OceanRep
Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic.
Kähler, Paul, Oschlies, Andreas , Dietze, Heiner and Koeve, Wolfgang (2010) Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic. Biogeosciences (BG), 7 (3). pp. 1143-1156. DOI 10.5194/bg-7-1143-2010.
Preview |
Text
kähler.pdf - Published Version Download (660kB) |
Abstract
The Beta Triangle, a region of the oligotrophic subtropical eastern North Atlantic Ocean, is notorious for its enigmatic oxygen, carbon, and nitrogen balances, in which nutrient supply is said to explain only a fraction of production necessary for estimated carbon export. Rates of dissolved organic carbon accumulation and dissolved organic nitrogen utilization in surface water and an assessment of oxygen utilized, organic matter consumed, and nitrate and phosphate regenerated in subsurface water, show that conventional production estimates miss substantial shares of biotic production.
The shallow export of total organic carbon, predominantly dissolved (DOC), by subduction is responsible for about 50–70% of apparent oxygen utilization in subsurface water between the base of the surface layer at ca. 140 m and ca. 195 m depth, but it is insignificant below. Additionally, there is an estimated accumulation of 1.0 to 1.75 mol DOC m−2 a−1 in surface water. Including DOC dynamics in its carbon balance reveals the surface of this ultra-oligotrophic part of the ocean to be net autotrophic.
Increasing subsurface values of excess nitrogen (DINxs) imply the export of nitrogen from surface water stemming from production not exclusively fuelled by new nitrate supplied from below. Total organic nitrogen (almost exclusively dissolved, DON) is consumed in the surface layer at a rate estimated at 0.13 to 0.23 mol m−2 a−1. There is no variation in dissolved organic phosphorus (DOP) in the same direction. DON utilization thus contributes to the pronounced subsurface DINxs signature.
DOC export and accumulation are important in the carbon balance in surface and near-surface water. DON utilization and, probably, N2 fixation contribute significant amounts to the nitrogen supply of surface water. These processes can close part of the enigmatic carbon and nitrogen balances in the Beta Triangle. There are, however, no comparable processes which can explain the equally enigmatic situation concerning phosphorus supply in this area.
Document Type: | Article |
---|---|
Keywords: | Biogeochemistry; RV Poseidon; POS273 |
Research affiliation: | OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling OceanRep > The Future Ocean - Cluster of Excellence |
Refereed: | Yes |
Open Access Journal?: | Yes |
Publisher: | Copernicus Publications (EGU) |
Projects: | Future Ocean |
Expeditions/Models/Experiments: | |
Date Deposited: | 08 Jun 2010 09:31 |
Last Modified: | 24 Nov 2015 13:22 |
URI: | https://oceanrep.geomar.de/id/eprint/8477 |
Actions (login required)
View Item |
Copyright 2023 | GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel | All rights reserved
Questions, comments and suggestions regarding the GEOMAR repository are welcomed
at bibliotheksleitung@geomar.de !