Detection of phycobilin pigments and their seasonal change in Lake Kasumigaura using a sensitive in situ fluorometric sensor

A two-channel fluorometric sensor system for the detection of the water blo om phytoplankton Microcystis aeruginosa has been developed. Excitation wave lengths of 620 nm and 440 nm were used; the former for detecting the cyanob acteria themselves, and the latter for subtracting the interference due to eukaryotic algae present in the sample. The fluorescence of the cyanobacter ia and eukaryotic algae was measured at 645 nm and 680 nm, respectively. Ap plied to real samples from Lake Kasumigaura, Japan, after ultrasonication, this fluorometric method is capable of the rapid determination of phycocyan in. We used this sensor system for monitoring surface water in Lake Kasumig aura in 9 months in laboratory experiments. Moreover, an automatic device b ased on this system was used for the continuous in situ monitoring of phyco cyanin in lakewater. As expected, higher levels of phycocyanin due to cyano bacteria were observed, compared to chlorophyll a due to eukaryotic algae i n summer.