Blue carbon ecosystems, such as coastal wetlands, saltmarshes and peatlands, store significant amounts of carbon through sequestration of atmospheric carbon dioxide. In fact, these ecosystems can store up to ten times more carbon per hectare than temperate forests, underscoring their strong potential for climate change mitigation. However, blue carbon ecosystems are also significant sources of methane, a potent greenhouse gas with ~80 times the global warming potential of carbon dioxide over a 20-year period and rising atmospheric concentrations. Therefore, understanding the extent of methane production from these ecosystems is essential.
In coastal environments, the majority of methane is produced by microbial degradation of one-carbon compounds such as methanol, methylamines (MAs) and dimethylsulfide (DMS). This is because coastal sediments typically have high salinity, and thus high sulfate levels. In high-sulfate ecosystems, sulfate-reducing bacteria (SRB) may outcompete methane-producers for compounds like acetate and hydrogen. However, SRB may not outcompete methanogens for one-carbon compounds. Yet, the impact of rising sea levels, which increase sulfate concentrations, on the activity of methane-producers and SRB, and consequent methane production rates, remains unclear.
Research from our group and others has shown that methane-producers from various genera (e.g. Methanomethylovorans, Methanolobus and Methanococcoides) can utilise one-carbon compounds to produce methane in diverse coastal sediments with varying sulfate availability such as saltmarshes and peatlands. Recent DNA-based studies have expanded our understanding of methanogens to novel phyla such as Bathyarchaeota and Methanomethyliaceae. These studies suggest that the degradation of one-carbon compounds plays a critical role in methane production in blue carbon ecosystems and that the diversity of methanogens in these settings is more widespread than previously thought. Still, there is a significant gap in our knowledge of the microbial diversity and metabolic pathways underpinning one-carbon compound degradation in coastal blue carbon sediments under changing climatic conditions (i.e. rising temperature and salinity). This multidisciplinary project will deliver the first comprehensive quantification of one-carbon compound cycling and associated methanogenesis in coastal sediments, and characterize, at unprecedented resolution, the microbial diversity and pathways driving these processes through an innovative combination of cultivation-dependent and -independent approaches.
This project is not suitable for CASE funding
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Methane and one-carbon compound turnover in anoxic coastal sediments. We will collect seasonal sediment samples (0-40 cm depth) from selected coastal wetlands, saltmarshes and peatlands to measure the standing stock concentrations of methane and one-carbon compounds over an annual cycle. To assess the impact of temperature and salinity on methane production rates, we will set up anaerobic incubations with selected samples different temperatures (in situ and 4°C higher) and salinities. We will measure the chemical concentrations using gas and ion chromatography.
Diversity and metabolism of the methanogens degrading one-carbon compounds in coastal sediments. We will employ DNA and RNA-based tools (amplicon sequencing, metagenomics and metatranscriptomics) to characterise the microbial community and metabolic pathways underlying methane production via one-carbon compound degradation in the samples. Additionally, we will use the stable isotope probing method with 13C-labelled methanol, methylamines and DMS, to identify microbes actively degrading these one-carbon compounds. We will also grow pure microbial cultures to study their physiology under changing climatic conditions.
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
The DR will receive comprehensive training across a range of technical skills. Initially, they will be trained in field sampling techniques, including the collection of sediment cores and the setup of microcosms for anaerobic biogeochemical and microbiological studies. Following this, they will develop analytical expertise, learning how to use gas chromatography and ion chromatography to quantify gas concentrations and other key chemicals (e.g., sulfate, trimethylamine). The training will also encompass microbial ecology and anaerobic microbiology focusing on stable-isotope probing, advanced DNA and RNA-based tools as well as the associated bioinformatics pipelines to analyse amplicon sequencing, metagenomics and metatranscriptomics data.
Not applicable.
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Journal:
Tsola, S. L., Zhu, Y., Chen, Y. et al. (2024) ‘Methanolobus use unspecific methyltransferases to produce methane from dimethylsulfide in Baltic Sea sediments’, Microbiome, 12, pp: 3.
Macreadie, P. T., Costa, M. D. P., Atwood, T. B. et al. (2021) ’ Blue carbon as a natural climate solution’, Nature Reviews Earth & Environment, 2, pp. 826-839.
Al-Haj, A. N. and Fulweiler, R. W. (2020) ‘A synthesis of methane emissions from shallow vegetated coastal ecosystems’, Global Change Biology, 26, pp. 2988-3005.
Jameson, E., Stephenson, J., Jones, H. et al. (2019) ‘Deltaproteobacteria and Methanococcoides are responsible for choline-dependent methanogenesis in a coastal saltmarsh sediment’, The ISME Journal, 13, pp. 277-289.
For any enquiries related to this project please contact Ozge Eyice, [email protected]
To apply to this project:
Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026.