Biological control of Stephanodiscus hantzschii (Bacillariophyceae) blooms in a field mesocosm by the immobilized algicidal bacterium Pseudomonas fluorescens HYK0210-SK09

Algicidal activity of the bacterium, Pseudomonas fluorescens SK09, to mitigate Stephanodiscus hantzschii (Bacillariophyceae) blooms using field mesocosms

“…The APVAS carrier was cut into cubes whose sides were 1 cm in length, dried in a dry oven at 60 C for 48 hours, and sterilized with ultraviolet radiation at a wavelength of approximately 180 to 250 nm for 4 hours. The bacteria were immobilized in the carrier as described previously by Jung et al (2009aJung et al ( , 2013: the sterilized cubes of the APVAS carrier were placed in 40 L of SK09 cells grown in NB medium in log phase to a cell density of over 10 10 cells/mL, and then incubated for 4 hours at 25 C and stirred at 30 rpm in the dark. This approach resulted in a cell density of approximately 10 10 cells per carrier.…”

“…To answer this question, we implemented two mesocosm experiments and studied direct application of immobilized SK09 cells in extremely low temperatures and analyzed the results. Some of the experimental data referred to in this work were obtained in our previous studies (Jung et al 2008(Jung et al , 2009a(Jung et al , 2010(Jung et al , 2013.…”

“…For the purposes of this study, the Nakdong River of South Korea is an optimal site for mesocosm study because S. hantzschii blooms there repeatedly in winter. Furthermore, this river is relatively shallow and has slow-moving water and a gentle slope into the littoral zone (Jung et al 2010(Jung et al , 2013. To evaluate the algicidal activities of SK09 (Experiment 1) and immobilized SK09 cells in APVAS carriers (Experiment 2) against S. hantzschii blooms and the consequent responses of biotic and abiotic factors, a field mesocosm study was carried out in the Nakdong River (35 22 0 28.12 00 N, 128 38 0 23.07 00 E; Table 1 and Figure 1), when natural S. hantzschii cells bloomed at a density of 2.04 £ 10 4 cells/mL.…”

“…Kilham et al 1986;Kobanova & Genkal 1989). In South Korea, S. hantzschii blooms occur annually and can reach a density of over 10 5 cells/mL during winter in the Han, Nakdong, and Yeongsan rivers (Jung et al 2009b(Jung et al , 2011(Jung et al , 2013Jeong et al 2014). These diatom blooms have adverse social, economic, and environmental effects, such as low water transparency, unpleasant water odor and taste, as well as clogging of and/or sedimentation in water treatment equipment (Oksiyuk 1965;Lee et al 2001;Kolmakov et al 2002;Hijnen et al 2007).…”

“…To shed further light on this issue, we investigated the immobilization of SK09 cells in activated carbon polyvinyl alcohol sponge (APVAS) carriers (Jung et al 2009a). Upon field application of SK09 cells immobilized with APVAS carriers, the number of S. hantzschii cells and inorganic nutrient concentrations showed a marked decrease (Jung et al 2013). Against this background, the following question arises: Can SK09 mitigate centric diatom blooms of S. hantzschii under any environmental conditions?…”