Colored Dissolved Organic Matter (CDOM)

Introduction

Colored (or chromophoric) dissolved organic matter (CDOM) is the part of organic matter that absorbs light in the blue and UV part of the electromagnetic spectrum, staining water a “tea-like” yellow-brown color. CDOM plays major roles in freshwater ecosystem processes, determining physical and chemical conditions and water quality in freshwaters, and it is the most abundant DOM fraction in forested watersheds with wetlands.

CDOM distribution in lakes across the NLF and NCHF ecoregions

We have examined CDOM distributions across two ecoregions, the Northern Lakes and Forests and North Central Hardwood Forests, that span the Upper Great Lakes states of Minnesota, Wisconsin and Michigan. Supported by a National Science Foundation grant this work included analysis of landscape conditions in watersheds that control CDOM levels in lakes.

The inset at the right shows that CDOM distribution is highly variable, even in small regions. The histograms show that the NLF has a much higher range and median CDOM levels than the NCHF ecoregion.

We began measuring CDOM by satellite imagery in 2014 (Olmanson et al. 2016) and expanded to statewide coverage in 2015 using Landsat 8 and Sentinel-2 (Olmanson et al. 2020). These data are being analyzed for statistical distributions and combined with earlier data for trend analyses. More detailed results for specific lakes are available on the LakeBrowser.

Statewide CDOM distribution based on averages for 2015 and 2016 imagery is shown above, and CDOM statistical distributions by major aquatic ecoregion are in the bar graphs around the map.