Organic carbon-mineral interactions in the marine system and its impact on global biogeochemical cycles

17.04.2025, 13:15 Uhr

MARUM Seminar room 2070

Oliver Moore

Department of Environment and Geography, University of York, York, UK

Variations in atmospheric CO₂ are regulated over two different timescales in the Earth system. On geological timescales, the amount of CO₂ in the atmosphere is regulated by the chemical weathering of silicate rocks together with the balance between the degradation and preservation of organic carbon (OC) in marine sediments. On timescales relevant to anthropogenic climate change, atmospheric CO₂ is regulated by the photosynthetic activity of marine algae and the ensuing biological pump, and again a balance between the degradation and preservation of OC, found this time in seawater, where recent work shows that a long-lived type of dissolved OC provides a reservoir for carbon, rivalling that present in the atmosphere [1]. Over these two different timescales it is apparent that the reactivity and cycling of OC is of vital importance to the Earth system, yet despite many years of research, we still do not fully understand how, or why, what is essentially labile OC can escape degradation and become preserved.

In this seminar I will present work by our group demonstrating that reactive Fe species present within the marine environment can act to protect OC [2] but also act as a catalyst for the geopolymerisation of small low molecular weight OC, into larger more complex OC via the Maillard Reaction [3]; where monosaccharides and amino acids, that are abundant in the marine environment, combine to form aromatic macromolecules termed Geopolymerised Substances (GPS), which may then escape hydrolysis [4] and therefore thought to be longer lived within the ocean.

Using a combined approach of synchrotron-based techniques, Nanoparticle Tracking Analysis and global biogeochemical modelling, this work suggests that the formation of GPS, in association with minerals/metals, occurs both within sediments (impacting carbon cycling on geological timescales) and within hydrothermal vent systems (impacting carbon cycling on timescales relevant to anthropogenic climate change). This interaction likely plays an important, yet hitherto unexplored role in not only the global carbon cycle but also the global oxygen cycle.

[1] Hansell, D.A. and Carlson, C.A., (2014) Biogeochemistry of marine dissolved organic matter. Academic press.

[2] Curti, L., Moore, O.W., Babakhani, P., Xiao, K.Q., Woulds, C., Bray, A.W., Fisher, B.J., Kazemian, M., Kaulich, B. and Peacock, C.L., (2021) Carboxyl-richness controls organic carbon preservation during coprecipitation with iron (oxyhydr) oxides in the natural environment. Nature Communications Earth & Environment, 2(1), p.229.

[3] Moore, O.W., Curti, L., Woulds, C., Bradley, J.A., Babakhani, P., Mills, B.J., Homoky, W.B., Xiao, K.Q., Bray, A.W., Fisher, B.J., Kazemian, M. and Peacock, C.L., (2023) Long-term organic carbon preservation enhanced by iron and manganese. Nature, 621(7978), pp.312-317.

[4] Loh, A.N., Bauer, J.E. and Druffel, E.R., (2004) Variable ageing and storage of dissolved organic components in the open ocean. Nature, 430(7002), pp.877-881.