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Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean

Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean
Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean
Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu and Ag display nutrient-like profiles similar to silicic acid, and of Cd similar to phosphate. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb concentrations are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water masses enriched in trace metals following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source of trace metals to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced dissolved Mn concentrations. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However, uptake by dino- and nano-flagellates may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical surface waters where phosphate concentrations were below 0.95 ?M. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd uptake induced by iron-limiting conditions in these high-nutrient–low-chlorophyll waters. Similarly, an increase of Mn uptake under Fe-depleted conditions may have caused the highest depletion of Mn relative to P in the surface waters of the Weddell Gyre. In addition, a cellular Mn-transport channel of Cd was possibly activated in the Weddell Gyre, which in turn may have yielded depletion of both Mn and Cd in these surface waters.
1726-4170
3231-3246
Boye, M.
6a3fb926-e1ed-40cc-87a0-63c9870f782b
Wake, B.D.
f9ab6e3f-6d4d-4c2b-8c8f-2b5c0b8edabe
Lopez Garcia, P.
cb6528d7-5178-4ab3-9708-ed8e87fbdf45
Bown, J.
d4d009c6-4312-4392-9a44-78fa7264f479
Baker, A.R.
2e470bae-1030-49cb-999e-1a0bfb0abfc9
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Boye, M.
6a3fb926-e1ed-40cc-87a0-63c9870f782b
Wake, B.D.
f9ab6e3f-6d4d-4c2b-8c8f-2b5c0b8edabe
Lopez Garcia, P.
cb6528d7-5178-4ab3-9708-ed8e87fbdf45
Bown, J.
d4d009c6-4312-4392-9a44-78fa7264f479
Baker, A.R.
2e470bae-1030-49cb-999e-1a0bfb0abfc9
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9

Boye, M., Wake, B.D., Lopez Garcia, P., Bown, J., Baker, A.R. and Achterberg, E.P. (2012) Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean. Biogeosciences, 9 (8), 3231-3246. (doi:10.5194/bg-9-3231-2012).

Record type: Article

Abstract

Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu and Ag display nutrient-like profiles similar to silicic acid, and of Cd similar to phosphate. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb concentrations are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water masses enriched in trace metals following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source of trace metals to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced dissolved Mn concentrations. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However, uptake by dino- and nano-flagellates may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical surface waters where phosphate concentrations were below 0.95 ?M. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd uptake induced by iron-limiting conditions in these high-nutrient–low-chlorophyll waters. Similarly, an increase of Mn uptake under Fe-depleted conditions may have caused the highest depletion of Mn relative to P in the surface waters of the Weddell Gyre. In addition, a cellular Mn-transport channel of Cd was possibly activated in the Weddell Gyre, which in turn may have yielded depletion of both Mn and Cd in these surface waters.

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Published date: 2012
Organisations: Ocean Biochemistry & Ecosystems

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Local EPrints ID: 347787
URI: https://eprints.soton.ac.uk/id/eprint/347787
ISSN: 1726-4170
PURE UUID: 328169b8-a283-430c-9e9c-60d4d0b24a08

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Date deposited: 30 Jan 2013 11:40
Last modified: 16 Jul 2019 21:45

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Contributors

Author: M. Boye
Author: B.D. Wake
Author: P. Lopez Garcia
Author: J. Bown
Author: A.R. Baker
Author: E.P. Achterberg

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