When direct mapping of diatoms reveals unexpected fate of trace metals in the twilight zone

Twining and co-authors (2014, see reference below) used synchrotron x-ray fluorescence mapping to measure macronutrients such phosphorus (P), sulphur (S), and silicon (Si), and also trace metals like iron (Fe), nickel (Ni) and zinc (Zn), in individual cells of a diatom specie during a spring bloom off New Zealand. They clearly show that P, S, Zn and Ni are released faster than Fe and Si from sinking cells in the upper 200 m. Although the metals are co-located with P and S at the surface, the scheme changes deeper. The relationships with P and S become weak while an association of Fe with Si appears, suggesting re-adsorption when particles are settling. Exciting results revealing that ratios of dissolved Fe to macronutrients in the water column likely underestimate stoichiometries in sinking cells.

14 twining l
Figure. Element maps (P, S, Fe ,and Zn) and associated scatterplots of Fe and S concentrations in each pixel of the scans for two diatom cells collected from 30m or 200m following a spring bloom off New Zealand.  The scatterplots show that Fe and S are spatially decoupled from each other when the diatom cells degrade as they sink through the upper water column.  S is lost more readily from the cells, while Fe appears to be retained or is re-scavenged.  Scale bar indicates 10um for each cell.  Adapted from Twining et al. (2014). Click here to view the figure larger.

 

Reference:

Twining, B. S., Nodder, S. D., King, A. L., Hutchins, D. A., LeCleir, G. R., DeBruyn, Jennifer M.; Maas, E. W., Vogt, S., Wilhelm, S. W., Boyd, P. W. (2014). Differential remineralization of major and trace elements in sinking diatoms. Limnology and Oceanography, 59(3), 689–704. doi:10.4319/lo.2014.59.3.0689 Click here to view the paper.

Latest highlights

Science Highlights

Retreat of large marine-terminating glaciers may increase iron supply to surface waters

The findings demonstrate that glacial retreat and loss of ice-shelves may potentially result in increases in dissolved Fe supply to surface waters downstream of large marine terminating glaciers in future.

31.05.2021

Science Highlights

When lateral advective transport explains between 80 and 100% of the dissolved aluminium distribution

This study evidence that the effect of advection cannot be neglected in areas where a conjunction of significant horizontal dissolved aluminium gradients and significant horizontal currents is found.

26.05.2021

Science Highlights

Variable dissolution rates and fates of lithogenic tracers at the air-sea interface

Roy-Barman and co-authors established the dissolution rates from Saharan dust reaching Mediterranean seawater.

21.05.2021

Science Highlights

Updated compilation of the global continental and marine lithogenic neodymium isotopic measurements

This new compilation and gridded datasets offer a concrete way forward to improve the application of Nd isotopes as a useful tracer of ocean circulation.

05.05.2021

Rechercher