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Biomedical subjects

J H Rodgers

Publications and source records attributed to J H Rodgers.

29 records · Page 2Linked to original sources
PubMed1997

Experimental factors that may affect toxicity of cadmium to freshwater organisms.

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.

Animals↗
PubMed1996

Design and construction of model stream ecosystems.

A series of 12 outdoor model stream mesocosms was designed to evaluate the effects of chemicals and mixtures on the biota in stream ecosystems. An integrated design plan incorporated physical, chemical, and biological factors as well as the specific experimental objectives and effects parameters to be evaluated. Analysis of biological assemblages such as macroinvertebrates and periphyton in the model stream mesocosms demonstrated the presence of diverse and sensitive taxa. These model stream mesocosms also included the ability to evaluate responses of sentinel fish species such as Pimephales promelas and Lepomis macrochirus as well as macrophytes. The design and construction of the stream are discussed in detail and a brief description of a typical experimental protocol is provided. Experiments, to date, have spanned 14-30 days pretreatment "colonization" with 30 days of treatment and 15 days of posttreatment observation. Precision and accuracy of test chemical delivery to the stream have been excellent and the overall experimental design has been useful for delivering threshold toxicity concentrations and evaluating ecosystem potency for the chemicals tested.

Analysis of Variance↗
PubMed1996

Assessing the effects of a C14-15 linear alcohol ethoxylate surfactant in stream mesocosms.

Fish, benthic macroinvertebrate, and plant responses to 30-day exposures of C14-15 linear alcohol ethoxylate surfactant with an average of 7 mol of ethylene oxide (LAE) were measured in flowthrough stream mesocosms. Replicate stream mesocosms were treated in two experiments with concentrations of LAE ranging from 80 to 550 microg/liter. Macroinvertebrates were relatively insensitive with the exception of Simuliidae density which was significantly affected at 160 microg/liter. Fathead minnow (Pimephales promelas R.) reproduction was significantly reduced at >280 microg/liter and larval survival decreased significantly at 330 microg/liter. Growth and mortality of bluegill sunfish (Lepomis macrochirus L.) were not affected at the highest exposure concentration of 330 microg/liter in the first experiment. No ecologically significant effects were observed for vascular aquatic plants or periphyton. The laboratory and stream mesocosm results were similar with NOECs ranging between 80 and 550 microg/liter surfactant. The study provided data for an improved risk assessment of this nonionic surfactant, by reducing the uncertainty associated with extrapolation from laboratory data.

Animals↗
PubMed1985

Compartmentalization and persistence of endothall in experimental pools.

The compartmentalization and persistence of endothall, an aquatic herbicide, was studied using static greenhouse experimental pools. An overall aqueous pseudo-first-order decay rate coefficient of 0.173 day-1 and a half-life of 4.01 days were observed at endothall treatment levels of 0.03, 1.6, and 4.5 mg liter-1. Instantaneous sediment partition coefficients (Kp) were calculated at maximum endothall concentrations in sediments and ranged from 51.4 to 127.7. Bioconcentration factors (BCF) for the submerged aquatic macrophyte, Myriophyllum spicatum, ranged from 3.9 to 768.9. These instantaneous BCF values were calculated at the maximum M. spicatum endothall concentrations. The short aqueous half-life for endothall compares well with previous studies; however, both the Kp and BCF were one to three orders of magnitude higher than observed in a previous laboratory study and calculated from regression equations based on endothall solubility. Experimental pool studies can be important steps in translation of data from the laboratory to field and in the development of field sampling protocols that require understanding of expected behavior of a chemical in aquatic systems.

Chemical Phenomena↗