Enhancement by Glycerol of Phototrophic Growth of Marine Planktonic Algae and its Significance to the Ecology of Glycerol Pollution

Abstract

The effects of low (0.05 M) and high (0.5–1.0 M) concentrations of glycerol on the growth of 18 species of marine phytoplankters belonging to 7 algal classes were studied. The algae were grown in axenic culture in sea water enriched with nitrate, orthophosphate, silicate, trace-metal ions, vitamin B12, thiamine, biotin, and buffered at pH 7.6–7.8. Apart from a chrysomonad (Prymnesium parvum) and a cryptomonad (Chroomonas salina), none of the species showed any significant growth on glycerol in the absence of light. However, in the presence of light, glycerol enhanced the growth of 16 species, in particular members of the Chrysophyceae and Cryptophyceae, one diatom (Phaeodactylum tricornutum), one rhodophyte (Porphyridium cruentum), and one chlorophyte (Nannochloris oculata). A high concentration of glycerol was required for inducing or asserting growth enhancement of certain species, but was equally effective as the low concentration or was inhibitory to other species. The enhancement effect was observed in the growth rate and in the peak population density, which in many instances was several times that from nonglycerinated cultures and suggested photoheterotrophic growth. Some species showed obvious cytological and metabolic changes from growth on glycerol. The ecological implications of glycerol pollution of sea water are discussed.