Colored dissolved organic matter

Very high concentrations of CDOM can have a limiting effect on photosynthesis and inhibit the growth of phytoplankton,[5][6][7][8] which form the basis of oceanic food chains and are a primary source of atmospheric oxygen.

However, the influence of CDOM on algal photosynthesis can be complex in other aquatic systems like lakes where CDOM increases photosynthetic rates at low and moderate concentrations, but decreases photosynthetic rates at high concentrations.

This bleaching (photodegradation) of CDOM produces low-molecular-weight organic compounds which may be utilized by microbes, release nutrients that may be used by phytoplankton as a nutrient source for growth,[15] and generates reactive oxygen species, which may damage tissues and alter the bioavailability of limiting trace metals.

Although variations in CDOM are primarily the result of natural processes including changes in the amount and frequency of precipitation, human activities such as logging, agriculture, effluent discharge, and wetland drainage can affect CDOM levels in fresh water and estuarine systems.

Traditional methods of measuring CDOM include UV-visible spectroscopy (absorbance) and fluorometry (fluorescence).

Variations in the concentration of colored dissolved organic matter as seen from space. The dark brown water in the inland waterways contains high concentrations of CDOM. As this dark, CDOM-rich water moves offshore, it mixes with the low CDOM, blue ocean water from offshore.
Peatland river water draining into coastal waters
South-East Asia is home to one of the world's largest stores of tropical peatland and accounts for roughly 10 % of the global land-to-sea dissolved organic carbon (DOC) flux. The rivers carry high coloured dissolved organic matter (CDOM) concentrations, shown here interfacing with ocean shelf water. [ 4 ]