Subcellular Accumulation and Depuration of Zinc in Periphytic Algae during Episodic and Continuous Exposures.

As the severity of extreme precipitation events increases with global climate change, so will episodic pulses of contamination into lotic systems. Periphytic algae represents bioindicator species in most freshwater systems due to their rapid accumulation of toxicants; therefore, it is vital to understand how accumulation in this group differs across temporally variable exposure regimes. The ability to rapidly accrue contaminants has additional implications for the trophic transfer of metals to primary consumers.

Copper toxicity in Bristol Bay headwaters: Part 1-Acute mortality and ambient water quality criteria in low-hardness water.

The world-class Alaskan Bristol Bay salmon fishery and vast deposits of copper (Cu) and other metals in the watershed warrant further investigation into the potential toxicity of Cu to salmonids under the low water-hardness conditions that occur in the watershed. Therefore we investigated the acute toxicity of Cu to rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas) in low-hardness water (∼ 30 mg/L as CaCO ) formulated in the laboratory and collected from the Bristol Bay watershed. The median lethal concentration (LC50) for rainbow trout exposed to Cu in low-hardness laboratory water was 16 μg Cu/L (95% confidence intervals [CIs]: 12, 21; dissolved Cu, filtered to 0.

Chronic Toxicity of Ferric Iron for North American Aquatic Organisms: Derivation of a Chronic Water Quality Criterion Using Single Species and Mesocosm Data.

Iron is a common pollutant in waters near coal and hard rock mine disturbances. The current 1000 µg/L total recoverable chronic criterion for iron (Fe) for protection of aquatic life in the United States was developed using very limited data in 1976 and has not been revised since. To develop a more scientifically based criterion, several chronic laboratory toxicity experiments (> 30 days) were conducted with ferric Fe at circumneutral pH on a taxonomically diverse group of organisms including brown trout (Salmo trutta), mountain whitefish (Prosopium williamsoni), boreal toad tadpoles (Bufo boreas), the oligochaete worm Lumbriculus variegatus, the mayfly Hexagenia limbata, and the planarian Dugesia dorotocephala.

The effects of chronological age and size on toxicity of zinc to juvenile brown trout.

A series of toxicity tests were conducted to investigate the role of chronological age on zinc tolerance in juvenile brown trout (Salmo trutta). Four different incubation temperatures were used to control the maturation of the juveniles before zinc exposures. These 96-h exposures used flow-through conditions and four chronological ages of fish with weights ranging from 0.

Application of a generalized linear mixed model to analyze mixture toxicity: survival of brown trout affected by copper and zinc.

Increased concerns about the toxicity of chemical mixtures have led to greater emphasis on analyzing the interactions among the mixture components based on observed effects. The authors applied a generalized linear mixed model (GLMM) to analyze survival of brown trout (Salmo trutta) acutely exposed to metal mixtures that contained copper and zinc. Compared with dominant conventional approaches based on an assumption of concentration addition and the concentration of a chemical that causes x% effect (ECx), the GLMM approach has 2 major advantages.

Acclimation and deacclimation of brown trout (Salmo trutta) to zinc and copper singly and in combination with cadmium or copper.

Brown trout (Salmo trutta) were chronically exposed to low and high levels of zinc (Zn) alone, copper (Cu) alone, a Zn-Cu mixture, and a Zn-cadmium (Cd) mixture all starting with eyed eggs and continuing through to the fingerling stage. Exposure to the metals and metal mixtures resulted in acclimation as measured by greater median lethal concentrations (LC50) values relative to metal-naïve fry. The degree of acclimation was similar between the low and high exposures except for Cu, where acclimation was observed at the high but not the low acclimation level.

Responses of aquatic insects to Cu and Zn in stream microcosms: understanding differences between single species tests and field responses.

Field surveys of metal-contaminated streams suggest that some aquatic insects, particularly mayflies (Ephemeroptera) and stoneflies (Plecoptera), are highly sensitive to metals. However, results of single species toxicity tests indicate these organisms are quite tolerant, with LC50 values often several orders of magnitude greater than those obtained using standard test organisms (e.g.

Acute toxicity of zinc to several aquatic species native to the Rocky Mountains.

National water-quality criteria for the protection of aquatic life are based on toxicity tests, often using organisms that are easy to culture in the laboratory. Species native to the Rocky Mountains are poorly represented in data sets used to derive national water-quality criteria. To provide additional data on the toxicity of zinc, several laboratory acute-toxicity tests were conducted with a diverse assortment of fish, benthic invertebrates, and an amphibian native to the Rocky Mountains.

Acute toxicity of aqueous copper, cadmium, and zinc to the mayfly Rhithrogena hageni.

Heptageniid mayfly nymphs have been suggested as sensitive indicators of metal contamination in streams based on biomonitoring studies, experimentation in situ, and experimentation in microcosm. Laboratory tests were conducted to evaluate the sensitivity of Rhithrogena hageni, a heptageniid mayfly, to waterborne copper, cadmium, and zinc. Tests were conducted with soft water (hardness = 40-50 mg/L) at about 12 degrees C.

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) at multiple water hardnesses.

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) was determined at multiple water hardnesses. Increasing water hardness decreased cadmium toxicity. Postswimup fry were much more sensitive than embryos and larvae.