Filamentous algal control using barley straw

Abstract

Year-round problems with dense growths of filamentous algae reduce the amenity and conservation value of Irish canals. Because algal control operations were relatively ineffective, trials using barley straw were undertaken. These commenced in October 1990 on a section of the Royal Canal where filamentous algae continuously interfered with amenity exploitation and water management. Bales of barley straw were anchored along the canal banks at roughly 50 m intervals. Further straw applications were made in 1991 and 1992. Algal growth in the control section broadly followed a cyclical pattern, with peak biomass between July and September and low production in February and March. In the treated section, however, algal biomass decreased from the time the straw was first introduced. Thereafter, as long as rotted straw was present, no filamentous algae were recorded. The absence of algae in this section between August 1991 and spring/summer 1993 permitted the recolonisation of higher plants, which are commonly less troublesome and more ecologically useful than algae.