Unbound phycocyanin as an indicator of cell lysis and dissolved toxin release in cyanobacteria

Rapid cell lysis events during cyanobacterial blooms may result in the release of large amounts of dissolved toxins, which, if occurring near a drinking water plant intake, may pose serious treatment challenges for plant managers. Catastrophic cell lysis can occur naturally, through the activity of cyanophages – as documented in Lake Erie during the Toledo Water Crisis of 2014, or through the overapplication of algicides and water treatment chemicals. Cell lysis is indicated by the release of ‘unbound phycocyanin’ which can be detected fluorometrically by instruments recently developed by bbe-moldaenke. In the present study, unbound phycocyanin in laboratory cultures was continuously monitored following three chemical treatments. Microcystis aeruginosa UTEX 2385 (70 µg/L) was exposed to copper sulfate, PAK-27 (hydrogen peroxide-based algaecide), and potassium permanganate for 96 hours. In a separate experiment Synechococcus sp. cultures were infected with cyanophages and monitored for 144 hours. For PAK-27, copper sulfate, and the phage infection, decline in cell number was preceded by or coincided with the appearance of unbound phycocyanin, suggesting that this real-time fluorescent measurement may be a good indicator of cell wall condition. Results obtained from the other treatments will be further collected and discussed.