Exploring the deep biosphere in an intercontinental, brackish basin for the first time, and how the deep biosphere responds to environmental change.

The sub-seafloor biosphere is one of the largest habitats for life on Earth, but nothing is known about microbial life in subsurface brackish water sediments. The Baltic Sea is one of the largest brackish water bodies in the world. Its continental drainage area is large (four times the basin size) and it has been accumulating sediments for several thousands of years under varying environmental conditions linked to changes in glaciation, sea level and gateway thresholds for seawater ingress. IODP Expedition 347 has obtained deep sediments from this location which will enable us to quantify sub-seafloor prokaryotic populations and their activities for the first time in brackish water deep sediments. This is particularly important because it has recently been suggested that these type of shallow water (~35 m to 451 m), high sedimentation rate sediments that are also close to land, should have particularly high prokaryotic populations, as these factors are thought to control the size of sub-seafloor biosphere globally. This will be the first test of this hypothesis. In addition, little is known about how changes in environmental conditions, including the source of newly deposited sediments, affect deep sub-seafloor populations. The deep Baltic Sea sediments are ideal samples to investigate how the sub-seafloor biosphere responds to environmental change. This is particularly important as these shallow water sediments can either reinforce climate changed (e.g. enhanced production of the potent greenhouse gases carbon dioxide and methane) or mitigate climate change (e.g. enabling preservation of deposited organic matter and/or enhanced methane oxidation). We also want to find out whether deep biosphere populations and activities represent freshwater/terrestrial deep biosphere communities, marine deep biosphere communities, a mixture of both, or something completely different.

The main beneficiaries from the specific results of this research will be microbial ecologists and geochemists interested in subsurface processes, and particularly, those involved with IODP research. As outlined in the Description of Work, although tremendous advances have been made in sub-seafloor biosphere research, only a very small area of the ocean has actually been studied and some major habitats, not at all. Hence, there is still a lot to discover about the variability of prokaryotic biomass, biodiversity and activity in sub-seafloor sediments. This including sites that are dominated by terrestrial input, as these may be the highest biomass sites, but also ones subject to considerable environmental change. The Baltic Sea is a globally important example of a terrestrially dominated marine environment with a continental drainage area, four times the basin size, and which has been accumulating sediments for the last 140,000 years of major environmental change. Also its buried glacial sediments may still be actively producing methane gas.
Environmental microbiologists will directly benefit from the proposed research in several ways, including:
a) Testing the Kallmeyer et al. (Kallmeyer et al., 2012) suggestion that sedimentation rate and distance from land are the major controls on prokaryotic biomass in sub-seafloor sediments, in the high sedimentation rate, intercontinental Baltic Sea sediments. b) Exploring the sub-seafloor biosphere in a brackish water, basin for the first time.
c) Contributing to the international research effort on the Baltic Drilling Expedition. d) Studying how deep biosphere prokaryotes respond to the variety and changing environmental conditions of the Baltic Sea (e.g. salinity, sedimentation, temperature, oxic/anoxic, organic matter supply), which will increase our understanding of the controls on sub-seafloor biosphere diversity activity and geochemical impact. e) Biogeochemists and global modellers will also be interested in these results as deep sediments have a direct impact on global biogeochemistry and the carbon cycle.

We will continue to publicise our Deep Biosphere Research by publication of high-profile papers, reviews and keynote talks at national and international meetings. For example, Professor Parkes was the 2009 ECORD Distinguished Lecturer and gave a number of lectures in the UK, Europe, Australia and New Zealand. We will use our extensive contacts in deep biosphere research to ensure that they are informed of new research results. Specifically, within the UK we will attend all UKIODP meetings, and we will organise meetings to publicise our new results, and deep biosphere research more generally, such as with the Society for General Microbiology and Royal Society Discussion meetings.

We will further communicate our research through the School web site. This will be supported by our contributions to more widely available literature such as the Encyclopaedia of Microbiology, Handbook of Hydrocarbon and Lipid Microbiology and Extremophiles Handbook, and most recently, contribution to a book on Life in Extreme Environments (De Gruyter, 2014) and a Sub-seafloor Biosphere Review for the 50th Anniversary volume of Marine Geology (2014, on-line).