title: The decline and fate of an iron-induced subarctic phytoplankton bloom.
abstract: Iron supply has a key role in stimulating phytoplankton blooms in high-nitrate low-chlorophyll oceanic waters. However, the fate of the carbon fixed by these blooms, and how efficiently it is exported into the ocean's interior, remains largely unknown. Here we report on the decline and fate of an iron-stimulated diatom bloom in the Gulf of Alaska. The bloom terminated on day 18, following the depletion of iron and then silicic acid, after which mixed-layer particulate organic carbon (POC) concentrations declined over six days. Increased particulate silica export via sinking diatoms was recorded in sediment traps at depths between 50 and 125 m from day 21, yet increased POC export was not evident until day 24. Only a small proportion of the mixed-layer POC was intercepted by the traps, with more than half of the mixed-layer POC deficit attributable to bacterial remineralization and mesozooplankton grazing. The depletion of silicic acid and the inefficient transfer of iron-increased POC below the permanent thermocline have major implications both for the biogeochemical interpretation of times of greater iron supply in the geological past, and also for proposed geo-engineering schemes to increase oceanic carbon sequestration.
authors.affiliation: NIWA Centre for Chemical and Physical Oceanography, Department of Chemistry, University of Otago, PO Box 56, Dunedin, 9003, New Zealand. p.boyd@niwa.co.nz
authors.forename: Philip W
authors.initials: PW
authors.lastname: Boyd
authors.forename: Cliff S
authors.initials: CS
authors.lastname: Law
authors.forename: C S
authors.initials: CS
authors.lastname: Wong
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Nojiri
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tsuda
authors.forename: Maurice
authors.initials: M
authors.lastname: Levasseur
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Takeda
authors.forename: Richard
authors.initials: R
authors.lastname: Rivkin
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Harrison
authors.forename: Robert
authors.initials: R
authors.lastname: Strzepek
authors.forename: Jim
authors.initials: J
authors.lastname: Gower
authors.forename: Mike
authors.initials: M
authors.lastname: McKay
authors.forename: Edward
authors.initials: E
authors.lastname: Abraham
authors.forename: Mike
authors.initials: M
authors.lastname: Arychuk
authors.forename: Janet
authors.initials: J
authors.lastname: Barwell-Clarke
authors.forename: William
authors.initials: W
authors.lastname: Crawford
authors.forename: David
authors.initials: D
authors.lastname: Crawford
authors.forename: Michelle
authors.initials: M
authors.lastname: Hale
authors.forename: Koh
authors.initials: K
authors.lastname: Harada
authors.forename: Keith
authors.initials: K
authors.lastname: Johnson
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kiyosawa
authors.forename: Isao
authors.initials: I
authors.lastname: Kudo
authors.forename: Adrian
authors.initials: A
authors.lastname: Marchetti
authors.forename: William
authors.initials: W
authors.lastname: Miller
authors.forename: Joe
authors.initials: J
authors.lastname: Needoba
authors.forename: Jun
authors.initials: J
authors.lastname: Nishioka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ogawa
authors.forename: John
authors.initials: J
authors.lastname: Page
authors.forename: Marie
authors.initials: M
authors.lastname: Robert
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Saito
authors.forename: Akash
authors.initials: A
authors.lastname: Sastri
authors.forename: Nelson
authors.initials: N
authors.lastname: Sherry
authors.forename: Tim
authors.initials: T
authors.lastname: Soutar
authors.forename: Nes
authors.initials: N
authors.lastname: Sutherland
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Taira
authors.forename: Frank
authors.initials: F
authors.lastname: Whitney
authors.forename: Shau-King Emmy
authors.initials: SK
authors.lastname: Wong
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshimura
mesh_terms: D000413:Alaska; D002244:Carbon / Q000378:metabolism; D003081:Cold Climate; D017377:Diatoms / Q000254:growth & development / Q000502:physiology; D007501:Iron / Q000032:analysis / Q000378:metabolism*; D009792:Oceans and Seas; D010839:Phytoplankton / Q000254:growth & development / Q000502:physiology*; D012623:Seawater / Q000382:microbiology*; D012824:Silicic Acid; D012822:Silicon Dioxide; D013997:Time Factors
chemical_list: D012824:Silicic Acid; D002244:Carbon; D012822:Silicon Dioxide; D007501:Iron