Combined use of chlorophyll a and phycocyanin fluorescence sensors for quantification and differentiation of phytoplankton: a useful approach for small surface water bodies

Sensors based on in vivo measurements of photosynthetic pigments fluorescence enable real-time phytoplankton monitoring with high spatial and temporal resolution. A combination of chlorophyll a (CHL) and phycocyanin (PC) fluorescence sensors was used for phytoplankton quantification and differentiation in two small water bodies, Koseze Pond and pond in Hotinja vas. The high correlation of CHL and PC fluorescence signals with biovolume was confirmed during the two-year monitoring in anatural pond environment in spite of a seasonal succession of the phytoplankton. Additionally, disturbances of the sensors were investigated. Water bodies containing predominantly algae yielded false positive signals of the PC sensor, which reached up to 1% of the intensity of the CHL signal. Similarly, underestimated counts of cyanobacteria measured with CHL fluorescence sensor can be adjusted using PC fluorescence sensor.