1
|
Periáñez R, Abascal-Ruíz U, López-Gutiérrez JM, Villa-Alfageme M. Sediments as sinks and sources of marine radionuclides: Implications for their use as ocean tracers. MARINE POLLUTION BULLETIN 2023; 194:115316. [PMID: 37517248 DOI: 10.1016/j.marpolbul.2023.115316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 07/10/2023] [Accepted: 07/17/2023] [Indexed: 08/01/2023]
Abstract
A Lagrangian transport model for the North Atlantic has been applied to simulate the historical releases of 137Cs, 129I and 236U from the European nuclear fuel reprocessing plants. Advection by currents, mixing and decay are included, as radionuclide interactions between water, sediments and suspended matter. The model was validated comparing predictions with measured radionuclide concentrations in water and sediments in several areas. 129I and 236U signals entering the Arctic Ocean have been compared with the input terms: the 236U signal is distorted, but the 129I signal preserves its shape. In the first moments after the releases, the sediments act as sinks for 236U, but not significantly for 129I and ultimately they become sources of 236U to the open sea. This results in a weaker correlation between input and output signals for 236U than for 129I. The same effects as for 236U have been found for 137Cs signal into the Arctic.
Collapse
Affiliation(s)
- Raúl Periáñez
- Dpt Física Aplicada I, ETSIA, Universidad de Sevilla, Ctra Utrera km 1, Sevilla, Spain.
| | - Unai Abascal-Ruíz
- Dpt Física Aplicada II, ETSIE, Universidad de Sevilla, Avda Reina Mercedes s/n, Sevilla, Spain
| | | | - María Villa-Alfageme
- Dpt Física Aplicada II, ETSIE, Universidad de Sevilla, Avda Reina Mercedes s/n, Sevilla, Spain
| |
Collapse
|
2
|
Kukkola AT, Senior G, Maes T, Silburn B, Bakir A, Kröger S, Mayes AG. A large-scale study of microplastic abundance in sediment cores from the UK continental shelf and slope. MARINE POLLUTION BULLETIN 2022; 178:113554. [PMID: 35390630 DOI: 10.1016/j.marpolbul.2022.113554] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 03/04/2022] [Accepted: 03/08/2022] [Indexed: 06/14/2023]
Abstract
To inform risk assessments, reliable, time efficient and affordable quantification methods are required for creating a microplastic (MP) pollution baseline in the world's oceans. To facilitate this, MP abundance was investigated in sediments of three contrasting areas of the UK continental shelf: North West of Jones Bank, the Canyons in the Celtic Sea and Dogger Bank in the North Sea, utilising the Nile Red tagging method to assess its time efficiency and cost. Average MP abundance in the top 10 cm was 1050-2700 MP kg-1. MP abundance decreased with increasing sediment depth and increased with increasing water depth. The findings emphasise the extent of MP pollution and illustrate the value of Nile Red for large scale mapping at relatively low cost.
Collapse
Affiliation(s)
- A T Kukkola
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK; School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT, UK
| | - G Senior
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - T Maes
- GRID-Arendal, Teaterplassen 3, 4836 Arendal, Norway
| | - B Silburn
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft NR33 0HT, UK
| | - A Bakir
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft NR33 0HT, UK
| | - S Kröger
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft NR33 0HT, UK
| | - A G Mayes
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
| |
Collapse
|
3
|
Phale PS, Mohapatra B, Malhotra H, Shah BA. Eco-physiological portrait of a novel Pseudomonas sp. CSV86: an ideal host/candidate for metabolic engineering and bioremediation. Environ Microbiol 2021; 24:2797-2816. [PMID: 34347343 DOI: 10.1111/1462-2920.15694] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 11/30/2022]
Abstract
Pseudomonas sp. CSV86, an Indian soil isolate, degrades wide range of aromatic compounds like naphthalene, benzoate and phenylpropanoids, amongst others. Isolate displays the unique and novel property of preferential utilization of aromatics over glucose and co-metabolizes them with organic acids. Interestingly, as compared to other Pseudomonads, strain CSV86 harbours only high-affinity glucokinase pathway (and absence of low-affinity oxidative route) for glucose metabolism. Such lack of gluconate loop might be responsible for the novel phenotype of preferential utilization of aromatics. The genome analysis and comparative functional mining indicated a large genome (6.79 Mb) with significant enrichment of regulators, transporters as well as presence of various secondary metabolite production clusters, suggesting its eco-physiological and metabolic versatility. Strain harbours various integrative conjugative elements (ICEs) and genomic islands, probably acquired through horizontal gene transfer events, leading to genome mosaicity and plasticity. Naphthalene degradation genes are arranged as regulonic clusters and found to be part of ICECSV86nah . Various eco-physiological properties and absence of major pathogenicity and virulence factors (risk group-1) in CSV86 suggest it to be an ideal candidate for bioremediation. Further, strain can serve as an ideal chassis for metabolic engineering to degrade various xenobiotics preferentially over simple carbon sources for efficient remediation.
Collapse
Affiliation(s)
- Prashant S Phale
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Mumbai, Maharashtra, 400076, India
| | - Balaram Mohapatra
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Mumbai, Maharashtra, 400076, India
| | - Harshit Malhotra
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Mumbai, Maharashtra, 400076, India
| | - Bhavik A Shah
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Mumbai, Maharashtra, 400076, India
| |
Collapse
|
4
|
Solan M, Bennett EM, Mumby PJ, Leyland J, Godbold JA. Benthic-based contributions to climate change mitigation and adaptation. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190107. [PMID: 31983332 DOI: 10.1098/rstb.2019.0107] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Innovative solutions to improve the condition and resilience of ecosystems are needed to address societal challenges and pave the way towards a climate-resilient future. Nature-based solutions offer the potential to protect, sustainably manage and restore natural or modified ecosystems while providing multiple other benefits for health, the economy, society and the environment. However, the implementation of nature-based solutions stems from a discourse that is almost exclusively derived from a terrestrial and urban context and assumes that risk reduction is resolved locally. We argue that this position ignores the importance of complex ecological interactions across a range of temporal and spatial scales and misses the substantive contribution from marine ecosystems, which are notably absent from most climate mitigation and adaptation strategies that extend beyond coastal disaster management. Here, we consider the potential of sediment-dwelling fauna and flora to inform and support nature-based solutions, and how the ecology of benthic environments can enhance adaptation plans. We illustrate our thesis with examples of practice that are generating, or have the potential to deliver, transformative change and discuss where further innovation might be applied. Finally, we take a reflective look at the realized and potential capacity of benthic-based solutions to contribute to adaptation plans and offer our perspectives on the suitability and shortcomings of past achievements and the prospective rewards from sensible prioritization of future research. This article is part of the theme issue 'Climate change and ecosystems: threats, opportunities and solutions'.
Collapse
Affiliation(s)
- Martin Solan
- School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK
| | - Elena M Bennett
- Department of Natural Resource Sciences and McGill School of Environment, McGill University-Macdonald Campus, 21,111 Lakeshore Road, St Anne-de-Bellevue, Quebec, Canada H9X 3 V9
| | - Peter J Mumby
- Marine Spatial Ecology Lab, School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Julian Leyland
- School of Geography and Environmental Science, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK
| | - Jasmin A Godbold
- School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK.,School of Biological Sciences, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK
| |
Collapse
|
5
|
Benoist NM, Morris KJ, Bett BJ, Durden JM, Huvenne VA, Le Bas TP, Wynn RB, Ware SJ, Ruhl HA. Monitoring mosaic biotopes in a marine conservation zone by autonomous underwater vehicle. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2019; 33:1174-1186. [PMID: 30859604 PMCID: PMC6850053 DOI: 10.1111/cobi.13312] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/19/2019] [Accepted: 03/04/2019] [Indexed: 05/19/2023]
Abstract
The number of marine protected areas (MPAs) has increased dramatically in the last decade and poses a major logistic challenge for conservation practitioners in terms of spatial extent and the multiplicity of habitats and biotopes that now require assessment. Photographic assessment by autonomous underwater vehicle (AUV) enables the consistent description of multiple habitats, in our case including mosaics of rock and sediment. As a case study, we used this method to survey the Greater Haig Fras marine conservation zone (Celtic Sea, northeast Atlantic). We distinguished 7 biotopes, detected statistically significant variations in standing stocks, species density, species diversity, and faunal composition, and identified significant indicator species for each habitat. Our results demonstrate that AUV-based photography can produce robust data for ecological research and practical marine conservation. Standardizing to a minimum number of individuals per sampling unit, rather than to a fixed seafloor area, may be a valuable means of defining an ecologically appropriate sampling unit. Although composite sampling represents a change in standard practice, other users should consider the potential benefits of this approach in conservation studies. It is broadly applicable in the marine environment and has been successfully implemented in deep-sea conservation and environmental impact studies. Without a cost-effective method, applicable across habitats, it will be difficult to further a coherent classification of biotopes or to routinely assess their conservation status in the rapidly expanding global extent of MPAs.
Collapse
Affiliation(s)
- Noëlie M.A. Benoist
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
- University of SouthamptonSouthamptonSO14 3ZHU.K.
| | - Kirsty J. Morris
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| | - Brian J. Bett
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| | - Jennifer M. Durden
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
- University of SouthamptonSouthamptonSO14 3ZHU.K.
- University of HawaiiHonoluluHI96822U.S.A.
| | - Veerle A.I. Huvenne
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| | - Tim P. Le Bas
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| | - Russell B. Wynn
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| | - Suzanne J. Ware
- Centre for Environment Fisheries and Aquaculture ScienceLowestoftNR33 0HTU.K.
| | - Henry A. Ruhl
- Ocean Biogeochemistry and EcosystemsNational Oceanography CentreSouthamptonSO14 3ZHU.K.
| |
Collapse
|
6
|
Snelgrove PVR, Soetaert K, Solan M, Thrush S, Wei CL, Danovaro R, Fulweiler RW, Kitazato H, Ingole B, Norkko A, Parkes RJ, Volkenborn N. Global Carbon Cycling on a Heterogeneous Seafloor. Trends Ecol Evol 2017; 33:96-105. [PMID: 29248328 DOI: 10.1016/j.tree.2017.11.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/25/2017] [Accepted: 11/07/2017] [Indexed: 10/18/2022]
Abstract
Diverse biological communities mediate the transformation, transport, and storage of elements fundamental to life on Earth, including carbon, nitrogen, and oxygen. However, global biogeochemical model outcomes can vary by orders of magnitude, compromising capacity to project realistic ecosystem responses to planetary changes, including ocean productivity and climate. Here, we compare global carbon turnover rates estimated using models grounded in biological versus geochemical theory and argue that the turnover estimates based on each perspective yield divergent outcomes. Importantly, empirical studies that include sedimentary biological activity vary less than those that ignore it. Improving the relevance of model projections and reducing uncertainty associated with the anticipated consequences of global change requires reconciliation of these perspectives, enabling better societal decisions on mitigation and adaptation.
Collapse
Affiliation(s)
- Paul V R Snelgrove
- Department of Ocean Sciences and Biology Department, Memorial University of Newfoundland, St John's NL A1C 5S7, Canada.
| | - Karline Soetaert
- Estuarine and Delta Systems, Netherlands Institute of Sea Research and Utrecht University, Yerseke, The Netherlands
| | - Martin Solan
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, UK
| | - Simon Thrush
- Institute of Marine Science, The University of Auckland, Auckland, 1142, New Zealand
| | - Chih-Lin Wei
- Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan
| | - Roberto Danovaro
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy; Stazione Zoologica Anton Dohrn, Naples, Italy
| | - Robinson W Fulweiler
- Departments of Earth and Environment and Biology, Boston University, Boston, MA, USA
| | - Hiroshi Kitazato
- Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Baban Ingole
- National Institute of Oceanography, Dona Paula, Goa 403004 , India
| | - Alf Norkko
- Tvärminne Zoological Station, University of Helsinki, Hanko, Finland; Stockholm University Baltic Sea Centre, 106 91 Stockholm
| | - R John Parkes
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, UK
| | - Nils Volkenborn
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, 11794-5000, USA
| |
Collapse
|
7
|
Aldridge JN, Lessin G, Amoudry LO, Hicks N, Hull T, Klar JK, Kitidis V, McNeill CL, Ingels J, Parker ER, Silburn B, Silva T, Sivyer DB, Smith HEK, Widdicombe S, Woodward EMS, van der Molen J, Garcia L, Kröger S. Comparing benthic biogeochemistry at a sandy and a muddy site in the Celtic Sea using a model and observations. BIOGEOCHEMISTRY 2017; 135:155-182. [PMID: 32009696 PMCID: PMC6961523 DOI: 10.1007/s10533-017-0367-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 07/22/2017] [Indexed: 06/10/2023]
Abstract
Results from a 1D setup of the European Regional Seas Ecosystem Model (ERSEM) biogeochemical model were compared with new observations collected under the UK Shelf Seas Biogeochemistry (SSB) programme to assess model performance and clarify elements of shelf-sea benthic biogeochemistry and carbon cycling. Observations from two contrasting sites (muddy and sandy) in the Celtic Sea in otherwise comparable hydrographic conditions were considered, with the focus on the benthic system. A standard model parameterisation with site-specific light and nutrient adjustments was used, along with modifications to the within-seabed diffusivity to accommodate the modelling of permeable (sandy) sediments. Differences between modelled and observed quantities of organic carbon in the bed were interpreted to suggest that a large part (>90%) of the observed benthic organic carbon is biologically relatively inactive. Evidence on the rate at which this inactive fraction is produced will constitute important information to quantify offshore carbon sequestration. Total oxygen uptake and oxic layer depths were within the range of the measured values. Modelled depth average pore water concentrations of ammonium, phosphate and silicate were typically 5-20% of observed values at the muddy site due to an underestimate of concentrations associated with the deeper sediment layers. Model agreement for these nutrients was better at the sandy site, which had lower pore water concentrations, especially deeper in the sediment. Comparison of pore water nitrate with observations had added uncertainty, as the results from process studies at the sites indicated the dominance of the anammox pathway for nitrogen removal; a pathway that is not included in the model. Macrofaunal biomasses were overestimated, although a model run with increased macrofaunal background mortality rates decreased macrofaunal biomass and improved agreement with observations. The decrease in macrofaunal biomass was compensated by an increase in meiofaunal biomass such that total oxygen demand remained within the observed range. The permeable sediment modification reproduced some of the observed behaviour of oxygen penetration depth at the sandy site. It is suggested that future development in ERSEM benthic modelling should focus on: (1) mixing and degradation rates of benthic organic matter, (2) validation of benthic faunal biomass against large scale spatial datasets, (3) incorporation of anammox in the benthic nitrogen cycle, and (4) further developments to represent permeable sediment processes.
Collapse
Affiliation(s)
- J. N. Aldridge
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - G. Lessin
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - L. O. Amoudry
- National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool, L3 5DA UK
| | - N. Hicks
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA UK
| | - T. Hull
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - J. K. Klar
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
- LEGOS, University of Toulouse, IRD, CNES, CNRS, UPS, 14 avenue Edouard Belin, 31400 Toulouse, France
| | - V. Kitidis
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - C. L. McNeill
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - J. Ingels
- Coastal and Marine Laboratory, Florida State University, 3618 Coastal Highway 98, St Teresa, 32358 FL USA
| | - E. R. Parker
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - B. Silburn
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - T. Silva
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - D. B. Sivyer
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - H. E. K. Smith
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - S. Widdicombe
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - E. M. S. Woodward
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - J. van der Molen
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - L. Garcia
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| | - S. Kröger
- Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT UK
| |
Collapse
|
8
|
Godbold JA, Hale R, Wood CL, Solan M. Vulnerability of macronutrients to the concurrent effects of enhanced temperature and atmospheric pCO 2 in representative shelf sea sediment habitats. BIOGEOCHEMISTRY 2017; 135:89-102. [PMID: 32009693 PMCID: PMC6961501 DOI: 10.1007/s10533-017-0340-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 05/26/2017] [Indexed: 05/26/2023]
Abstract
Fundamental changes in seawater carbonate chemistry and sea surface temperatures associated with the ocean uptake of anthropogenic CO2 are accelerating, but investigations of the susceptibility of biogeochemical processes to the simultaneous occurrence of multiple components of climate change are uncommon. Here, we quantify how concurrent changes in enhanced temperature and atmospheric pCO2, coupled with an associated shift in macrofaunal community structure and behavior (sediment particle reworking and bioirrigation), modify net carbon and nutrient concentrations (NH4-N, NOx-N, PO4-P) in representative shelf sea sediment habitats (mud, sandy-mud, muddy-sand and sand) of the Celtic Sea. We show that net concentrations of organic carbon, nitrogen and phosphate are, irrespective of sediment type, largely unaffected by a simultaneous increase in temperature and atmospheric pCO2. However, our analyses also reveal that a reduction in macrofaunal species richness and total abundance occurs under future environmental conditions, varies across a gradient of cohesive to non-cohesive sediments, and negatively moderates biogeochemical processes, in particular nitrification. Our findings indicate that future environmental conditions are unlikely to have strong direct effects on biogeochemical processes but, particularly in muddy sands, the abundance, activity, composition and functional role of invertebrate communities are likely to be altered in ways that will be sufficient to regulate the function of the microbial community and the availability of nutrients in shelf sea waters.
Collapse
Affiliation(s)
- Jasmin A. Godbold
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton, SO14 3ZH UK
- Biological Sciences, University of Southampton, Highfield Campus, Southampton, SO17 1BJ UK
| | - Rachel Hale
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton, SO14 3ZH UK
| | - Christina L. Wood
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton, SO14 3ZH UK
| | - Martin Solan
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton, SO14 3ZH UK
| |
Collapse
|
9
|
Silburn B, Kröger S, Parker ER, Sivyer DB, Hicks N, Powell CF, Johnson M, Greenwood N. Benthic pH gradients across a range of shelf sea sediment types linked to sediment characteristics and seasonal variability. BIOGEOCHEMISTRY 2017; 135:69-88. [PMID: 32009692 PMCID: PMC6961502 DOI: 10.1007/s10533-017-0323-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 03/16/2017] [Indexed: 05/27/2023]
Abstract
This study used microelectrodes to record pH profiles in fresh shelf sea sediment cores collected across a range of different sediment types within the Celtic Sea. Spatial and temporal variability was captured during repeated measurements in 2014 and 2015. Concurrently recorded oxygen microelectrode profiles and other sedimentary parameters provide a detailed context for interpretation of the pH data. Clear differences in profiles were observed between sediment type, location and season. Notably, very steep pH gradients exist within the surface sediments (10-20 mm), where decreases greater than 0.5 pH units were observed. Steep gradients were particularly apparent in fine cohesive sediments, less so in permeable sandier matrices. We hypothesise that the gradients are likely caused by aerobic organic matter respiration close to the sediment-water interface or oxidation of reduced species at the base of the oxic zone (NH4 +, Mn2+, Fe2+, S-). Statistical analysis suggests the variability in the depth of the pH minima is controlled spatially by the oxygen penetration depth, and seasonally by the input and remineralisation of deposited organic phytodetritus. Below the pH minima the observed pH remained consistently low to maximum electrode penetration (ca. 60 mm), indicating an absence of sub-oxic processes generating H+ or balanced removal processes within this layer. Thus, a climatology of sediment surface porewater pH is provided against which to examine biogeochemical processes. This enhances our understanding of benthic pH processes, particularly in the context of human impacts, seabed integrity, and future climate changes, providing vital information for modelling benthic response under future climate scenarios.
Collapse
Affiliation(s)
- B. Silburn
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| | - S. Kröger
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| | - E. R. Parker
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| | - D. B. Sivyer
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| | - N. Hicks
- Scottish Marine Institute, Oban, Argyll PA37 1QA UK
| | - C. F. Powell
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| | - M. Johnson
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
- University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ UK
| | - N. Greenwood
- Centre for Environment Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT UK
| |
Collapse
|
10
|
Klar JK, Homoky WB, Statham PJ, Birchill AJ, Harris EL, Woodward EMS, Silburn B, Cooper MJ, James RH, Connelly DP, Chever F, Lichtschlag A, Graves C. Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column. BIOGEOCHEMISTRY 2017; 135:49-67. [PMID: 32009691 PMCID: PMC6961528 DOI: 10.1007/s10533-017-0309-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/06/2017] [Indexed: 05/28/2023]
Abstract
Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2-5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe, <0.15 µm) mainly (>85%) consisted of Fe(II) and gradually increased from 0.4 to 15 μM at the sediment surface to ~100-170 µM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) (>85% sFe, <0.02 µm). Sub-surface dFe(II) maxima were enriched in light isotopes (δ56Fe -2.0 to -1.5‰), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to -3.0‰). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after >7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23-31 µmol m-2 day-1) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas.
Collapse
Affiliation(s)
- J. K. Klar
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
- Present Address: LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, 14 Avenue Edouard Belin, 31400 Toulouse, France
| | - W. B. Homoky
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK
| | - P. J. Statham
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - A. J. Birchill
- School of Geography, Earth and Environmental Science, University of Plymouth, Drake Circus, Plymouth, PL4 8AA UK
| | - E. L. Harris
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - E. M. S. Woodward
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - B. Silburn
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - M. J. Cooper
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - R. H. James
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - D. P. Connelly
- Marine Geosciences, National Oceanography Centre, European Way, Southampton, SO14 3ZH UK
| | - F. Chever
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - A. Lichtschlag
- Marine Geosciences, National Oceanography Centre, European Way, Southampton, SO14 3ZH UK
| | - C. Graves
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| |
Collapse
|