Carotenoid enhancement and its role in maintaining blue‐green algal (Microcystis aeruginosa) surface blooms1

Abstract

Photosynthetic pigment alteration by Microcystis aeruginosa in surface blooms was related to persistence and dominance by this blue‐green alga. The progression of summer blooms coincided with rising carotenoid : chlorophyll a ratios. When analyzed by high performance liquid chromatography (HPLC), carotenoids exhibited strong in vitro absorbance in the UV and near‐UV regions. Increased cellular carotenoid content was accompanied by increased surface photosynthesis as well as increased photosynthetic efficiencies in surface Microcystis populations. These data indicate that radiant energy is most effectively utilized as a source of photoreducing power in the presence of elevated cellular carotenoid : chlorophyll a ratios of surface populations. It is concluded that enhanced cellular carotenoid synthesis increases light utilization in the low and middle regions of the photosynthetically active radiation (PAR) spectrum and provides protection from UV damage. This is shown to have a positive effect on photosynthetic CO₂ fixation and bloom persistence in surface waters.