Hydrology and trophic status control lake dissolved organic matter concentration and composition at a continental scale

Dissolved organic matter (DOM) is a key component of the lake biogeochemistry. Hydrology links variables influencing lake DOM at local and watershed scales, but its role at macroscales remains poorly understood. We studied the DOM concentration and composition from 548 lakes across the five major Canadian continental basins, using absorption spectroscopy and parallel factor analysis, and ultra‐high resolution mass spectroscopy, and linked these to deuterium excess, derived from stable water isotopes as a proxy for evaporation and regional hydrology. DOM concentration and composition varied greatly within and across basins, with strong correlations between molecular and optical properties. At a continental scale, d-excess and TP concentration were the main drivers of DOM concentration and composition. TP positively influenced DOM concentration, and specific DOM components, likely mediated by nutrient-driven effects on lake metabolism. DOM concentration declined with d-excess, but the relationships between individual DOM molecular classes and d-excess differed among DOM components and basins, resulting in regional differences in DOM composition along hydrologic gradients. The inferred source composition of DOM based on these patterns had subtle regional differences, with Aliphatics linked to average regional altitude, and Aromatics linked to average regional soil organic content. We conclude that differences in DOM processing along the hydrologic continuum is the main factor driving differences in DOM composition in lakes at a continental scale.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Amir Reza Shahabinia, Université du Québec à Montréal (amir.shahabi66@gmail.com)

Authors:

Ryan Hutchins, Department of Chemistry and Biology, Toronto Metropolitan University  (hutchins.ryan@gmail.com)

Jean-François Lapierre, Department of Biological Sciences, University of Montreal, Montreal, Quebec, Canada.  (jean-francois.lapierre.1@umontreal.ca)

Paul del Giorgio, Department of Biological Sciences, University of Quebec at Montreal, Montreal, Quebec, Canada  (del_giorgio.paul@uqam.ca)