Direct measurement of fungal contribution to silicate weathering rates in soil

Bastien Wild,Damien Daval,Gwenaël Imfeld

doi:10.1130/g48706.1

Abstract

AbstractChemical weathering produces solutes that control groundwater chemistry and supply ecosystems with essential nutrients. Although microbial activity influences silicate weathering rates and associated nutrient fluxes, its relative contribution to silicate weathering in natural settings remains largely unknown. We provide the first quantitative estimates of in situ silicate weathering rates that account for microbially induced dissolution and identify microbial actors associated with weathering. Nanoscale topography measurements showed that fungi colonizing olivine [(Mg,Fe)2SiO4] samples in a Mg-deficient forest soil accounted for up to 16% of the weathering flux after 9 mo of incubation. A local increase in olivine weathering rate was measured and attributed to fungal hyphae of Verticillium sp. Altogether, this approach provides quantitative parameters of bioweathering (i.e., rates and actors) and opens new avenues to improve elemental budgets in natural settings.

Highlights

A frontier in quantitative modeling of silicate weathering in the critical zone, where “rocks meet life” (Brantley et al, 2011), is the incorporation of microbial activity in reactive transport models (RTMs; Frings and Buss, 2019; Goddéris et al, 2019)
We developed an approach to directly quantify in situ mineral weathering rates in natural environments, providing a joint evaluation of the fungal contribution to the overall weathering flux and the associated fungal diversity
The plot chosen for this study was part of an instrumented site of the Observatoire HydroGéochimique de l’Environnement (OHGE) critical zone observatory, which enabled us to retrieve environmental parameters monitored on site during sample incubation

Summary

Introduction

A frontier in quantitative modeling of silicate weathering in the critical zone, where “rocks meet life” (Brantley et al, 2011), is the incorporation of microbial activity in reactive transport models (RTMs; Frings and Buss, 2019; Goddéris et al, 2019). While most estimates of microbially mediated silicate weathering rates so far have been derived from laboratory experiments (Wild et al, 2018), a few pioneering studies have provided environmental estimates for naturally altered minerals in surface aquifers (Rogers and Bennett, 2004) or soil profiles (e.g., van Schöll et al, 2008, and references therein) based on scanning electron microscopy (SEM) analysis.

Results

Conclusion