Preliminary report on the concentration of neonicotinoid pesticides in the water of Lake Shinji, Japan

Although reductions in both the abundance of the zooplankton Chironomus plumosus and the fisheries yield of shrimps occurred immediately after the use of neonicotinoids began at Lake Shinji, Japan, there have been no studies on the actual concentration of neonicotinoids in the lake water. Thus, we performed a preliminary analysis of the concentration of neonicotinoids in the lake water and the water in the surrounding watershed. The concentration of neonicotinoids in the lake water at sampling sites influenced by the Hii River was under our detection limit, while lake water at sites influenced by the waste water from rice paddies contained neonicotinoids at concentrations more than the detection limit. The total concentration was below the chronic concentration. Because the concentration of neonicotinoids in the waste water from rice paddies was higher in June than in July, the concentration in Lake Shinji may become higher immediately after the planting of rice at this time.