Assessment of in situ fluorometry to measure cyanobacterial presence in water bodies with diverse cyanobacterial populations

•Good correlations found between phycocyanin (CPC) measurements and biovolume in 2 of 3 ponds.•Poor correlation in the third was due to an abundance of picoplanktonic cyanobacteria.•CPC measurements varied according to the dominant cyanobacteria in the ponds.•In situ CPC measurements did not correlate well with cyanobacterial cell counts.•In situ chlorophyll-a fluorescence was a poor measure of cyanobacterial biovolume.