Pyrophaeoporphyrins c1 and c2: grazing products of chlorophyll c in aquatic environments

Pyrophaeoporphyrins c1 and c2 (I a, b), transformation products of chlorophylls c1 and c2 (II a, b) occur as minor pigments in the surface sediment (0–5 cm) of Priest Pot, a small eutrophic lake (Cumbria, U.K.) and in the products from feeding the diatom Thalassiosira weissflogii to the copepod Calanus helgolandicus. These findings, based on comparisons with standards prepared from the chlorophylls c1 and c2, indicate that enzymatic removal of the C-132 carbomethoxy substituent, a prerequisite for the diagenetic transformation pathway of the chlorophylls c to a number of sedimentary alkyl porphyrins, occurs mainly in the water column as a result of zooplankton herbivory.