bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of food, aquatic humus, and alkalinity on methylmercury uptake by Daphnia magna
Authors: Monson Bruce A , Brezonik Patrick L
Published: March 2010

Six-day-old Daphnia magna were exposed to low concentrations (≤4 ng Hg/L) of methylmercury (MeHg) in synthetic freshwater and synthetic food. Uptake kinetics were determined in 24- to 72-h experiments, measuring both the loss of Hg from water and accumulation in D. magna. Dose-uptake response was linear for MeHg concentrations up to 4.0 ng/L; an initial concentration of 2.0 ng/L was used when other factors were varied. Concentrations of total Hg and MeHg in water and D. magna were measured in treatments with varied hardness and alkalinity, aquatic humus (AH), and food spiked with MeHg versus water spiked with MeHg. Uptake rate coefficients were derived from two versions of a first-order, two-compartment model. The first version assumed constant MeHg concentration; the second accounted for changing MeHg concentration in water over time. Both models accounted for a nonzero starting concentration of MeHg in plankton. Fitted rate coefficients were higher for the second model than the first: the uptake coefficient (ku) was nine times higher (81.6 L/g/h vs 9.00 L/g/h); the depuration coefficient (kd) was twice as high (0.174/h vs 0.084/h). Assuming a constant MeHg concentration for a one-time spike thus underestimates the rate coefficient. The source of MeHg was compared by exposing D. magna for 48 h to MeHg at 2 ng/L in food or water. Daphnia magna accumulated significantly more inorganic Hg (i.e., Hg2+) from spiked food than from spiked water, but accumulation of MeHg was the same from both sources. A similar response was found when D. magna were exposed to a lake water extract of AH at concentrations of C at 3 and 10 mg/L. At the higher AH concentration, total Hg in daphnids was higher, but MeHg was lower, suggesting that AH was a source of inorganic Hg but reduced the bioavailability of MeHg. Exposure of D. magna to MeHg at 2 ng/L in hard or soft water adjusted to pH 6.7 showed no significant difference in MeHg uptake, supporting an argument that hardness and alkalinity per se do not affect MeHg uptake by daphnids.
Ecological risk assessment in a large river-reservoir: 8. Experimental study of the effects of polychlorinated biphenyls on reproductive success in mink
Authors: Halbrook Richard S , Aulerich Richard J , Bursian Steven J , Lewis Lorin
Published: March 2010

As a component of an ecological risk assessment of Poplar Creek (located on the Oak Ridge Reservation [ORR]) and the Clinch River (a large river–reservoir system), fish from Poplar Creek, the Clinch River, and Atlantic Ocean were fed to ranch mink to evaluate reproductive success. Five diets, each composed of 75% fish and 25% normal ranch mink chow, were prepared. Two diets served as reference diets and contained 75% Atlantic Ocean fish or 75% Clinch River fish collected above the ORR. The fish portion of the remaining three diets contained 25, 50, and 75% fish collected from Poplar Creek and 50, 25, and 0% ocean fish, respectively. Five mink groups (eight females and two males each) were each fed one of the prepared diets for 196 days. Polychlorinated biphenyl concentrations were determined in diets and various mink tissues, ethoxyresorufin-O-deethylase (EROD) activity was determined in liver tissue, and reproductive success was evaluated. Concentrations of PCB were greatest in the diet composed of 75% Poplar Creek fish and in tissues from mink fed this diet and their offspring. There was a trend toward decreased adult female and kit weights and reduced mean litter size in mink fed diets containing 75% Poplar Creek fish; however, at 6 weeks of age, kit survival was similar among diet groups. Liver EROD activity significantly increased in adult female mink fed 50 and 75% Poplar Creek fish diets. Estimated dietary concentrations of PCBs were similar to or slightly lower than concentrations associated with adverse effects in experimentally dosed mink. Mercury (Hg) concentrations previously reported in these same mink were below that associated with adverse effects, and there was no indication of additive or synergistic effects from exposure to PCBs plus Hg. It is unlikely that population-level reproductive effects would be observed in mink consuming fish from Poplar Creek on the ORR.
The SED-TOX index: Toxicity-directed management tool to assess and rank sediments based on their hazard—concept and application
Authors: Bombardier Manon , Bermingham Norman
Published: March 2010

This article introduces the Sediment Toxicity (SED-TOX) Index for the assessment and ranking of toxic hazards in sediment. Major features include expression of toxicity responses on a single scale of measurement (dry weight–based toxic units), consideration of multiple routes of exposure (pore water, organic extract, wet sediment, and whole sediment), application of differential treatments to toxicity data depending on the level of response (acute lethal or chronic sublethal), and use of weighting factors to discriminate sediment exposure phases and effect endpoints on the basis of sensitivity. A battery of seven bioassays with four test species (Vibrio fischeri, Escherichia coli, Lytechinus pictus, and Amphiporeia virginiana) was conducted on 49 marine sediment samples collected from six sites at Anse-à-Beaufils and Cap-aux-Meules, which are in the Gulf of St. Lawrence. The SED-TOX scores were calculated for each sampling station and compared with sediment contaminant concentrations. Results indicate that physicochemical characterization is not sufficient to assess contaminated-sediment hazard for organisms; furthermore, using several exposure phases and test species belonging to various trophic levels increases the possibility of correctly identifying toxic sediments. The results of this study indicate that the SED-TOX approach is valuable as a toxicity assessment and ranking tool for sediments. It could easily be combined with other measures of ecosystem disturbance to discriminate between polluted and unpolluted sites.
Transgenerational toxicity of tributyltin and its combined effects with polychlorinated biphenyls on reproductive processes in Japanese medaka (Oryzias latipes)
Authors: Nirmala Kukuh , Oshima Yuji , Lee Richard , Imada Nobuyoshi , Honjo Tsuneo , Kobayashi Kunio
Published: March 2010

Japanese medaka (Oryzias latipes) were fed daily on one of four diets containing tributyltin (TBT), PCBs, a combination of TBT and PCBs, or a control diet (with nothing added). Contaminant doses were 1 μg/g body weight per day for 3 weeks. The combination of TBT and PCB showed additive effects on the spawning of medaka, resulting in a significant reduction in spawning frequency, and on the number of spawned eggs and fertilization success when compared with effects in fish fed either a TBT or PCB diet. The adverse effects on the reproductive success of medaka may have been due to endocrine disruption caused by accumulation of both TBT and PCB. The TBT treatment significantly reduced embryo and larval survival from eggs (279 ng TBT/g), which were spawned from females containing 2,390 ng TBT/g body weight from the TBT diet. This result indicates transgenerational toxicity. The PCB diet caused fewer adverse effects than the TBT diet with respect to spawning frequency, egg survival, hatching, and swim-up success of larvae. When both TBT and PCB were in the diet, there were additive effects on spawning success as noted above but antagonistic effects on embryological success of eggs and swim-up success of larvae.
Octylphenol induces vitellogenin production and cell death in fish hepatocytes
Authors: Toomey Barbara Holland , Monteverdi George H , Di Giulio Richard T
Published: March 2010

The effects of octylphenol (OP) on vitellogenin production and cell death in hepatocytes from brown bullhead catfish (Ameriurus nebulosus) were studied. Production of vitellogenin was induced in hepatocytes exposed to 10 to 50 μM OP, whereas a higher concentration of OP (100 μM) induced apoptotic cell death. By 3 h after the addition of 100 μM OP, dying cells showed chromatin condensation and DNA fragmentation as determined by fluorescence microscopy and gel electrophoresis. Later stages of cell death (nuclear membrane breakdown and cell fragmentation into apoptotic bodies) were identified in cells exposed to OP for at least 6 h. Hepatocytes exposed to 100 μM OP also produced less vitellogenin than cells exposed to 50 μM OP. An estrogen receptor antagonist, tamoxifen, greatly decreased vitellogenin production in OP-exposed hepatocytes from male fish but did not decrease cell death in these cells. Thus, although the ability of OP to induce vitellogenin production is likely mediated through interactions with the estrogen receptor, the induction of apoptotic cell death by OP does not appear to be dependent on its estrogenic activity but may be a more general toxic effect.
Efficiencies of polychlorinated biphenyl assimilation from water and algal food by the blue mussel (Mytilus edulis)
Authors: Björk Mikael , Gilek Michael
Published: March 2010

A novel method was used to estimate assimilation efficiencies (AEs) of dissolved and food associated PCBs (IUPAC 31, 49, and 153) by the Baltic Sea blue mussel (Mytilus edulis). Mussels were exposed to radiolabeled PCBs in a series of short-term toxicokinetic experiments at different algal food concentrations, both at apparent steady-state (ASS) and non-steady-state (NSS) conditions in respect to PCB partitioning between water and algae. The PCB AEs were calculated using a physiologically based bioaccumulation model where experimentally determined uptake and exposure rates at ASS and NSS conditions were combined into linear equation systems, which were solved for PCB AE from water and food. A positive relationship between PCB uptake and algae clearance by the mussels was observed for all three PCBs. The PCB AEs from both water and food increased with congener hydrophobicity (octanol/water partition coefficient [Kow]), but AEs decreased with increases in water pumping and filtration rate of the mussels, respectively. The average contribution of food-associated PCB to the total uptake also increased with Kow from approximately 30% for PCB 31 and PCB 49 to 50% for PCB 153, mainly as a consequence of increased sorption to the algal food.
Hydrophobic organic contaminants in surficial sediments of baltimore harbor: Inventories and sources
Authors: Ashley Jeffrey T.F , Baker Joel E
Published: March 2010

The heavily urbanized and industrialized Baltimore Harbor/Patapsco River/Back River system is one of the most highly contaminated regions of the Chesapeake Bay. In June 1996, surficial sediments were collected at 80 sites throughout the subestuarine system, including historically undersampled creeks and embayments. The samples were analyzed for a suite of hydrophobic organic contaminants (HOCs) consisting of 32 polycyclic aromatic hydrocarbons (PAHs) and 113 polychlorinated biphenyl (PCB) congeners. Total PAH and total PCB concentrations ranged from 90 to 46,200 and 8 to 2,150 ng/g dry weight, respectively. There was enormous spatial variability in the concentrations of HOCs, which was not well correlated to grain size or organic carbon content, suggesting nonequilibrium partitioning and/or proximity to sources as important factors explaining the observed spatial variability. High concentrations of both classes of HOCs were localized around major urban stormwater runoff discharges. Elevated PAH concentrations were also centered around the Sparrow's Point Industrial Complex, most likely a result of the pyrolysis of coal during the production of steel. All but 1 of the 80 sites exceeded the effects range-low (ERL) for total PCBs and, of those sites, 40% exceeded the effects range-medium (ERM), suggesting toxicity to marine benthic organisms would frequently occur. Polychlorinated biphenyl homolog patterns most closely resembled Aroclor 1260 at sites around areas of high concentration of industrial outflows and urban runoff. Conversely, those sites further from suspected municipal and industrial discharges had patterns resembling that of Aroclor 1254. We suggest the heavier chlorinated pattern is indicative of near-source emissions of PCBs. The lighter chlorinated PCB patterns observed are similar to those found in mainstem Chesapeake Bay sediments and may reflect a more weathered pattern or one derived, in part, from air-water exchange of gaseous PCBs. Using principal component analysis, differences in PAH signatures were discerned. Higher molecular weight PAHs were enriched in signatures from sediments close to suspected sources (i.e., urban stormwater runoff and steel production complexes) compared to those patterns observed at sites further from outfalls or runoff. Due to varying solubilities and affinities for organic matter of the individual PAHs, partitioning of the heavier weight PAHs may enrich settling particles with high molecular weight PAHs. Lower molecular weight PAHs, having lower affinity for particles, may travel from the source to a greater extent.
Modification of metal partitioning by supplementing acid volatile sulfide in freshwater sediments
Authors: Leonard Edward N , Mount David R , Ankley Gerald T
Published: March 2010

Acid volatile sulfide (AVS) is a component of sediments that complexes some cationic metals and thereby influences the toxicity of these metals to benthic organisms. Experimental manipulation of AVS in metal-contaminated sediments may provide a means to neutralize toxicity due to metals and thereby help assess the cause of sediment toxicity. This study evaluated the effect of spiking FeS, Na2S, and Na2S/FeSO4 combined on the concentration of AVS, simultaneously extracted metals (SEM), and pore-water metals in uncontaminated and metal-enriched sediments. Experiments with solid FeS showed comparatively low effectiveness in increasing AVS. Spiking with either Na2S or Na2 S/FeSO4 combined increased AVS and/or reduced SEM metal in Cd-, Zn-, and Ni-spiked sediments and in a Cu-contaminated sediment collected from the field. Spiking with Na2S/FeSO4 caused marked reductions in dissolved metal concentrations in the pore waters of these sediments; spiking with Na2S alone caused an apparent elevation in pore-water (Cu) metal that we believe is an artifact of metal sulfide formation in the filtered pore water. When the Na2S/FeSO4 treatment was evaluated under conditions simulating those in sediment toxicity tests, alterations of AVS/SEM were nearly quantitative, except for Ni-spiked sediment, which showed lower efficiency than the Cd, Zn, or Cu sediments. It appears that AVS spiking holds promise for the experimental manipulation of metal toxicity in sediments.
Rainbow trout cell bioassay-derived relative potencies for halogenated aromatic hydrocarbons: Comparison and sensitivity analysis
Authors: Villeneuve Daniel L , Richter Catherine A , Blankenship Alan L , Giesy John P
Published: March 2010

Rainbow trout hepatoma cells, stably transfected with a luciferase reporter gene under control of dioxin-responsive elements (RLT 2.0 cells) were used to derive relative potencies (RPs) for a variety of halogenated aromatic hydrocarbons (HAHs) that are structurally similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This in vitro bioassay utilizes 96-well microplates, which provide high sample throughput and assay efficiency without affecting sensitivity. The RLT 2.0-derived potencies for dioxin and furan congeners, relative to 2,3,7,8-TCDD, ranged from 0.917 for 1,2,3,4,7,8-hexachlorodibenzofuran to 0.208 for 1,2,3,7,8-pentachlorodibenzofuran. All mono- and di-ortho polychlorinated biphenyls (PCBs) tested had RPs that were orders of magnitude less than TCDD, but point estimates could not be determined. The RLT 2.0-derived RPs were found to be comparable to both other rainbow trout-specific RPs and RPs based on mammalian bioassays. Sensitivity analysis suggested that the range of uncertainty associated with TCDD equivalent (TEQ) estimates based on RLT 2.0-derived RPs is approximately 10-fold. Within this degree of uncertainty and the context of this study, the RLT 2.0 bioassay showed no definitive biases or inaccuracies relative to similar mammalian- or fish-specific in vitro bioassays. Thus, the RLT 2.0 bioassay appears to be a useful tool for evaluating dioxinlike potency of HAHs to fish.
Dietary uptake efficiency of 2,2ǐ,4,4ǐ,5,5ǐ-hexachlorobiphenyl in yellow perch and rainbow trout: Role of dietary and body lipids
Authors: Dabrowska Henryka , Fisher Susan W , Dabrowski Konrad , Staubus Alfred E
Published: March 2010

Dietary uptake efficiency (α) and elimination rate constants (kd) of 2,2ǐ,4,4ǐ,5,5ǐ-hexachlorobiphenyl (HCBP) were determined in two fish species, yellow perch and rainbow trout, to investigate the influence of dietary and body lipid levels on bioaccumulation. Groups of juvenile fish with significant differences in percent body lipid were fed with a low-fat(LF) or high-fat (HF) diet spiked with 5 or 50 ppb of 14C-HCBP for 32 d. Thereafter, fish were fed an uncontaminated LF or HF diet to allow for elimination of HCBP. Feeding and growth rates were quantified. There were eight fish lipid/dietary lipid/HCBP concentration exposure combinations for each species. Four fish from each exposure were collected at the beginning of the study and at 10-17-d intervals during exposure and elimination periods for lipid and 14C-HCBP analysis. The a values ranged from 74 to 95% in yellow perch and from 79 to 99% in rainbow trout. The greatest a values, of 95 to 99%, were found in fish given diets with 5 ppb HCBP. Uptake of HCBP was influenced by both dietary and body lipids and depended on the current status of both lipid pools. The elimination rate constants were in the range of 0.000 to 0.004 d−1 in yellow perch and 0.003 to 0.010 d−1 in rainbow trout. No significant differences in elimination rate constants between HF and LF fish groups were found. In fish on a constant dietary lipid regime, the kd values tended to be less in HF than in LF fish. However, in fish groups offered diets with a change in lipid regime, the kd tended to be greater. Lipid × time interactions in the HF and LF fish groups undergoing a change in lipid regime indicated that the kd values, like the a values, were influenced by both lipid pools. Changes in elimination rates due to dietary/body lipid status impacted BAFs more strongly than changes in uptake efficiencies. The BAFs were in the range of 1.11 to 2.49 in yellow perch and 1.5 to 4.3 in rainbow trout.
Sublethal responses of largemouth bass to parasites and organochlorines
Authors: Macrury Nicole K , Johnson Brett M
Published: March 2010

Largemouth bass (Micropterus salmoides) at the Rocky Mountain Arsenal National Wildlife Refuge (RMA) experience chronic organochlorine exposures and parasitism by nematodes (Contracaecum spiculigerum) and digenean flukes (Posthodiplostomum minimum centrarchi). We investigated the influences of nematode intensity, fluke intensity, and whole-body organochlorine concentrations on growth of juvenile RMA bass. Lifetime growth, or age-specific lengths, of bass in three RMA lakes were within the range observed for bass in five reference lakes. However, interlake comparisons can be confounded by differing environmental conditions. Therefore, we conducted mesocosm and laboratory studies to compare growth, consumption, and feeding behavior between RMA bass and bass that had little contaminant or parasite exposure. Mean growth rates of RMA bass were 45% lower compared with hatchery bass in experimental ponds. However, regression analysis revealed that parasite and organochlorine burdens were not negatively associated with either short-term growth or age-specific lengths of RMA bass. Hatchery bass growth was likely higher due to their experience with culture pond conditions. In feeding trials, RMA bass exhibited similar food conversion efficiency and consumption rates and significantly elevated feeding activity compared with hatchery bass. This research demonstrates that current parasite and organochlorine loads had benign influences on growth of juvenile RMA bass.
Costs of chronic waterborne zinc exposure and the consequences of zinc acclimation on the gill/zinc interactions of rainbow trout in hard and soft water
Authors: Alsop Derek H , McGeer James C , McDonald D Gordon , Wood Chris M
Published: March 2010

Juvenile rainbow trout were exposed to zinc in both moderately hard water (hardness = 120 mg CaCO3/L, pH = 8.0, Zn = 150 μg/L or 450 μg/L) and soft water (hardness = 20 mg CaCO3/L, pH = 7.2, Zn = 50 μg/L or 120 μg/L) for 30 d. Only the 450 μg/L zinc—exposed fish experienced significant mortality (24% in the first 2 d). Zinc exposure caused no effect on growth rate, but growth affected tissue zinc levels. Whole body zinc levels were elevated, but gills and liver showed no consistent increases relative to controls over the 30 d. Therefore, tissue zinc residues were not a good indicator of chronic zinc exposure. After the 30-d exposure, physiological function tests were performed. Zinc was 5.4 times more toxic in soft water (control 96 h LC50s in hard and soft water were 869 μg/L and 162 μg/L, respectively). All zinc-exposed trout had acclimated to the metal, as seen by an increase in the LC50 of 2.2 to 3.9 times over that seen in control fish. Physiological costs related to acclimation appeared to be few. Zinc exposure had no effect on whole body Ca2+ or Na+ levels, on resting or routine metabolic rates, or on fixed velocity sprint performance. However, critical swimming speed (UCrit) was significantly reduced in zinc-exposed fish, an effect that persisted in zinc-free water. Using radioisotopic techniques to distinguish new zinc incorporation, the gills were found to possess two zinc pools: a fast turnover pool (T1/2 = 3–4 h) and a slow turnover pool (T1/2 = days to months). The fast pool was much larger in soft water than in hard water, but at most it accounted for <3.5% of the zinc content of the gills. The size of the slow pool was unknown, but its loading rate was faster in soft water. Chronic zinc exposure was found to increase the size of the fast pool and to increase the loading rate of the slow pool.
Modeling the toxicity of amide herbicides using the electrotopological state
Authors: Gough Jonathan D , Hall Lowell H
Published: March 2010

The toxicity (rat, acute, oral LD50) of a set of 50 amides that serve as herbicides is modeled using the electrotopological state indices (E-state) with multiple linear regression. A five-variable model produces sound statistics: r2 = 0.75, s = 0.23. The cross-validation statistics indicate a model useful for prediction: r2press = 0.65, spress = 0.27. Further, a set of nine compounds was set aside for testing the model. The mean absolute error for the test set is MAE = 0.27, supporting the claim that the model may be used for prediction. Structure interpretation is given for each variable so that the model may be used to assist in design of molecules with lower toxicity.
Differentiation of polychlorinated dibenzo-p-dioxin and dibenzofuran sources in coastal British Columbia, Canada
Authors: Bright Doug A , Cretney Walter J , Macdonald Robie W , Ikonomou Michael G , Grundy Stephen L
Published: March 2010

Multivariate pattern analysis techniques, principal components analysis, and polytopic vector analysis (PVA) were used to apportion sources of dioxins and furans to Howe Sound and the lower Strait of Georgia marine ecosystem, British Columbia, Canada, based on deposition in recent sediments. In sediment cores collected in 1990, differences between congeners in the depth of maximum concentration suggested the influence over time of several different sources. Those with a predominance of hexachlorinated dibenzodioxins and 2,3,7,8-tetrachlorodibenzofuran comprised one of the major contributions to the sediment core samples and surficial samples collected from Howe Sound, consistent with past inputs of pulpmill effluent. For most sediment samples, however, over 50% of the composition was attributable to a separate source with octachlorodibenzo-p-dioxin (OCDD) as the dominant congener, followed by heptachlorodibenzo-p-dioxins with small amounts of heptachlorodibenzofuran and octachlorodibenzofuran (OCDF). This source signature is consistent with the composition of dioxins/furans in formulations of pentachlorophenol-based wood preservatives, which were used extensively in British Columbia, Canada prior to the mid-1980s. This major input signature to the greater Strait of Georgia cannot be unequivocally ascribed to PCP use and disposal, however, since several other dioxin/furan sources also exhibit a highly similar composition, one dominated by OCDD. For example, source signatures similar to PCP formulations include those from diesel emissions, coal combustion, municipal solid waste, or other incineration stack emissions (fly ash, in particular), chimney soot from oil central heating, black-liquor recovery furnace flue gas, and scrap wire and car incineration. Further research is required to discriminate among the OCDD-containing sources and, hence, provide for improved future source management.
Effects of organic enrichment and burrowing activity of the polychaeteNeries diversicoloron the fate of tetrachlorobiphenyl in marine sediments
Authors: Gunnarsson Jonas S , Hollertz Karin , Rosenberg Rutger
Published: March 2010

The effects of organic enrichment and burrowing activity of the infaunal polychaete Nereis (Hediste) diversicolor on the distribution of 14C-3,3′,4,4′-tetrachlorobiphenyl (TCB) were studied in an experimental benthic system. Organic enrichment of the sediment was provided by a mixture of the diatom Skeletonema costatum and the sea lettuce Ulva lactuca. Organic matter and TCB were both initially added to a surface sediment layer of the microcosms. A factorial design with organic enrichment (control vs enriched) and bioturbation (presence or absence of N. diversicolor) as fixed factors and concentration of TCB in sediment, water, and biota as dependent variables allowed us to test the four combinations. Release of TCB from the sediment to the water column was measured in the outflowing water of the aquaria. After 28 d of exposure, TCB concentrations were measured in animals, feces, sediment cores, burrows, sediment surface, and in sulfur bacteria mats. Both bioturbation and organic enrichment enhanced the release of TCB from the sediment to the water column. The greatest effect was caused by the combination of the two factors, which increased release rates by 280% compared with controls. No general downward transport and vertical redistribution of TCB in the sediment were observed. However, TCB concentrations were significantly higher in the burrow linings of the worms than in the bulk sediment. Increased TCB accumulation by the animals was observed following organic enrichment, which was considered to be the result of selective feeding on TOC-rich contaminated food particles. The organic enrichment also stimulated the production of sulfur bacteria mats, which were found to accumulate high TCB concentrations. Our results contradict those of several other studies that have reported a reduced bioavailability of organic contaminants with increasing sedimentary organic carbon content. Our study suggests that the quality of the organic matter should be considered in the evaluation of exposure in benthic organisms.
Efficient shedding of accumulated metals during metamorphosis in metal-adapted populations of the midge Chironomus riparius
Authors: Groenendijk Dick , Kraak Michiel H S , Admiraal Wim
Published: March 2010

Metal accumulation and loss during metamorphosis were investigated in Chironomus riparius populations in a metal contaminated lowland river. Cadmium and zinc levels were measured in imagoes and larvae at reference and metal-exposed sites. It was hypothesized that the relationship between metal concentrations in biota and environmental compartments would be influenced by the presence of metal-adapted chironomids. In contrast to the large interpopulation differences in larval body burdens of cadmium, body burdens in imagoes vanished to background levels for all midge populations. This indicated that any cadmium accumulated in larval stages was lost during metamorphosis. This nearly 100% efficiency in shedding of cadmium is most likely caused by an increased metal handling capacity present in exposed midges. In agreement with the cadmium measurements, larval body burdens of zinc showed also highly significant interpopulation differences. In contrast with the cadmium values, however, body burdens of zinc in imagoes showed highly significant interpopulation differences and differences were even recorded between the two exposed sites, indicating interpopulation differences in shedding capacity for zinc. It is concluded that the highly efficient shedding of accumulated metals reflected the metal adaptation recorded in earlier studies of metal-exposed C. riparius populations from the River Dommel. Based on the differences in metal accumulation and the differences found in shedding of metals between the two exposed midge populations, it was concluded that population differentiation due to metal stress is a gradual process rather than an all-or-nothing situation.
Bioassays for the detection of chemicals that can form bioactivation-dependent reactive free radicals
Authors: Sanderson J. Thomas , Commandeur Jan N. M , van Wezel Annemarie , Vermeulen Nico P E
Published: March 2010

In vitro bioassays were developed for the detection of chemicals that can be bioactivated to reactive free radical species in microsomal fractions. Two methods were deployed, a down-scaled spectrophotometric method for the detection of chemicals that can cause lipid peroxidation using the measurement of thiobarbituric acid-reactive substances (TBARS) and a fluorometric method for the detection of chemicals that can undergo redox cycling to generate superoxide radicals based on the detection of hydrogen peroxide. The response of these systems to prototypical and environmentally relevant chemicals, including tetrachloromethane and paraquat, was examined. The detection limit of the lipid peroxidation bioassay, based on the formation of TBARS, was about 1 μM for tetrachloromethane; that of the bioassay for redox cylers, based on the production of hydrogen peroxide, was about 2 μM for paraquat and about 100-fold lower for the potent redox cycler 2,3,5,6-tetramethylbenzoquinone (TMBQ). Several binary mixtures of chemicals were tested for potential nonadditive effects in both in vitro systems. Some antagonistic effects among halogenated methanes were observed in the lipid peroxidation assay. In the hydrogen peroxide production assay, greater than additive effects were seen between small concentrations of paraquat and TMBQ. A number of surface water concentrates from several locations in The Netherlands, with various levels of chemical contamination, exhibited a weak response in the hydrogen peroxide production assay. Acetone was found to interfere with the response of the bioassay to redox cyclers and, therefore, the water concentrates (originally in acetone) were transferred to ethanol prior to testing. A good correlation was observed between the response of the water concentrates in the hydrogen peroxide production assay and their acute toxicity in Daphnia magna. No correlation was observed between this bioassay response and toxicity in the MicrotoxTM assay using Photobacterium phosphoreum.
Empirical assessment of an ambient toxicity risk ranking model's ability to differentiate clean and contaminated sites
Authors: Hartwell S Ian
Published: March 2010

Ambient toxicity results were used to investigate statistical implications of sampling design options for an existing toxicological risk ranking model. A battery of water column and sediment toxicity bioassays measuring lethal and sublethal endpoints was employed with fish, invertebrates, vascular plants, and bacteria. Bioassays were conducted monthly from July through September 1995 with water from three stations in the South River estuary, Maryland, USA, and a reference station. Sediment bioassays were conducted in August with five discrete samples taken from each station. Water column assays indicated low-level contamination at the upstream stations. Sediment bioassays yielded greater toxic responses than water column assays. The toxicological risk ranking model identified a strong toxicity gradient from upstream to downstream in the South River. Toxicological risk scores for the downstream station in the South River were comparable to the reference station. Statistical analyses demonstrated that the risk ranking model does not require field sample replication for tributary-wide assessment. Characterization of an entire estuary does require broad coverage to assess the system as a whole, however. Threshold levels of toxic impact can be quantified with the model.
Minimum data required for deriving soil quality criteria from invertebrate ecotoxicity experiments
Authors: Vega Milagrosa M , Urzelai Arantzazu , Angulo Eduardo
Published: March 2010

The suitability of a new method to determine the minimum number of data required to stabilize a calculation is studied. Five different calculations have been computed, changing the order of data randomly. The statistical reliability of numerical values has also been calculated depending on the successive increase in the number of data included. In our study, when few data are considered, a great variation in the estimations is observed depending on the individual data included. The calculation is stabilized for a sample size between 5 and 15 data points, and the sample can therefore be considered representative enough. Results are in agreement with those presented by other authors.
Evaluating sediment chemistry and toxicity data using logistic regression modeling
Authors: Field L Jay , MacDonald Donald D , Norton Susan B , Severn Corinne G , Ingersoll Chris G
Published: March 2010

This paper describes the use of logistic-regression modeling for evaluating matching sediment chemistry and toxicity data. Contaminant-specific logistic models were used to estimate the percentage of samples expected to be toxic at a given concentration. These models enable users to select the probability of effects of concern corresponding to their specific assessment or management objective or to estimate the probability of observing specific biological effects at any contaminant concentration. The models were developed using a large database (n = 2,524) of matching saltwater sediment chemistry and toxicity data for field-collected samples compiled from a number of different sources and geographic areas. The models for seven chemicals selected as examples showed a wide range in goodness of fit, reflecting high variability in toxicity at low concentrations and limited data on toxicity at higher concentrations for some chemicals. The models for individual test endpoints (e.g., amphipod mortality) provided a better fit to the data than the models based on all endpoints combined. A comparison of the relative sensitivity of two amphipod species to specific contaminants illustrated an important application of the logistic model approach.
Patterns of groundwater concentration and fate of lindane in an irrigated semiarid area in Argentina
Authors: Ares Jorge O , Miglierina Ana María , Sánchez Ramón
Published: March 2010

The pattern of lindane breakthrough to groundwater and its mobilization thereafter were observed in a semiarid irrigated agricultural basin in southern Argentina. The pesticide half-life in the unsaturated vadose zone and the realized Koc were estimated through parameter optimization techniques on the basis of an ad hoc developed fugacity model, and two existing models of the transport of pesticides in soils (RITZ, PRZM2). Although the estimated half-life values are in agreement with values reported in the literature for other areas, the Koc was lower than usually reported, indicating that the adsorption of the pesticide is controlled by the kinetics of soil water infiltration. The lindane concentration and groundwater conductivity fields over an area of about 2,700 km2 were compared and similarities between the transport of the pesticide and soluble soil salts were inferred. These showed that lindane is transported dissolved in the upper aquifer and can accumulate at exfiltration areas at 10 to 30 km from the sites of its application. The relevance of considering the kinetic constraints imposed by the hydraulic conductivity of the soil profile and the partition with the soil organic matter are highlighted in relation to the prediction of pesticide environmental fate.
Coupling mercury methylation rates to sulfate reduction rates in marine sediments
Authors: King Jeffrey K. , Saunders F Michael , Lee Richard F , Jahnke Richard A
Published: March 2010

Anoxic slurry incubations were performed to examine the relationship between mercury methylation rates (MMR) and sulfate reduction rates (SRR) in salt marsh sediments from the southeastern United States. The MMR and SRR were similarly affected by temperature, addition of low-weight molecular organics, and microbial inhibitors. The MMR was at a maximum in the 12 h after inorganic mercury addition. Initial rates of Hg methylation are correlated with SRR. A significantly slower MMR observed after the initial 12 h following inorganic mercury addition suggested that sorption or precipitation reduced the availability of mercury for methylation. The MMR results for various concentrations of inorganic mercury indicate that saturation kinetics occur. Using this kinetic framework, a model for MMR based on SRR and inorganic Hg concentration was developed. This model was then used to predict the MMR reported in temperature and substrate/inhibitor experiments. The model provided a reasonable estimate of MMR observed in the initial 12 h of the slurry incubations. However, the sequestering of inorganic mercury into less reactive pools by sorption to surfaces or incorporation into other phases alters the amount of bioavailable Hg and hence MMR. Future models that assess the bioavailibility of Hg in the sediments must be developed to extend these observations to field sites.
Influence of ortho-substitution homolog group on polychlorobiphenyl bioaccumulation factors and fugacity ratios in plankton and zebra mussels (Dreissena polymorpha)
Authors: Willman Eric J , Manchester-neesvig Jon B , Agrell Cecilia , Armstrong David E
Published: March 2010

The accumulation of a set of non- and mono-ortho (coplanar) PCB congeners in aquatic ecosystems is of interest due to their dioxin-like toxicities. Chemical properties (octanol-water partition coefficients) suggest that the coplanar congeners may accumulate in organisms to a greater extent than homologs with greater ortho substitution. We analyzed a set of 65 PCB congeners with zero to four ortho-chlorines from seven homolog groups in water, suspended particulate matter, and zebra mussels from Green Bay, Wisconsin, USA, on four dates throughout the ice-free season. The suspended particulate matter was separated by size and characterized as phytoplankton or zooplankton using diagnostic carotenoid pigments and light microscopy. Median bioconcentration factors (BCFs) for accumulation from water by phytoplankton and bioaccumulation factors (BAFs) for accumulation from water plus food by zooplankton and zebra mussels ranged from 1 × 104 to 1 × 106 and were generally the greatest for the tetra- to heptachlorobiphenyls. The average coplanar congener BCFs and BAFs for accumulation from water by phytoplankton, zooplankton, and zebra mussels for the tri-, tetra-, and pentachlorobiphenyls were 54% larger than corresponding values for their homologs. Biomagnification factors (BMFs) of the tetra-, penta-, and hexachlorobiphenyls between zooplankton and zebra mussels and their food source, phytoplankton, typically ranged between 1 and 10, but the average coplanar congener BMFs were 25% less than values for their corresponding homologs. The tendency for coplanar congeners to accumulate to a lesser extent between trophic levels was not as large as their tendency to accumulate from water to a greater extent. Based on accumulation factors, we conclude that the dioxin-like tetra- and pentachlorobiphenyls generally accumulate in the phytoplankton, zooplankton, and zebra mussels of the Green Bay ecosystem to a greater extent than other congeners. Fugacity ratios suggest that, in phytoplankton and zooplankton, homolog concentrations were below equilibrium with water throughout the field season, particularly for the more chlorinated groups, but that concentrations in zebra mussels were at or above equilibrium with water.
Toxicity and bioavailability of the organophosphorus insecticide pirimiphos methyl to the freshwater amphipod Gammarus pulex L. In laboratory and mesocosm systems
Authors: Crane Mark , Attwood Claire , Sheahan Dave , Morris Steven
Published: March 2010

Insecticides must be tested to determine their nontarget toxicity when released into the environment. Currently, new insecticides registered in Europe are likely to be tested, at the highest tier, in microcosms or mesocosms, although the costeffectiveness of these systems has yet to be established. This study investigated the effects of the organophosphorus insecticide pirimiphos methyl on the amphipod Gammarus pulex L. in 250-ml laboratory beakers and 50,000-L pond mesocosms. Acetylcholinesterase activity and survival were used as indicators of the insecticide's bioavailability and toxicity. The results from beakers and mesocosms were indistinguishable, indicating that the former are efficient tools for predicting the bioavailability of chemicals such as pirimiphos methyl that have high toxicity but low persistence in the environment.
Phytotoxicity, uptake, and distribution of [14C] simazine in Canna hybrida ‘Yellow King Humbert’
Authors: Wilson P Chris , Whitwell Ted , Klaine Stephen J
Published: March 2010

Phytoremediation depends on the ability of plants to tolerate and assimilate contaminants. We have been interested in the use of common ornamental plants to ameliorate the impacts of pesticide waste on golf courses and ornamental plant nurseries. This research characterized the interaction between an ornamental, Canna hybrida ‘Yellow King Humbert,’ and the herbicide simazine. Simazine tolerance levels for C. hybrida were determined by exposing plants for 7 d to 0, 0.01, 0.03, 0.1, 0.3, 1.0, or 3.0 mg-simazine/L aqueous nutrient media. Response endpoints included fresh mass production after 7 d of exposure and 7 d postexposure and quantum efficiency using dark-adapted and light-adapted plants. Simazine uptake and distribution within the plant was determined by exposing plants to 2.02 μCi [14C]simazine in nutrient media (0.242 mg/L) for 1, 3, 5, or 7 d. Plant tissues were combusted and analyzed by liquid scintillation counting. Fresh mass production was reduced 66 and 78% for plants exposed to 1.0 and 3.0 mg/L, respectively. Photosynthetic efficiency measured in dark-adapted plants was reduced 34 and 60% at the same respective concentrations, whereas photosynthetic efficiency measured in light-adapted plants was reduced 76 and 92%, respectively. Simazine activity in solution was reduced 80% over 7 d. By day 7, simazine (and/or an impurity) was distributed throughout the plant, but predominantly occurred in the leaves. Uptake of simazine was correlated with water uptake throughout the 7 d. These results suggest that C. hybrida may be a good candidate for incorporation into a phytoremediation scheme for simazine.
Estimating time-to-gravid for a freshwater mussel, Utterbackia imbecillis (Unionidae), after temperature conditioning in the laboratory
Authors: Van Vreede Kelley B , Macintosh David L , Black Marsha C.
Published: March 2010

The juvenile of Utterbackia imbecillis has recently become an important toxicity test organism. However, in temperate climates, gravid U. imbecillis are not readily available during many months of the year, especially if shoreline collection methods are used. This shortage of gravid mussels presents a logistical problem for use of juvenile U. imbecillis as toxicity test organisms. Therefore, this study was designed to test the feasibility of delaying and manipulating glochidial maturation in the laboratory through temperature control, because temperature changes seem to cue the maturation of glochidia in gravid mussels in the natural environment. The objectives of this study were to determine whether glochidial maturation can be stalled by holding adult mussels at cold temperatures, to determine if glochidial maturation could be cued by increasing water temperature at the time juveniles are needed for toxicity testing, and to predict the time required for cold-stored mussels to become gravid (time-to-gravid). Results of this study suggest that glochidial maturation can be stalled by holding mussels at winter temperature. Furthermore, glochidial maturation can later be cued by increasing the water temperature. Additionally, a survival analysis method is suitable for estimating the time-to-gravid for cold-stored mussels. These results should be useful for researchers requiring year-round availability of U. imbecillis for toxicity testing.
Effects of sporophyll storage on giant kelp Macrocystis pyrifera (Agardh) bioassay
Authors: Gully Joseph R , Bottomley Jay P , Baird Rodger B
Published: March 2010

The giant kelp Macrocystis pyrifera (Agardh) is a U.S. Environmental Protection Agency (U.S. EPA)-approved west coast marine species for chronic toxicity monitoring and compliance in the National Pollution Discharge Elimination System (NPDES). The protocol allows field-collected sporophylls to be stored for up to 24 h at 9 to 12°C prior to use. However, the effects of sporophyll storage on the bioassay results have not been fully investigated, particularly with kelp collected from beds south of Point Conception, CA, USA. Therefore, 13 matched-pair reference toxicant bioassays using fresh and stored sporophylls collected from a subtidal kelp bed near Laguna Beach, CA, USA, were performed and compared. The results indicate that a lower percentage of spores germinate and the germ tube lengths are reduced when stored sporophylls are used. The intratest precision of the germination endpoint decreased as evidenced by significant increases in the percent minimum significant difference (%MSD) statistic. The intertest precision also decreased in the germination endpoint as demonstrated by significant increases in the coefficient of variation (CV) values at four effect levels. Conversely, a significant reduction in the CVs was observed in the germ tube length data, possibly as a consequence of the decrease in germ tube length associated with storage. Finally, significant decreases in mean effect concentrations in the germination endpoint in tests using stored sporophylls indicated that storage increased the sensitivity of the spores to the toxic effects of CuCl2. The toxicological sensitivity and intratest precision of the germ tube length endpoint were not significantly affected by storage of the sporophylls. The effects of sporophyll storage resulted in a high frequency of invalid tests, lower statistical power, less effective quality assurance standards, and apparent bias in the observed toxicity of CuCl2.
Is the per capita rate of increase a good measure of population-level effects in ecotoxicology?
Authors: Forbes Valery E , Calow Peter
Published: March 2010

In this paper we consider the relationships between effects of toxicants on population growth rate (r) and the individual-level traits (survival and reproduction) contributing to it by examining population dynamics theory and by reviewing the experimental work that has been carried out in this context. There was no consistent pattern in terms of which individual-level traits were most or least sensitive to toxicant exposure, and it is therefore impractical to select traits for ecotoxicological testing on this basis. Although percent changes in several of the individual-level traits showed significant overall correlations with percent changes in r, changes in any single trait could explain no more than about one-half of the percent change in r. Our conclusion is that r is a better measure of responses to toxicants than are individual-level effects, because it integrates potentially complex interactions among life-history traits and provides a more relevant measure of ecological impact.