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In a study area chosen outside the city of La Plata (Buenos Aires, Argentina), two zones were selected having different types and magnitudes of agrarian activity: one represented mainly by grasslands with a low degree of anthropic influence, the other by intensive cultivation under cover with a high level of anthropic impact. The first objective was to assess the toxicity of the sediments from the study areas to two local species and compare the responses of both bioassays (assessing mortality and growth inhibition) in a standardized test protocol. Hyalella curvispina ( Hc ) is a validated indicator of sediment toxicity; Boana pulchella ( Bp ) has likewise proven useful as a study model through its sensitivity to different pollutants. The comparison was performed by multivariate analyses at the time of evaluating sediment toxicity in a stretch of the Carnaval Stream that flows through an agroecosystem. The second objective was to evaluate the presence of morphologic abnormalities, among other supplemental endpoints (behavior and development), in tadpoles of Bp since those features are good indicators of sublethal effects. Hc turned out to be the more sensitive to the chemical profile of the agroecosystem. We detected two herbicides, trifluralin and acetochlor, and three insecticides, chlorpyrifos, endosulfan, and lambda-cyhalothrin and in this test proposed Bp as a second indicator of sediment toxicity. This research was the first to use larvae of Bp to evaluate the toxicity of sediments of a particular site. The analysis of the occurrence of morphologic abnormalities enabled the detection of toxicities in locations where other endpoints remained unaffected. We intend to incorporate this species into sediment testing since Bp is a prominent anuran in pampean agroecosystems whose utility in toxicity bioassays has been verified by numerous ecotoxicological studies. In conclusion, both the species Hc and Bp should be considered appropriate as tests organisms for the assessment of sediment quality as well as effective and promising environmental indicators. [ABSTRACT FROM AUTHOR]

Chemical and toxicological crude oil analysis was performed on water-accommodated fraction of oil (WAF). This study characterized the chemical composition of WAF and its dissipation over a period of 192 h. Acute (96 h) and chronic (14 d) toxicity of WAF were evaluated on Hyalella curvispina from both reference (Los Barreales lake, LB) and hydrocarbon-contaminated (Durán stream, DS) sites. The total hydrocarbon (TPHs) concentration in WAF was 2.18 mg L −1 . The dissipation rates of hydrocarbons in WAF showed a first-order kinetics, with half-lives ranging between 65 h-200 h. Amphipods from LB showed acute and chronic LC50 values of 0.33 and 0.018 mg L −1 , respectively. Amphipods from DS exposed to pure WAF showed no mortality in either acute or chronic assays. Further biochemical and molecular research is required to determine the mechanisms underlying the resistance to WAF exposure on DS amphipods. [ABSTRACT FROM AUTHOR]

During the last years, a carbaryl insecticide was extensively applied in the valley of Río Negro and Neuquén, North Patagonia Argentina, to manage codling moths ( Cydia pomonella ), the main pest of pear and apple trees. In this study carbaryl susceptibility and B-esterase activity from both insecticide-exposed and non-exposed field populations of amphipods Hyalella curvispina were studied. Two subpopulations, one susceptible to carbaryl (LC 50 = 213 ± 7.5 μg/L carbaryl) and one resistant to it (LC 50 = 14,663 ± 2379 μg/L carbaryl), were found in the agricultural area selected in this study. Both populations were, in turn, more resistant to carbaryl than the population from a pristine area (LC 50 = 11.31 ± 2.27 μg/L carbaryl). The in vivo 48h-IC 50 values for cholinesterase (ChE) were close to the corresponding 48h-LC 50 values as determined for the non-exposed population (IC 50 = 7.16 ± 0.86 μg/L carbaryl) and for the susceptible subpopulation from the insecticide-exposed site (IC 50 = 193 ± 99 μg/L carbaryl). Carbaryl exposure of the amphipods from the agricultural area mentioned above produced a significant decrease of carboxylesterase (CabE) activity, at a sublethal concentration (10 μg/L) that was not able to significantly inhibit ChE, thereby showing a protective role of CabE and its usefulness as early biomarker. However, at lethal concentrations the inhibition of ChE activity was higher than that of CabE. On the other hand, CabE of amphipods from the pristine site was less sensitive to carbaryl than ChE, suggesting a different participation of CabE in ChE protection in the susceptible population of H. curvispina. Pulse exposure to carbaryl for 2 h caused a significant inhibition of ChE in amphipods from both populations, with a fast recovery as expected for a carbamate insecticide. In conclusion, we proved that amphipods from the said agricultural area have developed resistance to carbaryl and showed the presence of two subpopulations with a different response to the insecticide. Moreover, these results reinforce the use of ChE together with CabE inhibition as indicators of carbamate exposure in H. curvispina . [ABSTRACT FROM AUTHOR]

As a result of the poor genome sequence coverage of crustacean amphipods, characterization of their evolutionary biology relies mostly on phenotypic traits. Here, we analyzed the proteome of ovaries from five amphipods, all from the Senticaudata suborder, with the objective to obtain insights into the core-proteome of female reproductive systems. These amphipods were from either the Gammarida infraorder: Gammarus fossarum , Gammarus pulex , Gammarus roeseli , or the Talitrida infraorder: Parhyale hawaiensis and Hyalella azteca . Ovaries from animals sampled at the end of their reproductive cycle were dissected. Their whole protein contents were extracted and their proteomes were recorded by high-throughput nanoLC–MS/MS with a high-resolution mass spectrometer. We interpreted tandem mass spectrometry data with the protein sequence resource from G. fossarum and P. hawaiensis , both recently established by RNA sequencing. The large molecular biodiversity within amphipods was assessed by the ratio of MS/MS spectra assigned for each sample, which tends to diverge rapidly along the taxonomic level considered. The core-proteome was defined as the proteins conserved along all samples, thus detectable by the homology-based proteomic assignment procedure. This specific subproteome may be further enriched in the future with the analysis of new species and update of the protein sequence resource. [ABSTRACT FROM AUTHOR]

Nickel bioavailability is reduced in the presence of dissolved organic carbon (DOC), suspended solids (TSS), and other complexing ligands; however, no studies have examined the relative importance of Ni exposure through different compartments (water, sediment, food). Hyalella azteca and Lymnaea stagnalis were exposed to Ni-amended water, sediment, and food, either separately or in combination. Both organisms experienced survival and growth effects in several Ni compartment tests. The DOC amendments attenuated L. stagnalis Ni effects (survival, growth, and 62 Ni bioaccumulation), and presence of TSS exposures demonstrated both protective and synergistic effects on H. azteca and L. stagnalis . 62 Ni trophic transfer from food to H. azteca and L. stagnalis was negligible; however, bioaccumulating 62 Ni was attributed to 62 Ni-water ( 62 Ni flux from food), 62 Ni-TSS, and 62 Ni-food. Overall, H. azteca and L. stagnalis Ni compartment toxicity increased in the following order: Ni-water >> Ni-sediment >> Ni-all (water, sediment, food) >> Ni-food. [ABSTRACT FROM AUTHOR]

Abstract: Chronic toxicity and bioaccumulation of decamethylcyclopentasiloxane (D5) to Hyalella azteca was examined in a series of spiked sediment exposures. Juvenile H. azteca were exposed for 28d (chronic) to a concentration series of D5 in two natural sediments of differing organic carbon content (O.C.) and particle size composition. The chronic, LC50s were 191 and 857μgD5g−1 dry weight for Lakes Erie (0.5% O.C.) and Restoule (11% O.C.) respectively. Inhibition of growth only occurred with the L. Restoule spiked sediment with a resultant EC25 of 821μgg−1 dw. Lethality was a more sensitive endpoint than growth inhibition. Biota sediment accumulation factors (BSAFs, 28d) were <1 indicating that D5 did not bioconcentrate based on lipid normalized tissue concentrations and organic carbon normalized sediment concentrations. Organic carbon (OC) in the sediment appeared to be protective, however normalization to OC did not normalize the toxicity. Normalization of D5 concentrations in the sediments to sand content did normalize the toxicity and LC50 values of 3180 and 3570μg D5g−1 sand dw were determined to be statistically the same. [Copyright &y& Elsevier]

Abstract: The acute toxicity of cypermethrin to the amphipod Hyalella curvispina was evaluated by means of a toxicity test under laboratory conditions. Cypermethrin is one of the most widely used insecticides in Argentina. H. curvispina is a widely distributed and commonly abundant component of the invertebrate assemblages in shallow waters of southern South America. The experiments were repeated three times. The mean 48-h LC50 value for H. curvispina was estimated at 0.066μg/l. H. curvispina represents a good model for exotoxicological risk assessment. [Copyright &y& Elsevier]

Abstract: The amphipod Hyalella azteca was exposed for 28d to different combinations of Zn contaminated sediment and food. Sediment exposure (+clean food) resulted in increased Zn body burdens, increased mortality and decreased body mass when the molar concentrations of simultaneously extracted Zn were greater than the molar concentration of Acid Volatile Sulfide (SEMZn–AVS>0), suggesting that dissolved Zn was a dominant route of exposure. No adverse effect was noted in the food exposure (+clean sediment), suggesting selective feeding or regulation. Combined exposure (sediment+food) significantly increased adverse effects in comparison with sediment exposure, indicating contribution of dietary Zn to toxicity and bioaccumulation. The observed enhanced toxicity also supports the assumption on the presence of an avoidance/selective feeding reaction of the amphipods in the single sediment or food exposures. During 14d post-exposure in clean medium, the organisms from the same combined exposure history received two feeding regimes, i.e. clean food and Zn spiked food. Elevated Zn bioaccumulation and reduced reproduction were noted in amphipods that were offered Zn spiked food compared to the respective organisms that were fed clean food. This was explained by the failure of avoidance/selective feeding behavior in the absence of an alternative food source (sediment), forcing the amphipods to take up Zn while feeding. Increasing Zn body burdens rejected the assumption that Zn uptake from food was regulated by H. azteca. Our results show that the selective feeding behavior should be accounted for when assessing ecological effects of Zn or other contaminants, especially when contaminated food is a potential exposure route. [Copyright &y& Elsevier]

Abstract: The Terraview–Willowfield Stormwater Management Facility (TWSMF) receives inputs of multiple contaminants, including metals, polycyclic aromatic hydrocarbons (PAHs), road salt, and nutrients, via highway and residential runoff. Contaminant concentrations in runoff are seasonally dependent, and are typically high in early spring, coinciding with the snowmelt. In order to investigate the seasonal fluctuations of contaminant loading and related changes in toxicity to benthic invertebrates, overlying water and sediment samples were collected in the fall and spring, reflecting low and high contaminant loading, respectively, and four-week sediment toxicity tests were conducted with Hyalella azteca. The effects of metals and PAHs are discussed here; the effects of salts, nutrients, and water quality are discussed in a companion paper. Survival and growth of Hyalella after exposure to fall samples were variable: survival was significantly reduced (64–74% of controls) at three out of four sites, but there were no significant growth effects. More dramatic effects were observed after Hyalella were exposed to spring samples: survival was significantly reduced at the two sites furthest downstream (0–75% of controls), and growth was significantly lower in four out of five sites when comparing Hyalella exposed to site sediment with overlying site water versus site sediment with overlying control water. These seasonal changes in toxicity were not related to metals or PAHs: 1. levels of bioavailable metals were below those expected to cause toxicity, and 2. levels of PAHs in sediment were lowest at sites with the greatest toxicity and highest in water and sediment at sites with no toxicity. Although not associated with toxicity, some metals and PAHs exceeded probable and severe effect levels, and could be a cause for concern if contaminant bioavailability changes. Toxicity in the TWSMF appeared to be primarily associated with water-borne contaminants. The cause(s) of these effects are discussed in our companion manuscript. [Copyright &y& Elsevier]

Abstract: The Terraview–Willowfield Stormwater Management Facility (TWSMF) features a tandem of stormwater management ponds, which receive inputs of multiple contaminants from highway and residential runoff. Previous research determined that benthic communities in the ponds were impacted by poor habitat quality, due to elevated sediment concentrations of metals and polycyclic aromatic hydrocarbons (PAHS), and salinity in the overlying water, but did not address seasonal changes, including those caused by the influx of contaminants with the snowmelt. In order to address this issue, water and sediment samples were collected from the TWSMF during the fall and spring, and four-week sediment toxicity tests were conducted with Hyalella azteca. The effects of metals and PAHs are discussed in a companion paper; the effects of road salt, nutrients, and water quality are discussed here. After exposure to fall samples, survival of Hyalella was reduced (64–74% of controls) at three out of four sites, but growth was not negatively affected. After exposure to spring samples, survival was 0–75% of controls at the two sites furthest downstream, and growth was significantly lower in four out of five sites when comparing Hyalella exposed to site water overlying site sediment versus control water overlying site sediment. Toxicity appeared to be related to chloride concentrations: little or no toxicity occurred in fall samples (200mgCl−/L), and significant effects on survival and growth occurred in spring samples above 1550mgCl−/L and 380mgCl−/L, respectively. Sodium chloride toxicity tests showed similar results: four-week LC50s and EC25s (growth) were 1200 and 420mgCl−/L, respectively. Although water quality and nutrients were associated with effects observed in the TWSMF, chloride from road salt was the primary cause of toxicity in this study. Chloride persists during much of the year at concentrations representing a significant threat to benthic communities in the TWSMF. [Copyright &y& Elsevier]

Abstract: Burrowing of the freshwater amphipod Hyalella azteca was evaluated under laboratory conditions similar to those recommended for standard sediment toxicity testing in Canada (EPS 1/RM/33; ) and the United States (EPA/600/R-99/064; ). Sediment type, time of day (light versus dark), size of animal, and the presence or absence of food were varied to assess their effects on burrowing activity. Hyalella azteca were found to burrow rapidly in fine, organic-rich sediments, but were slower to burrow in a sandy sediment. There was no increase in the number of animals occupying the sediment surface of a fine, organic-rich sediment after 4h of darkness compared to the previous 4h of light. Over a 9- to 10-d duration, a higher percentage of animals occupied the surface of the sandy sediment. The addition of food promoted burrowing in sandy sediment, as did using smaller animals. Overall, longer-duration tests involving older animals and coarse sediments may require formal observation to confirm burrowing and ensure adequate sediment exposure. The addition of food during a test may promote the burrowing of larger animals in coarse sediments, but may not be necessary in field-collected sediments that are not excessively sandy. [Copyright &y& Elsevier]

Abstract: Bifenthrin, a current-use pyrethroid insecticide, has been repeatedly identified as a major contributor to toxicity in urban and residential stream sediment. Within an urban stream multiple stressors exist. However, other than pesticides, the influence of secondary stressors on bifenthrin toxicity has not been studied. The goal of this project was to study how dissolved ions, based on the model salt KCl, influence bifenthrin toxicity. The presence of these dissolved ions could influence bifenthrin toxicity either through joint action as a secondary toxicant or through changing the partitioning or bioavailability of bifenthrin between the sediment matrix and overlying water or pore water. The first objective was to determine if mixtures of bifenthrin and KCl, a commonly utilized reference toxicant, display additive toxicity to the benthic invertebrates Hyalella azteca and Chironomus dilutus using concentration addition and independent action mathematical models. The second objective of the present study was to examine how KCl dissolved in the overlying water influences partitioning and bioavailability of a pyrethroid (bifenthrin). Joint toxicity of bifenthrin and KCl was less than predicted by both concentration addition and independent action models. However, both models predicted the joint toxicity within a factor of two. Partitioning of bifenthrin was not significantly influenced by KCl concentrations based on Koc determinations and desorption to Tenax beads. This indicates that the fate and bioavailability of bifenthrin are not likely different in aquatic environments with varying dissolved ion concentrations. Therefore, the toxicological interaction that results in the antagonistic joint action between bifenthrin and KCl is likely due to the physiological effects of exposure to hypertonic solutions of KCl rather than alterations to bifenthrin bioavailability. [Copyright &y& Elsevier]

Abstract: Diclofenac is a nonsteroidal anti-inflammatory drug widely used in Mexico where it is sold over the counter. It enters water bodies through municipal and industrial discharges, posing a risk to water systems and aquatic organisms. Diclofenac-enriched artificial sediment was used to evaluate the toxicity of this pharmaceutical on the sentinel species Hyalella azteca, using oxidative stress biomarkers in order to determine if the set of tests used in this study is a suitable early damage biomarker. The median lethal concentration (72-h LC50) was determined and oxidative stress was evaluated using lipid peroxidation, protein carbonyl content to evaluate oxidized protein content, and the activity of superoxide dismutase, catalase, and glutathione peroxidase. All biomarkers were significantly altered. Diclofenac induces oxidative stress in H. azteca and the set of tests used (lipid peroxidation, protein carbonyl content, antioxidant enzyme activities) constitutes an adequate early damage biomarker for evaluating the toxicity of this pharmaceutical group in aquatic species. [Copyright &y& Elsevier]

Abstract: Nonpolar organic chemicals such as polycyclic aromatic hydrocarbons and chlorobenzenes are expected to act additively when exposed as a mixture. The present study examined the toxicity of fluoranthene (FLU) and pentachlorobenzene (PCBz) individually and in a binary mixture using the whole-body residue as the dose metric. Body residues were based on the toxic equivalent body residue, which included the parent compound plus the organically extractable metabolites for FLU and the parent compound only for PCBz. Using a toxic unit (TU) approach, the binary mixtures of FLU and PCBz following 4- and 10-d water-only exposures acted additively. The lethal residue (LR50) values for mixtures of the compounds for Hyalella azteca were 1.26 (1.19–1.33) TU and 1.27 (1.20–1.34) TU for 4- and 10-d exposures, respectively. For Chironomus dilutus, the 4-d and 10-d values were 0.93 (0.90–0.97) TU and 1.01 (0.96–1.06) TU. Additionally, the total molar sum of PCBz and FLU whole-body residues in a mixture were compared to residues from single compound exposures. For both species tested, the LR50 values based on the total molar sum fell within the range of those determined from the single compound tests; providing additional support for molar additivity for nonpolar narcotic compounds. Assuming that residue-effects data among narcotic compounds (e.g., LR50) are similar, applying the molar sum methodology to narcotic compounds in tissues determined from routine biomonitoring programs and risk specific sampling may be a valuable tool to assess potential effects to biota in the field. [Copyright &y& Elsevier]

The kinetics of uptake and the effect of body size on uranium (U) bioaccumulation and toxicity to Hyalella azteca exposed to water-only U concentrations in soft water were evaluated. The effect of body size on U bioaccumulation was significant with a slope of ¿0.35 between log body concentration and log body mass. A saturation kinetic model was satisfactory to describe the uptake rate, elimination rate and the effect of gut-clearance on size-corrected U bioaccumulation in H. azteca. The one-week lethal water concentrations causing 50% mortality for juvenile and adult H. azteca were 1100 and 4000 nmol U/L, respectively. The one-week lethal body concentration causing 50% mortality was 140 nmol U/g for juvenile H. azteca and 220 nmol U/g for adult H. azteca. One-week bioaccumulation studies that properly account for body-size and gut-clearance times can provide valuable data on U bioavailability and toxicity in the environment. [Copyright &y& Elsevier]

Phase I whole sediment toxicity identification evaluation (TIE) methods have been developed to characterize the cause of toxicity as organic chemicals, metals, or ammonia. In Phase II identification treatments, resins added to whole sediment to reduce toxicity caused by metals and organics can be separated and eluted much like solid-phase extraction (SPE) columns are eluted for interstitial water. In this study, formulated reference sediments spiked with toxic concentrations of copper, fluoranthene, and nonylphenol were subjected to whole sediment and interstitial water TIE treatments to evaluate Phase I and II TIE procedures for identifying the cause of toxicity to Hyalella azteca. Phase I TIE treatments consisted of adding adsorbent resins to whole sediment, and using SPE columns to remove spiked chemicals from interstitial water. Phase II treatments consisted of eluting resins and SPE columns and the preparation and testing of eluates for toxicity and chemistry. Whole sediment resins and SPE columns significantly reduced toxicity, and the eluates from all treatments contained toxic concentrations of the spiked chemical except for interstitial water fluoranthene. Toxic unit analysis based on median lethal concentrations (LC50s) allowed for the comparison of chemical concentrations among treatments, and demonstrated that the bioavailability of some chemicals was reduced in some samples and treatments. The concentration of fluoranthene in the resin eluate closely approximated the original interstitial water concentration, but the resin eluate concentrations of copper and nonylphenol were much higher than the original interstitial water concentrations. Phase II whole sediment TIE treatments provided complementary lines of evidence to the interstitial water TIE results. [Copyright &y& Elsevier]

Abstract: Despite heavy insecticide usage in urban areas, only a few studies have investigated the impact of current-use insecticides on benthic invertebrates in urban streams. The objective of this study was to measure the presence and concentration of current-use pesticides in sediments of residential streams in central Texas. Additionally, toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a year, of which, 66% had greater than one toxic unit (TU) of insecticide. Bifenthrin was the greatest contributor accounting for 65% of the TUs, and sediment toxicity to H. azteca correlated with the magnitude of total insecticides and bifenthrin TUs. The results of this study further raise concerns over the environmental consequences posed by many current-use insecticides, especially pyrethroids, in urban settings. [Copyright &y& Elsevier]

Abstract: Specimens of the amphipod Hyalella azteca were deployed, in June–July 2003, along metal contamination gradients in two rivers affected by metal mining in the Abitibi – James Bay region, northwestern Québec. The amphipods were placed along with natural food items in small, acrylic cages and left in six riverine sites for 17 days. Twelve metals (As, Cu, La, Mn, Ni, Sb, Se, Tl, U, V, Zn, and CrO4 2− modelled by WHAM VI) in transplanted H. azteca varied along metal contamination gradients in a consistent manner, i.e., as a function of metal exposure. Bioaccumulation of As, Cr, La, Ni, Sb, Se, Tl, U and V, as defined by a field BCF, was significantly correlated with their chronic toxicity potential towards the amphipod. We conclude that H. azteca may be a useful field biomonitor for metal mining. In addition, our results suggest that such biomonitoring programs should include less studied elements such as Se in mining effluents. [Copyright &y& Elsevier]

Fluoxetine is a serotonin re-uptake inhibitor, generally used as an antidepressant. It is suspected to provoke substantial effects in the aquatic environment. This study reports the effects of fluoxetine on the life cycle of four invertebrate species, Daphnia magna, Hyalella azteca and the snail Potamopyrgus antipodarum exposed to fluoxetine spiked-water and the midge Chironomus riparius exposed to fluoxetine-spiked sediments. For D. magna, a multi-generational study was performed with exposition of newborns from exposed organisms. Effects of fluoxetine could be found at low measured concentrations (around 10μgl−1), especially for parthenogenetic reproduction of D. magna and P. antipodarum. For daphnids, newborns length was impacted by fluoxetine and the second generation of exposed individuals showed much more pronounced effects than the first one, with a NOEC of 8.9μgl−1. For P. antipodarum, significant decrease of reproduction was found for concentrations around 10μgl−1. In contrast, we found no effect on the reproduction of H. azteca but a significant effect on growth, which resulted in a NOEC of 33μgl−1, expressed in nominal concentration. No effect on C. riparius could be found for measured concentrations up to 59.5mgkg−1. General mechanistic energy-based models showed poor relevance for data analysis, which suggests that fluoxetine targets specific mechanisms of reproduction. [Copyright &y& Elsevier]

Abstract: Data on the toxicity of uranium in sediments to Hyalella azteca and the effect of overlying water chemistry are limited. This study exposed H. azteca to sediments spiked with U (0–10,000μgU/g dry weight) and five different overlying waters, which varied independently in hardness and alkalinity. Water pH had a major effect on U bioavailability and uptake by H. azteca. Uranium toxicity was higher when overlying water pH was low, while desorption of U into the overlying water increased with increasing pH. There appears to be little effect of Ca on U uptake, other than its influence on U speciation. Experiments with caged animals indicate that U accumulation and toxicity occur mainly through the dissolved phase rather than the solid phase. Uranium bioaccumulation is a more reliable indicator of U toxicity than U concentration in water or sediment. Uranium bioaccumulation in the H. azteca and U adsorption to sediment can be satisfactorily explained using saturation models. [Copyright &y& Elsevier]

Abstract: The present study investigated the effects of carbofuran on the energy metabolism (levels of glycogen, total proteins, total lipids, triglycerides, and lipoperoxidation), Na+/K+ATPase activity, and reproductive parameters (formation of couples, ovigerous females, and mean number of eggs) in the freshwater amphipods Hyalella pleoacuta and Hyalella curvispina. These crustaceans live in limnetic environments of the plateau (H. pleoacuta) and coastal plain (H. curvispina) of the state of Rio Grande do Sul in southern Brazil. The animals were collected in the winter of 2006 in the Vale das Trutas (28°47′00″S–49°50′53″W) in the Municipality of São José dos Ausentes, and in Gentil Lagoon (29°56′30″S, 50°07′50″W) in the Municipality of Tramandaí. In the laboratory, the amphipods were kept submerged in aquariums under controlled conditions of photoperiod (12 h light: 12 h dark), temperature (23 °C±1), and constant oxygenation. Animals were exposed to carbofuran at a dose of 5 or 50 μg/L for a period of 7 days. At the end of this period, the animals were immediately frozen for determination of the biochemical parameters, lipoperoxidation levels (TBARS), and enzyme Na+/K+ATPase activity. During each day of culture, several reproductive parameters were observed. Statistical analysis (ANOVA) revealed that carbofuran induces significant decreases in glycogen, proteins, lipids, triglycerides, and Na+/K+ATPase, as well as a significant increase in lipoperoxidation levels. Studies of all the biochemical parameters seem to be quite promising, in order to assess and predict the effects of toxicants on non-target organisms. The results also suggest that the reproductive parameters (formation of couples, ovigerous females and mean number of eggs) may provide sensitive criteria for assessing ecotoxicological effects. Furthermore, H. pleoacuta and H. curvispina are suitable organisms for use in toxicity tests, and we suggest that they are sensitive species that could be used in monitoring studies. [Copyright &y& Elsevier]

Minimum dissolved oxygen requirements are part of standard guidelines for toxicity testing of freshwater sediments with several benthic invertebrates, but the data underlying these requirements are somewhat sparse. We exposed three common test organisms to ranges of dissolved oxygen concentrations to determine their responses in 10-d exposures, relative to published guidelines for sediment toxicity tests. The oligochaete, Lumbriculus variegatus, showed 100% survival in all exposures down to the lowest concentration tested, 0.7mg O2 l−1. Midge (Chironomus dilutus) larva showed a more pronounced response; while survival was less than 90% only below 1.0mg O2 l−1, the biomass endpoint showed EC50, EC20, and EC10 values of 1.00 (0.91–1.10), 1.41 (1.16–1.71), and 1.67 (1.25–2.24) mg O2 l−1. The amphipod, Hyalella azteca, showed no adverse effects at concentrations as low as 2.12mg O2 l−1. The combination of these data with other literature data suggest that DO minima in current North American 10-d sediment test guidelines are reasonable. [Copyright &y& Elsevier]

Abstract: This study aimed at characterizing pairing and reproductive success in relation to male and female sizes of the sympatric freshwater gammarideans Hyalella pleoacuta and H. castroi from southern Brazil. These amphipods exhibit precopulatory mate guarding, in which a male will carry a potential mate beneath its ventral surface, guarding the female for several days until it molts and lays its eggs. The specimens were collected monthly with nets, from November 2003 to July 2004 in two trout aquaculture ponds at Sítio Vale das Trutas locality, São José dos Ausentes County, southern Brazil. The precopulatory pairs and ovigerous females were identified and separated in the field. In the laboratory, they were measured (cephalothorax length in mm), using a micrometer eyepiece in a stereoscopic microscope. Pairing success was estimated from the proportion of mating males and females related to their respective non-pairing individuals by size classes. Reproductive success was estimated from egg production. The mean cephalothorax length of paired males was larger than that of the unpaired males. For females, however, body size not affect pairing success for either species, because mean cephalothorax length of paired females did not differ significantly from unpaired females. Paired and unpaired males of both species of Hyalella were larger than the females. Positive assortative mating by size was observed in both species; i.e., larger males tended to pair with larger females. Male pairing success increased sharply with size. In both species, reproductive success in males increased with body size; however, the females of intermediate size classes showed greater reproductive success. This result supports the hypothesis that loading constraints play a part in structuring size-assortative pairing in these species. [Copyright &y& Elsevier]

Abstract: This work was performed with the aim to test theoretical predictions regarding that the sympatric species Hyalella pleoacuta and H. castroi might show distinct population biology to facilitate its coexistence. The specimens were collected monthly with nets from August 2003 through July 2004 in two trout ponds at Sítio Vale das Trutas locality, São José dos Ausentes County, southern Brazil. In the laboratory, the specimens were measured as cephalothorax length (mm), being the sex and ovigerous conditions checked. The species H. pleoacuta was 2.94 times more frequent than H. castroi. Males were significantly greater in size than females (H. pleoacuta—males: 0.74±0.002mm and females: 0.66±0.001mm; H. castroi—males: 0.84±0.00mm and females: 0.72±0.003mm). Males and females of H. castroi showed a greater mean body size than H. pleoacuta. Sexual maturity was attained at 0.53mm in males and 0.48mm in females of H. pleoacuta, and 0.72mm in males and 0.67mm in females of H. castroi. The frequency distribution in size classes was usually bimodal in H. pleoacuta and polymodal in H. castroi throughout the year. Sex ratio was female-biased in either species of Hyalella. Ovigerous females (carrying eggs or juveniles in the marsupium) were collected throughout the year in both Hyalella species, but H. pleoacuta and H. castroi were found with more frequency during the winter and fall, respectively. Recruitment occurred in all months of sampling, the juvenile frequency being more than 50% of the amphipods collected in almost all months in both species. The biological differences (especially body size, size at sexual maturity, number of specimens collected and reproductive peak) and microhabitat specialization can be facilitating factors in the coexistence of H. pleoacuta and H. castroi in artificial ponds raising trout. [Copyright &y& Elsevier]

Five benthic organisms commonly used for sediment toxicity testing were chronically (28 to 35 days) exposed to copper in standard laboratory-formulated sediment (following Organization for Economic Cooperation and Development guidelines) and lethal and sub-lethal toxicities were evaluated. Sub-lethal endpoints considered were reproduction and biomass production for Lumbriculus variegatus, growth and reproduction for Tubifex tubifex, growth and emergence for Chironomus riparius, and growth for Gammarus pulex and Hyalella azteca. Expressed on whole-sediment basis the observed lethal sensitivity ranking (from most to least sensitive) was: G. pulex > L. variegatus > H. azteca = C. riparius = T. tubifex, with median chronic lethal concentrations (LC50) between 151 and 327 mg/kg dry wt. The sub-lethal sensitivity ranking (from most to least sensitive, with the most sensitive endpoint between parentheses): C. riparius (emergence)> T. tubifex (reproduction)= L. variegatus (reproduction)> G. pulex (growth)> H. azteca (growth), with median effective concentrations (EC50) between 59.2 and 194 mg/kg dry wt. No observed effect concentrations (NOEC) or 10% effective concentrations (EC10) for the five benthic invertebrates were used to perform a preliminary risk assessment for copper in freshwater sediment by means of (a) the “assessment factor approach” or (b) the statistical extrapolation approach (species sensitivity distribution). Depending on the data (NOEC or EC10) and the methodology used, we calculated a Predicted No Effect Concentration (PNEC) for sediment between 3.3 and 47.1 mg Cu/dry wt. This range is similar to the range of natural (geochemical) background concentrations of copper in sediments in Europe, i.e. 90% of sediments have a concentration between 5 and 49 mg Cu/kg dry wt. A detailed analysis of the outcome of this preliminary exercise highlighted that multiple issues need to be explored for achieving a scientifically more sound risk assessment and for the development of robust sediment quality criteria for copper, including (i) the use of the assessment factor approach vs. the statistical extrapolation approach, (ii) the importance of bioavailability modifying factors (e.g., organic carbon, acid volatile sulfide), and (iii) the influence of prevailing geochemical (bioavailable) background concentrations on the copper sensitivity of local benthic biota. [Copyright &y& Elsevier]

Abstract: Aquatic organisms exist in a constantly fluctuating habitat, with changes in photoperiod, temperature, pH, dissolved organic content, dissolved oxygen and food supply. Organisms must alter past of their physiological and biochemical processes to cope with these changes. We compared the effect of seasonal variations in factors related to energy metabolism of two species of sympatric amphipods, Hyalella pleoacuta and Hyalella castroi. The animals were collected monthly from April 2004 through March 2006. Contents of glycogen, proteins, lipids, triglycerides and the levels of lipoperoxidation were determined in males and females throughout the year by using spectrophotometric methods. Observations revealed significant seasonal differences in biochemical composition, as well as differences among sexes and species. Environmental conditions (e.g., trophic conditions) and reproduction are supposed to be the main processes influencing the seasonal patterns of variation in biochemical composition. Both species of Hyalella show ecological and behavioral differences, especially by resources such as food, space and seasonal variations of energy metabolism, which might facilitate their coexistence in the same habitat. [Copyright &y& Elsevier]

Abstract: Mixtures were produced of “equi-toxic” concentrations of 10 elements at the 4-week LC25 for Hyalella azteca. Bioaccumulation was determined in 1-week exposures. The first mixtures tested included seven elements; As, Cd, Co, Cr, Ni, Pb and Tl. Copper, Mn and Zn were not included in the initial tests due to potential confounding effects, such as regulation of Cu and Zn by H. azteca and the high concentrations of Mn required to be “equi-toxic”, which might cause adsorption of metals to Mn hydroxides if these were formed. The second set of tests included the seven element mixture in combination with, Cu, Mn and Zn individually, the binary pairs, Cu–Mn, Cu–Zn and Mn–Zn; and the tertiary group Cu, Mn and Zn. Interaction factors (IF) were computed which quantified each element''s impact on the bioaccumulation of the other nine. Cobalt, Cd and Ni bioaccumulation was significantly inhibited with increasing number of metals in the mixture. Arsenic bioaccumulation was enhanced with increasing number of metals in the mixture exposure. Lead bioaccumulation was enhanced by some mixture combinations. Bioaccumulation of Cr, Cu, Mn, Tl and Zn were not significantly affected by exposure to other metals. [Copyright &y& Elsevier]

Three oxbow lakes in northwestern Mississippi, USA, an area of intensive agriculture, were assessed for biological impairment from historic and current-use pesticide contamination using the amphipod, Hyalella azteca. Surface water and sediment samples from three sites in each lake were collected from Deep Hollow, Beasley, and Thighman Lakes from September 2000 to February 2001. Samples were analyzed for 17 historic and current-use pesticides and selected metabolites. Ten-day H. Azteca survival and growth (as length and dry weight) were measured to determine the degree of biological impairment. Maximum number of detectable pesticides in surface water from Deep Hollow, Beasley and Thighman Lakes was 10, 11, and 17, respectively. Maximum number of detectable pesticides in lake sediments was 17, 17, and 15, respectively. Bioassay results indicated no observable survival effects on H. Azteca exposed to surface water or sediment from any lake examined and no growth impairment in animals exposed to lake sediments. However, growth was significantly impaired in surface water exposures from Deep Hollow Lake (2 sites) and Beasley Lake (1 site). Statistically significant relationships between growth impairment (length) and cyanazine, methyl parathion, λ-cyhalothrin, chlorfenapyr, and pp′DDE surface water concentrations in Deep Hollow Lake as well as trifluralin, atrazine, and methyl parathion in Beasley Lake were observed. Although pesticide frequency and concentrations were typically greater in sediment than surface water, bioassay results indicated decreased availability of these pesticides in sediment due to the presence of clay and organic carbon. Growth impairment observed in surface water exposures was likely due to complex interaction of pesticide mixtures that were present. [Copyright &y& Elsevier]

Chronic toxicity of As, Co, Cr and Mn to Hyalella azteca can be described using a saturation-based mortality model relative to total-body or water metal concentration. LBC25s (total-body metal concentrations resulting in 25% mortality in 4weeks) were 125, 103, 152 and 57,900nmolg−1 dry weight for As, Co, Cr and Mn respectively. LC50s (metal concentrations in water resulting in 25% mortality in 4weeks) were 5600, 183, 731, and 197,000nmolL−1, respectively. A hormesis growth response to As exposure was observed. Growth was a more variable endpoint than mortality for all four toxicants; however, confidence limits based on growth and mortality all overlapped, except Cr which had no effect on growth. Mn toxicity was greater in glass test containers compared to plastic. Bioaccumulation of As, Co, Cr, and Mn was strongly correlated with, and is useful for predicting, chronic mortality. [Copyright &y& Elsevier]

This paper reports results of genotoxicity and toxicity studies of water and sediment samples collected from the Estância Velha stream of southern Brazil, a stream transporting both domestic sewage and effluents from regional factories working in the leather industry. Three sites were selected: in the stream headwaters (Site 1), located downstream of an urban area (Site 2), and near the basin outfall (Site 3). Results obtained with Allium cepa showed no evidence of chromosomal mutation, either in water or in sediment, during winter or summer seasons, but samples collected below Site 1 showed high toxicity. Physical and chemical analyses showed high concentrations of pollutants at these sites. Ecotoxicity tests with Daphnia magna and Ceriodaphnia dubia measured toxicity in water from Sites 2 and 3 in summer 2004. A toxic effect on Hyalella azteca was only found in sediment from Site 3 during winter 2003 and summer 2004. The results suggest that the synergy among different compounds in domestic and industrial sewage discharges can make it difficult to maintain system stability. [Copyright &y& Elsevier]

Abstract: A mixture of seven common pharmaceutical agents (acetaminophen, diclofenac, gemfibrozil, ibuprofen, naproxen, salicylic acid, and triclosan) was tested for its effects on the freshwater amphipod Hyalella azteca over three generations. The target concentration of each chemical (100ngl−1) was representative of the upper range observed for these substances in Canadian fresh waters, except in the immediate vicinity of effluent discharges. No statistically significant effects were observed on survival, mating, body size or reproduction. The sex ratio changed slightly to 17% more males. The seven pharmaceuticals tested do not appear to be substances of major concern for Hyalella in most Canadian fresh waters, but significant impacts might be observed in areas closer to effluent discharges. [Copyright &y& Elsevier]

Hyalella were caged at three sites in each of the two rivers for 17 days. Food added to the cages consisted of plant and detrital material collected from the same, or other, sites. Concentrations of some metals in Hyalella (e. G. , Cd and Cu), but not others (e. G. , Se), appeared to reach steady-state within 5 days in one of the rivers. Metal accumulation was minimal by day 5 in the other river, possibly due to the very low temperatures in this river for the first part of the exposure period. Both analysis of variance and analysis of covariance, using site as a categorical variable and metal in food as either a categorical or continuous variable, indicated that Cd, Cu and Se were the only metals for which concentration in food had a significant effect on concentration in Hyalella. Nevertheless, water was still a major source for these metals as well. Other metals which varied by over fivefold in food but for which concentration in food had no effect on concentration in Hyalella included Ag, As, Bi, Sb, U and Zn. Concentrations of the remaining metals varied less than fourfold in food, making it difficult to determine if these were accumulated from food. [Copyright &y& Elsevier]

Abstract: Bioaccumulation of As, Co, Cr and Mn by the benthic amphipod Hyalella azteca in Burlington City tap (Lake Ontario) water was measured in 4-week tests. Bioaccumulation increased with exposure concentration and demonstrated an excellent fit to a saturation model (r 2: 0.819, 0.838, 0.895 and 0.964 for As, Co, Cr and Mn, respectively). The proportion of total body Mn eliminated during a 24-h depuration period decreased as Mn body concentration increased, apparently due to a saturation of the elimination rate. The high maximum body concentration of 116,000nmolg−1 appears to result from the saturation of the Mn excretion which is slightly greater than the maximum Mn uptake rate. Elimination rates for As, Co and Cr were not dependent on body concentration. The four elements were not physiologically regulated in Hyalella. Their body concentrations should be good indicators of bioavailability and useful for environmental assessment. [Copyright &y& Elsevier]

Abstract: To more fully assess the toxicity of water-soluble fullerene (nC60), acute toxicity assays were performed on several environmentally relevant species. Included were the freshwater crustaceans Daphnia magna and Hyalella azteca, and a marine harpacticoid copepod, and two fish species, fathead minnow Pimephales promelas and Japanese medaka Oryzias latipes. The latter two species were used to assess sublethal effects of fullerene exposure by also assessing mRNA and protein expression in liver. Because prior studies found that both sonication and using tetrahydrofuran to solubilize fullerene increased the toxicity of nC60, the nC60 used in this study was prepared by stirring. For the invertebrate studies, nC60 could not be prepared at high enough concentration levels to cause 50% mortality (LC50) at 48 or 96h. The maximum concentrations tested were 35ppm for freshwater and 22.5ppm for full-strength (35ppt) seawater, since at higher concentrations the nC60 precipitated out of solution. Daphnia 21-day exposures resulted in a significant delay in molting and significantly reduced offspring production at 2.5 and 5ppm nC60, which could possibly produce impacts at the population-level. For the fish, we found that neither the mRNA nor protein-expression levels of cytochrome P450 isozymes CYP1A, CYP2K1 and CYP2M1 were changed. The peroxisomal lipid transport protein PMP70 was significantly reduced in fathead minnow, but not medaka, indicating potential changes in acyl-CoA pathways. [Copyright &y& Elsevier]

Abstract: To determine changes in metal distribution, bioavailability and toxicity with sediment depth, two 20-cm-long replicate cores were collected from a lake historically subjected to the influence of metal mining and smelting activity. The vertical distribution of Pb, Cd and Cu in sediment was similar for all three metals, with the surface layers showing enrichment and the deeper (pre-industrial) layers showing lower concentrations. Toxicity of each sediment core section was determined in laboratory tests with the freshwater amphipod Hyalella azteca. Bioavailable metal in each sediment slice was estimated from metal concentrations in overlying water in these toxicity tests and, for Cd, also from metal bioaccumulation. The profile for Cd in tissue was comparable to Cd in sediment and overlying water, but relative Cd bioavailability from sediment increased with sediment depth. Survival increased with increasing sediment depth, suggesting that surface sediments were probably less or non-toxic before industrialization. [Copyright &y& Elsevier]

Abstract: The effect of major ions (Ca, Mg, Na, and K) and pH on Cu toxicity (LC50) to Hyalella azteca was determined in 1 week exposures. The simplest equation for describing Cu toxicity is a linear relationship between the total dissolved Cu LC50 and Ca and Na in water, ignoring pH. This equation would be useful in tier one of a two-tiered approach; if the measured dissolved Cu exceeds the value predicted from the equation, the sample should either be tested for toxicity, or a more detailed chemical speciation analysis can be conducted. The data were not consistent with a single-binding-site biotic ligand model, assuming that toxicity was due to the free Cu ion alone. However, toxicity could be predicted using a two-binding-site model. This requires separate coefficients to account for the effects of Ca and Na at low and high pH values (6.5–8.4), corresponding to the different binding sites (Mg and K did not affect toxicity). The single-binding-site BLM does not allow for this. Toxicity of Cu hydroxide or carbonate complexes does not need to be invoked, but cannot be excluded, and several models invoking the toxicity of these complexes can also explain the data. The free ion LC50 is strongly dependent on pH, but the LC50 for total dissolved Cu is almost pH independent. The effects of Ca and Na on the free ion LC50 are very different at high and low pH (contrary to single-site biotic ligand model predictions), but similar for total dissolved Cu. Published data suggest that the same model, with different coefficients, can also be applied to Daphnia and fish. A more critical evaluation of the effects of cations at both low and high pH for organisms other than Hyalella is needed to determine if the BLM needs to be adjusted to incorporate more than one binding site for other species as well. Hydrogen ions reduce the toxicity of free Cu ions to Hyalella, but Cu also reduces the toxicity of hydrogen ions. A mixture model accounting for the joint toxicity of Cu and pH, as well as their mutual antagonistic effects, is presented. [Copyright &y& Elsevier]

Abstract: An in situ toxicity and bioaccumulation assessment approach is described to assess stressor exposure and effects in surface waters (low and high flow), the sediment–water interface, surficial sediments and pore waters (including groundwater upwellings). This approach can be used for exposing species, representing major functional and taxonomic groups. Pimephales promelas, Daphnia magna, Ceriodaphnia dubia, Hyalella azteca, Hyalella sp., Chironomus tentans, Lumbriculus variegatus, Hydra attenuatta, Hexagenia sp. and Baetis tibialis were successfully used to measure effects on survival, growth, feeding, and/or uptake. Stressors identified included chemical toxicants, suspended solids, photo-induced toxicity, indigenous predators, and flow. Responses varied between laboratory and in situ exposures in many cases and were attributed to differing exposure dynamics and sample-processing artifacts. These in situ exposure approaches provide unique assessment information that is complementary to traditional laboratory-based toxicity and bioaccumulation testing and reduce the uncertainties of extrapolating from the laboratory to field responses. [Copyright &y& Elsevier]

The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the overlying water column (including water and food), not sediment or porewater. In laboratory sediment toxicity tests H. azteca is deprived of natural food sources such as algal communities on or above the sediments, and is subjected to constant light without any cover except that afforded by burial into the sediments. Under these constraining laboratory conditions, H. azteca has been reported to respond to sediment or porewater contamination. In nature, contamination of overlying water from sediment is less likely than in the laboratory because of the large, generally non-static sink of natural surface water. H. azteca does not appear to be the most appropriate test species for direct assessments of the bioavailability and toxicity of sediment contaminants, though it is probably appropriate for testing the toxicity of surface waters. Toxic and non-toxic responses will be highly conservative, though the latter are probably the most persuasive given the exposure constraints. Thus H. azteca is probably a suitable surrogate species for determining sediments that are likely not toxic to field populations; however, it is not suitable for determining sediments that are likely toxic to field populations. [Copyright &y& Elsevier]

Bioaccumulation by Hyalella of all metals studied so far in our laboratory was re-evaluated to determine if the data could be explained satisfactorily using saturation models. Saturation kinetics are predicted by the biotic ligand model (BLM), now widely used in modelling acute toxicity, and are a pre-requisite if the BLM is to be applied to chronic toxicity. Saturation models provided a good fit to all the data. Since these are mechanistically based, they provide additional insights into metal accumulation mechanisms not immediately apparent when using allometric models. For example, maximum Cd accumulation is dependent on the hardness of the water to which Hyalella are acclimated. The BLM may need to be modified when applied to chronic toxicity. Use of saturation models for bioaccumulation, however, also necessitates the need for using saturation models for dose–response relationships in order to produce unambiguous estimates of LC50 values based on water and body concentrations. This affects predictions of toxicity at very low metal concentrations and results in lower predicted toxicity of mixtures when many metals are present at low concentrations. [Copyright &y& Elsevier]

Sediments from lakes near Rouyn-Noranda, Quebec, contain elevated concentrations of several metals, including Cd, Cu, Pb and Zn. Amphipods, fingernail clams, mayflies and tanytarsid midges were absent, and sediment toxicity was observed in chronic tests with Hyalella in sediments from Lac Dufault, the lake closest to Rouyn-Noranda. Bioaccumulation by Hyalella demonstrated elevated bioavailability of Cd, Co, Cr, Pb and Tl, but only Cd was accumulated to levels close to the toxic threshold. Copper, which is regulated by Hyalella, was not elevated in these amphipods, but it was elevated in overlying water in the toxicity tests. Toxic effects in Lac Dufault sediments are probably caused primarily by Cd, at least in amphipods, with a possible minor contribution from Cu. An integrated assessment, including sediment chemistry, benthic community composition, sediment toxicity, metal bioaccumulation in benthos, and comparison of bioaccumulation and/or overlying water concentrations with threshold effect concentrations, provides the best indication of effects and their cause. [Copyright &y& Elsevier]

Deterioration of overlying water quality during toxicity tests with benthic invertebrates is a serious problem with some sediments. One solution is periodic renewal of overlying water. However, this is either labor intensive or requires construction and maintenance of special equipment. Furthermore, water renewal has the potential for flushing toxic chemicals out of the test chamber and establishes nonequilibrium conditions between the water and sediment. An alternative is testing under static conditions using atypical test vessels (e.g. Imhoff settling cones) with a large water volume (1 to l) overlaying a much smaller sediment volume (e.g. 15 ml). This results in dramatic improvement of overlying water quality compared to standard static toxicitytests. Compared to water renewal, the test method is much simpler, all toxic substances leached from the sediment are retained in the test vessel, and contaminant concentrations in water and sediment have more time to equilibrate. Chronic sediment toxicity tests (10-28 days)have been conducted successfully under these conditions with Chironomus riparius, Hexagenia sp., Hyalella azteca and Tubifex tubifex. [ABSTRACT FROM AUTHOR]