Zinc is vital for the physiology of oceanic phytoplankton. The striking similarity of the depth profiles of zinc to those of silicate suggests that the uptake of both elements into the opaline frustules of diatoms, and their regeneration from these frustules, should be coupled. However, the zinc content of diatom opal is negligible, and zinc is taken up into and regenerated from the organic parts of diatom cells. Thus, since opaline frustules dissolve deep in the water column while organic material is regenerated in the shallow subsurface ocean, there is little reason to expect the observed close similarity between zinc and silicate, and the dissimilarity between zinc and phosphate. Here we combine observations with simulations using a three-dimensional model of ocean circulation and biogeochemistry to show that the coupled distribution of zinc and silicate, as well as the decoupling of zinc and phosphate, can arise in the absence of mechanistic links between the uptake of zinc and silicate, and despite contrasting regeneration length scales. Our simulations indicate that the oceanic zinc distribution is, in fact, a natural result of the interaction between ocean biogeochemistry and the physical circulation through the Southern Ocean hub. Our analysis demonstrates the importance of uptake stoichiometry in controlling ocean biogeochemistry, and the utility of global-scale elemental covariation in the ocean in understanding these controls.
Institute of Geochemistry and Petrology, Department of Earth Sciences, ETH Zörich, Clausiusstrasse 25, Zörich, Switzerland; Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London, United Kingdom; Department of Earth Sciences, South Parks Road, Oxford, United Kingdom; School of Ocean and Earth Sciences, National Oceanography Centre, University of Southampton, Southampton, United Kingdom; NIOZ Royal Netherlands Institute for Sea Research, Department of Ocean Systems, Utrecht University, PO Box 59, Texel, Netherlands
Recommended Citation:
Vance D.,Little S.H.,De Souza G.F.,et al. Silicon and zinc biogeochemical cycles coupled through the Southern Ocean[J]. Nature Geoscience,2017-01-01,10(3)