Molecular controls on organic matter decomposition in lakes: new insights

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Heterotrophic decay of dissolved organic matter (DOM) contributes to widespread emission of greenhouse gases from lakes in the boreal zone. As a highly diverse environmental mixture DOM shows complex interactions in the environment. For example, it has been conclusively demonstrated that decomposition kinetics of lake DOM is a result of integrated behavior of a large number of DOM components. Now, another study has further examined how the decay of lake DOM components is linked to specific molecular characteristics.

The study was conducted as a series of incubation experiments, where DOM composition was characterized using ultrahigh resolution mass spectrometry (15 Tesla FT-ICR-MS), and an apparent decay coefficient was estimated for every identified molecular formula. The study compares the reactivity of major compound groups and looks at the isolated effects of saturation, aromaticity, molecular mass, oxygen content and nominal oxidation state of carbon on individual reactivities within DOM.

Patterns of reactivity acquired directly from the decomposition experiments show some important parallels with the patterns of compounds persistence across a large number of Swedish lakes. Yet, certain findings can be considered surprising and invite future work, especially in the other aquatic settings.

The study emphasizes the importance of intrinsic controls of DOM decomposition in lake water and can be interesting to anyone related to the biogeochemistry field.

The work received financial support from the Swedish Research Council and was conducted in collaboration with the University of Oldenburg, Germany.

Original article: Mostovaya, A., Hawkes, J. A., Dittmar, T., and Tranvik, L. J. (2017). Molecular Determinants of Dissolved Organic Matter Reactivity in Lake Water. Front. Earth Sci. 5:106. doi: 10.3389/feart.2017.00106.