Production of pheopigments by marine protozoa: results of laboratory experiments analysed by HPLC

Abstract

Pigment degradation by six species of herbivorous protozoa, fed a variety of phytoplankton foods, was studied in the laboratory. High-performance liquid chromatographic (HPLC) analysis showed that degradation products of chlorophylls a, b and c formed during every experiment; several carotenoid alteration products also were observed. Dominant chlorophyll a degradation products were a pheophytin a and two relatively non-polar pheophorbide a compounds. The latter may be useful markers for protozoan herbivory in the field. There were differences between the patterns of pheopigment production by ciliates and a heterotrophic dinoflagellate. Relative to macrozooplankton herbivores, chl a degradation by individual protozoa appeared to be less extensive (both the ratios of pheophytin a: pheophorbide a and pheopigment produced: chlorophyll ingested were high during the early part of time-series experiments). A grazing model demonstrates that loss of pheopigment and decrease in pigment conversion ratios during time-series experiments could have been due to reingestion of fecal material by protozoan grazers. Reingestion may lead to extensive degradation of pigments and a high particle recycling efficiency by microzooplankton communities in natural waters.