Steryl esters of pyrophaeophorbide b: a sedimentary sink for chlorophyll b

The production of steryl chlorin esters (SCEs) of both pyrophaeophorbide a and pyrophaeophorbide b has been demonstrated in a laboratory experiment in which the copepod Calanus helgolandicus grazed on the prasinophyte Tetraselmis suecica. Both algal sterols were converted into SCEs a and b with equal efficiency, indicating that in this case the SCE sterols were directly representative of the substrate. The sterols of the animal were also converted to SCEs, although with some change in the distribution as a result of cholesterol demand by the copepod. The results show that during herbivory chlorophyll b undergoes the same biotransformation to SCEs as reported for chlorophyll a and predict that SCEs b should occur in sediments beneath a phytoplankton population containing a significant contribution of chlorophyll b.