Nanoscale trace metal imprinting of biocalcification of planktic foraminifers by Toba\u2019s super-eruption

L Lemelle,W De Nolf,F Bassinot,A Bartolini,T De Garidel-Thoron,R Tucoulou,A Simionovici

doi:10.1038/s41598-020-67481-w

Abstract

Bioactive metal releases in ocean surface water, such as those by ash falls during volcanic super-eruptions, might have a potentially toxic impact on biocalcifier planktic microorganisms. Nano-XRF imaging with the cutting-edge synchrotron hard X-ray nano-analysis ID16B beamline (ESRF) revealed for the first time a specific Zn- and Mn-rich banding pattern in the test walls of Globorotalia menardii planktic foraminifers extracted from the Young Toba Tuff layer, and thus contemporaneous with Toba’s super-eruption, 74,000 years ago. The intra-test correlation of Zn and Mn patterns at the nanoscale with the layered calcareous microarchitecture, indicates that the incorporation of these metals is syngenetic to the wall growth. The preferential Mn and Zn sequestration within the incipient stages of chamber formation suggests a selective incorporation mechanism providing a resilience strategy to metal pollution in the test building of planktic foraminifers.

Highlights

Bioactive metal releases in ocean surface water, such as those by ash falls during volcanic supereruptions, might have a potentially toxic impact on biocalcifier planktic microorganisms
Planktic foraminifers can be exposed to releases of these bioactive metal cations by leaching of acid aerosols and metal salts adsorbed on the surface of ash, when ash-loaded falls come into contact with ocean surface w aters21,22. Mn2+ and Z n2+, essential to biological processes, can stimulate the primary productivity and enzymatic activity of p hytoplankton[21]
We investigate tests picked from the Young Toba Tuff layer, which are contemporaneous to the greatest volcanic cataclysm of the Quaternary: the Toba super-eruption, 74,000 years a go[26]

Summary

Introduction

Bioactive metal releases in ocean surface water, such as those by ash falls during volcanic supereruptions, might have a potentially toxic impact on biocalcifier planktic microorganisms. Mn2+ and Z n2+, essential to biological processes, can stimulate the primary productivity and enzymatic activity of p hytoplankton[21] If in excess, such as in the case of a super-eruption, a toxic impact on sensitive marine organisms, such as biocalcifying microorganisms, has been suggested[23]. The mechanism of incorporation of metals such as Zn and Mn during the formation of a new planktic foraminifer chamber has to be explored, especially in response to large volcanic eruptions For this purpose, we investigate tests picked from the Young Toba Tuff layer, which are contemporaneous to the greatest volcanic cataclysm of the Quaternary: the Toba super-eruption, 74,000 years a go[26]. Given the huge quantities of ashes ejected by Toba’s super-eruption (i.e. ~ 2,800 km[3] of magma)[26], high fluxes of ash leachate metal elements might have contaminated the ocean surface waters, in the proximal area of the volcano

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