Activated carbon stimulates microbial diversity and PAH biodegradation under anaerobic conditions in oil-polluted sediments

Stefano Bonaglia,Elias Broman,Björn Brindefalk,Erika Hedlund,Tomas Hjorth,Carl Rolff,Francisco J.A Nascimento,Klas Udekwu,Jonas S Gunnarsson

doi:10.1016/j.chemosphere.2020.126023

Stefano Bonaglia, Elias Broman + Show 7 more

Open Access

https://doi.org/10.1016/j.chemosphere.2020.126023

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Abstract

Biodegradation by microorganisms is a useful tool that helps alleviating hydrocarbon pollution in nature. Microbes are more efficient in degradation under aerobic than anaerobic conditions, but the majority of sediment by volume is generally anoxic. Incubation experiments were conducted to study the biodegradation potential of naphthalene—a common polycyclic aromatic hydrocarbon (PAH)—and the diversity of microbial communities in presence/absence of activated carbon (AC) under aerobic/anaerobic conditions. Radio-respirometry experiments with endogenous microorganisms indicated that degradation of naphthalene was strongly stimulated (96%) by the AC addition under anaerobic conditions. In aerobic conditions, however, AC had no effects on naphthalene biodegradation. Bioaugmentation tests with cultured microbial populations grown on naphthalene showed that AC further stimulated (92%) naphthalene degradation in anoxia. Analysis of the 16S rRNA gene sequences implied that sediment amendment with AC increased microbial community diversity and changed community structure. Moreover, the relative abundance of Geobacter, Thiobacillus, Sulfuricurvum, and methanogenic archaea increased sharply after amendment with AC under anaerobic conditions. These results may be explained by the fact that AC particles promoted direct interspecies electron transfer (DIET) between microorganisms involved in PAH degradation pathways. We suggest that important ecosystem functions mediated by microbes—such as hydrocarbon degradation—can be induced and that AC enrichment strategies can be exploited for facilitating bioremediation of anoxic oil-contaminated sediments and soils.

Highlights

This study clearly shows that under anaerobic conditions amendment with activated carbon (AC) significantly increased the biodegradation of naphthalene (Fig. 3a) and high molecular weight (HMW) polycyclic aromatic hydrocarbon (PAH) (Fig. S4)
Oil pollution is a serious threat to the environment, but microbial degradation of organic contaminants can facilitate in situ remediation strategies (Leahy and Colwell, 1990; Liang et al, 2009; Lu et al, 2011)
As most of the volume of contaminated sediment is anoxic, our research focused on a potential, affordable method to boost bioremediation under anaerobic conditions

Summary

Introduction

Low molecular weight (LMW) PAHs, such as naphthalene, are more water-soluble than high molecular weight (HMW) ones (Hylland, 2006), while HMW PAHS are of particular concern since they are potentially carcinogenic or teratogenic for marine organisms and humans. There are many natural HC-degrading microorganisms in marine ecosystems, such as Pseudomonas, Mycobacterium, Klebsiella, Acinetobacter, Micrococcus and Nocardia (Roy et al, 2002) These organisms can utilize PAHs as primary carbon source, which may lead to their complete mineralization from HMW to LMW PAHs and to carbon dioxide and inorganic nutrients (Atlas, 1981).

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