Denitrification in Lake 227 During Summer Stratification

1980 ◽  
Vol 37 (3) ◽  
pp. 506-512 ◽  
Author(s):  
Y. K. Chan ◽  
N. E. R. Campbell
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Euphotic Zone ◽  
Water Interface ◽  
Surficial Sediments ◽  
Anoxic Hypolimnion ◽  
Main Factors ◽  
Sediment Denitrification

In situ denitrification in Lake 227 was assayed by using 15N-labeled NO3− during summer stratification periods in 1973, 1974, and 1975. Dissolved oxygen and NO3− concentrations were the main factors controlling denitrification in the water column and in sediments. The epilimnetic sediment–water interface was a more significant site of natural denitrification when compared to the oxygen-limiting (dissolved oxygen less than 0.2 mg/L) thermocline and the anoxic hypolimnion. Epilimnetic sediment denitrification rates averaged about 15 mg N∙m−2∙d−1. Nearly all of the NO3− that mixed into the surficial sediments was denitrified. Alone, epilimnetic denitrification removed 1.4% of the NO3− added annually. Below the euphotic zone, sediments would provide an efficient sink for NO3−-N without simultaneous initiation of eutrophication.Key words: denitrification, nitrogen sink, nitrate in lakes, experimental lakes, summer stratification

scholarly journals Simple quality control technique to identify dissolved oxygen diffusion issues with biochemical oxygen demand bottle incubations

2017 ◽  
Author(s):  
Johnathan Daniel Maxey ◽  
Neil David Hartstein ◽  
Dorathy Penjinus ◽  
Alan Kerroux
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Biochemical Oxygen Demand ◽  
Oxygen Demand ◽  
Freshwater Ecosystems ◽  
Control Technique ◽  
Community Respiration ◽  
Parallel Diffusion ◽  
Quality Control Technique

Stratified estuaries are home to expanding aquaculture activities whose ecological footprints can be observed through trends in microbial community respiration in the water column. Bottle incubations are widely used to measure water column community respiration in marine and freshwater ecosystems by measuring the flux of dissolved oxygen occurring in the bottle over a period of time. When in situ dissolved oxygen (DO) concentrations are markedly different than DO concentration of the incubation medium the potential for diffusion of oxygen across the bottle opening is great and may be especially pronounced in strongly stratified systems with relatively low rates of pelagic oxygen consumption. We incubated 60 Biochemical Oxygen Demand (BOD) bottles filled with sterilized water with DO concentrations ranging from 2.51 mg O2 L-1 to 10.03 mg O2 L-1 for 24 hours in a temperature controlled water bath. There was a significant relationship when DO flux was set as a function of initial DO (DO Flux = -0.0017x + 0.0085, r2 = 0.72, p < 2.2 e-16). DO fluxes ranged from -0.012 mg O2 L-1 hour-1 to 0.005 mg O2 L-1 hour-1 for bottles incubated with initial DO ranging from 10.03 mg O2 L-1 to 3.31 mg O2 L-1, respectively. These results suggest that diffusion across the ground glass seal of BOD bottles is possible and that extra precaution through parallel diffusion controls should be considered when measuring pelagic respiration using BOD bottle incubations in systems with relatively low or relatively high in situ DO concentrations.

scholarly journals DOWNWELLING DIFFUSE ATTENUATION COEFFICIENTS FROM IN SITU MEASUREMENTS OF DIFFERENT WATER TYPES

2014 ◽  
Vol 10 (2) ◽  
Author(s):  
Bisman Nababan ◽  
Veronica S.A. Louhenapessy ◽  
Risti E Arhatin
Keyword(s):  
Water Column ◽  
Coastal Region ◽  
Euphotic Zone ◽  
Time Range ◽  
Water Type ◽  
Attenuation Coefficients ◽  
Water Types ◽  
Light Reduction ◽  
Ocean Ecosystem

Process of light reduction or loss (attenuation) by scattering and absorption is affected bysolar zenith, time, depth, and seawater constituents. Downwelling diffuse attenuation coefficient (Kd)is important to understand for light penetration and biological processes in ocean ecosystem. It is,therefore, important to know the Kd value and its variability in ocean ecosystem. The objective of thisstudy was to determine downwelling diffuse attenuation coefficients and its variability form in situmeasurements of different water types. In situ downwelling irradiances (Ed) were measured using asubmersible marine environmental radiometer instrument (MER) during a clear sky, calm watercondition, and at the time range of 10:30 a.m. up to 14:00 p.m. local time in the northeastern Gulf ofMexico in April 2000. In general, Ed values decreases exponentially with depth. Ed at 380 nmexhibited the lowest attenuation (the most penetrative light), while Ed at 683 nm exhibited the highestattenuation (the most light loss at the top of water column). Overall, the Kd patterns tended to decreasefrom 380 nm to 490 nm (blue-green wavelength), and increase from 490 nm to 683 nm (green-redwavelength). Kd values in offshore region were relatively lower than in coastal region. Kd can be usedto determine the depth of euphotic zone in offshore or teh case-1 water type and the depth of oneoptical depth (the water column depth where the ocean color satellite can possibly sense).

Dissolved Oxygen and Nutrient Fluxes Across the Sediment–Water Interface of the Neckar River, Germany: In Situ Measurements and Simulations

2006 ◽  
Vol 6 (5-6) ◽  
pp. 413-422 ◽  
Author(s):  
Ingo Haag ◽  
Gerhard Schmid ◽  
Bernhard Westrich
Keyword(s):  
Dissolved Oxygen ◽  
In Situ Measurements ◽  
Nutrient Fluxes ◽  
Water Interface

Deep winter ventilation dynamics in the south Adriatic convection area from in situ glider observations and model output

2020 ◽  
Author(s):  
Riccardo Martellucci ◽  
Elena Mauri ◽  
Riccardo Gerin ◽  
Giulio Notarstefano ◽  
Gianpiero Cossarini
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Deep Water ◽  
Inverse Correlation ◽  
Model Output ◽  
The South ◽  
Basin Scale ◽  
Oxygen Minimum ◽  
Ocean Processes

&lt;p&gt;Dissolved oxygen dynamics in the south Adriatic pit have been investigated between 2015 and 2019 through in situ measurements and numerical models. This area is characterized by a frequent occurrence of deep water convection phenomena during winter time. Such convection phenomena represent the main source of dense waters for the Eastern Mediterranean basin modulating the oxygen advection in the deep water.&lt;/p&gt;&lt;p&gt;In situ glider measurements in the south Adriatic pit were performed by the OGS Glider Team since 2013. Typically, these missions covered the transect from Bari to Dubrovnik. The glider missions aim to investigate the water masses before, during and after the convection period. Pre-convection missions were carried out between the end of November and the beginning of December. Convection missions were performed between the end of January and the beginning of May.&lt;/p&gt;&lt;p&gt;Over 3000 pro&amp;#64257;les from the surface to 950m depth were collected and used to better understand the physical and biogeochemical highly variable processes in the southern Adriatic pit.&lt;/p&gt;&lt;p&gt;During the pre-convection period the water column is generally stratified; recorded data show an inverse correlation between dissolved oxygen and salinity. The pre-convection periods in 2015 and 2016 present the highest variability; the water column is mainly characterized by vertical profiles with a double oxygen minimum, which corresponds to the highest salinity concentrations. During the 2017 pre-convex mission the water column is characterized by a vertical salinity gradient, whereas dissolved oxygen profiles show a double dissolved oxygen maximum both on the surface and at 300-400 m depth. The 2018 pre-convex mission shows a thin surface layer of low salinity and high dissolved oxygen, which extends from the surface down to 50 m depth. A nucleus of high salinity and low oxygen is present close to the Italian coast at about 80-200m depth.&lt;/p&gt;&lt;p&gt;The 2016 convex mission revealed an inverse correlation of oxygen and salinity profiles and a double oxygen minimum with slightly different characteristics with respect to the previous pre convection period. During 2018 and 2019 the missions occurred during the convection phenomenon. The water column is well mixed from the surface down to 600 m depth, suggesting the occurrence of deep winter convection, also confirmed by the increase in oxygen and salinity concentrations along the water column.&lt;/p&gt;&lt;p&gt;In order to fully understand the process development in the south Adriatic Pit, which are the combinatorial result of coastal and open ocean processes, we integrated our observations with numerical model outputs provided by the Copernicus Marine Environment Monitoring Services. As the sea glider allows us to observe a high degree of variability from mesoscale to sub-mesoscale, the model output was used to evaluate mesoscale and sub basin scale phenomena.&lt;/p&gt;&lt;p&gt;Such an integration of different datasets provide information at different temporal and spatial scales of water mass dynamics, thus underlying the fundamental role of integrating multi-platform contributions to gain knowledge of the ocean processes.&lt;/p&gt;

Nitrate applications to control phosphorus release from sediments of a shallow eutrophic estuary: an experimental evaluation

1998 ◽  
Vol 49 (6) ◽  
pp. 463 ◽  
Author(s):  
T. F. McAuliffe ◽  
R. J. Lukatelich ◽  
A. J. McComb ◽  
S. Qiu
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Oxygen Demand ◽  
Phosphorus Release ◽  
Carbon Limitation ◽  
Water Interface ◽  
Phosphate Release ◽  
Soluble Reactive Phosphate ◽  
Reactive Phosphate ◽  
Nitrate Consumption

Effects of nitrate on phosphate release from sediments of a eutrophic estuary were investigated under laboratory conditions, using reconstituted sediment–water cores. Application of nitrate (5–100 mg L-1 NO3-N) increased redox potential near the sediment–water interface from –200 mV to about 200 mV during 25 days of incubation. The effective concentration of nitrate differed between sediments, reflecting differences in sediment properties, particularly bioavailable carbon. Reduced phosphate after nitrate application is attributed mainly to: (1) increased iron (III) binding near the sediment–water interface; and (2) increased dissolved oxygen in the water column due to lowered oxygen demand, with increased oxidation of ferrous iron and substances binding soluble reactive phosphate. High nitrate concentrations (50 and 100 mg L-1 NO3-N) did not persist through a 155-day incubation, suggesting that without carbon limitation added nitrate will eventually be consumed by microbial activity, and increased phosphate release may occur. Nitrate application directly into the surface sediment increased nitrate consumption, and so was less effective than application to the water column. Frequent resuspension increased dissolved oxygen concentration, so reduced nitrate consumption and lowered concentration of soluble reactive phosphate.

Sediment Resuspension and Dissolved Oxygen Levels Associated with Ship Traffic: Implications for Habitat Remediation

1997 ◽  
Vol 32 (2) ◽  
pp. 421-438 ◽  
Author(s):  
K.N. Irvine ◽  
I.G. Droppo ◽  
T.P. Murphy ◽  
A. Lawson
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Water Column ◽  
Suspended Sediment ◽  
Life Stage ◽  
Sediment Resuspension ◽  
Bed Sediment ◽  
Sediment Samples ◽  
Slip Area

Abstract Many of the Great Lakes Areas of Concern include harbours and navigable channels that experience disturbance of bed sediment due to the passage of large ships. Sediment resuspension due to ship passage may impact efforts to restore habitat and remediate contaminated bed sediment through in situ treatment. To examine the impacts of ship passage, water column profiles of temperature, pH, turbidity and dissolved oxygen, as well as suspended sediment samples, were taken at varying distances behind ships entering an industrial slip area of the Hamilton Harbour Area of Concern during the summer of 1995. Weekly water column profiles and suspended sediment samples also were collected at three sites in the slip area and a harbour control site to characterize ambient water quality. Ship passage significantly increased turbidity above ambient levels due to sediment resuspension, although the increase was less in the deeper areas of the slip. Levels of turbidity and suspended sediment concentration associated with ship passage exceeded that recommended for a moderate level of fish habitat protection. In association with the increased turbidity, levels of dissolved oxygen declined and often were less than 5 and 6.5 mg L-1, the Canadian Water Quality Guideline for later life stage warm and cold water fisheries, respectively. Based on the sample data and in situ flume experiments, the estimated depth of bed erosion due to a ship passage ranged from 1 to 8 mm. The impacts of sediment disturbance due to a ship passage should be considered when selecting and designing appropriate sites and technologies for remediation.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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