[1] Geosmin, along with the irregular monoterpene 2-methylisoborneol, together account for the majority of biologically-caused taste and odor outbreaks in drinking water worldwide and in farmed fish.

[1][2] Geosmin is also responsible for the earthy taste of beetroots and a contributor to the strong scent, known as petrichor, that occurs when rain falls after a spell of dry weather or when soil is disturbed.

[5][6] Geosmin is produced as a secondary metabolite by various blue-green algae (cyanobacteria), filamentous bacteria in the class Actinomyces, other prokaryotes, and various eukaryotes.

[15] It is proposed that this extreme sensitivity to geosmin evolved in humans or their ancestors to aid them in their search for scarce water, but this is not conclusive.

[16] Geosmin is also implicated in the migratory patterns of eels, where its higher concentration in freshwater systems guides the fish from the ocean into estuaries and rivers.

[17] Geosmin is also likely involved in raccoon predation of turtle nests, where burrowing disturbs the soil and ejects the chemical and other volatile indicators into the air.

These systems rely on biological filtration using cultured microbial communities to process the nitrogenous waste from the fish (ammonia) into less harmful compounds (nitrite and nitrate) that can be tolerated at higher concentrations.