PIGMENT DYNAMICS ASSOCIATED WITH THE GRAZING OF A CILIATE AND A FLAGELLATE FEEDING ON A CYANOBACTERIUM

The egestion of particulate material as well as pigment degradation du ring microzooplankton grazing on phytoplankton are poorly known proces ses. In an attempt to evaluate these processes, changes in pigment con centrations within various size fractions were monitored in batch cult ures of an assemblage of a pelagic ciliate (Strombidium sulcatum) and a heterotrophic flagellate (Paraphysomonas sp.) feeding on a cyanobact erium (Synechococcus sp.) over a 10-day period. Chlorophyll a, caroten oids and phaeopigments were not found in the 0.1-0.7 mu m fraction whi le the pigments originally in the 0.7-3.0 mu m fraction (prey) were tr ansferred into the > 3.0 mu m size fraction (predator). During this tr ansfer, the carotenoids (zeaxanthin and B-carotene) were not degraded significantly. In contrast, chlorophyll a was degraded into phaeophyti n-like compounds which accounted for almost 100 % of the recorded phae opigments. The destruction of chlorophyll a varied with time ranging f rom 4 % (day 3) to almost 100 % tend of the experiment) and this destr uction was inversely related to micro-grazer ingestion rates. Microsco pic examinations of samples did not reveal any large egested particles > 3.0 mu m, suggesting that phaeopigments and carotenoids measured in this size fraction were accumulated inside the protozoa. Zeaxanthin w as very stable even when it was within the mice-grazer. (C) Elsevier, Paris.