I am the Director of the Cabot Institute which explores fundamental, applied and multidisciplinary approaches to understanding, adapting to and governing with environmental uncertainty.
Closer to home, I use a combination of organic geochemical tools to characterise organic matter in a variety of natural materials. These carry signatures that allow the investigation of past climates, microbial adaptation to the environment and biogeochemical processes. Topics of interest range from the East Asian Monsoon to rapid changes in the global carbon cycle.
I obtained a BSc in Geology from Case Western Reserve University (Cleveland, USA) in 1992, and a PhD in Geosciences from Penn State University in 1998. During my PhD, working with Kate Freeman, I conducted research on how organisms adapt to environmental conditions at the molecular level and how this generates biomarker and isotope signatures that can be preserved in rocks for hundreds of millions of years. In particular, I used recent analytical advances, that allowed the determination of algal lipids’ carbon isotopic compositions, to develop tools for the reconstruction of ancient carbon dioxide concentrations.
Upon completion of my PhD, I accepted a post-doctoral fellowship with Professor J. S. Sinninghe Damsté at the Netherlands Institute for Sea Research. This fostered a deeper training in analytical and organic geochemistry, which allowed a diversification of the challenges I would ultimately investigate. Particularly exciting was using carbon isotopes as tracers of microbial processes, such as the anaerobic oxidation of methane by Archaea and sulphate-reducing bacteria in marine sediments. Although these were fundamentally geological and/or environmental research questions, they illustrated the profound importance of analytical chemistry as a probe into the co-evolution of life and the environment of our planet.
In 2000 I became a Lecturer in Biogeochemistry in the Organic Geochemistry Unit of the School of Chemistry, University of Bristol, and I was promoted to Professor in 2010. While at Bristol, I have investigated a wide variety of biogeochemical processes in ancient and modern environments, with research topics ranging from the controls on arsenic release in contaminated aquifers to reconstruction of ancient greenhouse climates. My approach continues to be based on the application of isotopic and organic mass spectrometry to the most challenging and critical questions in these arenas. This research is inherently interdisciplinary, and I have worked with over 200 Bristol, UK and international collaborators. In particular, I work with those employing alternative geochemical approaches, microbiologists and earth system modellers. Such collaborations have created a fruitful environment in which to test ideas, challenge paradigms and generate new hypotheses. We have developed new biomarker proxies for past marine biotic change, including during mass extinctions; evaluated Earth system sensitivity using new carbon dioxide and temperature records; and examined how methane cycling responds to changes in monsoon systems or rapid global warming.
In 2013, I became Director of the Cabot Institute which engages interdisciplinary approaches to address the major environmental challenges of the 21st century. We explore the complex biogeochemical changes occurring in the Earth system but also the new technologies and social relationships required to build resilient infrastructure, low-carbon energy systems, and sustainable food and water security. Consequently, our research and engagement is broad, exemplified by a focus on understanding, mitigating and living with environmental uncertainty. During 2015, when Bristol serves as the first UK European Green Capital, we will explore this topic in detail in a series of events badged as The Uncertain World. Even as our understanding of climate and the environment improves and our climate models become more sophisticated, the continued physical, biological and chemical alteration of our environment is making it increasingly difficult to anticipate future change. Our research must become more targeted and more ambitious to help people live on our rapidly changing planet.
Organic matter preserved in ancient marine, lacustrine, and peat deposits are vast repositories of information on Earth’s climate through time. Biomarkers provide insight into the organisms living in the past, and the environmental conditions necessary for such organisms to thrive can then be elucidated.
Further information is provided by the isotopic compositions of such biomarkers. Because δ13C and δD values of biomass are governed by environmental conditions, compound-specific isotope proxies can be used to reconstruct ancient pCO2 levels, rainfall, temperature, food web structure, and methane cycling.
Our research focuses on the development and refinement of such proxies by using cultures and field samples to identify diagnostic compounds and the controls on their isotopic compositions. We are also engaged in research that applies those techniques to specific problems in Earth history, including mass extinctions, the transition into and out of greenhouse climates, and the evolution of life.
Bacteria and Archaea comprise two of the three Domains of life and are essentially ubiquitous on the Earth’s surface. Recent developments in genetic techniques have reinvigorated the field of geomicrobiology by prompting new discoveries and reaffirming the importance of microbes in biogeochemical processes.
At the same time, new analytical chemistry techniques now allow direct contributions to microbiology from molecular biogeochemists, particularly when novel biomarkers are integrated with isotopic determinations. Our work in this area includes studies of the microbiology of CO2 and methane cycling in peat deposits and the role of archaea in anaerobic methane oxidation.
We also study the archaea and bacteria present in extreme environments, such as hydrothermal vents and deep-sea brine lakes. Interest in extreme settings arises from the potential that extremophiles could generate medicinal compounds and the prevailing impression that such settings represent good models for life on the early Earth.
Photo of a cold seep where biomarkers have been used to identify AOM. Note extensive crusts and tube worms, both present due to AOM; photo taken from the submersible Nautile during the MEDINAUT Project.
The preservation of organic matter is a topic of much interest to a range of scientists: it is critical to the formation of fossil fuel deposits, has important implications for the global carbon cycle and is an essential process in the preservation of organic materials in the fossil record.
Our research focuses on both the types of environmental conditions in the past that would have favoured extensive organic matter burial and preservation (e.g. oceanic anoxic events) as well as the chemical transformation of biological organic matter into kerogen. This latter process is of much interest as it is still unclear from where the aliphatic signature of most sedimentary organic matter derives.
However, recent work in our group suggests that organic materials previously thought to be relatively labile, including lipids, could be bound into resistant ‘geomacromolecules’, playing an important role in organic matter preservation and governing its chemical structure.
A full list of my publications can be found in the University of Bristol publications system.