CHALLENGES IN AQUATIC SCIENCES Using an online phycocyanin fluorescence probe for rapid monitoring of cyanobacteria in Macau freshwater reservoir Yijun Kong • Inchio Lou • Yiyong Zhang • Chong U. Lou • Kai Meng Mok Received: 5 July 2013 / Accepted: 16 November 2013 / Published online: 29 November 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Monitoring of cyanobacteria and their toxins are traditionally conducted by cell counting, chlorophyll-a (chl-a) determination and cyanotoxin measurements, respectively. These methods are tedious, costly, time consuming, and insensitive to rapid changes in water quality and cyanobacterial abundance. We have applied and tested an online phycocyanin (PC) fluorescence probe for rapid moni- toring of cyanobacteria in the Macau Storage Reservoir (MSR) that is experiencing cyanobacterial blooms. The relationships among cyanobacterial abundance, biovo- lume, cylindrospermopsin concentration, and PC fluo- rescence were analyzed using both laboratory and in- the-field studies. The performance of the probe was compared with traditional methods, and its advantages and limitations were assessed in pure and mixed cyanobacterial cultures in the laboratory. The proposed techniques successfully estimated the species including Microcystis and Cylindrospermopsis, two toxic species recently observed in the MSR. During February– November, 2010, the PC probe detected high correla- tions between PC and cell numbers (R 2 = 0.71). Unlike the chl-a content, which indicates only the total algal biomass, the PC pigment specifically indicates cyano- bacteria. These results support the PC parameter as a reliable estimate of cyanobacterial cell number, espe- cially in freshwater bodies where the phytoplankton community and structure are stable. Thus, the PC probe is potentially applicable to online monitoring of cyanobacteria. Keywords Phycocyanin fluorescence probe Á Online measurement Á Cyanobacteria Á Freshwater reservoir Introduction As nutrients, particularly nitrogen and phosphorus, are increasingly discharged into freshwater systems, cyanobacterial blooms are becoming a problem in reservoirs around the world, including those used for drinking water. Cyanobacterial blooms are caused by the proliferation of cyanobacterial cells under favorable conditions in eutrophic water bodies, accompanied by potential increased release of cyanotoxins such as microcystins and cylindrospermopsins that may affect the health of human and animals (Paerl & Huisman, 2009). Cyanotoxins are carcinogens and have been associated with primary liver cancer (Kurmayer & Guest editors: Jiang-Shiou Hwang & Koen Martens / Challenges in Aquatic Sciences Y. Kong Á Y. Zhang Á C. U. Lou Laboratory & Research Center, Macao Water Co. Ltd., 718 Avenida do ConselheiroBorja, Macau SAR, China I. Lou (&) Á K. M. Mok Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Av. Padre Toma ´s Pereira Taipa, Macau SAR, China e-mail: iclou@umac.mo 123 Hydrobiologia (2014) 741:33–49 DOI 10.1007/s10750-013-1759-3