The main processes that remove DOC from the ocean water column are: (1) Thermal degradation in e.g., submarine hydrothermal systems; (2) bubble coagulation and abiotic flocculation into microparticles  or sorption to particles; (3) abiotic degradation via photochemical reactions; and (4) biotic degradation by heterotrophic marine prokaryotes. It has been suggested that the combined effects of photochemical and microbial degradation represent the major sinks of DOC.