Simple methodological approach for assessing microbial mineralization rates in an aqueous anaerobic medium

Marcela Bianchessi Da Cunha-Santino,Irineu Bianchini Junior

doi:10.1590/s2179-975x2721

Marcela Bianchessi Da Cunha-Santino, Irineu Bianchini Junior

Open Access

https://doi.org/10.1590/s2179-975x2721

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Abstract

Abstract: The aim of this study was to propose and discuss a simple manometric method to quantify the emission rates of gases resulting from the microbial anaerobic mineralization of organic resources, as leaves, thin branches, and macrophyte detritus. The proposed method can be used under laboratory conditions. The method consists of using a water pressure gauge attached to the reaction flask. The incubations were prepared with samples of water from Paranapanema River and Typha domingensis, the experiment lasted 9.8 months. The procedures for preparing the incubations are presented in detail, as well as the calculations for the conversion of the volumetric measurement into carbon mass (i.e., daily rate of carbon gas emissions). According to the results obtained from T. domingensis mineralization assays it was possible to demonstrate that, numerous events related to mineralization could be adequately addressed (e.g., the heterogeneous detritus composition). The results of this method were quite convergent with those obtained in kinetic experiments (used as a reference) after the 30th mineralization day, suggesting the use of this method mainly for medium- and long-term experiments. As exemplified by T. domingensis incubations, this method is particularly valuable for the systemic comparison of the several organic resources mineralization and for the primary measurement of the main parameters involved (e.g., reaction rates constants). This method combined with other short-term experiments can greatly improve the understanding of the cycling of organic resources in aquatic environments.

Highlights

Mineralization is a key process that determines the magnitude of organic matter stored in hydric soils and sediments, and the amount of greenhouse gas emissions (Heitkamp et al, 2012; Chapman et al, 2019)
The aim of this study was to propose and discuss a simple manometric method to quantify the emission rates of gases resulting from the microbial anaerobic mineralization of organic resources, as leaves, thin branches, and macrophyte detritus
According to the results obtained from T. domingensis mineralization assays it was possible to demonstrate that, numerous events related to mineralization could be adequately addressed

Summary

Introduction

Mineralization is a key process that determines the magnitude of organic matter stored in hydric soils and sediments, and the amount of greenhouse gas emissions (Heitkamp et al, 2012; Chapman et al, 2019). With the mineralization, the humification acts to transform a fraction of the plant residues into stable organic matter or humus (Dalmagro et al, 2017) In aquatic systems it prevails in the sediments they can occur in the water column. In the inner layers of sediments, anoxic conditions usually prevail, leading to the predominance of anaerobic catabolism In this environment, organic matter is mineralized associated with processes such as denitrification, sulfate reduction and fermentation (Reddy & DeLaune, 2008). Due to the methodological limitation, decomposition can be achieved by exclusive experiments to describe specific processes

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