Gerald T. Ankley

Bio: Gerald T. Ankley is an academic researcher from United States Environmental Protection Agency. The author has contributed to research in topics: Acute toxicity & Hyalella azteca. The author has an hindex of 6, co-authored 7 publications receiving 1319 citations.

Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates

Abstract: Procedures are described for testing freshwater organisms in the laboratory to evaluate the toxicity or bioaccumulation of contaminants associated with whole sediments. Sediments may be collected from the field or spiked with compounds in the laboratory. Toxicity methods are outlined for two organisms, the amphipod Hyalella azteca and the midge Chironomus tentans. The toxicity tests are conducted for 10d in 300-mL chambers containing 100 mL of sediment and 175 mL of overlying water. Overlying water is renewed daily and test organisms are fed during the toxicity tests. The endpoint in the toxicity test with H. azteca is survival and the endpoints in the toxicity test with C. tentans are survival and growth. Procedures are primarily described for testing freshwater sediments; however, estuarine sediments (up to 15% salinity) can also be tested with H. azteca. Guidance for conducting 28-d bioaccumulation tests with the oligochaete Lumbriculus variegatus is provided in this manual. Overlying water is renewed daily and test organisms are not fed during bioaccumulation tests. Methods are also described for determining bioaccumulation kinetics of different classes of compounds during 28-d exposures with L. variegatus.

Relative Sensitivity of Three Freshwater Benthic Macroinvertebrates to Ten Contaminants

Abstract: The objective of this study was to determine the suitability of Hyalella azteca, Chironomus tentans and Lumbriculus variegatus as representative species for the assessment of sediment toxicity. Ten chemicals were tested at the U.S. EPA Environmental Research Laboratory-Duluth, always using H. azteca and C. tentans and, occasionally, L. variegatus. The exposures were water-only, flow-through tests with measured chemical concentrations, which were conducted for 10 days in Lake Superior water. Chemicals tested included five metals (copper, lead, zinc, nickel, cadmium) and five pesticides (chlorpyrifos, dieldrin, p,p′-DDD, p,p′-DDE, p,p′-DDT). The amphipod was quite sensitive to the metals, while the midge often was exceptionally sensitive to the pesticides. No one of the three species was most (or least) sensitive to the toxicants. Toxicity of the contaminants to the three species was compared to the genus mean acute and chronic data found in U.S. EPA Water Quality Criteria (WQC) documents, as well as information from the AQUIRE database. The results of these comparisons indicated that the three species reasonably represent the range of sensitivities of other aquatic test species, and occasionally are among the most sensitive species when compared to others in the WQC database.

Evaluation of potential confounding factors in sediment toxicity tests with three freshwater benthic invertebrates

Abstract: We examined the effects of natural sediment physicochemical properties on the results of lab tests with the amphipod Hyalella azteca, the midge Chironomus tentans, and the ohgochaete Lumbriculus variegatus Ten-day exposures with the three species were conducted with 50 uncontaminated sediment samples from Lakes Erie, Huron, Superior, and Ontario, which differed markedly with regard to characteristics such as grain-size distribution, organic carbon content, and mineralogical composition Tests were conducted both with and without the addition of exogenous food Survival of Hyalella azteca, survival and growth of Chironomus tentans, and survival/reproduction and growth of Lumbriculus vanegatus were significantly greater in tests in which the animals were fed vs those in which they were not Approximately 10% of the tests in which Hyalella azteca was not fed and 80% of tests in which the amphipods were fed resulted in >80% survival, a common criterion for defining the acceptability of tests with Hyalella azteca in clean control sediments Similarly, a relatively high percentage of the tests in which Chironomus tentans was not fed would have failed a control survival criterion of 70% for the midge Hence, there is significant potential for false positive results if Hyalella azteca or Chironomus tentans is not fed during sediment tests Predictive modeling of the assay results in relationship to sediment physicochemical characteristics failed to reveal any additional factors that influenced survival of Hyalella azteca and Chironomus tentans, or reproduction and growth of Lumbriculus vanegatus in tests in which the organisms were fed However, linear modeling did suggest that growth of fed as well as unfed Chironomus tentans may have been influenced by gram size distribution of the test sediments

Organic carbon partitioning as a basis for predicting the toxicity of chlorpyrifos in sediments

Abstract: The objective of this study was to evaluate an organic carbon partitioning model for predicting bioavailability of the organophosphate chlorpyrifos in sediments, in support of the development of a sediment-quality criterion for the pesticide. Initial 10-d water-only toxicity tests were conducted with the midge Chironomus tentans to define the sensitivity of this species to chlorpyrifos. Two uncontaminated sediments with differing organic carbon contents (approximately 3 and 8.5%) were spiked with varying amounts of chlorpyrifos designed to result in equilibrium interstitial (pore) water concentrations that would bracket the effects concentrations observed in the water-only exposures. Ten-day toxicity tests with Chironomus tentans were conducted with the spiked sediments under conditions similar to those in the water-only exposure. Based on predicted pore-water concentrations of chlorpyrifos, results of the water-only and sediment tests were in close agreement. The water-only LC50 of chlorpyrifos to Chironomus tentans was 70 ng/L, whereas LC50 values based on predicted pore-water concentrations in the two test sediments were 40 and 70 ng/L. Total concentrations of chlorpyrifos measured in pore water from the test sediments were always at least an order of magnitude greater than predicted pore-water concentrations of the pesticide. However, upon correction for that fraction of the measured chlorpyrifos potentially bound to DOC in the pore water, measured and predicted chlorpyrifos concentrations were in much closer agreement, with the former typically about threefold greater than the latter. Overall, these results suggest that within the range of organic carbon tested in the present study, an equilibrium partitioning model based on organic carbon is appropriate for predicting the bioavailability of sediment-associated chlorpyrifos to benthic invertebrates.

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates

Abstract: Procedures are described for testing freshwater organisms in the laboratory to evaluate the toxicity or bioaccumulation of contaminants associated with whole sediments. Sediments may be collected from the field or spiked with compounds in the laboratory. Toxicity methods are outlined for two organisms, the amphipod Hyalella azteca and the midge Chironomus tentans. The toxicity tests are conducted for 10d in 300-mL chambers containing 100 mL of sediment and 175 mL of overlying water. Overlying water is renewed daily and test organisms are fed during the toxicity tests. The endpoint in the toxicity test with H. azteca is survival and the endpoints in the toxicity test with C. tentans are survival and growth. Procedures are primarily described for testing freshwater sediments; however, estuarine sediments (up to 15% salinity) can also be tested with H. azteca. Guidance for conducting 28-d bioaccumulation tests with the oligochaete Lumbriculus variegatus is provided in this manual. Overlying water is renewed daily and test organisms are not fed during bioaccumulation tests. Methods are also described for determining bioaccumulation kinetics of different classes of compounds during 28-d exposures with L. variegatus.

Responses of Hyalella azteca to acute and chronic microplastic exposures

Abstract: Limited information is available on the presence of microplastics in freshwater systems, and even less is known about the toxicological implications of the exposure of aquatic organisms to plastic particles. The present study was conducted to evaluate the effects of microplastic ingestion on the freshwater amphipod, Hyalella azteca. Hyalella azteca was exposed to fluorescent polyethylene microplastic particles and polypropylene microplastic fibers in individual 250-mL chambers to determine 10-d mortality. In acute bioassays, polypropylene microplastic fibers were significantly more toxic than polyethylene microplastic particles; 10-d lethal concentration 50% values for polyethylene microplastic particles and polypropylene microplastic fibers were 4.64 × 104 microplastics/mL and 71.43 microplastics/mL, respectively. A 42-d chronic bioassay using polyethylene microplastic particles was conducted to quantify effects on reproduction, growth, and egestion. Chronic exposure to polyethylene microplastic particles significantly decreased growth and reproduction at the low and intermediate exposure concentrations. During acute exposures to polyethylene microplastic particles, the egestion times did not significantly differ from the egestion of normal food materials in the control; egestion times for polypropylene microplastic fibers were significantly slower than the egestion of food materials in the control. Amphipods exposed to polypropylene microplastic fibers also had significantly less growth. The greater toxicity of microplastic fibers than microplastic particles corresponded with longer residence times for the fibers in the gut. The difference in residence time might have affected the ability to process food, resulting in an energetic effect reflected in sublethal endpoints. Environ Toxicol Chem 2015;34:2564–2572. © 2015 SETAC

Effect-directed analysis: a promising tool for the identification of organic toxicants in complex mixtures?

Abstract: Wastewater effluents, groundwater, surface water, sediments, soils and air particulate matter are often contaminated by a multitude of chemicals. Since often no a priori knowledge of relevant toxicants exists, chemical analysis alone is not an appropriate tool for hazard assessment. Instead, a linkage of effect data and hazardous compounds is required. For that purpose, effect-directed analysis (EDA) was developed, which is based on a combination of biotesting, fractionation procedures and chemical analytical methods. Since a controversial discussion about the prospects of success in relation to the expense exists, the current methodological state of EDA for organic toxicants in complex mixtures and important results are reviewed in this paper with the aim of establishing criteria for the successful use of this promising tool. While EDA is a powerful tool to identify specifically acting individual toxicants close to the source of emission, it is inappropriate for screening purposes and often may fail in remote areas where the concentrations of specific toxicants are too low relative to the nonspecific toxicity of the whole mixture of natural and anthropogenic compounds. The biological tools have to be carefully selected with respect to their ability to detect specific effects and their significance in hazard assessment. Sophisticated chemical tools are required to identify individual toxicants in mixtures of thousands of compounds, which are typical for contaminated environments.