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


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).

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Description/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.

Item Type: Article
ISSNs: 0967-0637 (print)
Keywords: Neutrally buoyant sediment traps; Thorium-234; Particulate organic carbon flux; North Atlantic spring bloom; Transparent exopolymer particles
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QH Natural history > QH301 Biology
Divisions: University Structure - Pre August 2011 > National Oceanography Centre (NERC)
University Structure - Pre August 2011 > School of Ocean & Earth Science (SOC/SOES)
National Oceanography Centre (NERC) > Ocean Biogeochemistry and Ecosystems
ePrint ID: 177839
Date Deposited: 21 Mar 2011 10:31
Last Modified: 27 Mar 2014 19:25
URI: http://eprints.soton.ac.uk/id/eprint/177839

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