Ecological effects of the aquatic herbicide cyanatryn on a drainage channel.
Part of a drainage channel was treated with cyanatryn at 0.2 mu g/g. Release of the herbicide was slower than expected. A peak concn. of 0.1 mu g/g was reached 3 months after treatment in the treated section. Leakage across a polythene barrier resulted in contamination of an adjacent area. A further section remained unaffected. Plants, mainly Myriophyllum spicatum and Vaucheria sp., were eradicated from the treated section after 12 weeks. Plants in the adjacent section were similarly affected but some suffered only temporary recession. Periphyton colonizing glass slides increased more rapidly in the treated section. After 10 weeks, numbers of Acnanthes sp. were 2800 plus or minus 400/mm2 and 230 plus or minus 116/mm2 in the treated and untreated sections, respectively. The invertebrate community associated with Myriophyllum spicatum was replaced, in the treated section, by one more typical of detritus. Although numbers of invertebrates did not change markedly, many species declined. Lymnaea peregra, the most abundant species initially, was almost eradicated from the treated section. Plants began to recolonize the treated section one year after treatment. The invertebrates originally associated with these plants gradually reappeared, with the return of more suitable conditions. From summary.