Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX
| Type | : | ACL |
|---|---|---|
| Nature | : | Production scientifique |
| Au bénéfice du Laboratoire | : | Oui |
| Statut de publication | : | Publié |
| Année de publication | : | 2013 |
| Auteurs (15) | : | MARTIN V VAN DER LOEFF Michiel,rutgers CASSAR Nicolas VANDROMME Pieter D'OVIDIO Francesco STEMMANN Lars RENGARAJAN R SOARES Melena GONZÁLEZ N EBERSBACH Friederike LAMPITT Richard SANDERS Richard BARNETT Bruce,a SMETACEK Victor NAQVI S,wajih,a |
| Revue scientifique | : | Global Biogeochemical Cycles |
| Volume | : | 27 |
| Fascicule | : | 3 |
| Pages | : | 871-881 |
| DOI | : | 10.1002/gbc.20077 |
| URL | : | <go to isi>://wos:000325488600023 |
| Abstract | : | 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 (F-V/F-M) increased from 0.33 to 0.40. Silicic acid (<2 mu mol L-1) 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 O-2:Ar ratios, averaged 21 mmol POC m(-2) d(-1), probably 20%. Th-234 profiles implied constant export of similar to 6.3 mmol POC m(-2) d(-1) in the patch, similar to unfertilized waters. The difference between NCP and Th-234-derived export partly accumulated in the mixed layer and was partly remineralized between the mixed layer and 100 m. Neutrally buoyant sediment traps at 200 and 450 m inside and outside the patch caught mostly <1.1 mmol POC m(-2) d(-1), predominantly of fecal origin; flux did not increase upon fertilization. Our data thus indicate intense flux attenuation between 100 and 200 m, and probably between the mixed layer and 100 m. We attribute the lack of fertilization-induced export to silicon limitation of diatoms and reprocessing of sinking particles by detritus feeders. Our data are consistent with the view that nitrate-rich but silicate-deficient waters are not poised for enhanced particle export upon iron addition. |
| Mots-clés | : | - |
| Commentaire | : | Times Cited: 4 Sanders, Richard/B-8717-2012 4 |
| Tags | : | - |
| Fichier attaché | : | - |
| Citation | : |
Martin V, Van der Loeff MR, Cassar N, Vandromme P, D'Ovidio F, Stemmann L, Rengarajan R, Soares M, González N, Ebersbach F, Lampitt R, Sanders R, Barnett BA, Smetacek V, Naqvi SWA (2013) Iron fertilization enhanced net community production but not downward particle flux during the Southern Ocean iron fertilization experiment LOHAFEX. Global Biogeochem Cy 27: 871-881 | doi: 10.1002/gbc.20077
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