Net community production, Thorium-234 activity and particle flux during the Southern Ocean iron fertilization experiment LOHAFEX ...

A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km**2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled af...

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Bibliographic Details
Main Authors: Martin, Patrick, Rutgers van der Loeff, Michiel M, Cassar, Nicolas, Vandromme, Pieter, d'Ovidio, Francesco, Stemmann, Lars, Rengarajan, Ramabadran, Soares, Melena, González, Humberto E, Ebersbach, Friederike, Lampitt, Richard Stephen, Sanders, Richard J, Barnett, Bruce A, Smetacek, Victor, Naqvi, Syed Wajih Ahmad
Format: Article in Journal/Newspaper
Language:English
Published: PANGAEA 2013
Subjects:
Marine Geochemistry @ AWI AWI_MarGeoChem
Southern Ocean
Copepods
Online Access:https://dx.doi.org/10.1594/pangaea.832525
https://doi.pangaea.de/10.1594/PANGAEA.832525
Description
Summary:A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km**2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yield (FV/FM) increased from 0.33 to >0.40. Silicic acid (<2 µmol/L) limited diatoms, which contributed <10% of phytoplankton biomass. Copepods exerted high grazing pressure. This is the first study of particle flux out of an artificially fertilized bloom with very low diatom biomass. Net community production (NCP) inside the patch, estimated from O2:Ar ratios, averaged 21 mmol POC/m**2/d, probably ±20%. 234Th profiles implied constant export of ~6.3 mmol POC/m**2/d in the patch, similar to unfertilized waters. The difference between NCP and 234Th-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 ... : Supplement to: Martin, Patrick; Rutgers van der Loeff, Michiel M; Cassar, Nicolas; Vandromme, Pieter; d'Ovidio, Francesco; Stemmann, Lars; Rengarajan, Ramabadran; Soares, Melena; González, Humberto E; Ebersbach, Friederike; Lampitt, Richard Stephen; Sanders, Richard J; Barnett, Bruce A; Smetacek, Victor; Naqvi, Syed Wajih Ahmad (2013): Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX. Global Biogeochemical Cycles, 27(3), 871-881 ...

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