Soybeans are intensively grown over large swaths of land in the Midwestern US. Introduction of the pathogenic fungus responsible for Soybean Rust (Phakopsora pachyrhizi) will likely result in a significant increase in the environmental load of strobilurin and conazole fungicides. We determined the toxicity of six such fungicides to the unicellular algae Pseudokirchneriella subcapitata and the aquatic invertebrate, Daphnia magna. We found that levels of concern of some fungicides were lower than annual average runoff concentrations predicted for Indiana. Our results suggest that pyraclostrobin and propiconazole, and to a lesser extent tebuconazole, may cause impacts to algae and daphnids in areas where soybeans are intensively grown. More studies are needed to describe the ecological effects of sublethal exposures to these fungicides, as well as monitoring environmental concentrations in watersheds where these fungicides are applied to soybeans.

Silver nanoparticles (Ag NPs) are gaining popularity as bactericidal agents in commercial products; however, the mechanisms of toxicity (MOT) of Ag NPs to other organisms are not fully understood. It is the goal of this research to determine differences in MOT induced by ionic Ag(+) and Ag NPs in Daphnia magna, by incorporating a battery of traditional and novel methods. Daphnia embryos were exposed to sublethal concentrations of AgNO3 and Ag NPs (130-650 ng/L), with uptake of the latter confirmed by confocal reflectance microscopy. Mitochondrial function was non-invasively monitored by measuring proton flux using self-referencing microsensors. Proton flux measurements revealed that while both forms of silver significantly affected proton efflux, the change induced by Ag NPs was greater than that of Ag(+). This could be correlated with the effects of Ag NPs on mitochondrial dysfunction, as determined by confocal fluorescence microscopy and JC-1, an indicator of mitochondrial permeability. However, Ag(+) was more efficient than Ag NPs at displacing Na(+) within embryonic Daphnia, based on inductively coupled plasma-mass spectroscopy (ICP-MS) analysis. The abnormalities in mitochondrial activity for Ag NP-exposed organisms suggest a nanoparticle-specific MOT, distinct from that induced by Ag ions. We propose that the MOT of each form of silver are complementary, and can act in synergy to produce a greater toxic response overall.

No abstract

The detection of harmful chemicals and biological agents in real time is a critical need for protecting water quality. We studied t he real -time eff ects of fiv e env ironmental c ontaminants with di ffering modes o f act ion (atrazi ne, pentachlorophenol, cadmium chloride, malathion, and potassium cyanide) on respiratory oxygen consumption in 2-day post-fertilization f athead m innow (Pimephales promelas) eg gs. Ou r o bjective was to a ssess t he se nsitivity o f f athead minnow eggs using the self-referencing micro-optrode technique to detect instantaneous changes in oxygen consumption after brief exposures to lo w c oncentrations of contaminants. Oxy gen co nsumption data i ndicated that the technique is indeed sensitive enough to reliably detect physiological alterations induced by all co ntaminants. After 2 h of exposure, we i dentified significant increases i n o xygen consumption u pon e xposure t o pen tachlorophenol (100 an d 1000 µ g/L), cadmium chloride (0.0002 and 0.002 µg/L), and atrazine (150 µg/L). In contrast, we observed a significant decrease in oxygen flux af ter e xposures to pot assium c yanide (5.2, 22, an d 44 µ g/L) a nd at razine ( 1500 µ g/L). N o ef fects were detected af ter e xposures t o malathion (200 an d 340 µ g/L). We h ave al so t ested t he s ensitivity o f Daphnia magna embryos as a nother a nimal model for real -time e nvironmental bio monitoring. Ou r res ults are s o f ar en couraging and support fu rther dev elopment of t his t echnology as a p hysiologically co upled bi omonitoring tool f or t he det ection o f environmental toxicants.

No abstract