Early detection and quantification of zooplankton grazers in algal cultures by FlowCAM

Algal cultivation and biomass production for biofuel and other products have many advantages over terrestrial crops. However, sustainable algal cultivation, especially in open ponds, is difficult due to opportunistic zooplankton grazers. There is an urgent need for the development of methods and procedures for early detection and quantification of zooplankton in algal cultures. In this study, the FlowCAM was able to detect and quantify Brachionus calyciflorus, a model organism, in algal cultures with a detection limit of < 1 individual/mL for B. calyciflorus in an algal (Chlorella sp.) cell density of 107 cells/mL. The methodology also allowed successful monitoring of rotifer population growth at low density (< 1 individual/mL of B. calyciflorus) in dense algal cultures. Furthermore, the methodology was also effective in detecting and quantifying other zooplankton grazers including ciliates, Poterioochromonas sp., and Euplotes sp. in outdoor open raceway cultures.