Limited effects of barley straw on algae and zooplankton in a midwestern pond

Researchers in the United Kingdom have reported that barley straw can be used to control a variety of planktonic algae, as well as the filamentous alga Cladophora spp. This method appears to be cost-effective, user-friendly, and environmentally sound. If these results could be obtained in the United States, using barley straw would be a good alternative to using copper sulfate. However, research has shown that barley straw must be subjected to well-oxygenated water for it to become anti-algal. Consequently, the sites of most studies conducted in the UK in which barley straw showed an effect have been somewhat lotic. Midwestern ponds are typically stagnant, and often become oxygen-poor during summer months, and therefore it is questionable whether barley straw would work. W e attempted to control algae (filamentous and planktonic) growing in replicated limnocorrals that were built inside of a 1-ha pond; limnocorrals were stocked with three levels of barley straw. In addition, we tested whether the straw had effects on zooplankton community structure. No consistent degree of algal growth inhibition was observed for either alga type, and zooplankton community structure was not affected throughout this 14-week study (P < 0.10). Our results, as well as those of some other US researchers, may be partly explained by inadequate levels of oxygen within the decomposing straw caused by a lack of water exchange between the interstices of the straw and the water body.