Chlorophyll breakdown in aquatic ecosystems

Abstract

The annual cycle of greening and degreening of plants is probably the most obvious sign of life on Earth. It is caused by the biosynthesis of ∼109 tons of chlorophylls (Chls) in spring and their degradation in fall. The biochemistry of Chl breakdown to linear tetrapyrroles has been worked out in land plants (1), but little was known about the process in marine organisms, which contribute a comparable share to global biomass production. In PNAS, Kashiyama et al. (2) now provide evidence for a rather different pathway that is widespread in aquatic ecosystems and relates to protist feeding on picoplankton.