Phycoerythrin is among the most dynamic phytoplankton pigments in the Baltic Sea. While Chlorophyll a provides information on bulk phytoplankton biomass and phycocyanin reflects the distribution of filamentous cyanobactreria, phycoerythrin signal originates mainly from picocyanobacteria, ciliate Mesodinium rubrum, cryptophytes and some dinoflagellates..

Phyco fluorescence has been measured operationally, using the Chelsea UniLux fluorometer, since 2016 from the Ferry Finnmaid commuting between Helsinki, Finland and Travemunde, Germany, as part of activities within Alg@line ferrybox project and EU RIA project JericoNEXT. Alg@line has for the last 25 years been conducting real-time algal monitoring in the Baltic Sea, largely based on ferrybox measurements and coordinated by the Finnish Environment Institute, SYKE.

The fluorescence results from 2016 and 2017 are encouraging, showing the early spring distribution of phyco in the middle of the Baltic Sea, obviously as an indication of mass occurrences of Mesodinium rubrum. Later in the summer, the origin of phycoerythrin fluorescence is more related to picocyanobactreria, as shown by several reference measurements from water samples. The Finnish Environment Institute have recently bought three more Chelsea UniLux fluorometers to include as part of measuring system in other ferries, research vessel and profiling buoy, to obtain more comprehensive information on the distribution of phycoerythrin.