School of Earth and Environment

Christian Dr Christian

Associate Professor: Biogeochemistry

Telephone number: +44(0) 113 34 31504
Email address: c.maerz@leeds.ac.uk
Room: 9.149

Affiliation: Earth Surface Science Institute

Biography

Link to my Personal homepage

Previous employment

Since 2016: Associate Professor in Biogeochemistry, Earth Surface Science Institute (ESSI), School of Earth and Environment (SEE), University of Leeds, UK

2013 - 2016: Lecturer in Geoscience, School of Civil Engineering and Geosciences (CEG), Newcastle University, UK

2012 - 2013: DFG Return Fellowship, Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Germany

2010 - 2012: DFG Research Fellowship, School of Civil Engineering and Geosciences (CEG), Newcastle University, UK

2008 - 2010: Postdoctoral Researcher, Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Germany

Qualifications

2004: German Diplom (MSc equivalent) in Geology, University of Heidelberg, Germany

2008: PhD in Marine Geochemistry, University of Bremen, Germany

Memberships/Fellowships

American Geophysical Union (AGU)

European Geosciences Union (EGU)

Deutsche Geologische Gesellschaft - Geologische Vereinigung (DGGV)

Geochemical Society (GS)

Committee Member of GeolSoc/MinSoc Geochemistry Group

Advisory Board Member of IASC Network Arctic in Rapid Transition (ART)

Research Interests

My general field of research is inorganic (bio)geochemistry. I am interested in the cycling and burial of carbon, sulfur, detrital elements (e.g., Al, Ti, Zr, K), biogenic elements and nutrients (e.g., P, Si), and metal (e.g., Fe, Mn, trace metals) in present and past marine environments, and the links with (micro)biology, mineralogy, depositional environment, and climate. Timescales of interest reach from the Present back through the Phanerozoic, and geographical spread of study sites from the tropics to the Arctic.

Studying marine pore waters and sediments, my analytical toolbox includes total HF digestions, sequential extractions (Fe, S, P, Si, Ba), XRF, ICP-OES, ICP-MS, AAS, IC, spectrophotometry, CNS elemental analysis, SEM-EDX, and XRD.

I am also a seagoing scientist and have participated in a number of research cruises onboard the Meteor, Heincke, Polarstern and the IODP drillship JOIDES Resolution, most recently to the Arctic Ocean and North Pacific.

My current research focus is on:

1) Diagenetic processes and benthic fluxes in modern marine sediments. Once they are deposited at the seafloor, many chemical elements (including carbon, sulfur, nutrients and metals) participate in a sequence of biogeochemical reactions that changes their phase association and/or redox state (early diagenesis). Following these reactions, elements can either be recycled back to the water column where they may fuel primary productivity, or they can be transformed into authigenic minerals that significantly alter the primary sediment composition. Although these diagenetic processes and their sedimentary expressions can occur long after the actual deposition of the sediments, they are often related to changes in depositional conditions (e.g., primary productivity, sedimentation rate) and can thus be useful for paleoenvironmental reconstructions.

2) Present and past oxygen-depleted marine environments. In parts of the ocean that experience high primary productivity and/or hydrographic restriction,the water column can become oxygen-depleted, anoxic, and even sulfidic. While these redox conditions favour the formation of organic-rich deposits ("black shales") and eventually hydrocarbon source rocks, they are also of crucial importance for the budgets and cycling of various nutrients and (trace) metals. In the modern ocean, anoxic to sulfidic water masses only occur in restricted basins (e.g., the Black Sea) or coastal upwelling areas (e.g., along the Eastern Pacific), but they are currently expanding as a result of anthropogenic activity (e.g., ocean warming, eutrophication). Ocean anoxia were also much more prevalent in the Mesozoic-Early Cenozoic "greenhouse oceans".

3) Biogeochemical processes in the modern and past Arctic Ocean. The Arctic Ocean has, over the last ~100 million year, undergone extreme climatic and environmental changes. From a restricted, brackish basin with black shale formation in the Cretaceous and Paleogene, it has developed into its current oligotrophic, ice-covered modern state. Reconstructing its development from sediment records informs us about its biogeochemical response to natural climatic variability, including past warm phases like the Pliocene or the last interglacial that might be analogues for future warming scenarios. Studying sub-recent Arctic sediments enables us to understand modern benthic processes and their response to climate change (e.g., retreating sea ice cover).

4) Coupled biogeochemical cycling of C, S, Fe, P and Si. Although chemical elements have very distinct characteristics and functions in nature, their biogeochemical cycles are often intimately linked. For example, the availability of excess hydrogen sulphide in sediments can enhance the preservation of organic carbon, with important implications for the global carbon cycle and hydrocarbon source rock formation. The interactions of the bioessential nutrients Fe and P are strongly redox-dependent, which can trigger far-reaching feedback mechanisms between ocean chemistry and climate change. The siliceous hard parts of marine algae can sequester bioessential nutrients and bury them into the seafloor.

Publications