HCNSO Student Theses and Dissertations

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Defense Date


Document Type

Thesis - NSU Access Only


Oceanographic Center

First Advisor

Gary L. Hitchcock

Second Advisor

Larry Brand

Third Advisor

Jerry T. Thornthwaite


Batch cultures of the cyanobacteria Synechococcus spp. (strains 48 Syn and 2346) and Porphyridium cruentum (Rhodophyta) were grown in nitrogen-limited (N:P=4:l) and phosphorus-limited (N:P=50:l) seawater media. Optical properties, including particle size (forward angle light scatter), particle granularity (right angle light scatter) and relative mean channel red (> 600 nm) and green (510-550 nm) fluorescence were measured for 10 days using a flow cytometer. Dissolved nitrogen (nitrate), phosphorus (phosphate), cell abundance and chlorophyll concentrations were also measured.

Results indicated that phosphorus-limited cultures yield higher chlorophyll concentration, fluorescence and granularity (right angle scatter) values than did nitrogen-limited cultures. Comparison of these samples with a preliminary investigation shows nutrient-rich cultures (N:P=4:l, N:P=50:l) have larger particle size and higher fluorescence values than relatively nutrient-poor cells cultured in f/20 media. Secondary (R2) populations have been determined for all samples, either by light scatter or fluorescence anomalies. Particularly notable was Synechococcus 2346 (phosphorus-limited) which exhibited a secondary population characteristic for more than half of the experiment. Highly fluorescent particles are suggested as either formative daughter cells, cellular “clumping" or a cellular optical response to batch culture turbidity; these particles have a profound influence on the relative refractive index of the culture with time.

Flow cytometric analysis can be an effective tool in the determination of not only differences in the optical properties and fluorescent signatures of various cyanobacterial strains, but also of population variation within a single strain.

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