Pigment-based chemotaxonomy of phytoplankton in Lake Okeechobee, Florida and effects of irradiance on cyanobacteria

The phytoplankton community of Lake Okeechobee, Florida, has been studied and algal divisions were identified. Chemotaxonomy is a process that assigns taxonomic divisions based on ratios of biomarker pigments to chlorophyll, as measured by high performance liquid chromatography (HPLC). Microscopic counts of taxonomic groups were compared to chemotaxonomic groups for lake samples for one year. Lab cultures of cyanobacteria grown at irradiance of 2 to 500 micromoles photons m-2 s-1 (muEinsteins) suggested that internal ratios of chlorophyll to both zeaxanthin and echinenone could be used to estimate abundance of cyanobacteria, as either alone missed certain populations. Lake water samples showed that both methods agreed that diatoms and cyanobacteria were the dominant groups, with moderate number of green algae and few dinoflagellates. HPLC evidence revealed cryptophytes more frequently than did microscopy. This suggested that cryptophytes may be more significant than has been previously reported.