Carbon in the land, air and water are interconnected. A significant amount of carbon stored in aquatic environments is thought to derive from carotenoids, antioxidant compounds produced by plants and algae, and widely found in nature. Exposure to sunlight and attack from radicals in the water break down large organic molecules into smaller, more resistant molecules. In this study, we identified the major degradation products of four carotenoids, some of which persisted in the samples and their chemical formulae were matched to those already found in a variety of water bodies. The identified structures, as well as the mechanisms via which they are formed, contribute to our knowledge on the fate and reactivity of the aquatic carbon.