NI: Microbial Dimethylsulphide Degradation in Anoxic Baltic Sea Sediments

Methane is a powerful greenhouse gas which significantly contributes to global warming. This gas is produced by microbes that live in environments that lack oxygen (anoxic). We have known for some time that marine environments produce substantial amounts of methane. However, the sources of methane in marine ecosystems have not been fully described, which is a barrier to correct calculation of methane emissions from these environments. In particular, we know very little about which microbes produce methane and what metabolic process they use.

Previous studies showed that microbes can use dimethylsulphide (DMS) to grow and produce methane. DMS is a gas, which can be found in very high concentrations in marine environments. DMS in these habitats is produced through the breakdown of another compound shortly called DMSP, which is released in huge amounts following a phytoplankton bloom.

The Baltic Sea is a unique environment. This is because it is one of the largest brackish (moderate to low salinity) seas in the world. It is also subjected to regular phytoplankton blooms. Overall, the Baltic Sea provides an excellent natural laboratory to study DMS use and methane generation by microbes. The brackish condition of the Baltic Sea is particularly important. Because, sulphate is one of the important ions that determine the salinity. Low-to-moderate salinity means there is sulphate available to microbes. This may however affect the activity of methane-producing microbes. This is because methane-producers compete with sulphate-users for carbon sources, in our case for DMS. Depending on the outcome of this interaction, the amount of methane produced in marine sediments may reduce significantly. Therefore, we aim to understand how this metabolic pathway works and which microbes are responsible of this process.

In order to achieve our aim, we initiate a new partnership with colleagues from Sweden, who have long-term experience in the Baltic Sea research and tools to analyse critical data using powerful computing facilities. We will use our novel microbial ecology approach that combines state-of-the-art techniques with advanced microbial identification tools called high-throughput sequencing. Firstly, we will determine the extent to which DMS contributes to methane production in anoxic, brackish Baltic Sea sediments. We will then use isotopically labelled DMS, which enables us to follow the fate of carbon in sediments. Then, we will use genetic material (DNA and RNA) from microbes in the labelled sediment samples to identify the microbes that use DMS (methane-producing or sulphate-using) and infer their metabolism. The results will tell us the magnitude of methane production via DMS, which microbes use DMS and produce methane and how they carry out this process in brackish conditions in the Baltic Sea sediments. Overall, the outcome of this project will greatly improve our understanding of methane production in marine sediments and help in calculating greenhouse gas budgets via improved climate models. This will ultimately help us tackling global warming and climate change.

The proposed project aims to foster a new international partnership to identify the microbial communities that degrade dimethylsulphide (DMS) and produce methane in anoxic Baltic Sea sediments. DMS and methane are two major climate-active gases and therefore, this project will have a substantial impact on the ecosystem services, public health and the UK (and international) economy as well as advancing academic knowledge. These impacts will be realised as follows:

1. Academic beneficiaries (explained separately)
2. Contribution to the UK research capacity
3. Engaging the public and policy makers

Contribution to academic knowledge and UK research capacity:
One of the main foci of the proposed project is to initiate and sustain a robust and long-term international partnership between the researchers in the UK and Sweden. The UK stands in a great position in terms of environmental microbiology research. However, the research capacity of the UK in the area of anaerobic sediment microbiology and bioinformatics fields are still in progress. The proposed project offers explicit ways to understand the microbiology of DMS and methane cycling in anoxic Baltic Sea sediments. The two partner institutions in Sweden have excellent facilities and expertise in the biogeochemistry of the Baltic Sea, anaerobic microbiology and bioinformatics. Hence, it will be invaluable to bring this expertise the UK and train the UK researchers in these fields. The state-of-the-art methods (e.g. stable isotope probing, metatranscriptomics) to be used within this project are adaptable to other microbial ecosystems. Since this project is interdisciplinary with international partners, it will be an excellent platform for the academics to network and create new projects.

The results of this research will be disseminated to the academic beneficiaries through publications and conference presentations, which is envisaged to contribute to improvement of UK research in this field. Therefore, this project will increase the scientific excellence of the UK in this field.

Engaging the public and policy makers with the importance microbial methane generation:
The findings of this study will be disseminated to as many audiences as possible by reaching out to the public in the UK and Sweden. We aim to establish "The Baltic Sea Network" within this project to foster a new and robust network in the future. It is envisaged that the outcome of this project will increase awareness of the public about the importance of marine habitats and their biodiversity. I will work closely with Queen Mary, Centre for Public Engagement to disseminate the findings of this project through press release. Furthermore, the findings in regards to the DMS degradation and methane generation in marine habitats will be of interest to the UK and European policymakers, as the data will help understand the extent of climate change across marine ecosystems and develop improved climate models. In the long term, understanding the role that microorganisms play in greenhouse cycling will enhance the quality of life by incorporating the data from this project into new and improved climate models.