Ecotoxicology (v.8, #4)
Acute and Sublethal Effects of a Non-Ionic Surfactant, Genapol OXD-080, on Mosquitofish Gambusia holbrooki (Girard)
by João A. Cabral; Sofia Ávila; João C. Marques (pp. 245-252).
Application of the biodegradable non-ionic surfactant Genapol OXD-080, a fatty alcohol polyglycol ester, in rice paddies has been considered as a method to mitigate damage caused by the Louisiana red swamp crayfish, Procambarus clarkii, to rice crops. The damages are a consequence of crayfish digging activities. The acute and sublethal effects of Genapol on a non-target key species were examined to assess the potential risk of contaminating the irrigation channels following its application in the rice paddies. Mosquitofish, Gambusia holbrooki, due to its abundance in irrigation channels, and because it is a predator with an intermediate position in the food chain, was selected as the key non-target species. The LC50 value for Genapol to mosquitofish was 2.9 mg l-1, a value 17.2 times lower than the Genapol concentration needed to decrease crayfish digging activity (50 mg l-1). For sublethal tests, three biological parameters were considered in laboratory experiments with mosquitofish: respiratory metabolism, food (energetic) consumption, and clutch survival. A significant decrease in the resting metabolism of mosquitofish was observed, even when Genapol exposure concentrations were very low (e.g., 0.75 mg l-1). Thus, oxygen consumption rates of mosquitofish are strongly affected by to the presence of this surfactant in water. In contrast, mosquitofish food consumption and clutch survival seemed not to be affected by sub-lethal concentrations of Genapol. Yet, sub-lethal effect concentrations for mosquitofish are so much lower than the concentration necessary to decrease significantly crayfish activity, we conclude that there is a reasonable potential risk of damaging local mosquitofish populations if contamination of the irrigation channels with Genapol occurs.
Keywords: mosquitofish; Gambusia holbrooki; surfactant; LC50; respiratory metabolism; food consumption; clutch survival
The Effect of Sewage on Two Bioindicators at Port Stephens, New South Wales, Australia
by P. A. Ajani; D. E. Roberts; A. K. Smith; M. Krogh (pp. 253-267).
The effect of secondary treated sewage discharged from a recently commissioned extended ocean outfall at Boulder Bay, New South Wales, Australia on two bioindicators (oysters and kelp) was examined. Sydney rock oysters, Saccostrea commercialis Iredale and Roughley, were deployed at the study outfall location and control locations for three months after which time they were retrieved and analysed for trace metal and organochlorine concentrations. This process was repeated every six months on a total of eight sampling times, three times before and five times after the commissioning of the extended ocean outfall. The abundance and recruitment of adult and juvenile kelp plants, Ecklonia radiata were also investigated. At the outfall and control locations counts were made for a total of three periods, one before and two after the commissioning of the outfall. Within each period kelp abundance was determined on three random occasions. Univariate statistics were used to test the hypothesis of an outfall effect over and above variation between the control locations. Only three organochlorines (technical chlordane and the DDT metabolites DDE and DDD) were detected in oysters across the entire sampling period. Due to the low frequency or low mean concentrations of organochlorines an impact versus control comparison was not feasible for this study. Mean concentrations of trace metals in oysters were highly variable across all sampling periods. No obvious changes in the contaminant concentrations were noticed over time. Statistical comparisons of the data collected before and after commissioning of the extended ocean outfall revealed no short-term differences in trace metal concentrations between outfall and control locations. Analysis of variance results for both adult and juvenile kelp abundance revealed no outfall effect over and above the variation found at control locations. Student Newman-Keuls tests, however, revealed a significantly higher abundance of both adult and juvenile kelp plants immediately after the commissioning of the outfall. The value of these bioindicators for detecting impacts at small secondary treated outfalls is discussed.
Keywords: bioindicators; environmental monitoring; sewage; oysters; kelp
Uptake of Copper by Neon Tetras (Paracheirodon innesi) in the Presence and Absence of Particulate and Humic Matter
by Shu Tao; Tao Liang; Changfa Liu; Shangping Xu (pp. 269-275).
Neon tetras Paracheirodon innesi were exposed to various species of copper during exposures to evaluate the bioavailability of free copper (0 to 2 mg/l), copper apparently complexed to humic substances (0 to 160 mg/l), and copper adsorbed on kaolin clays (0 to 182 mg/l). The results of the experiments demonstrated that free copper is the most bioavailable form. Both humic substances and kaolin clay particulates reduced copper bioavailability to the fish. However, fish accumulated a fraction of copper complexed to humic substances and part of copper adsorbed on kaolin clays.
Keywords: fish; speciation; copper; bioavailability; bioaccumulation
Acclimation to Contaminants by the Grass Shrimp Palaemonetes pugio: Individual Contaminants vs. Mixtures
by Paul L. Klerks (pp. 277-286).
In acclimation, a pre-exposure to a sublethal level of a contaminant results in an increased resistance in a subsequent exposure to a higher concentration of this contaminant. This research, using the grass shrimp Palaemonetes pugio as a model species, compared the occurrence of acclimation to individual contaminants to that for contaminant mixtures. Grass shrimp collected from Pass Fourchon (a produced-water discharge site with highly-elevated sediment PAH levels as well as elevated metal levels) and conspecifics collected from a nearby control site did not differ in resistance in laboratory exposures to Pass Fourchon sediment. Similarly, grass shrimp collected from the control area and kept for two weeks in enclosures at different sites along the pollution gradient in Pass Fourchon, did not differ in resistance in subsequent laboratory exposures to contaminated sediment. To investigate if these absences of acclimation could be explained by contamination complexity, pre-exposures were then conducted in the laboratory, where specific metals and PAHs in solution were used instead of field-collected contaminated sediments. Typical acclimation responses (an increased resistance at low pre-exposure levels, declining to a reduced resistance at higher pre-exposure levels) were observed for zinc and for naphthalene. No acclimation was observed for phenanthrene, for the combination of zinc and naphthalene, or for a mixture of three metals and three PAHs. These results indicate that acclimation may become less likely as the number of contaminants increases. Potential mechanisms for such a pattern are that one contaminant may inhibit the detoxification of another contaminant, that the energetic requirements (for repair/detoxification) for exposure to one contaminant may compete with those for another contaminant, or that increases in resistance for some contaminants may be offset by decreases in resistance for other contaminants.
Keywords: acclimation; grass shrimp; complex mixtures; metals; PAHs
Rubidium and Cesium Kinetics and Tissue Distributions in Channel Catfish (Ictalurus punctatus)
by Eric L. Peters; Irvin R. Schultz; Michael C. Newman (pp. 287-300).
We used a two-compartment, clearance volume-based model to examine rubidium and cesium pharmacokinetics in channel catfish (Ictalurus punctatus) after intravascular administration. We compared the apparent volumes of distribution in the central and peripheral compartments and the intercompartmental and whole-body clearances of both metals at 20.0 °C and 27.5 °C. Biological half-times of Rb were 15 to 16 d at both temperatures, but Cs biological half-times averaged 101 d and 85 d at 20.0 °C and 27.5 °C, respectively (5 to 7 times longer than those of Rb in the same individual). Both the intercompartmental and total body clearances of Rb were also 6 to 7 times greater than those of Cs. The apparent volumes of distribution for Rb in the central compartments were twice those of Cs and remained constant with temperature. The apparent volumes of distribution of both elements in peripheral compartments were large compared with their corresponding central compartments, and decreased by a similar extent with increased temperature. Cesium tissue to blood ratios were greatest for white muscle, with more than 85% of the Cs present in this tissue. Partitioning of Cs in peripheral tissues apparently decreased with increased temperature conditions. Our results indicate that application of pharmacokinetic modeling techniques can enhance studies of radionuclide kinetics by helping to identify rate-limiting processes within individuals that may control uptake and elimination.
Keywords: rubidium; cesium; kinetics; clearance-volume model; fish
On the Utility of Heteroplasmy in Genotoxicity Studies: An Example from Chornobyl
by Robert J. Baker; J. Andrew Dewoody; Amanda J. Wright; Ronald K. Chesser (pp. 301-309).
We examine the utility of mtDNA heteroplasmy in assessing genetic damage due to environmental insult. Site heteroplasmy was quantified in a 400 bp portion of the cytochrome b gene in voles from a contaminated area near Chornobyl, Ukraine and from a relative control site by examining pregnant females and their embryos. A four hundred base pair segment was sequenced from approximately ten clones from each mother and embryo. Taq and/or cloning mutations were evaluated to estimate technical error. Although the rates of substitutions in clonal variants for experimentals, biological controls and technical controls were 1 in 1,840 bp, 1 in 2,280 bp, and 1 in 3,333 bp, respectively, we could not reject the null hypothesis that the variants were the result of a single, combined, mutation rate. However, multiple substitutions and transversions were restricted to clones from the Chornobyl samples. Bootstrap analyses indicate that these aspects of variation were significantly different from the controls. Examination of the mitochondrial genome by cloning individual molecules for site heteroplasmy to estimate effects of pollution on mutation rate in free-living organisms appears to warrant additional study.
Keywords: heteroplasmy; Chornobyl; ionizing radiation; mitochondrial DNA; Clethrionomys glareolus
Studies on the Decontamination of Air by Plants
by J. J. Cornejo; F. G. Muñoz; C. Y. Ma; A. J. Stewart (pp. 311-320).
We conducted laboratory tests with six species of plants to determine their ability to remove benzene, trichloroethylene (TCE) and toluene from air. The objective of this proof-of-principal study was to evaluate the idea that phytoremediation techniques might be used to lower the concentrations of indoor air pollutants, such as volatile or semi-volatile organic compounds. Plants were exposed to the pollutants singly or in mixtures in an airtight chamber, and concentrations of the pollutants in the chamber were monitored through time to assess plant effects on the pollutants. In several experiments, we measured air temperature and CO2, as well. Lower surfaces of leaves of several of the species we tested were also examined by scanning electron microscopy to determine stomate abundance and size, and to provide information about leaf-surface elemental composition (by X-ray emission spectroscopy). Several of the species demonstrated an extensive ability to remove benzene from air. Gas chromatography methods allowed a reasonably direct, continuous monitoring of the kinetics and overall efficiency of the pollutant-removal process. We found that pollutant removal efficiency varied in response to plant species and the pollutant. Of the pollutants tested, benzene was most efficiently removed from air by Pelargonium domesticum, Ficus elastica and Chlorophytum comosum. Kalanchoe blossfeldiana, a common ornamental plant, appeared to take up benzene selectively over toluene, and TCE was removed efficiently from the air by C. comosum. Pentane, sometimes used as an internal standard in GC/MS, was removed from air by at least four of the species. For C. comosum, TCE appeared to lower the removal rates of benzene and pentane. Low-vacuum scanning electron microscopy provided information on stomate size and density and permitted rapid initial elemental analysis of the plant-leaf surface by X-ray emission spectroscopy. Our results indicate that simple tests for pollutant uptake, morphological and chemical features of plants, and plant detoxification enzyme activity might be used in multivariate fashion to identify plant species capable of removing volatile or semi-volatile pollutants from air.
Keywords: phytoremediation; VOCs; volatile organic pollutants; air cleansing by plants