ALBERT

Notes: Abstract. The effects of exposure duration, test organism, and test endpoint on the toxicity of cadmium to a variety of freshwater species were evaluated. Toxicity of cadmium was assessed by monitoring the survival and reproduction of Ceriodaphnia dubia Richard; the survival of Daphnia magna Straus; and the survival and growth of Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque. Organisms were exposed in static systems for 48 h, 96 h, 7 d, 10 d, and 14 d to determine acute and chronic toxicity. Relative sensitivities of test organisms exposed to aqueous cadmium varied with test duration and test endpoint. In general, H. azteca was the most sensitive organism tested, followed in decreasing sensitivity by P. promelas, C. dubia, D. magna, and C. tentans. Mortality of C. dubia and D. magna was consistent up to 7 d, after which little additional mortality occurred. Effects of test duration on cadmium toxicity were most pronounced for H. azteca and C. tentans, with mortality and growth becoming increasingly sensitive with increasing test duration.

Notes: Abstract. Laboratory toxicity data contrasting responses of aquatic organisms to insecticides are important for focusing on sensitive species (steepest exposure-response slope) exposed to aqueous concentrations of these insecticides in field studies. These data also allow prediction of expected responses of aquatic species to a range of insecticide concentrations in situ. Aqueous 48-h toxicity tests were performed to contrast responses of Daphnia magna Straus, Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque to acetylcholinesterase-inhibiting insecticides: chlorpyrifos, aldicarb, and chlordane. As expected, invertebrates tested (H. azteca, C. tentans, and D. magna) were ≥ 200 times more sensitive than the vertebrate P. promelas to chlorpyrifos exposures. H. azteca was approximately 3.5 times more sensitive to chlorpyrifos (453% mortality/μg/L) than D. magna (128% mortality/μg/L). For both aldicarb and chlordane, C. tentans was the most sensitive species tested (2.44 and 2.54% mortality/μg/L, respectively). Differences in chlordane potency for test species varied only by a factor of approximately 2–3 (0.88% mortality/μg/L for H. azteca to 2.54% mortality/μg/L for C. tentans). Although point estimates of population responses such as LC50s, NOECs, and LOECs are of some utility for predicting effects of pesticides in aquatic systems, exposure-response slopes are also useful for extrapolation of laboratory data to diverse field situations, especially where sediment sorption may regulate insecticide exposure or bioavailability.

Notes: Abstract. Because of recent concerns regarding the ability of acute (48–96 h) sediment toxicity tests to accurately assess the potency of sediment-bound contaminants, effects of exposure duration, test organism selection, and test endpoint on the observed toxicity of aqueous phase copper and a copper-contaminated freshwater sediment were evaluated. Toxicity of sediment-bound copper was assessed by monitoring survival and reproduction of Ceriodaphnia dubia Richard, survival of Daphnia magna Straus and Hyalella azteca Saussure, and survival and growth of Chironomus tentans Fabricius and Pimephales promelas Rafinesque. Organisms were exposed in static systems for 48 h, 96 h, 7 d, 10 d, and 14 d, which enabled measurement of acute and chronic toxicity. Relative sensitivities of test organisms exposed to copper in water and copper-contaminated sediment varied with test duration and test endpoint. In general, C. dubia was the most sensitive organism tested, followed in decreasing sensitivity by D. magna, P. promelas, H. azteca, and C. tentans. A temporal mortality threshold was demonstrated by C. dubia and D. magna when exposed to copper, with little mortality occurring after 96 h of exposure. Effects of test duration on copper toxicity were most pronounced for H. azteca and C. tentans, with mortality and growth effects becoming increasingly sensitive with increasing test duration. Formulated sediment served as a suitable control and reference sediment in this study, and matched a variety of field-collected test sediment characteristics. In tests utilizing copper-contaminated sediments, observed responses (mortality, growth, reproduction) corresponded with overlying water concentration of copper rather than concentration of copper in bulk sediment or pore water.

Notes: Abstract. To accurately determine the relative potency of contaminated sediments that exhibit toxicity in screening tests, definitive toxicity tests are conducted by diluting test sediment with a nontoxic reference sediment of similar characteristics. To demonstrate the usefulness of formulated sediment as a reference and dilution sediment, the relative potency of a copper-contaminated sediment was assessed by diluting with a formulated sediment. Toxicity of sediment-bound copper was assessed by monitoring the survival of Ceriodaphnia dubia Richard, Daphnia magna Straus, Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque. Organisms were exposed in static systems for 10 d using test sediment dilutions that produced mortality in range-finding tests. Formulated sediment served as a suitable control sediment, with organism survival ranging from 85–100%. Formulated sediment was prepared and matched ten of eleven characteristics of the field-collected test sediment. When used to dilute the copper-contaminated sediment, formulated sediment resulted in decreased concentrations of copper in sediment, pore water, and overlying water with concomitant increases in test dilution. Thus, formulated sediment served as a suitable reference and dilution sediment in this study. Evidence indicates that formulated sediments could be used in this capacity when suitable natural reference sediments are otherwise unavailable.

Notes: Abstract. Sediments were collected from Steilacoom Lake, Pierce County, in Washington State, and amended with copper sulfate (nominal concentrations of 800, 1,000, 1,500, and 2,000 mg Cu/kg dry weight) to assess copper bioavailability to Hyalella azteca, Chironomus tentans, or Ceriodaphnia dubia. H. azteca survival and C. tentans survival and growth were not significantly affected, with 10-day no observed effects concentrations (NOEC) and lowest observed effects concentrations (LOEC) of 2,010 and 〉2,010 mg Cu/kg, respectively. C. dubia was the most sensitive organism tested with 10-day NOEC and LOECs for survival and reproduction of 906 and 1,469 mg Cu/kg, respectively. Sediment AVS concentrations were 〈0.15 μmol/g, while simultaneously extracted metal (SEM) concentrations were ≥5.71 μmol Cu/g. Dissolved interstitial water concentrations ranged from below detection (0.010 mg/L) to 0.24 mg Cu/L, with interstitial water toxicity units as high as 3.4. Based on this study, effects to C. dubia may occur at bulk sediment concentrations 〉906 mg Cu/kg. Further, AVS and interstitial water concentrations are not accurate predictors of copper bioavailability in Steilacoom Lake.

Notes: Abstract. Effects of a homologous series of three primarily linear alcohol ethoxylate surfactants were studied in laboratory flow-through 28-day early-life-stage tests with fathead minnow (Pimephales promelas Rafinesque). Surfactants were a C9–11, C12–13, and C14–15 with an average of 6, 6.5, and 7 ethylene oxide units per mole of alcohol, respectively. Average measured surfactant recoveries were 103%, 81%, and 79% of nominal concentrations for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 studies, respectively. Embryo survival at 48 h was not adversely affected at any of the concentrations tested. Impaired hatching and deformed fry were observed only in the C12–13 EO 6.5 study. The 28-day LC50 values were 4.87, 2.39, and 1.02 mg/L for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 surfactants, respectively. The corresponding NOECs for survival were 1.01, 1.76, and 0.74 mg/L. Posthatch fry growth was more sensitive than survival for the C12–13 EO 6.5 and C14–15 EO 7 surfactants. Survival of posthatch fry decreased with increasing surfactant alkyl chain length. Twenty-eight-day laboratory data were compared to 96-h laboratory, 10-day laboratory and 30-day stream mesocosm data for fathead minnow previously determined for these surfactants. Survival endpoints from the different exposures were comparable and only varied within a factor of two. Similarity of results suggests that it is possible to effectively use 96-h, 10-day, or 28-day laboratory data to predict environmental effects concentrations of these surfactants for fish.

Notes: Abstract In designing aquatic herbicides containing copper, an important goal is to maximize efficacy for target species while minimizing risks for nontarget species. To have a margin of safety for nontarget species, the concentration, duration of exposure (i.e., uptake), and form (i.e., species) of copper used for herbicidal properties should not elicit adverse effects on populations of nontarget species. To determine the potential for risk or adverse effects (conversely the margin of safety), data regarding the comparative toxicity of copper-containing herbicides are crucial. A series of comparative toxicity experiments was conducted, including baseline estimates of toxicity (LC50s, LOECs), sensitive species relationships (thresholds and exposure-response slopes), and bioavailability of toxic concentrations and forms of copper 7 days after initial herbicide application. Aqueous 48-h toxicity experiments were performed to contrast responses of Daphnia magna Strauss, Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque to copper herbicides: Clearigate®, Cutrine®-Plus, and copper sulfate. D. magna was the most sensitive aquatic animal tested for all three herbicides; 48-h LC50s for organisms exposed to Clearigate, Cutrine-Plus, and copper sulfate were 29.4, 11.3, and 18.9 μg Cu/L, respectively. In terms of potency (calculated from the linearized portion of the exposure-response curves, which included 50% mortality), D. magna was the most sensitive animal tested. Organisms exposed to Clearigate, Cutrine-Plus, and copper sulfate had exposure-response slopes of 2.55, 8.61, and 5.07% mortality/μg Cu/L, respectively. Bioavailability of Clearigate and Cutrine-Plus was determined by comparing survival data (LC50s) of test organisms exposed to herbicide concentrations during the first and last 48-h of a 7-day exposure period. Even in these relatively simplified water-only exposures, a transformation of copper to less bioavailable species over time was observed with a 100–200% decrease in toxicity (i.e., an increase in 48-h LC50s) for all four test animals. This series of laboratory experiments provides a worst-case scenario for determining the risk associated with the manufacturer's recommended application rates of Clearigate (100–1,000 μg Cu/L), Cutrine-Plus (200–1,000 μg Cu/L), and copper sulfate (100–500 μg Cu/L) in natural waters for four nontarget freshwater animals.