Organic matter remineralization and porewater exchange rates in permeable South Atlantic Bight continental shelf sediments

Jahnke, Richard A.; Richards, Mary; Nelson, James R.; Robertson, C.; Rao, Alexandra; Jahnke, Deborah

doi:10.1016/j.csr.2005.04.002

Cited by 99 publications

(109 citation statements)

References 31 publications

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“…Separating these chl a results into temperature-defined categories used in the paper by Jahnke et al [2005] (warm = bottom water >23°C; cool = bottom water <23°C) suggests that chl a concentrations in warm seasons are higher and substantially more variable than cool periods (21.4 ± 15.1 versus 11.1 ± 3.6 mg m À2 ). However, this difference becomes statistically insignificant if the two highest midsummer values (30 July 2003 and 2 August 2000) are omitted, suggesting that water temperature alone (as a proxy for season) is not the controlling factor for chl a biomass (Table 1).…”

Section: Benthic Particulate Organic Matter and Chl Amentioning

confidence: 99%

“…Instead, as suggested by Nelson et al [1999], light and the frequency of sediment disturbance are more likely to influence the development of higher benthic microalgal biomass on the sediment surface. Quiescent periods in warm, well-illuminated conditions favor microalgal layers, supported in part by enhanced release of nutrients from anoxic underlying sediments that develop in the summer [Jahnke et al, 2005]. Table 1)) and for six additional stations in 1996 (open circles).…”

Section: Benthic Particulate Organic Matter and Chl Amentioning

confidence: 99%

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Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high‐resolution, continuous in situ PAR records

et al. 2008

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[1] Continuous, 7 year records of above-water, near-surface water column and nearbottom measurements of photosynthetically active radiation (PAR) were used in conjunction with in situ chamber measurements to estimate magnitude and seasonal variations in benthic primary productivity (BPP) on the Georgia continental shelf. Correlation between BPP and PAR flux was established with 19 light/dark benthic chamber and PAR flux measurements at water depths from 14 to 40 m. No substantial improvement in the relationship is observed by inclusion of benthic chlorophyll biomass and water temperature, apparently because variations in benthic chlorophyll concentrations are moderated by physical mixing processes and seasonal temperature ranges are relatively modest. Best fit for the data set is described by a simple power function [mg carbon fixed m À2 d À1 = 132(mol photon m À2 d À1 ) 1.45 ]. In situ, continuous PAR measurements indicate temporal variations and seasonal trends not revealed by previous ship-based measurements. Importantly, calculations of PAR flux and resulting BPP are significantly less than earlier estimates of benthic PAR derived via local insolation and water column light attenuation from ship-based light profiling. Furthermore, benthic PAR flux based on continuous above-water and near-surface inwater PAR measurements fails to correctly reflect seasonal trends for near-bottom PAR. Analysis of the time series data suggests that estimates of the vertical attenuation coefficient for PAR (k PAR ) values from ship-based measurements are biased to calmer conditions while variations in the vertical profile of light attenuation prevent accurate estimates of benthic PAR from near-surface or above-water measurements. Accurate estimates of the benthic light field and BPP over the annual cycle require in situ, continuous, high-resolution near-bottom measurements provided by ocean observatories.

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Section: Benthic Particulate Organic Matter and Chl Amentioning

confidence: 99%

Section: Benthic Particulate Organic Matter and Chl Amentioning

confidence: 99%

Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high‐resolution, continuous in situ PAR records

et al. 2008

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“…Continental shelf sediments play a vital role in biogeochemical cycling, accumulating and burying organic matter (Jahnke et al 2005;Woulds et al 2007). Shelf sediments receive up to 50% of primary productivity from the overlying surface waters (Stahl et al 2004a), and as this source of carbon reaches the benthos it is recycled, mineralised or buried (Canfield et al 1993;Glud 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Advective permeable sediments are estimated to cover over 70% of the coastal shelf (de Haas et al 2002;Glud 2008;Hall 2002), yet benthic process studies on sandy sediments are relatively sparse compared to cohesive sediments, partly due to the difficulty in sampling intact and undisturbed sand cores (Jahnke et al 2005;Rao et al 2007). In addition, ex situ incubation experiments designed for cohesive sediment dynamics can be less effective in permeable sediments as they may restrict advective flow and hence affect solute transport and the distribution of these compounds within the sediment (Ehrenhauss et al 2004;Huettel and Webster 2001;Tengberg et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Most studies that have examined the vertical distribution of oxygen and variability in uptake rates in continental sediments have focused on single study sites (Janssen et al 2005;Stahl et al 2004c) or sediment types Huettel et al 1996;Jahnke et al 2005;Stahl et al 2004c); or one sampling time point along a transect in a specific study area (Hartnett et al 1998). Very few studies (Berelson et al 2003;Fuchsman et al 2015;Neubacher et al 2012) have systematically investigated seasonal variability of benthic oxygen dynamics and carbon cycling across several sediment types.…”

Section: Introductionmentioning

confidence: 99%

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Oxygen dynamics in shelf seas sediments incorporating seasonal variability

et al. 2017

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Shelf sediments play a vital role in global biogeochemical cycling and are particularly important areas of oxygen consumption and carbon mineralisation. Total benthic oxygen uptake, the sum of diffusive and faunal mediated uptake, is a robust proxy to quantify carbon mineralisation. However, oxygen uptake rates are dynamic, due to the diagenetic processes within the sediment, and can be spatially and temporally variable. Four benthic sites in the Celtic Sea, encompassing gradients of cohesive to permeable sediments, were sampled over four cruises to capture seasonal and spatial changes in oxygen dynamics. Total oxygen uptake (TOU) rates were measured through a suite of incubation experiments and oxygen microelectrode profiles were taken across all four benthic sites to provide the oxygen penetration depth and diffusive oxygen uptake (DOU) rates. The difference between TOU and DOU allowed for quantification of the fauna mediated oxygen uptake and diffusive uptake. High resolution measurements showed clear seasonal and spatial trends, with higher oxygen uptake rates measured in cohesive sediments compared to the permeable sediment. The significant differences in oxygen dynamics between the sediment types were consistent between seasons, with increasing oxygen consumption during and after the phytoplankton bloom. Carbon mineralisation in shelf sediments is strongly influenced by sediment type and seasonality.

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Radium isotopes as a tracer of sediment‐water column exchange in the North Sea

Burt

Thomas

Pätsch

et al. 2014

Global Biogeochemical Cycles

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Sediment-water column exchange plays an important role in coastal biogeochemistry. We utilize short-lived radium isotopes ( 224 Ra and 223 Ra) to understand and quantify the dominant processes governing sediment-water column exchange throughout the North Sea. Our comprehensive survey, conducted in September 2011, represents the first of its kind conducted in the North Sea. We find that two main sources regulate surface Ra distributions: minor coastal input from rivers and shallow mudflats and North Sea sediments as the dominant source. Pore waters show 100-fold larger activities than the water column. North Sea sediment characteristics such as porosity and mean grain size, as well as turbulence at the sediment-water interface, are the dominant factors contributing to variability of Ra efflux. Ra inventory and mass balance approaches consistently yield high benthic Ra effluxes in the southern North Sea, driven by strong tidal and wind mixing, which in turn cause high sediment irrigation rates. These results exceed incubation-based Ra flux estimates and the majority of previously reported Ra flux estimates for other regions. Ra-based estimates of benthic alkalinity fluxes compare well to observed values, and the high rates of Ra efflux imply a potentially significant exchange of other products of sedimentary reactions, including carbon and nutrient species. Passive tracer simulations lend strong support to the Ra source attribution and imply seasonal variation in the surface water Ra distribution depending on stratification conditions.

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Organic matter remineralization and porewater exchange rates in permeable South Atlantic Bight continental shelf sediments

Cited by 99 publications

References 31 publications

Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high‐resolution, continuous in situ PAR records

Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high‐resolution, continuous in situ PAR records

Oxygen dynamics in shelf seas sediments incorporating seasonal variability

Radium isotopes as a tracer of sediment‐water column exchange in the North Sea

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