Unified concepts for understanding and modelling turnover of dissolved organic matter from freshwaters to the ocean: the UniDOM model

Anderson, T.R. ORCID:; Rowe, E.C.; Polimene, L.; Tipping, E.; Evans, C.D.; Barry, C.D.G.; Hansell, D.A.; Kaiser, K.; Kitidis, V.; Lapworth, D.J. ORCID:; Mayor, D.J. ORCID:; Monteith, D.T.; Pickard, A.E.; Sanders, R.J. ORCID:; Spears, B.M.; Torres, R.; Tye, A.M.; Wade, A.J.; Waska, H.. 2019 Unified concepts for understanding and modelling turnover of dissolved organic matter from freshwaters to the ocean: the UniDOM model. Biogeochemistry, 146 (2). 105-123.

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The transport of dissolved organic matter (DOM) across the land-ocean-aquatic-continuum (LOAC), from freshwater to the ocean, is an important yet poorly understood component of the global carbon budget. Exploring and quantifying this flux is a significant challenge given the complexities of DOM cycling across these contrasting environments. We developed a new model, UniDOM, that unifies concepts, state variables and parameterisations of DOM turnover across the LOAC. Terrigenous DOM is divided into two pools, T1 (strongly-UV-absorbing) and T2 (non- or weakly-UV-absorbing), that exhibit contrasting responses to microbial consumption, photooxidation and flocculation. Data are presented to show that these pools are amenable to routine measurement based on specific UV absorbance (SUVA). In addition, an autochtonous DOM pool is defined to account for aquatic DOM production. A novel aspect of UniDOM is that rates of photooxidation and microbial turnover are parameterised as an inverse function of DOM age. Model results, which indicate that ~ 5% of the DOM originating in streams may penetrate into the open ocean, are sensitive to this parameterisation, as well as rates assigned to turnover of freshly-produced DOM. The predicted contribution of flocculation to DOM turnover is remarkably low, although a mechanistic representation of this process in UniDOM was considered unachievable because of the complexities involved. Our work highlights the need for ongoing research into the mechanistic understanding and rates of photooxidation, microbial consumption and flocculation of DOM across the different environments of the LOAC, along with the development of models based on unified concepts and parameterisations.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Soils and Land Use (Science Area 2017-)
Water Resources (Science Area 2017-)
UKCEH Fellows
ISSN: 0168-2563
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: terrigenous dissolved organic matter, land ocean aquatic continuum (LOAC), biogeochemical model, biogeochemistry, photooxidation
NORA Subject Terms: Ecology and Environment
Date made live: 06 Dec 2019 12:56 +0 (UTC)

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