A WIDESPREAD CHLOROPHYLL TRANSFORMATION PATHWAY IN THE AQUATIC ENVIRONMENT

Combined liquid chromatography mass spectrometry studies of the pigment distributions of a variety of lake and marine sediments from different depositional settings reveal the presence of steryl chlorin esters as significant components of the chlorin assemblages. The components are water column transformation products of phytoplankton chlorophyll a, and it is suggested that they form through an enzymatic esterification or transesterification process during senescence or decay. Remarkably, the steroidal alcohols are esterified mainly to a common nucleus, pyrophaeophorbide a. The transformation pathway involved appears to be a ubiquitous one in marine and lacustrine environments, and the components represent a significant sedimentary ''sink'' for the chlorophyll biosynthesised in the euphotic zone. Future water column studies of the changes in photosynthetic pigments in phytoplankton blooms and of pigment fluxes should take into account the likely presence of steryl chlorin esters.