Aphotic N2 fixation in the Eastern Tropical South Pacific Ocean.

ABSTRACT: We examined rates of N2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niño (2010) and La Niña (2011). Replicated vertical profiles performed under oxygen-free conditions show that N2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 µmol N m(-2) d(-1) in 2010 and 24±14 to 118±87 µmol N m(-2) d(-1) in 2011. In the aphotic layers, volumetric N2 fixation rates were relatively low (<1.00 nmol N L(-1) d(-1)), but when integrated over the whole aphotic layer, they accounted for 87-90% of total rates (euphotic+aphotic) for the two cruises. Phylogenetic studies performed in microcosms experiments confirm the presence of diazotrophs in the deep waters of the Oxygen Minimum Zone (OMZ), which were comprised of n

SUBMITTER: Bonnet S 

PROVIDER: S-EPMC3861260 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature