Pesticide mixtures are common in streams with agricultural or urban influence in the watershed. The Pesticide Toxicity Index (PTI) is a screening tool to assess potential aquatic toxicity of complex pesticide mixtures by combining measures of pesticide exposure and acute toxicity in an additive toxic-unit model. The PTI is determined separately for fish, cladocerans, and benthic invertebrates. ...

The acute toxicity of sulfate to Ceriodaphnia dubia, Chironomus tentans, Hyalella azteca, and Sphaerium simile was assessed to support potential updates of Illinois (USA) sulfate criteria for the protection of aquatic life. The mean lethal concentrations to 50% of a sample population (LC50s), expressed as mg S04(-2)/L, in moderately hard reconstituted water (MHRW) were as follows: 512 mg/L for ...

Direct and indirect effects of the fungicide carbendazim on ecosystem structure and functioning were studied < or =8 weeks after application (nominal concentrations: 0, 3.3, 33, 100, and 1000 microg/L) to outdoor microcosms in Thailand. Direct effects on macroinvertebrates are discussed in detail in a separate article. The present article presents the effects on other end points and discusses t...

Theory predicts that inter-patch dispersal rates and patterns of patch heterogeneity both have the potential to alter patterns of local and regional species diversity. To test this, we manipulated both rates of habitat connectivity and the geometric arrangement of habitat heterogeneity within regions of experimental zooplankton communities. We found no effects of habitat geometry on any metric ...

The large bloom-forming flagellate Gonyostomum semen has been hypothesized to be inedible to naturally occurring zooplankton due to its large cell size and ejection of long slimy threads (trichocysts) induced by physical stimulation. In a grazing experiment using radiolabelled algae and zooplankton collected from lakes with recurring blooms of G. semen and lakes that rarely experience blooms, w...

The ever increasing industrial and consumer applications of titanium dioxide nanoparticles (TiO2 NPs) raise concern over the possible risk associated with their environmental exposure. Still, the knowledge regarding nanoparticle behavior in a freshwater ecosystem is lacking. The current study focuses on the toxicity of TiO2 NPs towards Ceriodaphnia dubia (a dominant daphnid isolated from the fr...

Fish farming in net cages causes changes in environmental conditions. We evaluated the resilience of zooplankton concerning this activity in Rosana Reservoir (Paranapanema River, PR-SP). Samples were taken near the net cages installed at distances upstream and downstream, before and after net cage installation. The resilience was estimated by the decrease in the groups' abundance after installi...