Tracer Studies of Biological Carbon Cycling in Chemosynthetic Communities of the Southern Ocean

When marine organisms die they sink , and some of their organic matter is deposited in seafloor sediments. Understanding the fate of that organic matter is important because long term burial of organic matter is a way of removing carbon from the atmosphere and locking it away. Also, most ecosystems on the ocean floor depend entirely on such sinking organic matter as their food source
Hydrothermal vent occur where volcanic activity heats the rocks of the seafloor. The heat drives a circulation of seawater, sucking it into the rocks, where it dissolves minerals and is heated. The hydrothermal fluid thus created is then vented back into the cold ocean, either through chimneys called black smokers, or in diffuse form, by filtering through the sediment. At these hydrothermal vents, unique and interesting suites of microbes have evolved, which can derive chemical energy from the minerals dissolved in the hydrothermal fluid. In a process called chemosynthesis, they use this energy to create organic matter, just as plants at the Earth's surface use the sun's energy to grow. Therefore, organisms living near to hydrothermal vents have two sources of food; sinking organic matter, and bacteria producing new organic matter at the seafloor.
Hydrothermal vents and chemosynthesis are fairly newly discovered, and we do not yet know which microbes are involved in the production and decay of organic matter. Further, many other organisms live in hydrothermal sediments, and we do not know what types of organic matter they feed on, or how they are arranged in food webs. Finally, we do not know how different types of organic matter (that from the ocean surface and that produced at the sefloor) are cycled and buried in these settings.
This project aims to fill these gaps in our knowledge. To this end, experiments were conducted at diffuse hydrothermal vent sites in the Southern Ocean, close to the Antarctic Peninsula. Sediment samples were collected, and a range of chemical labels were added to them aboard the ship. The samples were then kept in the dark at seafloor temperature for several days, during which their normal microbial and animal activity continued. At the end of the experiments, samples of sediment, water and animals were preserved. Experiments were conducted at several different chemosynthetic sites, as well as one normal deep ocean site, where hydrothermal venting was not present.
This proposal is an application for funds to analyse the samples collected, in order to find out where the chemical labels has gone. Samples of animals living in the sediment will be analysed, and the amount of chemical label they contain will allow us to tell which animals fed on each type of organic matter. Analysis of water samples will allow us to quantify how much organic matter of each type was decayed and returned to the water as carbon dioxide, instead of being buried in the sediment. We will also measure a carefully chosen range of fatty chemicals (lipids). These chemicals are each produced by only a narrow range of microbes. By detecting our chemical label in these lipids we will be able to tell for the first time which groups of microbes are most important in producing and decaying the different types of organic matter. This will include looking at lipids which indicate the activity of archaea, a recently discovered group of microscopic organisms which may be as abundant as bacteria in the ocean, but about the functioning of which we know very little.
In summary, this project will provide vital information for understanding carbon cycling and burial in a previously unstudied type of seafloor setting. It will also provide new information and progress in understanding the feeding behaviour and ecology of faunal and microbial (including archaeal) communities living close to hydrothermal vents.

The proposed project is best described as blue skies research; therefore its impact beyond the academic community will be focused on broadening the general public's engagement with and understanding of science. The research concerns Southern Ocean/Antarctic fieldwork focusing on chemosynthetic environments, which are suggested to resemble those where life began. It also includes questions regarding archaea, a relatively newly discovered form of life. Further, it will make use of cutting edge analytical instrumentation and techniques. Therefore it is particularly well placed capture the public's attention and imagination.
Aspects of the proposed research will be incorporated into outreach activities and events which are already planned. These include three types of scheme:
1) Lecturers into Schools and Leeds Science Roadshow are schemes run by the Geographical Association and the outreach office at the University of Leeds. The PI will participate in the schemes by delivering lectures containing elements of the background, objectives and findings of the proposed research.
2) Adopt A Scientist. The PI is involved in the creation of a new outreach scheme which will see school students interacting with their 'adopted' scientist over extended periods of time, via online and face-to-face activities. The PI has well established links with two schools, and she will pilot the Adopt A Scientist scheme in partnership with them during the course of the proposed project. During school visits, aspects of the proposed work will be communicated to students from a range of year-groups. A-level chemistry and biology classes will be specifically targeted through a classroom activity using real data from the proposed research. This will give them a genuine flavour of research, and will support the items in their syllabuses relating to microbiology/ecology, the carbon cycle, and mass spectrometry as a technique used in organic chemistry.
3) Bristol Festival of Nature. The School of Chemistry, where analyses are to be run, participates annually in this Bristol-based science festival. The rationale and findings of the proposed research will be included in their exhibits in poster and video format.
In addition, the proposed research is linked, through the ChEsSo project and beyond, to our knowledge and understanding of the importance of chemosynthetic ecosystems, and also of Antarctica and the Southern Ocean in the whole Earth system. It will also enhance our understanding of the global carbon cycle. Therefore the findings of this project will contribute to large bodies of work which will ultimately help to inform policy regarding conservation and exploitation of hydrothermal vents, Antarctica and climate. In order to facilitate this impact, the profile of the proposed work and its findings will be raised through press releases via the University of Leeds press office, items on the School of Geography website, and through articles in broadly distributed publications such as Planet Earth.