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

Lead Research Organisation: University of Leeds
Department Name: Sch of Geography

Abstract

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.

Planned Impact

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.

Publications

10 25 50
 
Description On the South Georgia shelf, results indicate that chemosynthesis occurs, despite this not being an environment usually associate with such a process. Although rates are low, and fauna are dominantly sustained by photosynthetic organic matter, there is nonetheless direct evidence of transfer of chemosynthetic carbon to the macrofauna. Macrofauna were important agents in the short-term processing of organic matter, and both macrofaunal C uptake and total community respiration rates were slowed by the low temperature of the site. Results from the Bransfield Strait suggest similar conclusions, and these results are currently in preparation for publication.
Exploitation Route The findings from my experiments will aid with the design of further experiments in similar or related environments. They may also be compared with similar results from sites with differing degrees of hydrothermal influence, in order to provide an understanding of the range of effects that hydrothermal influence may have. Finally, the extent to which chemosynthesis occurs in marine sediments is a question receiving considerable interest at the moment, and this project will help to provide the answer.
Sectors Education,Environment

 
Description This grant has allowed me to involve three undergraduate students directly in my research, giving them beneficial experience, and inspiring projects. One student analysed some of my Southern Ocean samples for his final year dissertation, one has conducted a research placement module working for me, and one was awarded an undergraduate research scholarship, which paid her to contribute to my project. Some of the findings from this project have now been submitted in a manuscript to the journal Antarctic Science. The title of the paper is 'Temperature and organic Carbon supply control short-term biological Carbon processing in methane rich sediments on the South Georgia margin'. The key conclusions are that direct evidence was found for chemosynthesis in the methane rich sediments on the South Georgia shelf. Rates were very low, but nonetheless there was some evidence of transfer of chemosynthetic C into the macrofauna. In accordance with their high biomass, macrofauna were important agents in short-term C cycling, but the low temperature of the site meant that both macrofaunal C uptake and total community respiration rates were lower than observed elsewhere.
First Year Of Impact 2014
Sector Education
 
Description UoL/NHM joint studentship 
Organisation Natural History Museum
Country United Kingdom 
Sector Public 
PI Contribution Primary supervision of a joint PhD student, and specialist input of biogeochemical expertise. Use of a joint sample set.
Collaborator Contribution PhD student supervision, training in taxonomy of benthic fauna, and specialist input of ecological expertise. Use of a joint sample set.
Impact The jointly supervised PhD student has a manuscript in press. This will be reported through the relevant studentship grant.
Start Year 2013
 
Description Challenger Society Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Conference presentation at the biannual meeting of the UK Challenger Society for Marine Science.
Year(s) Of Engagement Activity 2016
 
Description EGU 2013 Oral Presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Oral presentation at the annual European Geosciences Union conference. Presentation title '13C Pulse Chase Studies of C Cycling at Chemosynthetic Sites'.
Year(s) Of Engagement Activity 2013
 
Description Life at Sea Blog 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact While at sea on research cruise JC80 in the Southern Ocean I kept a blog, including some video diary entries posted on UTube. This was followed by schools (contact established before the cruise), as well as family and friends of many of the people on board.
Year(s) Of Engagement Activity 2012
 
Description Q and A with school students 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact I talked live to a classroom of 60 secondary school pupils by telephone from a research ship in the Southern Ocean. I explained my science, and answered questions about what it was like to live and work at sea.
Year(s) Of Engagement Activity 2012
 
Description Schools Visits with Leeds Festival of Science Roadshow 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Talks given in three schools about the research, fieldwork, and preliminary findings, reaching over 100 pupils. Positive feedback from teachers received stated that pupils had been inspired by seeing where science could take them.
Year(s) Of Engagement Activity 2016
 
Description Woman's Hour Interview 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact I was interviewed from a research ship in the Southern Ocean by the BBC Radio 4 programme Woman's Hour. I was part of a group of 4 female scientists interviewed about working at Christmas, and the interview was broadcast on Christmas Day.
Year(s) Of Engagement Activity 2012