title: Diatom carbon export enhanced by silicate upwelling in the northeast Atlantic.
abstract: Diatoms are unicellular or chain-forming phytoplankton that use silicon (Si) in cell wall construction. Their survival during periods of apparent nutrient exhaustion enhances carbon sequestration in frontal regions of the northern North Atlantic. These regions may therefore have a more important role in the 'biological pump' than they have previously been attributed, but how this is achieved is unknown. Diatom growth depends on silicate availability, in addition to nitrate and phosphate, but northern Atlantic waters are richer in nitrate than silicate. Following the spring stratification, diatoms are the first phytoplankton to bloom. Once silicate is exhausted, diatom blooms subside in a major export event. Here we show that, with nitrate still available for new production, the diatom bloom is prolonged where there is a periodic supply of new silicate: specifically, diatoms thrive by 'mining' deep-water silicate brought to the surface by an unstable ocean front. The mechanism we present here is not limited to silicate fertilization; similar mechanisms could support nitrate-, phosphate- or iron-limited frontal regions in oceans elsewhere.
authors.affiliation: National Oceanography Centre, Southampton SO14 3ZH, UK. jta@noc.soton.ac.uk
authors.forename: John T
authors.initials: JT
authors.lastname: Allen
authors.forename: Louise
authors.initials: L
authors.lastname: Brown
authors.forename: Richard
authors.initials: R
authors.lastname: Sanders
authors.forename: C Mark
authors.initials: CM
authors.lastname: Moore
authors.forename: Alexander
authors.initials: A
authors.lastname: Mustard
authors.forename: Sophie
authors.initials: S
authors.lastname: Fielding
authors.forename: Mike
authors.initials: M
authors.lastname: Lucas
authors.forename: Michel
authors.initials: M
authors.lastname: Rixen
authors.forename: Graham
authors.initials: G
authors.lastname: Savidge
authors.forename: Stephanie
authors.initials: S
authors.lastname: Henson
authors.forename: Dan
authors.initials: D
authors.lastname: Mayor
mesh_terms: D001267:Atlantic Ocean; D001692:Biological Transport; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D017377:Diatoms / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010788:Photosynthesis; D010839:Phytoplankton / Q000378:metabolism; D017640:Silicates / Q000378:metabolism*
chemical_list: D009566:Nitrates; D010710:Phosphates; D017640:Silicates; D002734:Chlorophyll; D002244:Carbon