This data product comprises 5 files, containing marine sediment pore water and solid phase leachate silicon (Si) isotopic and element concentration data, as well as benthic silica flux magnitudes derived from core incubation experiments and sediment biogenic silica contents. Samples were collected over three cruises of the Changing Arctic Ocean Seafloor (ChAOS) project summer sampling campaigns in the Barents Sea between 2017 and 2019 aboard the RRS James Clark Ross (cruises JR16006, JR17007 and JR18006). The aim of this study was to improve our mechanistic understanding of the cycling of Si within the Arctic Ocean seafloor through measurement of stable Si isotopes in the dissolved Si pool and the solid phase sources.
This project was part of the Changing Arctic Ocean programme, funded by the Natural Environment Research Council (NERC) (grant no. NE/P005942/1).
Arctic Ocean, Barents Sea, benthic flux, biogenic silica, core incubation, pore water, silicon isotopes
Ward, J., Henley, S., Faust, J., & Sales de Freitas, F. (2021). Benthic silica flux magnitudes and silicon isotopic composition of marine sediment pore waters and solid phase leachates for the Barents Sea (summer 2017-2019) (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/8933af23-e051-4166-b63e-2155330a21d8
|Use Constraints:||Data released under Open Government Licence V3.0: http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/.|
|ISO Topic Categories:||
|Organisation||British Antarctic Survey|
|Name||Mr James P J Ward|
|Organisation||University of Bristol|
|Name||Dr Sian F Henley|
|Organisation||University of Edinburgh|
|Name||Dr Johan C Faust|
|Organisation||University of Bremen|
|Name||Dr Felipe Sales de Freitas|
|Organisation||University of Bristol|
|Reference:||DeMaster, D. (1981). The supply and accumulation of silica in the marine environment. Geochimica et Cosmochimica Acta, 45(10):1715-1732. https://doi.org/10.1016/0016-7037(81)90006-5.
De Souza, G. F., Reynolds, B. C., Rickli, J., Frank, M., Saito, M. A., Gerringa, L. J., and Bourdon, B. (2012). Southern Ocean control of silicon stable isotope distribution in the deep Atlantic Ocean. Global Biogeochemical Cycles, 26(2):GB2035. https://doi.org/10.1029/2011GB004141.
Faust, J. C., Tessin, A., Fisher, B. J., Zindorf, M., Papadaki, S., Hendry, K. R., Doyle, K. A., and Maerz, C. (2021). Millennial scale persistence of organic carbon bound to iron in Arctic marine sediments. Nature Communications, 12(275). https://doi.org/10.1038/s41467-020-20550-0.
Freitas, F. S., Hendry, K. R., Henley, S. F., Faust, J. C., Tessin, A. C., Stevenson, M. A., Abbott, G. D., Maerz, C., and Arndt, S. (2020). Benthic-pelagic coupling in the Barents Sea: an integrated data-model framework. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 378(20190359). https://doi.org/10.1098/rsta.2019.0359.
Georg, R. B., Reynolds, B. C., Frank, M., and Halliday, A. N. (2006). New sample preparation techniques for the determination of Si isotopic compositions using MC-ICPMS. Chemical Geology, 235(1-2):95-104. https://doi.org/10.1016/j.chemgeo.2006.06.006.
Grasse, P., Brzezinski, M. A., Cardinal, D., De Souza, G. F., Andersson, P., Closset, I., Cao, Z., Dai, M., Ehlert, C., Estrade, N., Francois, R., Frank, M., Jiang, G., Jones, J. L., Kooijman, E., Liu, Q., Lu, D., Pahnke, K., Ponzevera, E., Schmitt, M., Sun, X., Sutton, J. N., Thil, F., Weis, D., Wetzel, F., Zhang, A., Zhang, J., and Zhang, Z. (2017). GEOTRACES inter-calibration of the stable silicon isotope composition of dissolved silicic acid in seawater. Journal of Analytical Atomic Spectrometry, 32(3):562-578. https://doi.org/10.1039/C6JA00302H.
Hendry, K. R. and Andersen, M. B. (2013). The zinc isotopic composition of siliceous marine sponges: Investigating nature's sediment traps. Chemical Geology, 354:33-41. https://doi.org/10.1016/j.chemgeo.2013.06.025.
Hendry, K. R., Leng, M. J., Robinson, L. F., Sloane, H. J., Blusztjan, J., Rickaby, R. E., Georg, R. B., and Halliday, A. N. (2011). Silicon isotopes in Antarctic sponges: An interlaboratory comparison. Antarctic Science, 23:34-42. https://doi.org/10.1017/S0954102010000593.
Hendry, K. R. and Robinson, L. F. (2012). The relationship between silicon isotope fractionation in sponges and silicic acid concentration: Modern and core-top studies of biogenic opal. Geochimica et Cosmochimica Acta, 81:1-12. https://doi.org/10.1016/j.gca.2011.12.010.
Karl, D. M. and Tien, G. (1992). MAGIC: A sensitive and precise method for measuring dissolved phosphorus in aquatic environments. Limnology and Oceanography, 37(1):105-116. https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1992.37.1.0105.
Kim, J., Dong, H., Seabaugh, J., Newell, S. W., and Eberl, D. D. (2004). Role of Microbes in the Smectite-to-illite Reaction. Science, 303. https://doi.org/10.1126/science.1093245.
Koning, E., Epping, E., and Van Raaphorst, W. (2002). Determining biogenic silica in marine samples by tracking silicate and aluminium concentrations in alkaline leaching solutions. Aquatic Geochemistry, 8:37-67. https://doi.org/10.1023/A:1020318610178.
Middag, R., de Baar, H. J., Laan, P., and Bakker, K. (2009). Dissolved aluminium and the silicon cycle in the Arctic Ocean. Marine Chemistry, 115(3-4):176-195. https://doi.org/10.1016/j.marchem.2009.08.002.
Mortlock, R. A. and Froelich, P. N. (1989). A simple method for the rapid determination of biogenic opal in pelagic marine sediments. Deep Sea Research Part A, Oceanographic Research Papers, 36(9):1415-1426. https://doi.org/10.1016/0198-0149(89)90092-7.
Pickering, R., Cassarino, L., Hendry, K., Wang, X., Maiti, K., and Krause, J. (2020). Using Stable Isotopes to Disentangle Marine Sedimentary Signals in Reactive Silicon Pools. Geophysical Research Letters, 47(15). https://doi.org/10.1029/2020GL087877.
Rahn, K. A. (1976). Silicon and aluminum in atmospheric aerosols: Crust-air fractionation? Atmospheric Environment (1967), 10:597-601. https://doi.org/10.1016/0004-6981(76)90044-5.
Ren, H., Brunelle, B. G., Sigman, D. M., and Robinson, R. S. (2013). Diagenetic aluminum uptake into diatom frustules and the preservation of diatom-bound organic nitrogen. Marine Chemistry, 155:92-101. https://doi.org/10.1016/j.marchem.2013.05.016.
Strickland, J. and Parsons, T. (1972). A Practical Handbook of Seawater Analysis, volume 167. Fisheries Research Board of Canada. https://epic.awi.de/id/eprint/39262/1/Strickland-Parsons_1972.pdf.
van Bennekom, A. J., Fred Jansen, J. H., van der Gaast, S. J., van Iperen, J. M., and Pieters, J. (1989). Aluminium-rich opal: an intermediate in the preservation of biogenic silica in the Zaire (Congo) deep-sea fan. Deep Sea Research Part A, Oceanographic Research Papers, 36(2):173-190. https://doi.org/10.1016/0198-0149(89)90132-5.
|Lineage:||ChAOS_1_Pore_Water_DSi: dissolved silicic acid (DSi) concentrations of pore water extracted from sediment cores collected from 6 stations (B03, B13, B14, B15, B16, B17). Three separate Multicorer deployments were carried out at each station for all three cruise years, denoted by the event number. Samples were combined from 4 separate cores of each Multicorer deployment to ensure adequate sample volume was collected. Samples were stored in the dark at 4°C and analysed within 12 hours of collection. Core top water samples were extracted first from sediment cores sampled with the Multicorer, followed by the pore water samples. Pore waters were extracted with Rhizon filters, attached to 30mL plastic syringes using spacers to create a vacuum (resolution of 1 cm from 0.5-2.5 cm below seafloor (cmbsf), 2 cm to 20.5 cmbsf and 5 cm to 35.5 cmbsf), placed in pre-drilled coring tube holes and collected in acid cleaned bottles, which were then acidified with Romil UpA HCl. On-board measurements of DSi concentrations in the pore water samples were carried out with a Lachat Quickchem 8500 flow injection autoanalyzer using certified reference materials for sea water to define the accuracy (KANSO Ltd., Japan), which averaged 2.8% across the three cruises (1.5-5%).
ChAOS_2_Pore_Water_Isotopes: Si isotopic composition of the pore water DSi pool (delta30SiDSi-PW per mil). Samples from one Multicorer deployment from each station and cruise year were sampled for isotopic analysis. B13, B14 and B15 were selected for isotopic analysis as they span the three main hydrographic domains of the Barents Sea (Atlantic Water, Oceanic Polar Front, Arctic Water). Isotopic composition is given in delta notation as a deviation relative to NBS28 Si standard in units of per mil. This sheet also includes pore water NO3- and Fe concentrations, previously published in Freitas et al., (2020) and Faust et al., (2021) respectively. Isotopic analysis was carried out in a clean setting in the Bristol Isotope Group (BIG) laboratory at the University of Bristol. Samples were concentrated using the Mg-induced co-precipitation method (MAGIC) of Karl and Tien (1992) and De Souza et al., (2012). Concentrated samples were then passed through cation exchange columns (Georg et al., 2006) filled with a Bio-Rad AG50W-X12 resin to remove cations. Samples were then doped with H2SO4 (ROMIL-UpA) and 1 M HCl (in-house distilled) prior to isotopic analysis to counteract any potential anionic matrix effects. Isotope data quality was assessed through plotting delta29Si vs delta30Si. Data included in this archive were found to lie along a line of gradient 0.5119, in between that expected of kinetic and equilibrium Si isotopic fractionation. In addition, 71% of samples were measured in duplicate or triplicate (see 'n' for number of replicate measurements of a given sample and ±2 sigma for the standard deviation) and reference Si standards were analysed every 5 samples to determine the long term reproducibility. Measured standards in this study (Diatomite +1.24 ±0.14 per mil (n=116); LMG08 -3.47 ±0.13 per mil (n=46); ALOHA1000 =1.23 ±0.17 per mil (n=30)) agree well with published values (+1.26 ±0.2 per mil; -3.43 ±0.15 per mil; +1.24 ±0.2 per mil respectively) (Hendry et al., 2011; Hendry and Robinson, 2012 ; Grasse et al., 2017).
ChAOS_3_Core_Incubation: results of core incubation experiments carried out on-board (JR18006) for cores collected from stations B03, B13, B14, B15 and B16 to quantify the magnitude of the benthic flux of DSi. Includes DSi concentrations for samples extracted from the core top water at 3 hourly intervals over 24 hours and the Si isotopic composition (delta30SiInc per mil) of such samples at time 0hr, 3hr and 24hr. For B15, 0/6 hr and 21/24 hr samples were combined due to a lack of adequate sample volume. The gradient of the linear regression of core top DSi concentration (µM) of each extraction plotted against the ratio of time:core top height (day m-1) gives the flux magnitude (mmol m-2 d-1). Samples were extracted with a 60 mL plastic syringe through an Acrodisc filter (0.2µm) that connected to an air tight cap that sealed the core tube. The cap included a magnetic stirrer attached to the base to gently homogenise the core top water throughout the incubation period. 50 mL of core top water was extracted for each sample and the core tube measured 100 mm in diameter.
ChAOS_4_Solid_Phase_Isotopes: results of a sequential digestion experiment carried out to determine the biogenic silica (BSi) content (in wt % and µg Si g dry wt-1) of the surface sediment samples at B13, B14 and B15, as well as to access operationally defined reactive pools of Si (following Pickering et al., (2020)). Also includes the Si isotopic composition of the reactive pool phases, including that of the weak acid leachate (0.1 M HCl- delta30SiHCl per mil), weak alkaline leachate (0.1 M Na2CO3- delta30SiAlk per mil) and the harsh alkaline leachate (4 M NaOH- delta30SiNaOH per mil). Solid phase samples were collected by placing the sampled sediment core onto a manual core extruder and taking slices with a Perspex plate (at 0.5 cm intervals from 0-2 cmbsf, 1 cm from 2 cmbsf), which were stored at -20°C. Sediment digestions were carried out at the University of Bristol. Triplicate 50-75 mg sub samples of thawed sediment slices was digested in sequence with the following: 0.1 M HCl for 18 hours to remove authigenic metal oxide phases, 0.1 M Na2CO3 for 5 hours in an 85°C water bath to remove BSi and thus determine the BSi content following the traditional intercept method of DeMaster (1981) (2, 3 and 5 hr aliquots), followed by a 2 hour 4 M NaOH digestion to activate the lithogenic Si (LSi) pool, which is also thought to remove residual, recalcitrant BSi. In addition, a 30 minute leach with 10% H2O2 was carried out after the HCl step to remove diluting organic phases (Mortlock and Froelich, 1989). The isotopic composition of BSi (delta30SiAlk) was determined following Pickering et al., (2020), by measurement of a Na2CO3 sample extracted after a 20 minute digestion. The Na2CO3 and sediment sample were removed from the water bath after 20 minutes and neutralised with in-house distilled HCl to terminate the reaction. Al/Si (see file ChAOS_5_Solid_Phase_ICP_OES) of the 20 minute 0.1 M Na2CO3 (average 0.024) phase is within range of that expected of BSi (2.1x10-5 to 0.165, average 0.029) (Middag et al., 2009; van Bennekom et al., 1989; Hendry and Andersen 2013; Ren et al., 2013 and references therein), whereas Al/Si in the 4 M NaOH leachate (0.57-0.67) is more consistent with that of common clay minerals (0.48-0.96) (Kim et al., 2004; Koning et al., 2002; Rahn 1976).
ChAOS_5_Solid_Phase_ICP_OES: element concentrations (in µmol g dry wt-1) of the three aforementioned reactive pool leachates were measured by spectrophotometry (Si) and ICP-OES (Al, Fe, Mg, Mn, Ti, V) at the University of Bristol. Si concentrations of the leachate samples were determined chlorometrically by the Heteropoly Blue Method (Strickland and Parsons, 1972) using a VWR V-1200 spectrophotometer. Prior to each analytical session, Milli-Q (18.2 omega) and regent blanks were analysed, as well as a series of 10 Si standard solutions of known concentration in order to obtain a calibration curve. This spectrophotometry method was found to have an analytical precision of 2-3%. For the ICP-OES concentration analysis, performance was monitored through repeat measurement of a selected calibration standard throughout each measurement session, presenting with an analytical precision of 2.7% across three sessions.
|Min Depth||294 m|
|Max Depth||367 m|
|Data Collection:||Megacorer (multicoring device with up to 12 core tubes), National Marine Facilities
Lachat Quickchem 8500 flow injection autoanalyzer
VWR V-1200 spectrophotometer, University of Bristol
Finnigan Neptune Plus High Resolution MC-ICP-MS by Thermo Fisher Scientific, University of Bristol
Agilent Technologies 710 ICP-OES, University of Bristol
|Data Storage:||The dataset consists of 5 .csv files (for details see the section Lineage) and 1 text file with sampling station locations.|