Examination of the Effects of Barley Straw (Hordeurn vulgare) on Freshwater Algae in the Field and Laboratory

Abstract

Laboratory and field experiments were conducted to determine the efficacy of barley straw in controlling algal growth. Laboratory experiments were conducted on twelve species of algae representing three phyla. Barley straw extract inhibited the growth of Synura sp. and Microcystis. aeruginosa. However, Selenastrum capricornulum, Spirogyra sp., Oscillatoria lutea var. contorta, and Navicula .sp. displayed significantly increased growth. The growth of the remainder, Ulothrix fimbriate, Scenedesmus quadricauda, Chlorella vulgaris, Anabaena flos-aquae, Synedra sp., and Dinobyron sp. showed no significant difference from the control. Field monitoring of eight ponds was inconclusive. All ponds cleared over the course of the season. Bioassays on the filamentous mats from the ponds in the lab yielded either increased growth or decreased decline in treated samples five out of six times. The surveys of pond managers indicated 87% of respondents felt that the barley straw was effective at controlling the algal problems in their pond. These experiments support a portion of the published research but also create a number of questions regarding the mechanism of control, the types of algae controlled, and the methods of experimental design to evaluate the efficacy of barley straw as an algae control treatment. These results combined with earlier studies suggest that the mechanism(s) of barley straw in altering the algal composition of ponds is more complex than direct inhibition of algae and may include both inhibition and stimulation of different algal species.