Controlling the growth of a cyanobacterial contaminant, Synechoccus sp., in a culture of Tetraselmis chui (PLY429) by varying pH: Implications for outdoor aquaculture production

In aquaculture, large volumes of phytoplankton are often grown outdoors to reduce costs. However, growing microalgae in an environment not as well-controlled as in the laboratory can lead to unwanted phytoplankton, including cyanobacteria, contaminating a culture. A cyanobacterial contaminant was isolated from an outdoor culture of Tetraselmis chui (PLY429) at the Milford Laboratory. This study investigated the growth of PLY429 and the cyanobacterium in pure cultures and a mixed culture in a pH range of 6.5–9.5. The division of PLY429 was greater at a pH range of 7.0–8.0; whereas, for the cyanobacterium, higher growth was obtained at pH 8.0–9.0. Results from combined cultures of PLY429 and the cyanobacterium grown at various pHs indicated that maintaining pH near 7.1 yields higher growth of PLY429 than those of the cyanobacterium. These findings suggest that controlling pH may reduce the population of a cyanobacterial contaminant in an aquaculture feed culture.