Abstract
<p> <p id="x-x-sp0005"> Zinc (Zn) is an essential micronutrient, playing an important role in several key processes in marine <a title="Learn more about phytoplankton from ScienceDirect's AI-generated Topic Pages"> phytoplankton </a> . Here, we present the first high-resolution depth profiles for dissolved Zn and δ <sup> 66 </sup> Zn from all major zones of the <a title="Learn more about Southern Ocean from ScienceDirect's AI-generated Topic Pages"> Southern Ocean </a> , collected during the Antarctic Circumnavigation Expedition in Austral Summer 2016/2017. The dataset reveals that Zn cycling changes between different regions of the Southern Ocean. Within the Antarctic <a title="Learn more about Circumpolar Current from ScienceDirect's AI-generated Topic Pages"> Circumpolar Current </a> (ACC), Zn cycling is closely linked to phosphate (PO <sub> 4 </sub> ), governed by uptake and regeneration, seasonal mixing, and upwelling. Here, uptake by phytoplankton is associated with a very small fractionation (α = 0.99995), resulting in slightly elevated surface δ <sup> 66 </sup> Zn (up to +0.67‰), overlying a shallow subsurface δ <sup> 66 </sup> Zn minimum (+0.36‰ at ∼200 m). South of the ACC, a partial coupling of Zn and silicate (Si) results in a shift of the <a title="Learn more about Zn isotope from ScienceDirect's AI-generated Topic Pages"> Zn isotope </a> systematics and a deep enrichment of Zn and Si. Two possible mechanisms could potentially cause this change: 1) reversible scavenging onto sinking particulates, or, 2) association of isotopically heavy Zn with diatom frustules. We also observe the effects of regional processes on Zn in the surface Southern Ocean: firstly, natural Fe fertilization near the Balleny Islands appears to lead to reduced Zn uptake (relative to phosphate) by phytoplankton, that is associated with a greater apparent Zn isotope fractionation than elsewhere in the Southern Ocean (α = 0.99987); secondly, <a title="Learn more about meltwater from ScienceDirect's AI-generated Topic Pages"> meltwater </a> inputs from the Mertz Glacier add small amounts of isotopically light Zn to surface waters near the Antarctic shelf. Overall, we propose that the lack of distinct δ <sup> 66 </sup> Zn signatures transported in intermediate waters of the lower latitude global oceans is due to near-complete uptake of Zn by phytoplankton in the surface Southern Ocean with only a small isotope fractionation, in contrast to elements like cadmium and silicon. </p></p>
Original language | American English |
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Journal | Geochimica et Cosmochimica Acta |
Volume | 268 |
DOIs | |
State | Published - Jan 1 2020 |
Keywords
- Trace metals
- Biogeochemistry
- Zinc
- Antarctic circumpolar current
- Isotopes
- Nutrient cycling
Disciplines
- Life Sciences