ABSTRACT Dissolved Organic Matter (DOM) represents a mixture of organic molecules that vary due to different source materials and degree of processing. Characterizing how DOM composition evolves along the aquatic continuum can be difficult. Using a size-exclusion chromatography technique (LC-OCD), we assessed the variability in DOM composition from both surface and groundwaters across a number of Canadian ecozones (mean annual temperature spanning −10 to +6 C). A wide range in DOM concentration was found from 0.2 to 120 mg C/L. Proportions of different size-based groupings across ecozones were variable, yet similarities between specific water-body types, regardless of location, suggest commonality in the processes dictating DOM composition. A PCA identified 70% of the variation in LC-OCD derived DOM compositions could be explained by the water-body type. We find that DOM composition within a specific water-body type is similar regardless of the differences in climate or surrounding vegetation where the sample originated from. Highlights * Size-exclusion chromatography (using LC-OCD) is a fast and effective tool to quantify differences in DOM composition across different environments * Proportions of biopolymers and low molecular weight fractions can distinguish between surface and groundwater DOM * Similar water-body types have comparable DOM size compositions across ecozones that range in annual air temperatures from –10 to 6ºC Competing Interest Statement The authors have declared no competing interest. Footnotes * SCIENTIFIC SIGNIFICANCE STATEMENT Aquatic health and drinking water quality are affected by the differing mixtures of molecules that comprise dissolved organic matter (DOM), yet quantifying differences in DOM mixtures has been mostly focussed on light-absorbing techniques or confined to specific water-body types (i.e. only lakes). This makes it difficult to fully understand how DOM composition, and its reactivity, differs across the aquatic continuum, let alone across climatic gradients. This study uses molecular size-based groupings of DOM to quantify differences in DOM composition from both ground and surface waters across a range of Canadian ecozones, finding that DOM size distribution is quite similar within a water-body type regardless of surrounding vegetation and climate. * DATA & CODE AVAILABILITY STATEMENT All data and metadata is available in the Wilfrid Laurier University Dataverse data repository and can be accessed at https://doi.org/10.5683/SP2/ZRGXQ5 while all R code can be accessed at https://github.com/paukes/canada-ecozone-DOM. * Focussed objectives and discussion on differences in water body type (not water body type vs ecozone); added info on 'aquatic continuum' and why we expect differences in DOM composition...

Size-Based Characterization of Freshwater Dissolved Organic Matter finds Similarities within a Water Body Type across Different Canadian Ecozones

10.1101/2020.04.03.024174