Unexpected Increases in Fecundity of Ceriodaphnia dubia Exposed to Reused Rice Irrigation Water.

Steady increases in agricultural irrigation raise concerns about environmental impacts. Rice producing regions face declining irrigation groundwater and have started reusing irrigation water as a substitute. The goal of this project was to determine if reused irrigation water is potentially toxic compared to conventional well irrigation water.

Nutrient Mitigation Efficiency in Agricultural Drainage Ditches: An Influence of Landscape Management.

Drainage systems are integral parts of agricultural landscapes and have the ability to intercept nutrient loading from runoff to surface water. This study investigated nutrient removal efficiency within replicated experimental agricultural drainage ditches during a simulated summer runoff event. Study objectives were to examine the influence of routine mowing of vegetated ditches on nutrient mitigation and to assess spatial transformation of nutrients along ditch length.

Water-quality analysis of an intensively used on-farm storage reservoir in the northeast Arkansas delta.

The use of farm reservoirs for supplemental irrigation is gaining popularity in the Mississippi Alluvial Plain (MAP). Due to depletions of several aquifers, many counties within the MAP have been designated as critical-use groundwater areas. To help alleviate stress on these aquifers, many farmers are implementing storage reservoirs for economic and conservation benefits.

Effects of acid-volatile sulfide on metal bioavailability and toxicity to midge (Chironomus tentans) larvae in black shale sediments.

Metal bioavailability and toxicity to aquatic organisms are greatly affected by variables such as pH, hardness, organic matter, and sediment acid-volatile sulfide (AVS). Sediment AVS, which reduces metal bioavailability and toxicity by binding and immobilizing metals as insoluble sulfides, has been studied intensely in recent years. Few studies, however, have determined the spatial variability of AVS and its interaction with simultaneously extracted metals (SEM) in sediments containing elevated concentrations of metals resulting from natural geochemical processes, such as weathering of black shales.

Comparative acute toxicity of potassium permanganate to nontarget aquatic organisms.

Potassium permanganate (KMnO4) is used worldwide in freshwater pond aquaculture for treatment and prevention of waterborne external parasitic, bacterial, and fungal diseases. Nevertheless, KMnO4 has not been approved by the U.S.

Bioaccumulation and trophic transfer of polychlorinated biphenyls by aquatic and terrestrial insects to tree swallows (Tachycineta bicolor).

Insectivorous passerines often bioaccumulate polychlorinated biphenyls (PCBs) via trophic transfer processes. Tree swallows (Tachycineta bicolor) frequently are used for estimating PCB bioaccumulation, yet the focus on specific trophic links between contaminated sediment and bird has been limited. Bioaccumulation of PCBs from sediment to tree swallows was examined with focus on trophic pathways by simultaneously examining PCBs in emergent aquatic and terrestrial insects and gut contents of nestlings.

Interaction of chemical cues from fish tissues and organophosphorous pesticides on Ceriodaphnia dubia survival.

Cladocera are frequently used as test organisms for assessing chemical and effluent toxicity and have been shown to respond to stimuli and cues from potential predators. In this study, the interactive effects of visual and chemical cues of fish and two organophosphorous pesticides on survival of Ceriodaphnia dubia were examined. A significant chemical cue (homogenized Pimephales promelas) and malathion interaction was observed on C.

Monitoring exposure of northern cardinals, Cardinalis cardinalis, to cholinesterase-inhibiting pesticides: enzyme activity, reactivations, and indicators of environmental stress.

Northern cardinals (Cardinalis cardinalis) frequently use agricultural field edges in northeast Arkansas, USA, and may be at risk of exposure to cholinesterase (ChE)-inhibiting pesticides. We monitored northern cardinal exposure to ChE-inhibiting pesticides by comparing plasma total ChE (TChE) activity to reference-derived benchmarks and TChE reactivations. Total ChE and acetylcholinesterase (AChE) were measured for 128 plasma samples from 104 northern cardinals from nine study sites.

The effect of sex on avian plasma cholinesterase enzyme activity: a potential source of variation in an avian biomarker endpoint.

Accurate identification of contaminant exposure to nontarget organisms involves understanding sources of variation associated with contaminant specific biomarkers. Cholinesterase (ChE) enzyme activity is the biochemical endpoint most often used to assess organism exposure to organophosphorus (OP) pesticides. A potential source of variation for this biomarker is sex, however, a generalized pattern of sex as a source of variation for avian ChE levels remains equivocal.

Methyl parathion toxicity in vegetated and nonvegetated wetland mesocosms.

Methyl parathion (MeP) was introduced into constructed wetlands for the purpose of assessing the influence of emergent vegetation on transport and toxicity of the pesticide. Two vegetated (90% cover, mainly Juncus effusus) and two nonvegetated wetland cells (each with a water body of 50 x 5.5 x 0.