Journal
GLOBAL BIOGEOCHEMICAL CYCLES
Volume 28, Issue 1, Pages 44-56Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013GB004637
Keywords
Zinc; Biogeochemistry; South Atlantic; Chemical oceanography; GEOTRACES
Funding
- National Environmental Research Council (NERC) [NE/H004475/1, NE/G52388X/1]
- NERC [NE/H004289/1, NE/H004475/1] Funding Source: UKRI
- Natural Environment Research Council [NE/H004475/1, NE/H004289/1] Funding Source: researchfish
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The biogeochemical cycle of zinc (Zn) in the South Atlantic, at 40 degrees S, was investigated as part of the UK GEOTRACES program. To date there is little understanding of the supply of Zn, an essential requirement for phytoplankton growth, to this highly productive region. Vertical Zn profiles displayed nutrient-like distributions with distinct gradients associated with the water masses present. Surface Zn concentrations are among the lowest reported for the world's oceans (< 50 pM). A strong Zn-Si linear relationship was observed (Zn (nM)=0.065 Si (M), r(2)=0.97, n=460). Our results suggest that the use of a global Zn-Si relationship would lead to an underestimation of dissolved Zn in deeper waters of the South Atlantic. By utilizing Si* and a new tracer Zn* our data indicate that the preferential removal of Zn in the Southern Ocean prevented a direct return path for dissolved Zn to the surface waters of the South Atlantic at 40 degrees S and potentially the thermocline waters of the South Atlantic subtropical gyre. The importance of Zn for phytoplankton growth was evaluated using the Zn-soluble reactive phosphorus (SRP) relationship. We hypothesize that the low Zn concentrations in the South Atlantic may select for phytoplankton cells with a lower Zn requirement. In addition, a much deeper kink at similar to 500m in the Zn:SRP ratio was observed compared to other oceanic regions. Key Points
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