DOM concentration and reactivity along the boreal aquatic network of La Romaine River, Québec, Canada

Dissolved organic matter (DOM) exported from terrestrial ecosystems to freshwaters plays a central role in the global carbon cycle, undergoing biological and photochemical degradation to CO₂ along the aquatic continuum. Hydrology, and in particular water residence time, is a major control on biological and photochemical reactivity at the watershed scale. Here, we investigate DOM dynamics throughout the aquatic network of a large boreal watershed by tracking DOM concentration and biological and photochemical reactivity. We sampled groundwater, lakes, streams and rivers from orders 1 to 8 (La Romaine River) within the watershed to assess how concentration and reactivity evolve along the continuum. Preliminary results show a net loss of ~40 % of DOC between order-1 and order-6 rivers, as well as a decrease in photochemical reactivity along the continuum, indicating progressive DOM removal, particularly in lakes. However, biological reactivity shows little change and localized increases in DOC concentration and reactivity also occur, pointing to DOM replenishment. Overall, our findings highlight water residence time as a major control on DOM concentration and reactivity in freshwaters, while demonstrating that lateral inputs can substantially modulate its influence at the watershed scale.

Presentation Preference: Poster

Primary Presenter: Camille St-Arneault, Université du Québec à Montréal (st-arneault_sergerie.camille@courrier.uqam.ca)

Authors:

Camille St-Arneault, Groupe de recherche interuniversitaire en limnologie (GRIL), Université du Québec à Montréal  (st-arneault_sergerie.camille@courrier.uqam.ca)

Masumi Stadler, Université du Québec à Montréal  (m.stadler.jp.at@gmail.com)

Marie Laure Gérardin, Communauté d'agglomération de Saint-Dié des Vosges  (marielauregerardin@gmail.com)

Yves Prairie, Groupe de recherche interuniversitaire en limnologie (GRIL), Université du Québec à Montréal  (prairie.yves@uqam.ca)

Paul del Giorgio, Groupe de recherche interuniversitaire en limnologie (GRIL), Université du Québec à Montréal  (del_giorgio.paul@uqam.ca)