EFFECTS OF BARLEY STRAW EXTRACT ON GROWTH OF FIVE SPECIES OF PLANKTONIC ALGAE

Holz, J. C. 1 , Fessler, C. J. 2 , Severn, A. A. 1 & Hoagland, K. D. 11 School of Natural Resource Sciences, University of Nebraska, 103 Plant Industry Bldg., Lincoln, NE, 68583‐0814; 2 Biology Department, Nebraska Wesleyan University, 5000 St. Paul Ave., Lincoln, NE, 68504; Phone: 402‐472‐6648; Fax: 402‐472‐2964 The effects of exposure to barley straw extract and the timing of exposure on the growth of four common cyanophyte species and one species of green algae were investigated in two laboratory experiments. Clonal cultures of Anabaena cylindrica, Cylindrospermum sp., Gloeocapsa sp., Eucapsis sp., and Chlorella vulgaris were obtained from culture collections. In both experiments, the algae were cultured in Guillard's WC medium at 20 °C on a 12:12 L/D photoperiod. In the first experiment, the algae were dosed with four concentrations of barley straw extract at the beginning of the experiment (day 0) and growth was monitored every second day using fluorometric detection of chlorophyll a for 14 d. In the second experiment, the algae were dosed with the same extract concentrations, but the extract was not added until the algae were in exponential growth phase (day 6). Both experiments also had control treatments (i.e. no extract) and each extract and control treatment was replicated five times. Growth of C. vulgaris was inhibited by all doses in both experiments, but inhibition was 22% greater when the extract was added on day 0. Growth Gleocapsa sp. was slightly inhibited by all doses when the extract was added on day 0, but not when it was added on day 6. No other species were inhibited, regardless of dose or timing of dose. The results of this study and other bioassay studies suggest that differential susceptibility to barley straw among algae is common and may reduce the effectiveness of barley straw as an algal control technique.