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Benthic Flux

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William M Berelson – 1st expert on this subject based on the ideXlab platform

  • Dissolved oxygen and suspended particles regulate the Benthic Flux of iron from continental margins
    Marine Chemistry, 2020
    Co-Authors: William B Homoky, William M Berelson, Silke Severmann, James Mcmanus, Timothy E Riedel, P J Statham, Rachel A Mills

    Abstract:

    We present ex situ sediment incubation results from the California and Oregon shelves and compare the calculated Benthic Flux of dissolved Fe with those from in situ incubations and pore water concentration profiles. We also examine the influence of oxygen depletion and sediment re-suspension on Benthic Fe exchange. Ex situ incubation of the California and Oregon shelf sites yielded average Benthic Fe Fluxes of 3.5 and 8.3μmolm
    -2day
    -1, respectively, compared to 17 and 55μmolm
    -2day
    -1 from the in situ Lander determinations, and 73 and 103μmolm
    -2day
    -1 from modeling of pore water concentration profiles. Differences between Benthic Fe Flux estimates are primarily accounted for by [1] differences in Fe (II) oxidation kinetics, which result from distinct oxygen consumption rates between incubation methods, and the absence of kinetic considerations in the overlying bottom water in pore water Flux calculations, and [2] the effects of biological sediment irrigation that are best represented by in situ incubations due to their sampling area and preservation of bottom water conditions. Bottom water oxygen concentrations were higher at the California shelf site than that at the Oregon shelf site, and probably accounted for the greater discrepancy between methods used to determine Benthic Fe Flux. The comparison of techniques used to determine Benthic Fe Flux indicates that the concentration of bottom water oxygen exerts a principle control over the fate of dissolved Fe entering the overlying bottom water – supporting the view that the expansion of coastal hypoxia has the potential to enhance the Benthic supply of Fe (II) to shelf waters. An episode of surface sediment re-suspension during ex situ incubation led to a rapid removal of 76-89% of dissolved Fe from seawater, followed by a steady return towards initial seawater concentrations during particle settling, indicating that diffusive inputs of dissolved Fe from sediment pore water are rapidly adsorbed and desorbed by particles during periods of Benthic re-suspension. The findings suggest that dissolved Fe concentrations in bottom waters may reflect an equilibrium concentration of non-stabilized aqueous Fe and particle-adsorbed Fe phases – where the addition of suspended particles to bottom waters leads to scavenging of dissolved Fe into labile particulate Fe phases. Thus we suggest that suspended particles are a significant buffer of dissolved Fe released from shelf sediments, an important transport mechanism for Benthic Fe inputs, and a regulator of dissolved Fe concentrations in seawater. © 2012 Elsevier B.V

  • spatial patterns of Benthic silica Flux in the north pacific reflect upper ocean production
    Deep Sea Research Part I: Oceanographic Research Papers, 2019
    Co-Authors: Douglas E Hammond, William M Berelson, Nathaniel Kemnitz, Jess F Adkins, Abby Lunstrum

    Abstract:

    Diatoms are the dominant algal group that cycles dissolved silicic acid in the ocean; they also play an important role in the oceanic carbon cycle. It is therefore important to quantify the spatial distribution of silica cycling for defining global ocean biogeochemical cycles. On the research cruise CDisK-IV, water samples and sediment cores were collected at 5 stations along a North Pacific transect near 150oW from 22oN to 50oN to evaluate Benthic remineralization rates of biogenic silica (bSi). Two independent methods, core incubation and diffusive transport based on porewater profiles, were utilized to estimate Benthic silicic acid Fluxes, and these independent methods yield Fluxes that agree within uncertainties. The Benthic Fluxes are reported as 0.04 ± 0.01, 0.04 ± 0.01, 0.05 ± 0.01, 0.67 ± 0.14, 0.40 ± 0.08 mmol Si m^(−2) day^(−1) for Stations 1 to 5, south to north, respectively. Burial Fluxes were estimated using measurements of solid phase bSi in sediments and literature values of sediment accumulation rate. Burial efficiencies of bSi at all stations were <5% and show reasonable agreement with previous estimates. When burial rates were added to Benthic Fluxes to calculate rain rates, the rain observed under the subarctic gyre (Stations 4–5), was far larger than in the lower latitudes of the subtropics (Stations 1–3), corresponding to higher surface diatom productivity at higher latitudes. At the two northern stations, the bottom 500 m of the water column shows a near-bottom increase in silicic acid that is consistent with the measured Benthic Flux and the estimated vertical eddy diffusivity. Above this horizon, water column density stratification increases and vertical diffusivity decreases, but the silicic acid gradient decreases. This reduction in gradient indicates that above this horizon, horizontal transport by deep waters, rather than vertical diffusion, becomes the dominant process removing the silicic acid released by Benthic remineralization.

  • vitamin b1 in marine sediments pore water concentration gradient drives Benthic Flux with potential biological implications
    Frontiers in Microbiology, 2015
    Co-Authors: Danielle R Monteverde, William M Berelson, Laura Gomezconsarnau, Lynda S Cutter, Lauren Chong, Sergio A Sanudowilhelmy

    Abstract:

    Vitamin B1, or thiamin, can limit primary productivity in marine environments, however the major marine environmental sources of this essential coenzyme remain largely unknown. Vitamin B1 can only be produced by organisms that possess its complete synthesis pathway, while other organisms meet their cellular B1 quota by scavenging the coenzyme from exogenous sources. Due to high bacterial cell density and diversity, marine sediments could represent some of the highest concentrations of putative B1 producers, yet these environments have received little attention as a possible source of B1 to the overlying water column. Here we report the first dissolved pore water profiles of B1 measured in cores collected in two consecutive years from Santa Monica Basin, CA. Vitamin B1 concentrations were fairly consistent between the two years ranging from 30 pM up to 770 pM. A consistent maximum at ~5 cm sediment depth covaried with dissolved concentrations of iron. Pore water concentrations were higher than water column levels and represented some of the highest known environmental concentrations of B1 measured to date, (over two times higher than maximum water column concentrations) suggesting increased rates of cellular production and release within the sediments. A one dimensional diffusion-transport model applied to the B1 profile was used to estimate a diffusive Benthic Flux of ~0.7 nmol m 2 d-1. This is an estimated Flux across the sediment-water interface in a deep sea basin; if similar magnitude B-vitamin Fluxes occur in shallow coastal waters, Benthic input could prove to be a significant B1-source to the water column and may play an important role in supplying this organic growth factor to auxotrophic primary producers.

Stefano Covelli – 2nd expert on this subject based on the ideXlab platform

  • Mobility of heavy metals from polluted sediments of a semi-enclosed basin: in situ Benthic chamber experiments in Taranto’s Mar Piccolo (Ionian Sea, Southern Italy)
    Environmental Science and Pollution Research, 2016
    Co-Authors: Andrea Emili, Stefano Covelli, Alessandro Acquavita, Lucia Spada, Santina Giandomenico, Nicola Cardellicchio

    Abstract:

    In situ Benthic Flux experiments were conducted at two stations in the Mar Piccolo of Taranto (Italy), one of the most industrialised and contaminated coastal areas of the Mediterranean. Sediments of the two stations are notably different in their trace metal content, with a station closer to a Navy harbour showing higher mean concentrations of almost all investigated metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn). Conversely, both stations are characterised by significant Hg contamination, compared to the local baseline. Results of a sequential extraction scheme on surface sediments suggest a relatively scarce mobility of the examined metals (Zn > Ni > Cr > As > Cu > Pb). A Hg-specific extraction procedure showed that most of the element (93.1 %) occurs in a fraction comprising Hg bound to Fe/Mn oxi-hydroxides. Reduction of these oxides may affect Hg remobilisation and redistribution. Porewater profiles of dissolved trace metals were quite similar in the two sites, although significant differences could be observed for Al, Cu, Fe and Hg. The highest diffusive Fluxes were observed for As, Fe and Mn. Mobility rates of several trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) were directly measured at the sediment–water interface. Results from Benthic in situ incubation experiments showed increasing dissolved metal concentrations with time, resulting in higher Fluxes for Cu, Fe, Hg, V and Zn in the most contaminated site. Conversely, Fluxes of Mn, Ni and Pb were comparable between the two stations. The estimated Flux of Hg (97 μg m^−2 day^−1) was the highest observed among similar experiments conducted in other highly contaminated Mediterranean coastal environments. Benthic Fluxes could be partially explained by considering rates of organic matter remineralisation, dissolution of Fe/Mn oxy-hydroxides and metal speciation in sediments. Seasonal and spatial variation of biogeochemical parameters can influence metal remobilisation in the Mar Piccolo area. In particular, metals could be promptly remobilised as a consequence of oxygen depletion, posing a serious concern for the widespread fishing and mussel farming activities in the area.

  • Benthic Flux measurements of hg species in a northern adriatic lagoon environment marano and grado lagoon italy
    Estuarine Coastal and Shelf Science, 2012
    Co-Authors: Andrea Emili, Stefano Covelli, Jadran Faganeli, Milena Horvat, Alessandro Acquavita, Neža Koron, Suzana žižek, Vesna Fajon

    Abstract:

    As part of the “MIRACLE” project, the biogeochemical cycling of mercury (Hg) at the sediment–water interface was studied in the field in the Marano and Grado Lagoon (Northern Adriatic Sea). Seasonal investigations were conducted at selected experimental sites, where Manila Clams (Tapes philippinarum) were previously seeded. Measurements were performed seasonally during three campaigns, using two Benthic chambers, one transparent and one dark, to evaluate the effect of light on Hg cycling. Total dissolved Hg (THg), methylmercury (MeHg), and dissolved gaseous Hg (DGM) species were considered. Diurnal Benthic Fluxes were found to significantly exceed the diffusive Fluxes at all stations. The assessment of the annual recycling of Hg species from sediments to the water column showed that up to 99% of MeHg is recycled annually to the water column, while Hg recycling ranges from 30 to 60%. MeHg poses the higher risk for potential bioaccumulation in clams, but it is partially mitigated by Hg reduction, which seems to be an important process leading to evasion losses of Hg from these environments. Estimated Benthic Fluxes suggest that Hg recycling at the sediment–water interface is more active in the Grado sector. Hence, based on the estimated release of MeHg from sediments, it is suggested that the western sector seems to be more suitable for clam farming and the extension of rearing activities.

  • does anoxia affect mercury cycling at the sediment water interface in the gulf of trieste northern adriatic sea incubation experiments using Benthic Flux chambers
    Applied Geochemistry, 2011
    Co-Authors: Andrea Emili, Stefano Covelli, Jadran Faganeli, Alessandro Acquavita, Neža Koron, S. Predonzani, Cinzia De Vittor

    Abstract:

    Abstract Coastal areas in the northernmost part of the Adriatic Sea (Gulf of Trieste and the adjacent Grado Lagoon) are characterized by high levels of Hg, both in sediments and in the water column, mainly originating from the suspended material inflowing through the Isonzo/Soca River system, draining the Idrija (NW Slovenia) mining district, into the Gulf of Trieste. Hypoxic and anoxic conditions at the sediment–water interface (SWI) are frequently observed in the Gulf of Trieste and in the lagoon, due to strong late summer water stratification and high organic matter input. Mercury mobility at the SWI was investigated at three sampling points located in the Gulf of Trieste (AA1, CZ) and in the Grado Lagoon (BAR). Experiments were conducted under laboratory conditions at in situ temperature, using a dark Flux chamber simulating an oxic–anoxic transition. Temporal variations of dissolved Hg and methylmercury (MeHg) as well as O2, NH 4 + , NO 3 – + NO 2 – , PO 4 3 – , H2S, dissolved Fe and Mn, dissolved inorganic C (DIC) and dissolved organic C (DOC) were monitored simultaneously. Benthic Hg Fluxes were higher under anoxic conditions than in the oxic phase of the experiment. Methyl Hg release was less noticeable (low or absent) in the oxic phase, probably due to similar methylation and demethylation rates, but high in the anoxic phase of the experiment. The MeHg Flux was linked to SO4 reduction and dissolution of Fe (and Mn) oxyhydroxides, and formation of sulphides. Re-oxygenation was studied at sampling point CZ, where concentrations of MeHg and Hg dropped rapidly probably due to re-adsorption onto Fe (Mn) oxyhydroxides and enhanced demethylation. Sediments, especially during anoxic events, should be, hence, considered as a primary source of MeHg for the water column in the northern Adriatic coastal areas.

Andrea Emili – 3rd expert on this subject based on the ideXlab platform

  • Mobility of heavy metals from polluted sediments of a semi-enclosed basin: in situ Benthic chamber experiments in Taranto’s Mar Piccolo (Ionian Sea, Southern Italy)
    Environmental Science and Pollution Research, 2016
    Co-Authors: Andrea Emili, Stefano Covelli, Alessandro Acquavita, Lucia Spada, Santina Giandomenico, Nicola Cardellicchio

    Abstract:

    In situ Benthic Flux experiments were conducted at two stations in the Mar Piccolo of Taranto (Italy), one of the most industrialised and contaminated coastal areas of the Mediterranean. Sediments of the two stations are notably different in their trace metal content, with a station closer to a Navy harbour showing higher mean concentrations of almost all investigated metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn). Conversely, both stations are characterised by significant Hg contamination, compared to the local baseline. Results of a sequential extraction scheme on surface sediments suggest a relatively scarce mobility of the examined metals (Zn > Ni > Cr > As > Cu > Pb). A Hg-specific extraction procedure showed that most of the element (93.1 %) occurs in a fraction comprising Hg bound to Fe/Mn oxi-hydroxides. Reduction of these oxides may affect Hg remobilisation and redistribution. Porewater profiles of dissolved trace metals were quite similar in the two sites, although significant differences could be observed for Al, Cu, Fe and Hg. The highest diffusive Fluxes were observed for As, Fe and Mn. Mobility rates of several trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) were directly measured at the sediment–water interface. Results from Benthic in situ incubation experiments showed increasing dissolved metal concentrations with time, resulting in higher Fluxes for Cu, Fe, Hg, V and Zn in the most contaminated site. Conversely, Fluxes of Mn, Ni and Pb were comparable between the two stations. The estimated Flux of Hg (97 μg m^−2 day^−1) was the highest observed among similar experiments conducted in other highly contaminated Mediterranean coastal environments. Benthic Fluxes could be partially explained by considering rates of organic matter remineralisation, dissolution of Fe/Mn oxy-hydroxides and metal speciation in sediments. Seasonal and spatial variation of biogeochemical parameters can influence metal remobilisation in the Mar Piccolo area. In particular, metals could be promptly remobilised as a consequence of oxygen depletion, posing a serious concern for the widespread fishing and mussel farming activities in the area.

  • Benthic Flux measurements of hg species in a northern adriatic lagoon environment marano and grado lagoon italy
    Estuarine Coastal and Shelf Science, 2012
    Co-Authors: Andrea Emili, Stefano Covelli, Jadran Faganeli, Milena Horvat, Alessandro Acquavita, Neža Koron, Suzana žižek, Vesna Fajon

    Abstract:

    As part of the “MIRACLE” project, the biogeochemical cycling of mercury (Hg) at the sediment–water interface was studied in the field in the Marano and Grado Lagoon (Northern Adriatic Sea). Seasonal investigations were conducted at selected experimental sites, where Manila Clams (Tapes philippinarum) were previously seeded. Measurements were performed seasonally during three campaigns, using two Benthic chambers, one transparent and one dark, to evaluate the effect of light on Hg cycling. Total dissolved Hg (THg), methylmercury (MeHg), and dissolved gaseous Hg (DGM) species were considered. Diurnal Benthic Fluxes were found to significantly exceed the diffusive Fluxes at all stations. The assessment of the annual recycling of Hg species from sediments to the water column showed that up to 99% of MeHg is recycled annually to the water column, while Hg recycling ranges from 30 to 60%. MeHg poses the higher risk for potential bioaccumulation in clams, but it is partially mitigated by Hg reduction, which seems to be an important process leading to evasion losses of Hg from these environments. Estimated Benthic Fluxes suggest that Hg recycling at the sediment–water interface is more active in the Grado sector. Hence, based on the estimated release of MeHg from sediments, it is suggested that the western sector seems to be more suitable for clam farming and the extension of rearing activities.

  • does anoxia affect mercury cycling at the sediment water interface in the gulf of trieste northern adriatic sea incubation experiments using Benthic Flux chambers
    Applied Geochemistry, 2011
    Co-Authors: Andrea Emili, Stefano Covelli, Jadran Faganeli, Alessandro Acquavita, Neža Koron, S. Predonzani, Cinzia De Vittor

    Abstract:

    Abstract Coastal areas in the northernmost part of the Adriatic Sea (Gulf of Trieste and the adjacent Grado Lagoon) are characterized by high levels of Hg, both in sediments and in the water column, mainly originating from the suspended material inflowing through the Isonzo/Soca River system, draining the Idrija (NW Slovenia) mining district, into the Gulf of Trieste. Hypoxic and anoxic conditions at the sediment–water interface (SWI) are frequently observed in the Gulf of Trieste and in the lagoon, due to strong late summer water stratification and high organic matter input. Mercury mobility at the SWI was investigated at three sampling points located in the Gulf of Trieste (AA1, CZ) and in the Grado Lagoon (BAR). Experiments were conducted under laboratory conditions at in situ temperature, using a dark Flux chamber simulating an oxic–anoxic transition. Temporal variations of dissolved Hg and methylmercury (MeHg) as well as O2, NH 4 + , NO 3 – + NO 2 – , PO 4 3 – , H2S, dissolved Fe and Mn, dissolved inorganic C (DIC) and dissolved organic C (DOC) were monitored simultaneously. Benthic Hg Fluxes were higher under anoxic conditions than in the oxic phase of the experiment. Methyl Hg release was less noticeable (low or absent) in the oxic phase, probably due to similar methylation and demethylation rates, but high in the anoxic phase of the experiment. The MeHg Flux was linked to SO4 reduction and dissolution of Fe (and Mn) oxyhydroxides, and formation of sulphides. Re-oxygenation was studied at sampling point CZ, where concentrations of MeHg and Hg dropped rapidly probably due to re-adsorption onto Fe (Mn) oxyhydroxides and enhanced demethylation. Sediments, especially during anoxic events, should be, hence, considered as a primary source of MeHg for the water column in the northern Adriatic coastal areas.