Detecting presence of phytoplankton groups with non-specific pigment signatures

The use of pigment ratios and sizefractionation was investigated fordetecting the presence of phytoplanktongroups with non-specific pigmentsignatures. These groups includeprymnesiophytes, chlorophytes,prasinophytes and cyanobacteria. Prasinophytes without the diagnosticpigment prasinoxanthin could be identifiedby calculating ratios ofprasinoxanthin/chlorophyll b andlutein/chlorophyll b on data setsfrom two Danish estuaries. Furthermore,these pigment ratios could be used toexclude the presence of chlorophytes, andratios of zeaxanthin/chlorophyll brevealed that cyanobacteria wereoccasionally present. This information isimportant when selecting whichphytoplankton groups to load in the CHEMTAXprogram for calculating the chlorophylla biomass of the individualphytoplankton groups. Subtypes ofprymnesiophytes were detected by sizefractionations on samples from a mesocosmexperiment. The size fractionations,although time-consuming and not alwaysfeasible, and the pigment ratiocalculations proved to be able to providethe desired information as to whichphytoplankton groups to load in the CHEMTAXprogram.