Some ecological effects of the use of paraquat for the control of weeds in small lakes.
In 2 experimental lakes at Oxton, Nottinghamshire, paraquat at 0.5 rng/litre eradicated Elodea canadensis and all other submerged and floating plants except Polygonum amphibium and Chara sp. within 32 days of application. One of the lakes remained substantially free from vegetation for 2 years after treatment. Except for one colony of Typha latifolia there was no significant damage to shoreline plants. No mats of filamentous fungi developed in the treated lakes although they were widespread in adjacent untreated lakes. Despite a change in a number of environmental factors as a result of the removal of most of the plant life neither aquatic invertebrates, fish nor breeding birds appeared to suffer changes in species or population during the study period from 1965 to '67.
Disappearance of paraquat from the water was rapid, significant quantities being found in the weed within 24 h of application. A gradual build-up of paraquat residues in deposits at the lake bottom was recorded up to 32 days and subsequently 197 days after application with a marked fall-off at 364 days. [See also W.A. 19: 2514]. F.s.-M.Y.