Effects of Lindane on the Planktonic Community in Freshwater Microcosms

Effects of lindane on natural planktonic communities were investigated in aquatic indoor microcosms. Lindane was dosed to eight 300-liter microcosms for 2 weeks, and effects and recovery processes were monitored over 12 weeks. Mean measured water concentrations of lindane during the exposure period were 3, 6, 13, 27, 55, 102, 230, and 455 μg/liter. Zooplankton was severely affected by lindane. The most sensitive organisms were nauplii of copepodes which were affected at all treatment levels ≥6 μg/liter during exposure (Days 2–14). Recovery of nauplii abundance was concentration-dependent at concentrations ≤55 μg/liter lindane, whereas at concentrations ≥102 μg/liter recovery was negligible.Cladoceraabundance decreased during exposure to ≥102 μg/liter lindane and did not recover to original levels until the end of the study. For phytoplankton, decreased population densities ofChlorophyceaeand microalgae (<5 μm) were observed at lindane concentrations ≤55 μg/liter, where zooplankton was only temporarily affected. At higher lindane concentrations (≥102 μg/liter) effects on phytoplankton were not clear, as also increases in abundances were observed, probably as a consequence of minimized grazing pressure, due to high zooplankton mortality. Comparison of these results with data obtained in complex outdoor systems demonstrates the practicability and sensitivity of indoor microcosms and emphasizes the importance of long-term testing and assessment of recovery processes for prediction of environmental effects.