Chlorophyllase distribution in ten classes of phytoplankton: A problem for chlorophyll analysis

Abstract

Chlorophyllase activity, which degrades chlorophyll a to chlorophyhde a, was investigated in 93 species (113 isolates) of unicellular algae from 10 classes. Chlorophyllide a formation was measured by a simple incubation test in 50 % acetone, followed by chromatography and phase separation techniques. High activity of the acetone-activated chlorophyllase was found in one third of the 68 diatom isolates tested. These included the pennate diatoms Asterionella glacialis, Cylindrotheca fusdormis, Delphinejs sp., Grammatophora oceanica, Navicda sp., Nitzschia (2 spp.),Phaeodactylum tncornutum and Thalassionerna nitzschioides, and the important bloom-forming centric d~atoms Chaetoceros (5 spp.), Detonula pumila, Ditylurn bnghtwellii, Eucampia zodiacus, Lithodesmium undulatum, Skeletonema costaturn, Stephanopyxis turris and Streptotheca tamesis. High activity was also found in 2 out of 3 chrysophyte isolates and 2 out of 7 chlorophyte isolates. In contrast, representatives of 7 other classes showed zero or low activ~ty:dinoflagellates (11 isolates), most prymnesiophytes (9 isolates), cryptophytes (5 isolates), prasinophytes (4 isolates), chloromonads (2 isolates), 1 rhodophyte and 2 cyanophytes. Significant strain-specific differences in chlorophyllase activity in 6 out of 13 diatom species, 1 chrysophyte, 1 prymnesiophyte and 1 chlorophyte were also observed. A serious problem for chlorophyll analysis is that chlorophyllase can be activated by harvesting techniques before extraction takes place. Filtration causes the most extensive conversion of chlorophyll a to chlorophyllide a, particularly in old cultures, but harvesting by centrifugation also causes chlorophyhde formation in some species. The effects are more pronounced in diatoms than other algal groups. The further degradabon of chlorophyllide a to pheophorbide a was seldom encountered. Whlle spectrophotometric and fluorimetric methods would not be seriously affected by chlorophyllase activity (provided pheophorbide a is a minor end product), TLC and HPLC techniques for chlorophylls may be rendered invalid due to artefact formation.