respiration in the upper ocean is thought to result from coupling between microheterotrophic populations and the reactive soluble components of planktonic primary and secondary production. However, we know little about the potential turnover of these components and the concomitant growth of bacteria under conditions of intermittent or transient inputs of natural dissolved organic matter (DOM) compared to quasi-steady state, low DOM conditions. The present study evaluated the short-term (similar to3 d) rates and net extents of utilization (as measured losses) of selected constituents of plankton-derived DOM (DOMPD) by indigenous bacterioplankton populations in eastern North …
High Rates Of Ammonium Recycling Drive Phytoplankton Productivity In The Offshore Mississippi River Plume, B Wawrik, Jh Paul, Da Bronk, Et Al
High Rates Of Ammonium Recycling Drive Phytoplankton Productivity In The Offshore Mississippi River Plume, B Wawrik, Jh Paul, Da Bronk, Et Al
VIMS Articles
As part of an integrated study of the regulation of carbon fixation in the offshore Mississippi River plume, we measured the rates of N-15-labeled ammonium and nitrate uptake in the surface plume waters from offshore to nearshore along the plume axis towards the Mississippi Delta. Concentrations of nitrate in the plume ranged from 0.19 to 2.5 muM with the highest concentrations primarily in the shoreward stations, while ammonium ranged from 0.17 to 0.44 muM, showing little spatial variability. Rates of ammonium uptake ranged from 16.5 to 260 nM h(-1), and showed a strong trend of increasing values from offshore towards …
Linking Watershed Loading And Basin-Level Carrying Capacity Models To Evaluate The Effects Of Land Use On Primary Production And Shellfish Aquaculture, Mark Luckenbach, Harry V. Wang
Linking Watershed Loading And Basin-Level Carrying Capacity Models To Evaluate The Effects Of Land Use On Primary Production And Shellfish Aquaculture, Mark Luckenbach, Harry V. Wang
VIMS Articles
Aquaculture production of hard clams, Mercenaria mercenaria, in the lower Chesapeake Bay, Virginia, U.S.A., has increased dramatically within the last decade. In recent years concern has been raised that some growing areas may be approaching the exploitation carrying capacity for clam production. Preliminary calculations indicate that large-scale intensive clam aquaculture may be controlling nutrient and phytoplankton dynamics in this system. To date, carrying capacity models have not been applied to this system, but we are in the process of building models for that purpose. Moreover changing land use in the watersheds surrounding the clam-producing areas raises the need for an …
Assessing Sources And Ages Of Organic Matter Supporting River And Estuarine Bacterial Production: A Multiple-Isotope (D14c, D13c, And D15n) Approach, S. Leigh Mccallister, James E. Bauer, J Cherrier, Hugh W. Ducklow
Assessing Sources And Ages Of Organic Matter Supporting River And Estuarine Bacterial Production: A Multiple-Isotope (D14c, D13c, And D15n) Approach, S. Leigh Mccallister, James E. Bauer, J Cherrier, Hugh W. Ducklow
VIMS Articles
We used radiocarbon (D14C) and stable isotopic (d13C, d15N) signatures of bacterial nucleic acids to estimate the sources and ages of organic matter (OM) assimilated by bacteria in the Hudson River and York River estuary. Dualisotope plots of D14C and d13C coupled with a three-source mixing model resolved the major OM sources supporting bacterial biomass production (BBP). However, overlap in the stable isotopic (d13C and d15N) values of potential source end members (i.e., terrestrial, freshwater phytoplankton, and marsh-derived) prohibited unequivocal source assignments for certain samples. In freshwater regions of the York, terrigenous material of relatively recent origin (i.e., decadal in …
Examination Of Reference Concentration Under Waves And Currents On The Inner Shelf, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
Examination Of Reference Concentration Under Waves And Currents On The Inner Shelf, Guan-Hong Lee, W. Brian Dade, Carl T. Friedrichs, Chris E. Vincent
VIMS Articles
[ 1] We examine reference concentration using three different data sets of near-bed suspended sediment concentration observed under combined waves and currents. The data include observations made at 15 and 20 m depth off Dounreay, Scotland, UK, and observations obtained at 13 m depth off Duck, North Carolina, USA. These data accommodate different dynamic conditions ( from wave-dominated conditions at Dounreay to wind-driven, current-dominated conditions at Duck) and sediment properties ( median size of bed sediment ranging from 120 to 350 mm). Near-bed concentration profiles to elevations of about 80 cm were obtained using acoustic backscatter sensors with 1 cm …