Constraining the microbial carbon pump by characterising the chemical composition and functionality of autochthonous dissolved organic matter

The oceans contain a massive amount of carbon (hundreds of times as much as the atmosphere) which, because it is not in the atmosphere, can't contribute to trapping heat inside the Earth system via the greenhouse effect. Therefore, we want to understand how big this pool is, what makes it and whether it is getting bigger or smaller. There are several separate processes which regulate the size of this carbon store: 1) The solubility pump: Carbon dioxide from the atmosphere just dissolves into the ocean, 2) the biological carbon pump: small marine plants grow in the surface ocean, sink and then dissolve back to carbon dioxide in the deep ocean and 3) the microbial carbon pump: some of the carbon-containing matter that marine plants make during photosynthesis is so hard to break down (recalcitrant) that it just sits in the ocean for thousands of years. Of these three we know the least about the microbial carbon pump. Because the recalcitrant matter pool is so old and the flux into it is very small we have tended to concentrate on 'pumps' other than the microbial carbon pump which have larger fluxes. But the recalcitrant matter pool is actually very big, certainly big enough that if it stopped then carbon dioxide levels in the atmosphere would increase enough over time to impact our climate. So what are the chances of it changing? Well, we don't know. We do know the pool is big and ancient, on average the matter it contains is 5,000 years old, but what we don't know in detail is how it is made. For example, do small marine plants just leak a tiny amount of their cell contents into the water or do they release a bit when they get eaten? Or do viruses and pathogens in the sea infect and kill them and cause this material to be formed? Could it be that recalcitrant matter is only made when the tiny microbes abundant in the sea eat part of the plants and release unwanted molecules? The answers to these questions are important, because the oceans are likely to change and it might be, that the key process which keeps this pool topped up gets smaller. In my proposal I plan to answer the question 'how does it get made?'. I will take common species of plants and microbes from around the oceans, especially the ones that make a lot of carbon and which form signals you can see from outer space, grow them in the lab and then kill them in a variety of ways. These include starving them to death in the dark, feeding them to their predators and infecting them with pathogens; the same ways they would die in the real world. Then I will see what sort of matter they make when they die in these different ways. My research has indicated that the way they die will affect what they release into the water column. For example, if they get eaten then whatever eats them will probably take all the nutritious matter and excrete low value waste material. I will compare this to the sort of matter found at the bottom of the ocean to see which processes are making the recalcitrant pool. One complication when doing this work is that I don't know exactly which characteristic of the organic matter will be the most suitable to use for the comparison. Because of this I will use some powerful analysis techniques that allow me to characterise the chemical makeup of every single carbon-containing molecule in a massive pool made up of thousands of different chemicals. My project will tell us which processes are important in production of recalcitrant matter and which aren't. In collaboration with modelling experts this information will be used in mathematical models which help us understand how the ocean carbon cycle works. The data I generate will help to make these models more realistic and fast and hence answer the question 'what will happen to the microbial carbon pump in a changing world?'.

The project has relevance to government and regulatory agencies with responsibility for the Marine Strategy Framework Directive, the Water Framework Directive and the Marine and Climate Acts (e.g. DEFRA, the Marine Management Organization (MMO) and Marine Scotland). The results will improve the accuracy and resolution of UK Met Office models. In the first instance improved model accuracy will be realised via collaboration with Dr Luca Polimene (see letter of support) to improve DOM parameterisations in simple models, which can then be directly embedded into the ERSEM model. ERSEM has been used as part of the EU FP7 EuroBASIN project both to model ocean carbon storage and to quantify the economic value of this major service to mankind. Via this pathway the outcomes of this project will also serve to assist the further development of indicators and targets required to implement the Marine Strategy Framework Directive beyond 2018. Furthermore, non-governmental organizations with an interest in climate change and/or the functioning of marine systems, for example the World Wide Fund for Nature (WWF) could use such outcomes to inform lobbying.
The capacity of coastal ecosystems to store carbon and the potential to trade this carbon termed "Blue Carbon" automatically assigns a potential value to processes which sequester carbon. Thus an improved understanding of how microbial mortality and metabolism controls the vast reservoir of recalcitrant dissolved organic matter in the oceans is a step towards constraining and valuing Blue Carbon with UK coastal waters and all marine environments. I have established a link with Dr Martin Johnson (University of East Anglia) of the CEBlue Carbon project which is part of the NERC/DEFRA Shelf Sea Biogeochemistry Programme, the aims of which include extending the definition of Blue Carbon to deep storage sites. I will supply data on how marine microbial mortality and exudation influences the microbial carbon pump and thus support their objectives.
The project will also have benefit to those in the commercial sector with an interest in the characterization of organic molecules, in the first instance through the industrial project partner Waters Corporation. Resulting technologies developed and protocols optimized will benefit a myriad of commercial stakeholders in fields such as water quality testing, and pharmacology. In order to maximize the impact of technological advances made by the project a two day workshop will be held the National Oceanography Centre (NOC) to bring together international stakeholders with an interest in the characterization of small organic molecules using the developing technology Convergence Chromatography. Funds for this activity have been requested and detailed in the Justification of Resources statement as well as the provision of some funding by my industrial partner Dr Tim Jenkins of Waters Corporation (letter of support included).
As the project has relevance to understanding the availability of commercially valuable marine species and predicting potential changes in climate it has obvious benefits and interest to the general public. Throughout the project a website will be maintained to convey the projects aims and findings and feature a video log of life at sea. All opportunities to raise the project's profile via media activities will be taken and I will maximise my efficiency in this endeavour by attending the NERC training course "Engaging the public with your research". News releases and editorial feature pitches will be issued to the mainstream media and specialist environmental interest outlets via the NOC Communications Office. I will contribute to the NOC news letter, NOC open day, Marine Life talks and the NERC publication Planet Earth. A school programme will be conducted and I will participate in the Royal Society MP pairing scheme.