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Cyanobacteria blooms can complicate the economical or recreational use of waters. Many of the bloom forming species are also potential producers of harmful cyanotoxins. The standard method for quantifying phytoplankton biomass, based on inverted microscopy, has high accuracy and is the only one producing biomass results on taxonomic level, but it requires specialized expertise and is time-consuming. Phycocyanin (PC) pigment concentration has been proven as a useful proxy for the concentration of cyanobacteria. Since 2006, we have studied practical solutions of in-situ monitoring of cyanobacteria using PC fluorescence probes. We have studied two eutrophic lakes, Lake Littoistenjärvi and Lake Kuralanjärvi in southwestern Finland using stationary monitoring stations equipped with PC probes. The fluorescence results were compared to independent water samples analyzed using standard methods. The PC fluorescence was positively correlated to cyanobacteria biomass in both lakes. Using site-specific post-calibrations of biomass, PC fluorescence can be used to estimate the absolute biomass of cyanobacteria. The monitoring techniques used in these studies are an applicable and relatively low-cost method to monitor cyanobacteria abundance. With nearly real-time data transfer possibilities, they can be used in management and early warning applications to minimize the harmful effects of cyanobacteria blooms.

Due to the eutrophication of water bodies, large and intense phytoplankton blooms, most commonly associated to cyanobacteria, have been increasingly reported. Cyanobacteria blooms can cause negative socioeconomic effects or even pose a serious risk to human and animal health. To minimize possible harmful effects, the authorities need to monitor and report the bloom situations to the public. The standard laboratory methods for quantifying phytoplankton biomass are accurate, but have flaws in practical management use: specialized expertise is required, and they are time-consuming. We have tested practical solutions to monitor cyanobacteria nearly real-time by using probes measuring phycocyanin fluorescence, which can be used as a proxy for cyanobacteria biomass. In the basic application, a fluorescence probe is mounted in a datalogger monitoring station in the field and the results calibrated to cyanobacteria concentration are transferred via GSM to a web page available to the authorities and the public. To indicate the risk levels of cyanobacteria concentration to the public we have used a 3-scale ‘traffic light’ system. The automated monitoring station applications used in our studies, with nearly real-time web results, are an applicable and relatively low-cost method to monitor sensitive sites like water intakes, aquaculture and recreational areas.