bluuebunny/crossref_metadata_2025 huggingface dataset:
The fungicide propiconazole interferes with embryonic development of the crustacean Daphnia magna
Authors: Kast-Hutcheson Karen , Rider Cynthia V , LeBlanc Gerald A
Published: March 2010

Propiconazole is a fungicide used in a variety of agricultural applications. Preliminary studies had suggested that embryos of the crustacean Daphnia magna are particularly susceptible to the toxicity of this chemical. The goals of the present study were to define endpoints of daphnid embryonic development that could be routinely used to assess the embryo toxicity of chemicals and to characterize definitively the embryo toxicity of propiconazole to daphnids. Daphnid embryonic development was characterized into six readily distinguishable stages based on the degree of tissue differentiation. Embryonic development could be monitored either in the brood chamber of the maternal organism or using embryos removed from the brood chamber and incubated ex vivo. Standard toxicity assessment revealed that propiconazole elicited no significant adverse effects on daphnid survival or fecundity during a 21-d exposure to concentrations as high as 0.25 mg/L. Exposure to 0.25 mg/L propiconazole, however, caused a significant incidence of developmental abnormalities and embryonic death. Abnormalities were consistent with developmental arrest at later stages of embryonic maturation. Propiconazole elicited a steep concentration-response curve with respect to embryo toxicity, with a 10% and a 90% incidence of embryo toxicity measured at 0.50 and 0.82 mg/L, respectively. Direct exposure of embryos to propiconazole resulted in toxicity, though the incidence and characteristics of developmental abnormalities were not consistent with that observed during chronic exposures. However, maternal exposure to propiconazole followed by transfer of early embryos to propiconazole-free media resulted in embryo toxicity consistent with that observed during chronic exposure. These results indicate that propiconazole interferes with the later stages of daphnid embryonic development, and that this toxicity is manifested largely via maternal exposure to the fungicide.
Occurrence and potential adverse effects of semivolatile organic compounds in streambed sediment, United States, 1992–1995
Authors: Lopes Thomas J , Furlong Edward T
Published: March 2010

The occurrence and potential adverse effects of select semivolatile organic compounds (SVOCs) in streambed sediment were assessed at 536 sites in 20 major river basins across the United States from 1992 to 1995. Fifty-six SVOCs were detected at one or more sites, and one or more SVOCs were detected at 71% of sites. The northeastern and Great Lakes regions and large metropolitan areas have the highest SVOC concentrations. Polycyclic aromatic hydrocarbons (PAHs) were detected most frequently and at the highest concentrations. Concentrations of PAHs and phthalates were about 10 times higher at sites influenced by urban activities than at sites in other land-use areas. Semivolatile organic compounds were significantly (α = 0.05) correlated with land use and population density, and PAHs also correlated with physical/chemical properties. On the basis of sediment-quality guidelines, adverse effects are probable at 7.5% and possible at 16.2% of the sites. Most of the potential for adverse effects is due to PAHs. The median percentage of urban land use was 8% at sites with possible adverse effects and 16% at sites with probable adverse effects. Urbanization profoundly affects sediment quality, even though it comprised a small percentage of most drainage basins.
Polychaete indicator species as a source of natural halogenated organic compounds in marine sediments
Authors: Fielman Kevin T , Woodin Sarah A , Lincoln David E
Published: March 2010

Studies of pollutant impact on the marine environment assume that organic contaminants are anthropogenic in origin. However, many common polychaete worms and sediments contain readily detectable concentrations of brominated natural products that are often analogues of chlorinated anthropogenic contaminants. Both polychaetes and sediments are used extensively in environmental toxicology and monitoring, and the extent to which natural halometabolites may confound these studies is unknown. To characterize further the relationship among infauna, indicator species, and sedimentary halogenated organics, we examined sediments and infauna from a pristine habitat and animals maintained under laboratory culture for haloorganics using gas chro-matography/mass spectrometry. Natural haloorganics are a consistent feature of pristine marine soft-bottom habitats, and their spatial and temporal variation correlates with the abundance of infauna that produce these metabolites. Abundant organohalogens are also present in the widespread polychaete indicator species Capitella sp. I and Streblospio benedicti but absent from the marine invertebrate toxicology model Neanthes arenaceodentata. Studies from the individual to the community level within the fields of ecology, toxicology, and environmental chemistry could be readily confounded by failing to consider these novel animal and habitat characteristics.
Reproduction success of American kestrels exposed to dietary polychlorinated biphenyls
Authors: Fernie Kimberly J. , Smits Judit E , Bortolotti Gary R , Bird David M
Published: March 2010

While reproduction of wild birds is adversely affected by multiple environmental contaminants, we determined that polychlorinated biphenyls (PCBs) alone alter reproduction. Captive American kestrels (Falco sparverius), fed PCB-spiked (Aroclor® 1248:1254:1260) food (7 mg/kg body weight/d) prior to and during the first breeding season only (100 d) laid eggs with environmentally relevant levels of total PCBs (34.0 μg/g whole egg wet wt vs 0 μg/g for controls). Reproduction changed during, not after, PCB exposure in this two-year study. The PCB-exposed pairs laid smaller clutches later in the season and laid more totally infertile clutches. Hatching success was reduced in PCB-exposed pairs, and 50% of PCB nestlings died within 3 d of hatching. Nearly 60% of PCB-exposed pairs with hatchlings failed to produce fledglings. Higher levels of total PCB residues and congeners were associated with later clutch initiation and fewer fertile eggs, hatchlings, and fledglings. We suggest that nonpersistent PCB congeners have a greater influence on reproduction than do persistent congeners.
Comparing representations of the environmental spatial scale of organic chemicals
Authors: Beyer Andreas , Scheringer Martin , Schulze Carsten , Matthies Michael
Published: March 2010

Long-range transport potential is one of the criteria proposed to identify chemicals as persistent organic pollutants. Here, different approaches to determine the spatial scale of an environmental area or region that can be impacted by an emitted chemical are investigated. A ranking of chemicals according to the spatial range R on a limited scale, as suggested by Scheringer, is equivalent to the characteristic travel distance L according to Bennett et al. on a linear, open scale. However, the methods are different with respect to the weighting of differences between the chemicals and according to their comparability with persistence. The characteristic travel distance L and the overall persistence are both plotted on open log-linear scales, whereas the spatial range R is represented on a limited scale. Various approaches of how to account for the mode of entry of chemicals are compared, and it is argued that relative measures are more appropriate to describe the long-range transport potential of chemicals than absolute numbers.
Metabolism of the polycyclic aromatic hydrocarbon fluoranthene by the polychaete Capitella capitata species I
Authors: Forbes Valery E , Andreassen Mai S H , Christensen Lene
Published: March 2010

Previous studies have shown that infaunal deposit feeders may enhance the loss of organic contaminants from sediments. However, the extent to which this occurs as a result of sediment microbial stimulation, porewater flushing, or biotransformation by infauna remains unclear. The purpose of this study was to determine whether the infaunal polychaete Capitella sp. I is able to metabolize the polycyclic aromatic hydrocarbon (PAH) fluoranthene and to provide an initial characterization of the metabolites produced. Our results showed that Capitella sp. I is able to metabolize fluoranthene to more hydrophilic products and that, after 24 h in clean sediment, fluoranthene could no longer be detected in worm tissues whereas a number of fluoranthene-derived metabolites were present. None of the metabolites released or retained by worms resembled known bacterial metabolites, suggesting that Capitella, and not bacteria associated with its gut or body surface, were responsible for the biotransformation of fluoranthene in our system. On the basis of ultraviolet maxima, peak shape, relative height, and order of elution, tentative identities of two metabolites (i.e., 3- and 8-hydroxyfluoranthene) are proposed. The results demonstrate that, in addition to their effects on sediment geochemical properties, infaunal polychaetes such as Capitella can enhance the degradation of sediment-associated contaminants by directly metabolizing them.
A large-scale categorization of sites in San Francisco Bay, USA, based on the sediment quality triad, toxicity identification evaluations, and gradient studies
Authors: Hunt John W , Anderson Brian S , Phillips Bryn M , Tjeerdema Ron S , Taberski Karen M , Wilson Craig J , Puckett H Max , Stephenson Mark , Fairey Russell , Oakden James
Published: March 2010

Sediment quality was assessed in San Francisco Bay, California, USA, using a two-tiered approach in which 111 sites were initially screened for sediment toxicity. Sites exhibiting toxicity were then resampled and analyzed for chemical contamination, recurrent toxicity, and, in some cases, benthic community impacts. Resulting data were compared with newly derived threshold values for each of the metrics in a triad-based weight-of-evidence evaluation. Sediment toxicity test results were compared with tolerance limits derived from reference site data, benthic community data were compared with threshold values for a relative benthic index based on the presence and abundance of pollution-tolerant and -sensitive taxa, and concentrations of chemicals and chemical mixtures were compared with sediment quality guideline-based thresholds. A total of 57 sites exceeded threshold values for at least one metric, and each site was categorized based on triad inferences. Nine sites were found to exhibit recurrent sediment toxicity associated with elevated contaminant concentrations, conditions that met program criteria for regulatory attention. Benthic community impacts were also observed at three of these sites, providing triad evidence of pollution-induced degradation. Multi- and univariate correlations indicated that chemical mixtures, heavy metals, chlordanes, and other organic compounds were associated with measured biological impacts in the Bay. Toxicity identification evaluations indicated that metals were responsible for pore-water toxicity to sea urchin larvae at two sites. Gradient studies indicated that the toxicity tests and benthic community metrics employed in the study predictably tracked concentrations of chemical mixtures in Bay sediments.
Factors affecting reproduction and the importance of adult size on reproductive output of the midgeChironomus tentans
Authors: Sibley Paul K , Ankley Gerald T , Benoit Duane A
Published: March 2010

We conducted two spearate tests to evaluate the influence of several factors that could affect estimation and interpretation of effects on reproductive output of Chironomus tentans in sediment toxicity tests. Specifically, the influence of adult size, mating frequency in males (♂), and age of both males and females (♀) at first mating on mating success (number of successful matings), fecundity (number of eggs/female), percentage hatch, and number of offspring (number of hatched eggs) was assessed. In the first experiment, the influence of adult size on reproductive output was determined by growing midges fed a low (0.29 mg/individual/ d) and a high (0.42 mg/individual/d) amount of food to produce small (S) and large (L) adults, respectively. The adults were then mated in one of four scenarios: S ♂ × S ♀, S♂ × L ♀, L ♂ × S♀, and L ♂ × L ♀. An increase in male weight at a constant female weight had no significant effect on fecundity, whereas an increase in female weight yielded 49.5 and 60.7% increases in fecundity when mated with low- and high-fed males, respectively. Similarly, mean number of offspring (fecundity × percent hatch) increased by 19.8 and 48.3% when male weight was increased and female weight was held constant and by 141.9 and 180.4% when female weight was increased and male weight was held constant. In the second experiment, conducted at a single feeding rate, fecundity increased significantly with an increase in female weight but not male weight. The number of offspring was not significantly influenced by adult weight. The age of males or females at first mating, the frequency with which males were mated (up to seven consecutive days), and the proportion of males successfully mating had no effect on fecundity or number of offspring; however, large increases in variability about mean estimates were observed in some endpoints for older males. These results suggest that adult female size is the most important factor affecting reproductive output in C. tentans, and that enhanced performance of the life-cycle test with respect to all reproductive endpoints might be achieved if males are not mated for more than five consecutive days.
An assessment of the toxicity of phthalate esters to freshwater benthos. 1. Aqueous exposures
Authors: Call Daniel J , Markee Thomas P , Geiger Dianne L , Brooke Larry T , VandeVenter Fred A , Cox Dean A , Genisot Kristen I , Robillard Kenneth A , Gorsuch Joseph W , Parkerton Thomas F , Reiley Mary C , Ankley Gerald T , Mount David R
Published: March 2010

Tests were performed with the freshwater invertebrates Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus to determine the acute toxicity of six phthalate esters, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DHP), and di-2-ethylhexyl phthalate (DEHP). It was possible to derive 10-d LC50 (lethal concentration for 50% of the population) values only for the four lower molecular weight esters (DMP, DEP, DBP, and BBP), for which toxicity increased with increasing octanol–water partition coefficient (Kow) and decreasing water solubility. The LC50 values for DMP, DEP, DBP, and BBP were 28.1, 4.21, 0.63, and 0.46 mg/L for H. azteca; 68.2, 31.0, 2.64, and > 1.76 mg/L for C. tentans; and 246, 102, 2.48, and 1.23 mg/L for L. variegatus, respectively. No significant survival reductions were observed when the three species were exposed to either DHP or DEHP at concentrations approximating their water solubilities.
Vitellogenin gene transcription: A relative quantitative exposure indicator of environmental estrogens
Authors: Lattier David L , Gordon Denise A , Burks Douglas J , Toth Gregory P
Published: March 2010

We report the development of a quantifiable exposure indicator for measuring the presence of environmental estrogens in aquatic systems. Synthetic oligonucleotides, designed specifically for the vitellogenin gene (Vg) transcription product, were used in a reverse transcription–polymerase chain reaction (RT-PCR) protocol. This extremely sensitive and rapid method was able to detect vitellogenin gene transcription in male common carp (Cyprinus carpio) injected with 17β-estradiol. Sequence analysis of the induced mRNA product confirmed a vitellogenin gene transcript with homology to rainbow trout and fathead minnow vitellogenin cDNA sequences. Relative levels of vitellogenin gene induction among individuals were quantified by incorporating 18S ribosomal RNA universal primers and Competimers® in a PCR multiplex reaction with primers for vitellogenin. This method is more sensitive than current protocols, such as mortality, visible signs of stress, or other techniques that look for unscheduled gene expression, because it measures the appearance of primary transcripts at the nanogram level. In addition, this procedure does not sacrifice accuracy or reliability, even though the exposure to estrogen is within 1 d. This research will support the construction of regional stressor profiles, thereby providing a method for comparative environmental exposure assessment. It may also provide an in vivo screening method for potential endocrine-disrupting compounds.
Laboratory and field studies on the effect of molinate, clomazone, and thiobencarb on nontarget aquatic invertebrates
Authors: Burdett Ayesha S , Stevens Mark M , Macmillan David L
Published: March 2010

The midge Chironomus tepperi was used in laboratory experiments to assess the relative toxicity of formulated molinate, clomazone, and thiobencarb, three herbicides used in Australian rice crops. Static bioassays were initiated with first-instar larvae at herbicide concentrations between 0.0625 and 2 times the anticipated field concentrations (AFCs) expected from the registered application rates. Adult emergence success, development time, and wing length were used as indices of the effect of each herbicide. Clomazone had no effect on any parameters at concentrations up to 0.288 mg/L (p > 0.05). Molinate significantly increased development time at concentrations equivalent to the AFC (3.6 mg/L) and above (p < 0.05). Thiobencarb reduced emergence success of adult C. tepperi at 0.0625 times the AFC (0.1875 mg/L) as well as decreasing male adult size and increasing development time for males and females at 0.125 times the AFC (p < 0.05). Nontarget effects of the herbicides on aquatic invertebrate communities were assessed in shallow experimental ponds using commercial application rates. One week after treatment, only thiobencarb had a significant effect, suppressing populations of chironomids, calanoids, and cyclopoids (p < 0.05). Four weeks later, all populations had recovered, equaling or exceeding control densities.
Resistance to copper toxicity in populations of the earthworms Lumbricus rubellus and Dendrodrilus rubidus from contaminated mine wastes
Authors: Langdon Caroline J , Piearce Trevor G , Meharg Andrew A , Semple Kirk T
Published: March 2010

Two arsenic and heavy metal—contaminated mine spoil sites, at Carrock Fell, Cumbria, United Kingdom, and Devon Great Consols Mine, Devon, United Kingdom, have been found to support populations of the earthworms Lumbricus rubellus Hoffmeister and Dendrodrilus rubidus (Savigny). Lumbricus rubellus and D. rubidus collected from the Devon site and an uncontaminated site were kept for 28 d in uncontaminated soil and in soil containing 750 mg/kg CuCl2, the state of the specimens being recorded using a semiquantitative assessment of earthworm health (condition index). The condition index remained high for all specimens except those of L. rubellus and D. rubidus from uncontaminated sites, which displayed 100% mortality. Bioavailability of Cu in the soils from one uncontaminated and two contaminated sites and in the uncoutaminated soil treated with CuCl2 was determined using sequential extraction. Soils from Devon Great Consols had the greatest availability of Cu, Carrock Fell the lowest. Total tissue Cu for L. rubellus and D. rubidus from the contaminated sites did not change significantly for each species during the experiment. Total tissue concentrations of Cu for L. rubellus and D. rubidus from uncontaminated sites increased significantly during the first 7 d, after which mortality was 90%, making it impossible to continue the analysis.
Joint action of chemicals in algal toxicity tests: Influence of response level and dose—response regression model
Authors: Christensen Erik R. , Chen Dongxu , Nyholm Niels , Kusk K. Ole
Published: March 2010

The joint toxicity of nonylamine and decylamine and of atrazine and decylamine was evaluated in assays with the green alga Selenastrum capricornutum based on an isobologram method. In this method, curves of constant response, isoboles, are plotted versus concentrations of two toxicants. The response parameter was growth rate based on biomass, and several response levels were used. Dose—response curves were developed for dilution series using fixed ratios between concentrations in toxic units of the compounds. Probit and Weibull dose—response curves were then determined by nonlinear regression. A model for isoboles for partially similar action was used when applicable. The no-effect concentration (NEC or EC0) was estimated based on a newly proposed model containing median effective concentration (EC50) and EC0 as explicit variables. Results show that nonylamine and decylamine are nearly concentration additive at EC50 and EC10 (similarity parameter Λ = 0.70—0.76) and to a lesser extent at ECO. By contrast, the mixtures of atrazine and decylamine show antagonism in that atrazine acts as an antidote to decylamine. The shapes of these isoboles are independent of response level. The EC50 values (mg/L) for chemicals acting singly were 0.090 (nonylamine), 0.039 to 0.044 (decylamine), and 0.225 (atrazine). In order to determine NEC effectively, the level of inhibition must be fairly low, with observed growth rates between 0.6 and 1.0 times the average growth rate of the controls.
Potential nitrification rate as a tool for screening toxicity in metal-contaminated soils
Authors: Smolders Erik , Brans Kris , Coppens Filip , Merckx Roel
Published: March 2010

A potential nitrification rate test (PNR) was used to identify metal toxicity in field-contaminated soils. The test was applied to metal salt–spiked soils, to 27 uncontaminated soils, and to 15 soils that are contaminated by former metal smelting activities. Four agricultural soils (pH 4.5–6.6) were spiked with various rates of CdCl2 (0–200 mg Cd/kg dry wt) or ZnCl2 (0–3,000 mg Cd/kg dry wt) and were equilibrated more than nine months prior to testing. The soil Zn EC50s of the PNR were between 150 and 350 mg Zn/kg dry weight. No continuous decrease of the nitrification with increasing Cd application was observed. The nitrification rate was reduced by between 50 and 80% at the highest Cd application in all soils. The PNRs of 27 uncontaminated soils varied widely (0–21 mg N/kg/d), but most of this variability is explained by soil pH (R2 = 0.77). The PNRs of the 15 contaminated soils were 0 to 44% of the values predicted for an uncontaminated soil at corresponding pH. Significant toxicity in field-contaminated soils was identified if the PNR was outside the 95% prediction interval of the PNR for an uncontaminated soil at corresponding pH and was found in seven soils. These soils contain 160 to 34,000 mg Zn/kg dry weight and 5 to 104 mg Cd/kg dry weight and had a pH >5.7. No toxicity could be detected below pH 5.6, where even a zero PNR value is within the 95% prediction interval of uncontaminated soils. It is concluded that the nitrification is sensitive to metal stress but that its power as a soil bioassay is low because of the high variability of the endpoint between uncontaminated soils. The ecological significance of the assay is discussed.
Combined effects of predatory fish and sublethal pesticide contamination on the behavior and mortality of mayfly nymphs
Authors: Schulz Ralf , Dabrowski James M
Published: March 2010

We evaluated the potential interaction of pesticide effect and predatory fish on behavior and mortality of a stream mayfly. Experiments in laboratory stream microcosms compared the activity, drift, and mortality of Baetis mayfly nymphs in the absence of fish with that in the presence of Cape galaxias (Galaxias zebratus), both species inhabiting the same stream environments in the Western Cape of South Africa. These two predator treatments were combined with exposure either to no pesticide or to 0.2 μg/L of the organophosphate insecticide azinphos-methyl (AZP) or 0.2 μg/L of the pyrethroid insecticide fenvalerate (FV). Such pesticide levels are known from transient spraydrift- or runoff-related pesticide input into running waters. Each of the six combinations was replicated six times as 30-min trials during the day and effects were analyzed using 2 × 2 factorial analysis of variance (ANOVA). A single exposure to either fish or pesticide significantly increased the absolute activity of mayflies, measured as number of animals visible on top of stones, and the absolute mayfly drift in the fish treatment and in the FV treatment but did not increase the mortality above 0.8%. The combination of predator presence and sublethal pesticide exposure resulted in a significant increase in the mortality rate, to about 9% in the AZP × fish and 25% in the FV × fish treatment, although the activity and drift rates were not increased compared with the single-stressor treatments. Two-by-two factorial ANOVA and the comparison of expected and measured responses indicated that the mortality resulted from a synergistic interaction of the two stressors. The observed mortality was without exception caused by predation of the fish on drifting mayflies. The relative drift rate in the FV × fish treatment was decreased, again due to a synergistic interaction, which suggests an active drift avoidance reaction of the mayflies exposed to the combined pesticide × fish treatment, in contrast with those exposed just to FV. We conclude that the drift response of mayflies to transient sublethal pesticide exposure results in a synergistically increased adverse effect in the presence of predatory fish.
Synthesis and characterization of metal sulfide clusters for toxicological studies
Authors: Bowles Karl C. , Bell Russell A. , Ernste Michael J. , Kramer James R. , Manolopoulos Helen , Ogden Nancy
Published: March 2010

Zinc sulfide clusters were synthesized and characterized at low micromolar concentrations to assess the effect of metal-sulfide ligands on metal toxicity to aquatic organisms in oxic environments. Recommended preparation times are greater than 2 h initial reaction of equimolar sodium sulfide and zinc nitrate, followed by oxic aeration for 3 d. Ionic strength, pH, and anoxic stabilization time were found to be relatively unimportant in controlling the final yield. Adsorptive losses of zinc sulfide (ZnS) clusters to surfaces, however, were significant for a variety of vessel materials and membrane filters. Ionic strength and pH were found to be important factors controlling the extent of adsorptive losses with minimal loss for pHs greater than 9 and for soft waters. The Ag(I), Cu(II), and Hg(II) as metal sulfides completely suppress the analysis of sulfide, whereas Pb(II), Mn(II), and Co(II) partially suppress the analysis of sulfide by the methylene blue technique. Ultraviolet and fluorescence spectra are shown for synthesized ZnS clusters.
The chemical toxic benzo[a]pyrene perturbs the physical organization of phosphatidylcholine membranes
Authors: Jiménez María , Aranda Francisco J. , Teruel J. Antonio , Ortiz Antonio
Published: March 2010

The interaction of the chemical carcinogen benzo[a]pyrene (BaP) with phosphatidylcholine membranes has been investigated by using various physical techniques. Differential scanning calorimetry showed that BaP, at concentrations as low as 2 mol% in mixtures with dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine, abolished the pretransition and broadened and shifted to lower temperatures the main gel-to-liquid crystalline phase transition. The effect was stronger as the lipid acyl chain length decreased. Infrared spectroscopy indicated that inclusion of BaP had a strong influence on the carbonyl (C=O) stretching band. Fitting of this band resulted in the presence of three components in the case of samples containing BaP, centered at 1,742, 1,727, and 1,704 cm−1 (only two components, at 1,742 and 1,727 cm−1, were observed for pure DMPC). The component at 1,704 cm−1 corresponded to a disolvate and strongly supported the notion that inclusion of BaP increases hydration of the bilayer C=O. Small-angle x-ray diffraction showed that incorporation of 10 mol% BaP into DMPC increased bilayer thickness from 66.7 to 71 A in the gel state and from 58.9 to 60.9 A in the fluid phase. It is proposed that, when BaP is incorporated into a phospholipid bilayer, it locates in the most apolar region of the phospholipid palisade, resulting in expansion and swelling of the membrane. These two effects will facilitate water penetration into the polar region of the membrane, as observed by the increased hydration of the C=O groups, and thus perturb both membrane integrity and functionality.
A methodology for inferring the causes of observed impairments in aquatic ecosystems
Authors: Suter Glenn W. , Norton Susan B. , Cormier Susan M.
Published: March 2010

Biological surveys have become a common technique for determining whether aquatic communities have been injured. However, their results are not useful for identifying management options until the causes of apparent injuries have been identified. Techniques for determining causation have been largely informal and ad hoc. This paper presents a logical system for causal inference. It begins by analyzing the available information to generate causal evidence; available information may include spatial or temporal associations of potential cause and effect, field or laboratory experimental results, and diagnostic evidence from the affected organisms. It then uses a series of three alternative methods to infer the cause: Elimination of causes, diagnostic protocols, and analysis of the strength of evidence. If the cause cannot be identified with sufficient confidence, the reality of the effects is examined, and if the effects are determined to be real, more information is obtained to reiterate the process.
Inhibition of digestive enzyme activities by copper in the guts of various marine benthic invertebrates
Authors: Chen Zhen , Mayer Lawrence M. , Weston Donald P. , Bock Michael J. , Jumars Peter A.
Published: March 2010

Digestive systems of deposit and suspension feeders can be exposed to high concentrations of copper (Cu) by ingestion of contaminated sediments. We assessed a potential impact of this Cu exposure on digestive enzyme activities in a wide range of benthic organisms by monitoring enzyme activities in their gut fluids during in vitro titrations with dissolved Cu, which mimics Cu solubilization from sediments. Increasing Cu inhibited digestive protease activities at threshold values, which varied widely among organisms, from 8 μM for an echinoderm to 0.4 M for an echiuran. More Cu was required to inhibit proteases in guts containing higher amino acid concentrations because strong Cu-binding sites on amino acids prevent Cu interaction with the enzymatically active sites. Threshold Cu concentrations were similar for proteases, esterases, lipases, and α- and β-glucosidases, suggesting the same inhibition mechanism. Copper was less effective at inhibiting enzymes at lower pH, suggesting that protons can compete with Cu ion for binding to enzymatically active sites or that enzyme conformation is less vulnerable to Cu inhibition at lower pH. These results lead to the counterintuitive conclusion that deposit feeders with low enzyme activity, low amino acid concentration, and high pH values are most vulnerable to harm from sedimentary Cu by this mechanism, although they solubilize less sedimentary Cu than their counterparts with high enzyme activity, high amino acid concentrations, and low gut pH. In general, digestive systems of echinoderms may therefore be more susceptible to Cu contamination than those of polychaetes, with various other phyla showing intermediate susceptibilities. If threshold Cu values are converted to solid-phase sedimentary Cu concentrations, the thresholds are at least consistent with Cu loadings that have been observed to lead to biological impacts in the field.
Evaluation of the effect of reactive sulfide on the acute toxicity of silver (I) toDaphnia magna. Part 2: Toxicity results
Authors: Bianchini Adalto , Bowles Karl C. , Brauner Colin J. , Gorsuch Joseph W. , Kramer James R. , Wood Chris M.
Published: March 2010

The protective effect of reactive sulfide against AgNO3 toxicity to Daphnia magna neonates was studied. Acute (48-h) toxicity tests were performed in the absence (<5 nM) and presence of low (∼25 nM) and high (∼250 nM) concentrations of zinc sulfide clusters under oxic conditions. In both the presence and the absence of sulfide, lower mean lethal concentration (LC50) values were observed when measured as opposed to nominal silver concentrations were used in calculations. This reflected the fact that measured total silver concentrations were lower than nominal concentrations due to losses of silver from solution observed during the experiment. High concentration (∼250 nM) of sulfide completely protected against toxicity up to the highest silver concentration tested (2 μg/L [19 nM]) with measured silver data. In the presence of environmentally realistic levels of sulfide (∼25 nM) in receiving waters, acute silver toxicity was reduced by about 5.5-fold. However, when filtered (0.45 μm) silver concentrations alone were considered, toxicity (48-h LC50) was similar in the absence (0.22 μg/L) and presence (0.28 μg/L) of sulfide. The difference between measured total and filtered silver was attributed to chemisorption of the metal sulfide onto the membrane filter and provides evidence that the toxic fraction of silver is that which is unbound to sulfide. Accumulation of silver was greater in daphnids exposed to silver in the presence of sulfide than in its absence, even though a toxic effect was not observed under these conditions. In this case, silver appears to be incorporated by daphnids rather than merely adsorbed on the surface. Our results point out the need to incorporate sulfide into the acute biotic ligand model and to assess its potentially large role in preventing chronic toxicity.
Accumulation and elimination of lanthanum by duckweed (Lemna minorL.) As influenced by organism growth and lanthanum sorption to glass
Authors: Weltje Lennart , Brouwer Anke H. , Verburg Tona G. , Wolterbeek Hubert Th. , de Goeij Jeroen J. M.
Published: March 2010

Lanthanide emissions to the environment increase as a result of the growing industrial applications of these elements. However, robust data to evaluate the environmental fate of lanthanides are scarce. This article describes the accumulation and elimination of lanthanum (La) by common duckweed (Lemna minor L.). Speciation modeling was performed to assure that solubility products were not exceeded. It also showed that La was predominantly associated with ethylenediaminetetraacetic acid (EDTA). Lanthanum concentrations in plants and medium and the amounts sorbed to glass vessels were quantified by using the radioisotope 140La. The amount of La adsorbed on the glass reached values of 25% of the total La present. A model was formulated to describe La uptake in exponentially growing duckweed in the presence of an adsorptive surface. Growth-induced dilution appeared more efficient in lowering plant La concentrations than actual elimination. An elimination study revealed two compartments, of which the smallest eliminated 50 times faster than the bigger compartment, which eliminated mainly by growth dilution. The average bioconcentration factor was 2,000 L/kg fresh weight and 30,000 L/kg dry weight, comparable with those of other higher plants. At the applied concentration of 10 nM, no effects were observed on duckweed growth. However, the high bioconcentration factor warrants monitoring of lanthanide emissions.
Development of a Monte Carlo sampling shell for the pesticide root zone model and its application by the Federal Insecticide, Fungicide, and Rodenticide Act Environmental modeling validation Task Force
Authors: Havens Patrick L. , Carbone John P. , Warren-Hicks William , Fouch Michael A.
Published: March 2010

A user interface to the U.S. Environmental Protection Agency pesticide root zone model (PRZM) was constructed to allow Monte Carlo sampling of input parameter distributions. The interface was constructed employing the Visual Basic for Applications development environment, along with the functionality of the Crystal Ball Professional forecasting and risk analysis package. The tool has been utilized by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Environmental Model Validation Task Force to perform detailed statistical analyses of model input parameter uncertainty and the propagation of this uncertainty on the model outputs as well as comparisons of modeled and field-measured data.
Accumulation of heavy metals in water spinach (Ipomoea aquatica) cultivated in the Bangkok region, Thailand
Authors: Göthberg Agneta , Greger Maria , Bengtsson Bengt-Erik
Published: March 2010

The aquatic plant water spinach (Ipomoea aquatica), either wild or cultivated, is found throughout Southeast Asia and is a widely consumed vegetable in the region. Many of the waters where I. aquatica grows serve as recipients for domestic and other types of wastewater. Because these waters contain not only nutrients, but often also a wide variety of pollutants such as heavy metals from various human activities, many people risk intoxication. To estimate the accumulation of lead (Pb), cadmium (Cd), total mercury (total Hg), and methylmercury in I. aquatica and the potential hazard to human health via consumption, nine sites for cultivation of I. aquatica in the greater Bangkok region of Thailand were sampled. At seven of the sites, I. aquatica was cultivated for the local food market. The concentrations of methylmercury, total Hg, Pb, and Cd in I. aquatica were 0.8 to 221, 12 to 2,590, 40 to 530, and ≤10 to 123 μg/kg dry weight, respectively. At all sites at least one element showed relatively high concentrations and no reference site could be established. From threshold values for highest tolerable intake of these metals by humans and information about consumption of I. aquatica among local people, Pb and Cd concentrations in I. aquatica do not seem to be a direct threat to human health. However, concentrations of Hg were very high at some sites, and were higher in leaves (highest mean value: 1,440 μg/kg dry wt) than in stems (highest mean value: 422 μg/kg dry wt). This might be a threat, especially to children and fetuses, because Hg in I. aquatica was composed of methylmercury, partly or totally, at most sites to 11% or less and at one site from 50 to 100%. At the latter site, I. aquatica was not cultivated for the food market. Because other food sources, such as fish, may have high concentrations of methylmercury, these results indicate a need for monitoring of Hg, especially methylmercury, in different foodstuffs in the region.
Acute and chronic toxicity of nickel to marine organisms: Implications for water quality criteria
Authors: Hunt John W. , Anderson Brian S. , Phillips Bryn M. , Tjeerdema Ron S. , Puckett H. Max , Stephenson Mark , Tucker David W. , Watson Daniel
Published: March 2010

Acute and chronic toxicity tests were conducted to determine the effects of nickel on three U.S. west coast marine species: a fish (the topsmelt, Atherinops affinis), a mollusk (the red abalone, Haliotis rufescens), and a crustacean (the mysid, Mysidopsis intii). The 96-h median lethal concentration (LC50) for topsmelt was 26,560 mg/L, and the chronic value for the most sensitive endpoint in a 40-d exposure was 4,270 mg/L. The median effective concentration (EC50) for 48-h abalone larval development was 145.5 μg/L, and the chronic value for juvenile growth in a 22-d exposure through larval metamorphosis was 26.43 mg/L. The mysid 96-h LC50 was 148.6 μg/L, and the chronic value for the most sensitive endpoint in a 28-d, whole life-cycle exposure was 22.09 μg/L. The abalone and mysid acute values were lower than other values available in the literature. Acute-tochronic ratios for nickel toxicity to the three species were 6.220, 5.505, and 6.727, respectively, which were similar to the only other available saltwater value of 5.478 (for Americamysis [Mysidopsis] bahia) and significantly lower than the existing values of 35.58 and 29.86 for freshwater organisms. Incorporation of data from the present study into calculations for water quality criteria would lower the criterion maximum concentration and raise the criterion continuous concentration for nickel.
Application of sewage sludge to arable land–soil concentrations of polybrominated diphenyl ethers and polychorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls, and their accumulation in earthworms
Authors: Matscheko Nadja , Tysklind Mats , de Wit Cynthia , Bergek Sture , Andersson Rolf , Sellström Ulla
Published: March 2010

Soils from five agricultural sites, three research sites, and two privately owned farms were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybronimated diphenylethers (PBDEs). In soils that had not been treated with sludge (reference soils), the international toxic equivalents (I-TEQs) were 0.6 to 1.5 pg/g dry matter (DM) for the PCDD/Fs, which are low compared to generally reported background soil levels in Europe. The concentrations of sum of six penta- and hexa-PCBs were 450 to 1,400 pg/g DM. The PBDEs 47 and 99 dominated among the tri- to hepta-PBDEs analyzed (8–80 pg/g DM). The impact of adding 1 to 3 tonnes of sludge (DM) per hectare per year on the concentrations was studied at the three research sites by calculating ratios of the compounds in sludge-treated soil to reference soil (S/R ratio). The concentrations of I-TEQs did not increase in the sludge-treated soil, whereas the S/R ratios for PBDEs were greater than one. Also, although the PCB contents were higher in the sludge-treated soils, the background sources were more important for the concentrations of PCBs than of PBDEs. The largest increase in the S/R ratios was found at a private farm where large amounts of sludge had been used in the past. Accumulation of the compounds in earthworms from the sites also was investigated. The biota-soil accumulation factors (BSAFs) of the tested compounds declined in the following order: ortho-PCBs ∼ PBDEs > non-ortho-PCBs > 2,3,7,8-substituted PCDD/Fs. The average BSAF for ortho-PCBs was five (organic matter/lipids), and the lowest BSAFs (0.1–0.8) found were for octachlorodibenzo-p-dioxin. To our knowledge, accumulation of PBDEs in earthworms has not been published previously.
Toxicity of aqueous and sediment-associated fluoride to freshwater organisms
Authors: Metcalfe-Smith Janice L. , Holtze Keith E. , Sirota Gary R. , Reid James J. , de Solla Shane R.
Published: March 2010

Inorganic fluorides were declared toxic under the Canadian Environmental Protection Act in 1993 based on their potential to cause long-term harmful effects in aquatic and terrestrial ecosystems, but information on the toxicity of sediment-associated fluoride to freshwater benthic organisms was considered incomplete. The purpose of this study was to determine the toxicity of aqueous and sediment-associated fluoride to several species of freshwater organisms and to determine if toxic effects could be expected under environmentally realistic exposures. Toxicity of fluoride (as NaF) in short-term (48–96-h) lethality tests was greatest for the amphipod Hyalella azteca (median lethal concentration [LC50] = 14.6 mg F−/L), followed by the mayfly Hexagenia limbata (32.3), the midge Chironomus tentans (124.1), the fathead minnow Pimephales promelas (262.4), and the cladoceran Daphnia magna (282.8). Relative toxicity in long-term (10–28-d) growth and survival tests in spiked sediment was similar. Hyalella azteca was the most sensitive species for growth (25% inhibitory concentration [IC25] = 290.2 μg F−/g), followed by C. tentans (661.4), H. limbata (1,221.3), and P. promelas (>5,600); H. azteca was also the most sensitive species for survival (LC50 = 1,114.6 μg F−/g), followed by H. limbata (1,652.2) and P. promelas and C. tentans (>5,600 for both). Concentrations of fluoride measured in sediments near some industrial point sources exceed some of these toxicity thresholds. Fluoride is highly mobile in aquatic systems and could potentially reach toxic levels in the water column during dredging to remove fluoride-contaminated sediment.
Cosolvent effects of phenanthrene sorption-desorption on a freshwater sediment
Authors: Bouchard Dermont C.
Published: March 2010

This study evaluated the effects of the water-miscible cosolvent methanol on the sorption-desorption of phenanthrene by the natural organic matter (NOM) of a freshwater sediment. A biphasic pattern was observed in the relationship between the log of the carbon-normalized sorption distribution coefficient (Koc) and the volumetric fraction of water-miscible cosolvent (fc), in this case methanol, that was accounted for with phenanthrene solubility data. Results also indicated that methanol elicited additional effects on phenanthrene sorption beyond the solution phase effects. The level of fc was observed to have a significant effect on sorption-desorption hysteresis, with hysteresis being greater for treatments where phenanthrene and sediment were equilibrated with methanol-phenanthrene solutions but desorbed with aqueous solutions. These results are discussed in light of the deformable pore network of the rubbery/glassy NOM polymer construct.
Induction of an estrogen-responsive reporter gene in rainbow trout hepatoma cells (RTH 149) at 11 or 18°C
Authors: Hornung MichaeL W. , Ankley Gerald T. , Schmieder Patricia K.
Published: March 2010

The potential for temperature to influence estrogen-mediated responses in poikilothermicanimals suggested that temperature may be an important variable to consider when using an estrogen-responsive reporter gene in a rainbow trout cell line to test chemicals for estrogenic activity. Rainbow trout hepatoma cells (RTH 149) incubated at 11 or 18°C were cotransfected with an estrogen-responsive luciferase reporter plasmid and a plasmid containing a constitutively expressed rainbow trout estrogen receptor. The RTH-149 cells were then exposed to estradiol, with samples collected at 24-h intervals. The 72-h effective concentration for 50% maximal response (EC50) for estrogen-responsive luciferase activity at 11°C was 3.8 × 10−9 M and 7.4 × 10−10 M at 18°C. The efficacy of estradiol was lower at 11°C. The maximal response to estradiol in cells at 11°C was generally two- to threefold greater than controls (mean = 2.6-fold), whereas the maximal response at 18°C was three- to fourfold greater than controls (mean = 3.2-fold). Ethinylestradiol, a strong estrogen receptor agonist, was similar to estradiol in potency (relative potency = 0.8) and efficacy at the two temperatures. The EC50 of the weak estrogen receptor agonist 4-tert-pentylphenol was 7.6 × 10−7 M at 11°C and 6.9 × 10−7 M at 18°C; its potency relative to 17β-estradiol was not significantly different at the two temperatures, 0.00036 and 0.00054 at 11°C and 18°C, respectively. The estrogen-responsive reporter gene activity produced by 10−8 M estradiol was completely inhibited by the two estrogen hormone receptor antagonists, ZM 189,154 and ICI 182,780, at 10−6 M concentration of either antagonist. Although there may be slight differences in responses between the two temperatures tested here, this assay can be used to effectively determine the relative estrogenic activity of chemicals within the physiological temperature range of rainbow trout.