Preprints
https://doi.org/10.5194/bg-2021-131
https://doi.org/10.5194/bg-2021-131

  02 Jun 2021

02 Jun 2021

Review status: this preprint is currently under review for the journal BG.

No evidence of a human influence on the mineralization of terrestrial dissolved organic matter (DOM) in Alpine fluvial networks

Thibault Lambert, Pascal Perolo, Nicolas Escoffier, and Marie-Elodie Perga Thibault Lambert et al.
  • Faculty of Geoscience and Environment, Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland

Abstract. The influence of human activities on the role of inland waters in the global carbon (C) cycle is poorly constrained. In this study, we investigated the impact of human land use on the degradation of terrestrial dissolved organic matter (DOM) and its potential impact on bacterial respiration in ten independent catchments of the Lake Geneva Basin. Sites were selected along a gradient of human disturbance (agriculture and urbanization), and we monitored bacterial respiration in parallel to DOM bioavailability. Fluorescence spectroscopy was used to determine the influence of human land uses on DOM sources and composition as well as the dynamic of degradation or production of the fluorophores identified in our study sites. Higher bacterial respiration measured in agro-urban streams related to a short-term bioreactive pool (0–6 days of incubation) from autochthonous origin, whose the size increased with human disturbance. On the other hand, the degradation of terrestrial DOM was not impacted by human activities and was not found to contribute substantially to aquatic bacterial respiration. Although human land uses controlled DOM sources, composition and bioavailability at the basin scale, our results showed that human activities in the Lake Geneva Basin had a limited impact on the net C exchanges between inland waters and the atmosphere related to DOM mineralization. Considering that greater proportion of autochthonous-DOM signature is a common feature in human-impacted catchments, the implications of our results likely apply more widely. Yet, on a global scale, the influence of human activities remains to be determine given the large diversity of effects of agriculture and urbanization on freshwater DOM depending on the local environmental context.

Thibault Lambert et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-131', Anonymous Referee #1, 06 Jul 2021
    • AC1: 'Reply on RC1', Thibault Lambert, 08 Sep 2021
  • RC2: 'Comment on bg-2021-131', Anonymous Referee #2, 22 Jul 2021
    • AC2: 'Reply on RC2', Thibault Lambert, 08 Sep 2021

Thibault Lambert et al.

Thibault Lambert et al.

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Short summary
The bacterial mineralization of dissolved organic matter (DOM) in inland waters contributes to CO2 emissions to the atmosphere. Human activities affect DOM sources, however the implications on DOM mineralization are poorly known. Combining sampling and incubations, we showed that higher bacterial respiration in agro-urban streams related to a labile pool from aquatic origin. Therefore, human activities may have a limited impact on the net carbon exchanges between inland waters and atmosphere.
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