Effects of nickel and cobalt on methane production and methanogen abundance and diversity in paddy soil

Abstract

BackgroundPaddies are an important anthropogenic source of methane emissions to the atmosphere, and they are impacted by heavy metal pollution. Nickel (Ni) and cobalt (Co) pollution might either enhance or mitigate CH4 emission from paddy soils due to the total amounts of metals, bioavailability and functional microbial activity and composition.MethodsAn incubation experiment was conducted, and different Ni and Co concentrations were added to test the effects of trace metals on methane production in paddy soil. The archaea community structure and the abundance of methanogen functional groups in the paddy soil with added Ni and Co were detected using high-throughput sequencing and quantitative PCR based on the 16S rRNA and mcrA (methyl coenzyme M reductase) genes, respectively.ResultsThe highest methane production rate was 561 mg CH4 kg−1 dry soil d−1 with the addition of 50 mg kg−1 Ni and 684 mg CH4 kg−1 dry soil d−1 with the addition of 25 mg kg−1 Co. Accordingly, the mcrA gene was most abundant in the 50 mg kg−1 Ni addition (3.1 × 106 ± 0.5 × 106 copies g−1 dry soil). The lowest mcrA gene abundance was detected in the 500 mg kg−1 Co addition (9.2× 105 ± 0.4 × 105 copies g−1 dry soil). The dominant methanogens were Methanobacterium, Methanosarcina, Methanocella, Methanomassiliicoccus, Bathyarchaeota, and Rice Cluster I (RC-I), and the relative abundances of these groups were higher than 1% in the Ni and Co treatments. Additionally, the archaeal compositions differed significantly in the soils with various Ni and Co additions. The most abundant Methanococcus spp. represented 51.3% of the composition in the 50 mg kg−1 Ni addition, which was significantly higher than that of the control (12.9% to 17.5%).DiscussionOur results indicated that the contamination of soil by Ni and Co significantly affected total methanogens abundance and specific methanogen functional groups. Ni and Co additions to paddy soil promoted methanogenic activity at low concentrations, while they had inhibitory effects at high concentrations. Because paddy soils largely contribute to methane emissions and are increasingly exposed to heavy metal pollution, our results show that future assessments of greenhouse gas flux from paddy soils should take into account the effects of pollution by Ni and Co.

Nutrient and trace element concentrations influence greenhouse gas emissions from Malaysian tropical peatlands

“…Considering that cobalt concentrations were very low in the studied sites, increase in such concentrations positively increased CH 4 production by promoting methanogens. Similar positive correlation was also observed in paddy fields, where cobalt promoted the abundance and activity of methanogens (Wang et al., 2019). The same study also found that optimum cobalt concentrations for CH 4 production in paddy soil are 50 mg kg −1 , which is multi‐fold higher than the concentrations in studied tropical peatlands, showing a strong potential for further increase in CH 4 emissions with changes in cobalt concentrations.…”

“…The concentrations of these nutrients and heavy metals in peat can influence greenhouse gas emissions via a few different pathways: (a) directly through chemical and mechanistic control over processes (Warren et al., 2017); (b) indirectly through changes in microbial community properties such as community structure, diversity, activity and biomass (Dowrick et al., 2006; Wang et al., 2019); (c) in natural habitats, nutrients and trace elements can also influence plant species distribution (John et al., 2007) that affects microbial communities through rhizosphere or plant litter inputs, which can further impact GHG emissions (Bezemer et al., 2006; Burns et al., 2015; Fan et al., 2019). However, the lack of research on nutrient and trace element concentrations in different peatlands, particularly tropical peatlands leave these processes and interrelations unexplored.…”

Beyond the usual suspects: methanogenic communities in eastern North American peatlands are also influenced by nickel and copper concentrations

“…However, very high concentrations of nickel have also been associated with detrimental effects on methanogens and methane productions (Chen, Cheng and Creamer 2008). Peatlands with low concentrations of nickel have communities dominated by Methanocellales and Methanosarcina, suggesting that these methanogenic groups may be inhibited by higher concentrations of nickel in soil (Figure S4, Supporting Information; Paulo et al 2017;Wang et al 2019). In contrast, the Methanomicrobiales appear to thrive with elevated concentrations of nickel, possibly due to the diversity of Methanomicrobiales, effective mechanisms for regulating or tolerating metal uptake, or other factors in the environment that covary with the high metal concentrations, such as Sphagnum loss in the three impacted sites, Long, Daisy and Whitson (Carson 2018).…”

Dynamic Effect of Operational Regulation on the Mesophilic BioMethanation of Grape Marc

“…Shi et al [55] observed that, in the treatment of lignocellulosic biomass, a prior acclimation period of the microbes contained in the inoculum was necessary for immediate biogas production in digesters. Additionally, a sufficient contact time reduced the magnitude of the microbial response to potentially toxic compounds, namely excessive levels of ammonia, volatile fatty acids, and heavy metals that can exert bacteriostatic and even bactericidal effects [56][57][58].…”