Buried particulate organic carbon stimulates denitrification and nitrate retention in stream sediments at the groundwater–surface water interface

2015 ◽  
Vol 34 (1) ◽  
pp. 161-171 ◽  
Author(s):  
Robert S. Stelzer ◽  
J. Thad Scott ◽  
Lynn A. Bartsch
Keyword(s):  
Surface Water ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Stream Sediments ◽  
Water Interface ◽  
Nitrate Retention

scholarly journals Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

2006 ◽  
Vol 3 (3) ◽  
pp. 803-836 ◽  
Author(s):  
M. Gehlen ◽  
L. Bopp ◽  
N. Emprin ◽  
O. Aumont ◽  
C. Heinze ◽  
...  
Keyword(s):  
Particle Size ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Carbon Fluxes ◽  
Ocean Model ◽  
Size Spectrum ◽  
Water Interface ◽  
Standard Version ◽  
Surface Ocean ◽  
Organic Carbon Fluxes

Abstract. This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1) the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2) an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3) a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. The integrated representation of material fluxes from the productive surface ocean down to the sediment-water interface allows taking advantage of surface ocean observations, sediment trap data and exchange fluxes at the sediment-water interface. The capability of the model to reproduce yearly averaged particulate organic carbon fluxes and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Model results obtained with the standard version and with the one including a particle size spectrum and prognostic sinking speed are not significantly different. Both model versions overestimate particulate organic carbon between 1000 and 2000 m, while deep fluxes are of the correct order of magnitude. Predicted benthic oxygen fluxes correspond with respect to their large scale distribution and magnitude to data based estimates. Modeled particulate organic C fluxes across the mesopelagos are most sensitive to the intensity of zooplankton flux feeding. An increase of the intensity of flux feeding in the standard version results in lower mid- and deep-water particulate organic carbon fluxes, shifting model results to an underestimation of particulate organic carbon fluxes in the deep. The corresponding benthic oxygen fluxes are too low. The model version including the mineral ballast parameterization yields an improved fit between modeled and observed particulate organic carbon fluxes below 2000 m and down to the sediment-water interface. Our results suggest that aggregate formation alone might not be sufficient to drive an intense biological pump. The later is most likely driven by the combined effect of aggregate formation and mineral ballasting.

scholarly journals Spatial distribution of epifaunal communities in the Hudson Bay system

Elem Sci Anth ◽  
2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Marie Pierrejean ◽  
David G. Babb ◽  
Frédéric Maps ◽  
Christian Nozais ◽  
Philippe Archambault
Keyword(s):  
Surface Water ◽  
Organic Carbon ◽  
Primary Production ◽  
Particulate Organic Carbon ◽  
Environmental Drivers ◽  
Hudson Bay ◽  
Organic Carbon Content ◽  
Substrate Type ◽  
Annual Primary Production ◽  
Epibenthic Communities

The seasonal sea ice cover and the massive influx of river runoff into the Hudson Bay System (HBS) of the Canadian Arctic are critical factors influencing biological production and, ultimately, the dynamics and structure of benthic communities in the region. This study provides the most recent survey of epibenthic communities in Hudson Bay and Hudson Strait and explores their relationships with environmental variables, including mean annual primary production and particulate organic carbon in surface water, bottom oceanographic variables, and substrate type. Epibenthic trawl samples were collected at 46 stations, with a total of 380 epibenthic taxa identified, representing 71% of the estimated taxa within the system. Three communities were defined based on biomass and taxonomic composition. Ordination analyses showed them to be associated primarily with substrate type, salinity, and annual primary production. A first community, associated with coarse substrate, was distributed along the coastlines and near the river mouths. This community was characterized by the lowest density and taxonomic richness and the highest biomass of filter and suspension feeders. A second community, composed mostly of deposit feeders and small abundant epibenthic organisms, was associated with soft substrate and distributed in the deepest waters. A third community, associated with mixed substrate and mostly located near polynyas, was characterized by high diversity and biomass, with no clearly dominant taxon. The overall analysis indicated that bottom salinity and surface-water particulate organic carbon content were the main environmental drivers of these epibenthic community patterns. In the face of climate change, projections of increased river inflow and a longer open water season for the HBS could have major impacts on these epibenthic communities, emphasizing a need to continually improve our ability to evaluate and predict shifts in epibenthic richness and distribution.

scholarly journals Water column distribution and carbon isotopic signal of cholesterol, brassicasterol and particulate organic carbon in the Atlantic sector of the Southern Ocean

2013 ◽  
Vol 10 (4) ◽  
pp. 2787-2801 ◽  
Author(s):  
A.-J. Cavagna ◽  
F. Dehairs ◽  
S. Bouillon ◽  
V. Woule-Ebongué ◽  
F. Planchon ◽  
...  
Keyword(s):  
Surface Water ◽  
Organic Carbon ◽  
Southern Ocean ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Environmental Changes ◽  
Surface Concentration ◽  
Polar Front ◽  
Atlantic Sector ◽  
Organic C

Abstract. The combination of concentrations and δ13C signatures of Particulate Organic Carbon (POC) and sterols provides a powerful approach to study ecological and environmental changes in both the modern and ancient ocean. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (February–March 2008) from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC) and δ13C signatures of cholesterol and brassicasterol combined with CO2 aq. surface concentration variation. While the relationship between CO2 aq. and δ13C of bulk POC and biomarkers have been reported by others for the surface water, our data show that this persists in mesopelagic and deep waters, suggesting that δ13C signatures of certain biomarkers in the water column could be applied as proxies for surface water CO2 aq. We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effects, selective feeding on larger cells by zooplankton, and growth rate related effects. Our data suggest a key role of zooplankton fecal aggregates in carbon export for this part of the Southern Ocean (SO). Additionally, in the southern part of the transect south of the Polar Front (PF), the release of sea-ice algae during the ice demise in the Seasonal Ice Zone (SIZ) is hypothesized to influence the isotopic signature of sterols in the open ocean. Overall, the combined use of δ13C values and concentrations measurements of both bulk organic C and specific sterols throughout the water column offers the promising potential to explore the recent history of plankton and the fate of organic matter in the SO.

scholarly journals Whole water column distribution and carbon isotopic composition of bulk particulate organic carbon, cholesterol and brassicasterol from the Cape Basin to the northern Weddell Gyre in the Southern Ocean

2012 ◽  
Vol 9 (2) ◽  
pp. 1667-1709 ◽  
Author(s):  
A.-J. Cavagna ◽  
F. Dehairs ◽  
V. Woule-Ebongué ◽  
S. Bouillon ◽  
F. Planchon ◽  
...  
Keyword(s):  
Surface Water ◽  
Organic Carbon ◽  
Southern Ocean ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Environmental Changes ◽  
Carbon Isotopic Composition ◽  
Organic C ◽  
Weddell Gyre ◽  
Cape Basin

Abstract. The combination of concentrations and δ13C signatures of Particulate Organic Carbon (POC) and sterols provides a powerful approach to study ecological and environmental changes both in the modern and ancient ocean, but its application has so far been restricted to the surface area. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (Feb–Mar 2008) from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC) and δ13C signatures of cholesterol and brassicasterol from the Cape Basin to the northern Weddell Gyre combined with CO2 aq. surface concentration variation. While relationships between surface water CO2 aq. and δ13C of bulk POC and biomarkers have been previously established for surface waters, our data show that these remain valid in deeper waters, suggesting that δ13C signatures of certain biomarkers could be developed as proxies for surface water CO2 aq. Our data suggest a key role of zooplankton fecal aggregates in carbon export for this part of the Southern Ocean. We observed a general increase in sterol δ13C signatures with depth, which is likely related to a combination of particle size effects, selective feeding on larger cells by zooplankton, and growth rate related effects Additionally, in the southern part of the transect south of the Polar Front (PF), the release of sea-ice algae is hypothesized to influence the isotopic signature of sterols in the open ocean. Overall, combined use of δ13C and concentrations measurements of both bulk organic C and specific sterol markers throughout the water column shows the promising potential of analyzing δ13C signatures of individual marine sterols to explore the recent history of plankton and the fate of organic matter in the SO.

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