Light scatter from Emiliania huxleyi in relation to nutrient availability

Data collected in controlled laboratory experiments indicate that nutrient concentration can induce changes in the singlecell light scatter properties, as measured using flow cytometry, and beam attenuation of the marine phytoplankton Emiliania huxleyi. Nutrient-induced optical variability is due primarily to the production of external scales called coccoliths, which are composed almost entirely of calcium carbonate. Coccolith production appears to be inversely related to the concentration of nitrate. Cultures maintained in low nitrate conditions are heavily plated and ten to twenty times as many individual coccoliths are found suspended within the media. The result is an increased single-cell light scatter in both the forward and side directions. Cells grown in high nutrient conditions are either lightly plated or completely nude and fewer detached coccoliths are found within the media. As a result, single-cell light scatter is decreased. In either case, beam attenuation at 670 nm appears to be dominated by light scatter from coccoliths rather than absorption by chlorophyll.