Dark Carbon Fixation: An Important Process in Lake Sediments

Ana Lúcia Santoro,Lars Tranvik,Cristian Gudasz,Alex Enrich-Prast,David Bastviken,Simon Thrush

doi:10.1371/journal.pone.0065813

Ana Lúcia Santoro, Lars Tranvik + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0065813

Copy DOI

Abstract

Close to redox boundaries, dark carbon fixation by chemoautotrophic bacteria may be a large contributor to overall carbon fixation. Still, little is known about the relative importance of this process in lake systems, in spite the potentially high chemoautotrophic potential of lake sediments. We compared rates of dark carbon fixation, bacterial production and oxygen consumption in sediments from four Swedish boreal and seven tropical Brazilian lakes. Rates were highly variable and dark carbon fixation amounted up to 80% of the total heterotrophic bacterial production. The results indicate that non-photosynthetic carbon fixation can represent a substantial contribution to bacterial biomass production, especially in sediments with low organic matter content.

Highlights

The incorporation of inorganic carbon into organic matter, i.e. carbon fixation, is one of the essential functions in ecosystems
We demonstrate that dark carbon fixation (DCF) rates can be relatively high and can represent an important contribution to bacterial biomass production, especially in sediments with low organic matter content
A separate test with sediment from the same core incubated using both Brazilian and Swedish protocols confirmed that the differences in terms of how microbial activity was stopped or how much isotope was added did not affect the results of bacterial production or dark carbon fixation assays

Summary

Introduction

The incorporation of inorganic carbon into organic matter, i.e. carbon fixation, is one of the essential functions in ecosystems. In this study we compared sediment DCF, bacterial production (BP), and oxygen consumption (SOC) rates from boreal lakes in Sweden and tropical lakes in Brazil. We demonstrate that DCF rates can be relatively high and can represent an important contribution to bacterial biomass production, especially in sediments with low organic matter content.

Results

Conclusion