Benthic flux of biogenic elements on the Southeastern US continental shelf: influence of pore water advective transport and benthic microalgae

Jahnke, Richard A.; Nelson, James R.; Marinelli, Roberta L.; Eckman, James E.

doi:10.1016/s0278-4343(99)00063-1

Cited by 179 publications

(128 citation statements)

References 23 publications

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“…GPP 80 rates for the 1-to 5-m sites (44-490 mg C m Ϫ2 d Ϫ1 ) are within the range of those reported for littoral and intertidal sediments in temperate areas (Underwood and Kromkamp 1999). However, it is more interesting to com- Gillespie et al 2000), as well as those measured for sandy shelf sediments in North Carolina and Georgia at 14-40 m (250-400 mg C m Ϫ2 d Ϫ1 ) (Cahoon and Cooke 1992;Jahnke et al 2000). Whether these differences are due to differences in microphytobenthic biomass (Chl a) we do not know, since we used HPLC, while most of the cited studies used spectrophotometry.…”

Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 73%

“…On an ecosystem scale, the regulating role of MPB should be particularly important in shallow (microtidal) areas, where a large portion of the benthos is within the photic zone (e.g., in the Adriatic Sea [Blackford 2002] and the Kattegat [Granéli and Sundbäck 1986;Sundbäck et al 1991]). Similar conditions also exist on continental shelf sediments off macrotidal coasts (e.g., Jahnke et al 2000) and on subtidal sediments in clear-water tropical areas. Therefore, when studying benthic nutrient turnover in such areas, the role of MPB must be taken into account.…”

Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 55%

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Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Sundbäck

Linares

Larson

et al. 2004

Limnology & Oceanography

128

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In littoral sediments, microphytobenthic (MPB) nitrogen assimilation often exceeds nitrogen removal by denitrification, partly because MPB activity suppresses denitrification. Little is known about the balance between these two processes at sublittoral depths. Benthic pigment composition, light and dark oxygen, and nutrient fluxes (NO 3 Ϫ , NH 4 ϩ , dissolved organic nitrogen (DON), PO , Si(OH) 4 ), as well as denitrification were measured between 1 and 3Ϫ 4 15 m in depth in Gullmar Fjord (Skagerrak) in spring and autumn. The hypothesis was that the assimilation/ denitrification ratio would decrease with depth, along with decreasing MPB activity caused by light limitation. MPB photosynthesis occurred along the entire depth gradient, although sediments were net autotrophic only above 5 m. Inorganic nitrogen (DIN) (and silica) flux changed along the depth gradient, the general pattern being sediment uptake at Յ5 m and efflux at Ն10 m depth. DON flux (ϳ50% of total dissolved nitrogen flux) showed a less clear pattern. Two trends regarding DIN fluxes and denitrification-significant light effects and negative correlations with gross primary productivity-showed that MPB activity influenced nitrogen (N) turnover. Although denitrification increased with depth, rates remained low (Ͻ0.4 mmol N m Ϫ2 d Ϫ1 ), and MPB assimilation (0.2-3.6 mmol N m Ϫ2 d Ϫ1 ) exceeded or equaled denitrification. MPB incorporated ϳ35% of the remineralized N along the depth gradient, whereas denitrification removed ϳ20%. Thus, the influence of MPB on benthic nitrogen turnover, denitrification included, extends to sublittoral depths. Further, denitrification does not necessarily remove more N in the deeper, heterotrophic part of the photic zone, compared to the littoral, autotrophic zone.

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Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 73%

Section: Autotrophy and Heterotrophy Along The Depth Gradient-supporting

confidence: 55%

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Sundbäck

Linares

Larson

et al. 2004

Limnology & Oceanography

128

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“…The 27 m isobath approximates the area-weighted mean depth of the entire SAB shelf area. Previous deployments conducted in 1996 as described in the paper by Jahnke et al [2000] are included here for comparison. Chamber measurements are also compared to sensor measurements from the adjacent SABSOON observatory sites.…”

Section: In Situ Light/dark Benthic Experimental Chamber Instrument (mentioning

confidence: 99%

“…Once the instrument was placed on the seafloor and the surface float was released from the ship, a hydraulic system closed the chamber lids and started the incubation. At preset time intervals (generally 19 to 25 min), an automated sampler [Jahnke et al, 2000] removed 50 mL samples of chamber waters for subsequent shipboard analysis (several samples for Winkler calibration of the O 2 sensor readings and the remaining samples for nutrient analysis and determination of chamber volume; see below). Samples for calibration of the O 2 sensors were collected in 11 mL glass ampules connected in-line with the 50 mL sampling syringes.…”

Section: In Situ Light/dark Benthic Experimental Chamber Instrument (mentioning

confidence: 99%

“…Recent studies have revealed that benthic primary productivity (BPP) can be an important process influencing carbon cycling on continental shelves [Jahnke et al, 2000;Gattuso et al, 2006]. While direct measurements via paired light/ dark benthic chamber experiments convincingly demonstrate the occurrence of BPP, assessment of the integrated BPP over time periods of weeks to years requires an accurate knowledge of the magnitude and variability of the light flux to the seafloor.…”

Section: Introductionmentioning

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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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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Benthic flux of biogenic elements on the Southeastern US continental shelf: influence of pore water advective transport and benthic microalgae

Cited by 179 publications

References 23 publications

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

Benthic nitrogen fluxes along a depth gradient in a microtidal fjord: The role of denitrification and microphytobenthos

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

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

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