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Export and mesopelagic particle flux during a North Atlantic spring diatom bloom

Export and mesopelagic particle flux during a North Atlantic spring diatom bloom
Export and mesopelagic particle flux during a North Atlantic spring diatom bloom
Spring diatom blooms are important for sequestering atmospheric CO2 below the permanent thermocline in the form of particulate organic carbon (POC). We measured downward POC flux during a sub-polar North Atlantic spring bloom at 100 m using thorium-234 (234Th) disequilibria, and below 100 m using neutrally buoyant drifting sediment traps. The cruise followed a Lagrangian float, and a pronounced diatom bloom occurred in a 600 km2 area around the float. Particle flux was low during the first three weeks of the bloom, between 10 and 30 mg POC m?2 d?1. Then, nearly 20 days after the bloom had started, export as diagnosed from 234Th rose to 360–620 mg POC m?2 d?1, co-incident with silicate depletion in the surface mixed layer. Sediment traps at 600 and 750 m depth collected 160 and 150 mg POC m?2 d?1, with a settled volume of particles of 1000–1500 mL m?2 d?1. This implies that 25–43% of the 100 m POC export sank below 750 m. The sinking particles were ungrazed diatom aggregates that contained transparent exopolymer particles (TEP). We conclude that diatom blooms can lead to substantial particle export that is transferred efficiently through the mesopelagic. We also present an improved method of calibrating the Alcian Blue solution against Gum Xanthan for TEP measurements.
Neutrally buoyant sediment traps, Thorium-234, Particulate organic carbon flux, North Atlantic spring bloom, Transparent exopolymer particles
0967-0637
338-349
Martin, Patrick
01ce1c59-3926-46c9-a556-fac39e0ee16b
Lampitt, Richard S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Perry, Mary Jane
6726c842-d32c-44e2-b157-257aea49e074
Sanders, Richard
02c163c1-8f5e-49ad-857c-d28f7da66c65
Lee, Craig
18487421-c75c-4c22-ae85-fed310da234c
D'Asaro, Eric
2fc1c4ef-2619-497b-a651-850df8938799
Martin, Patrick
01ce1c59-3926-46c9-a556-fac39e0ee16b
Lampitt, Richard S.
dfc3785c-fc7d-41fa-89ee-d0c6e27503ad
Perry, Mary Jane
6726c842-d32c-44e2-b157-257aea49e074
Sanders, Richard
02c163c1-8f5e-49ad-857c-d28f7da66c65
Lee, Craig
18487421-c75c-4c22-ae85-fed310da234c
D'Asaro, Eric
2fc1c4ef-2619-497b-a651-850df8938799

Martin, Patrick, Lampitt, Richard S., Perry, Mary Jane, Sanders, Richard, Lee, Craig and D'Asaro, Eric (2011) Export and mesopelagic particle flux during a North Atlantic spring diatom bloom. Deep Sea Research Part I: Oceanographic Research Papers, 58 (4), 338-349. (doi:10.1016/j.dsr.2011.01.006).

Record type: Article

Abstract

Spring diatom blooms are important for sequestering atmospheric CO2 below the permanent thermocline in the form of particulate organic carbon (POC). We measured downward POC flux during a sub-polar North Atlantic spring bloom at 100 m using thorium-234 (234Th) disequilibria, and below 100 m using neutrally buoyant drifting sediment traps. The cruise followed a Lagrangian float, and a pronounced diatom bloom occurred in a 600 km2 area around the float. Particle flux was low during the first three weeks of the bloom, between 10 and 30 mg POC m?2 d?1. Then, nearly 20 days after the bloom had started, export as diagnosed from 234Th rose to 360–620 mg POC m?2 d?1, co-incident with silicate depletion in the surface mixed layer. Sediment traps at 600 and 750 m depth collected 160 and 150 mg POC m?2 d?1, with a settled volume of particles of 1000–1500 mL m?2 d?1. This implies that 25–43% of the 100 m POC export sank below 750 m. The sinking particles were ungrazed diatom aggregates that contained transparent exopolymer particles (TEP). We conclude that diatom blooms can lead to substantial particle export that is transferred efficiently through the mesopelagic. We also present an improved method of calibrating the Alcian Blue solution against Gum Xanthan for TEP measurements.

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More information

Published date: April 2011
Keywords: Neutrally buoyant sediment traps, Thorium-234, Particulate organic carbon flux, North Atlantic spring bloom, Transparent exopolymer particles
Organisations: Ocean and Earth Science, Marine Biogeochemistry, National Oceanography Centre,Southampton

Identifiers

Local EPrints ID: 177839
URI: http://eprints.soton.ac.uk/id/eprint/177839
ISSN: 0967-0637
PURE UUID: 388e1099-382c-46ab-a861-cebc13efddd9

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Date deposited: 21 Mar 2011 10:31
Last modified: 14 Mar 2024 02:44

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Contributors

Author: Patrick Martin
Author: Richard S. Lampitt
Author: Mary Jane Perry
Author: Richard Sanders
Author: Craig Lee
Author: Eric D'Asaro

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