Myriophyllum aquaticum versus Lemna minor: Sensitivity and Recovery Potential After Exposure to Atrazine

Abstract

The relative sensitivity and recovery potential of two aquatic macrophyte species, Lemna minor and Myriophyllum aquaticum exposed to atrazine (concentration ranges 80 – 1280 μg/L and 40 – 640 μg/L, respectively) was evaluated using slightly adapted standard protocol for Lemna spp: relative growth rates (RGR) and yield of both plants were measured in 3 d long intervals during the exposure and recovery phase. M. aquaticum was also exposed to atrazine-spiked sediment (0.1-3.7 μg/g) in water free system. The results of M. aquaticum sediment contact test showed that root and shoot-based growth parameters are equally sensitive endpoints. In the water (sediment free) test system, M. aquaticum reacted with a delay, but was more sensitive to atrazine than L. minor. Lemna recovered after short (3 d) and longer exposure (7 d) to all atrazine concentrations after only 5 to 6 d long recovery phase. The recovery of M. aquaticum after short exposure was slower and less efficient: after 12 d of recovery phase the final biomass of plants exposed to 380 and 640 μg/L was below the initial values. However, based on RGR for the last assessment interval (day 12 to 15) no significant differences were indicated for any treatment. The last interval RGR (RGR calculated for the final 3 d long interval of the recovery phase) provides a good indication of plant recovery potential regardless of species growth strategy. If compared to L. minor, the difference in growth rate, sensitivity, lag phase and recovery potential from water-column substances, and also suitability for studies investigating the effect of sediment-bound pollutants advocates the use of M. aquaticum as an additional macrophyte species in risk assessment.