Fig. 3.

Terrestrial dissolved and particulate organic matter (tDOM and POM, respectively) absorb solar UV and visible radiation in fresh and marine waters. This light absorption results in the photodissolution of POM and the photodegradation of tDOM to greenhouse gases (mainly CO₂), and to smaller molecules that are readily degraded by microbes to CO₂ (i.e., respiration). Reactive oxygen species produced by photo-excited tDOM and POM help to breakdown tDOM and POM to greenhouse gases and smaller organic molecules (modified from Sulzberger and Arey, 2016 ¹²).