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.

Integrated Assessment of Chemical and Biological Recovery After Diversion and Treatment of Acid Mine Drainage in a Rocky Mountain Stream.

Responses of stream ecosystems to gradual reductions in metal loading following remediation or restoration activities have been well documented in the literature. However, much less is known about how these systems respond to the immediate or more rapid elimination of metal inputs. Construction of a water treatment plant on the North Fork of Clear Creek (NFCC; CO, USA), a US Environmental Protection Agency Superfund site, captured, diverted, and treated the two major point-source inputs of acid mine drainage (AMD) and provided an opportunity to investigate immediate improvements in water quality.

Stream Mesocosm Experiments Show no Protective Effects of Calcium on Copper Toxicity to Macroinvertebrates.

Although the concept and modeling of metal bioavailability and toxicity have been well developed based largely on laboratory experiments with standard test species, additional evidence is required to demonstrate their applicability for macroinvertebrates typically found in natural lotic ecosystems. We conducted 10-day stream mesocosm experiments to test the hypothesis that increased water hardness (in the present study, the calcium [Ca] concentration was increased by adding CaCl ) would mitigate the effects of copper (Cu) on natural benthic macroinvertebrate communities. Exposure of macroinvertebrate communities to 25 μg/L Cu for 10 days in stream mesocosm experiments resulted in significant decreases in total abundance, in number of taxa, and in abundance of many macroinvertebrate taxa.

Before-After Control-Impact field surveys and novel experimental approaches provide valuable insights for characterizing stream recovery from acid mine drainage.

Mineral extraction has resulted in widespread stream impairment due to habitat degradation and water quality impacts from acid mine drainage (AMD). The North Fork of Clear Creek (NFCC), Colorado, USA was historically impaired by AMD from two major point-source inputs, with some stream segments devoid of aquatic life prior to remediation. In the summer of 2017, the North Clear Creek Water Treatment Plant (NCCWTP) began AMD water treatment.

Size-Dependent Sensitivity of Aquatic Insects to Metals.

Laboratory assessments of aqueous metal toxicity generally demonstrate aquatic insects tolerate relatively high concentrations of metals in aqueous exposures; however, mesocosm experiments and field biomonitoring often indicate effects at relatively low metal concentrations. One hypothesis proposed to reconcile this discrepancy is an increased sensitivity of smaller size classes of organisms. We exposed field colonized benthic communities to aqueous metals in a series of mesocosm experiments.

Indirect Effects of Iron Oxide on Stream Benthic Communities: Capturing Ecological Complexity with Controlled Mesocosm Experiments.

Ferric iron (Fe(III)) oxyhydroxides commonly precipitate at neutral pH and in highly oxygenated conditions in waterways receiving acid mine drainage, degrading stream benthic communities by smothering of habitat, primary producers, and aquatic invertebrates. Stream mesocosms were used to expose naturally colonized benthic communities to a gradient of ferric Fe (0-15 mg/L) for 14 days to estimate the effects of Fe precipitates on primary production, larval and emerging adult aquatic insects, and the macroinvertebrate community structure. Community composition was significantly altered at concentrations near or below the US Environmental Protection Agency chronic Fe criterion (1.

Context-Dependent Responses of Aquatic Insects to Metals and Metal Mixtures: A Quantitative Analysis Summarizing 24 Yr of Stream Mesocosm Experiments.

Modernizing water quality criteria to predict how contaminants affect natural aquatic communities requires that we utilize data obtained across multiple lines of evidence, including laboratory, mesocosm, and field studies. We report the results of 29 mesocosm experiments conducted from 1994 to 2017 at the Colorado State University Stream Research Laboratory (Fort Collins, CO, USA). The primary goal of the present study was to quantify responses of aquatic insect communities collected from 8 different locations to different combinations of cadmium (Cd), copper (Cu), iron (Fe), and zinc (Zn).

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.

Structural and functional responses of periphyton and macroinvertebrate communities to ferric Fe, Cu, and Zn in stream mesocosms.

Two mesocosm experiments were conducted to examine effects of ferric iron (Fe) and mixtures of ferric Fe with aqueous metals (Cu, Zn) on stream benthic communities. Naturally colonized benthic communities were exposed to a gradient of ferric Fe (0, 0.4, 1.

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.

Comparison of different predictors of exposure for modeling impacts of metal mixtures on macroinvertebrates in stream microcosms.

Knowledge about which predictors of metal exposure are best to model the impacts of metal mixtures on river macroinvertebrates remains uncertain. A new predictor based on the amount of metals binding to humic acid, which is assumed to be a proxy of non-specific biotic ligand sites, has been proposed. The amount can be calculated using Windermere Humic Aqueous Model (WHAM), which we will refer to as the WHAM-HA approach.