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Impact of resuspension of cohesive sediments at the Oyster Grounds (North Sea) on nutrient exchange across the sediment-water interface

Impact of resuspension of cohesive sediments at the Oyster Grounds (North Sea) on nutrient exchange across the sediment-water interface
Impact of resuspension of cohesive sediments at the Oyster Grounds (North Sea) on nutrient exchange across the sediment-water interface
Benthic-pelagic exchange processes are recognised as important nutrient sources in coastal areas, however, the relative impact of diffusion, resuspension and other processes such as bioturbation and bioirrigation are still relatively poorly understood. Experimental ship-based data are presented showing the effects of diffusion and resuspension on cohesive sediments at a temperate shelf location in the North Sea. Measurements of diffusive fluxes in both spring (1.76, 0.51, ?0.91, 17.6 ?mol/m2/h) and late summer (8.53, ?0.03, ?1.12, 35.0 ?mol/m2/h) for nitrate, nitrite, phosphate and dissolved silicon respectively, provided comparisons for measured resuspension fluxes. Increases in diffusive fluxes of nitrate and dissolved silicon to the water column in late summer coincided with decreases in bottom water oxygen concentrations and increases in temperature. Resuspension experiments using a ship board annular flume and intact box core allowed simultaneous measurement of suspended particulate matter, water velocity and sampling of nutrients in the water column during a step wise increase in bed shear velocity. The resuspension of benthic fluff led to small but significant releases of phosphate and nitrate to the water column with chamber concentration increasing from 0.70–0.76 and 1.84–2.22 ?mol/L respectively. Resuspension of the sediment bed increased water column concentrations of dissolved silicon by as much as 125% (7.10–15.9 ?mol/L) and nitrate and phosphate concentrations by up to 67% (1.84–3.08 ?mol/L) and 66% (0.70–1.15 ?mol/L) respectively. Mass balance calculations indicate that processes such as microbial activity or adsorption/desorption other than simple release of pore water nutrients must occur during resuspension to account for the increase. This study shows that resuspension is potentially an important pathway for resupplying the water column with nutrients before and during phytoplankton blooms and should therefore be considered along with diffusive fluxes in future ecosystem models.
Resuspension, Nutrients, Cohesive sediment, Flume, Oyster Grounds, North Sea
0168-2563
37-52
Courceiro, F.
753e173b-47bc-4557-a532-0b13d7d9a27e
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Thompson, C.E.L.
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Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Sivyer, D.B.
f550fb9a-700f-441b-adb7-a22b7a5dc700
Parker, R.
32c1d9ec-5abc-44e6-ae06-f5b43cfdb730
Kelly-Gerreyn, B.A.
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Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c
Courceiro, F.
753e173b-47bc-4557-a532-0b13d7d9a27e
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Thompson, C.E.L.
2a304aa6-761e-4d99-b227-cedb67129bfb
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Sivyer, D.B.
f550fb9a-700f-441b-adb7-a22b7a5dc700
Parker, R.
32c1d9ec-5abc-44e6-ae06-f5b43cfdb730
Kelly-Gerreyn, B.A.
1434d5fd-49f7-4774-b5ff-ddf334a3dcc2
Amos, C.L.
d0a18a13-bccd-4fdc-8901-aea595d4ed5c

Courceiro, F., Fones, G.R., Thompson, C.E.L., Statham, P.J., Sivyer, D.B., Parker, R., Kelly-Gerreyn, B.A. and Amos, C.L. (2013) Impact of resuspension of cohesive sediments at the Oyster Grounds (North Sea) on nutrient exchange across the sediment-water interface. Biogeochemistry, 113 (1-3), 37-52. (doi:10.1007/s10533-012-9710-7).

Record type: Article

Abstract

Benthic-pelagic exchange processes are recognised as important nutrient sources in coastal areas, however, the relative impact of diffusion, resuspension and other processes such as bioturbation and bioirrigation are still relatively poorly understood. Experimental ship-based data are presented showing the effects of diffusion and resuspension on cohesive sediments at a temperate shelf location in the North Sea. Measurements of diffusive fluxes in both spring (1.76, 0.51, ?0.91, 17.6 ?mol/m2/h) and late summer (8.53, ?0.03, ?1.12, 35.0 ?mol/m2/h) for nitrate, nitrite, phosphate and dissolved silicon respectively, provided comparisons for measured resuspension fluxes. Increases in diffusive fluxes of nitrate and dissolved silicon to the water column in late summer coincided with decreases in bottom water oxygen concentrations and increases in temperature. Resuspension experiments using a ship board annular flume and intact box core allowed simultaneous measurement of suspended particulate matter, water velocity and sampling of nutrients in the water column during a step wise increase in bed shear velocity. The resuspension of benthic fluff led to small but significant releases of phosphate and nitrate to the water column with chamber concentration increasing from 0.70–0.76 and 1.84–2.22 ?mol/L respectively. Resuspension of the sediment bed increased water column concentrations of dissolved silicon by as much as 125% (7.10–15.9 ?mol/L) and nitrate and phosphate concentrations by up to 67% (1.84–3.08 ?mol/L) and 66% (0.70–1.15 ?mol/L) respectively. Mass balance calculations indicate that processes such as microbial activity or adsorption/desorption other than simple release of pore water nutrients must occur during resuspension to account for the increase. This study shows that resuspension is potentially an important pathway for resupplying the water column with nutrients before and during phytoplankton blooms and should therefore be considered along with diffusive fluxes in future ecosystem models.

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e-pub ahead of print date: February 2012
Published date: May 2013
Keywords: Resuspension, Nutrients, Cohesive sediment, Flume, Oyster Grounds, North Sea
Organisations: Marine Biogeochemistry, Ocean Biochemistry & Ecosystems, Coastal & Shelf Research

Identifiers

Local EPrints ID: 349730
URI: http://eprints.soton.ac.uk/id/eprint/349730
ISSN: 0168-2563
PURE UUID: c896589e-b1af-4309-afac-b68e7ee57695
ORCID for C.E.L. Thompson: ORCID iD orcid.org/0000-0003-1105-6838

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Date deposited: 11 Mar 2013 09:35
Last modified: 15 Mar 2024 03:05

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Contributors

Author: F. Courceiro
Author: G.R. Fones
Author: C.E.L. Thompson ORCID iD
Author: P.J. Statham
Author: D.B. Sivyer
Author: R. Parker
Author: B.A. Kelly-Gerreyn
Author: C.L. Amos

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