Freshwater Amphipod Hyalella Azteca Research Articles

Insights into the neurotoxicity and oxidative stress to the freshwater amphipod Hyalella azteca induced by hexafluoropropylene oxide trimer acid

With the regulation and phase-out of conventional per- and polyfluoroalkyl substances (PFAS), there is a growing trend towards seeking alternatives that are less toxic and less persistent. Hexafluoropropylene oxide trimer acid (HFPO-TA) is one of the alternatives to perfluorooctanoic acid (PFOA), the latter being widely present in the environment globally. However, there is limited information regarding the biological toxicity of HFPO-TA to aquatic organisms. In this study, the freshwater benthic amphipod, Hyalella azteca, was used to assess the acute and chronic toxicity of HFPO-TA in both water and sediment. HFPO-TA was found to be more toxic to H. azteca than PFOA, as indicated by greater production of reactive oxygen species (p < 0.05) and increasing catalase activity (p < 0.05). In addition, exposure to HFPO-TA affected the swimming behavior and the acetylcholinesterase (AChE) activity of the amphipod. Molecular docking models revealed that HFPO-TA can bind to AChE with a stronger binding affinity than PFOA. Furthermore, an integrated biomarker response index indicated that environmentally relevant concentration (1–100 μg/L) of HFPO-TA may cause toxicity to H. azteca, encompassing oxidative stress and neurotoxicity. This study provides new insights into the toxicity mechanisms of HFPO-TA and is valuable for assessing the ecological safety of this compound.

Utilization of a Gender-Based Sorting Machine for Crustacean Selection in Bioconcentration Studies with the Freshwater Amphipod Hyalella azteca.

Bioconcentration factors (BCFs) are determined by fish flow-through tests performed according to Organisation for Economic Co-operation and Development test guideline 305. These are time-consuming and expensive and use a large number of animals. An alternative test design using the freshwater amphipod Hyalella azteca for bioconcentration studies has been recently developed and demonstrated a high potential. For bioconcentration studies using H. azteca, male amphipods are preferred compared with female organisms. Manual sexing of male adult amphipods is, however, time-consuming and requires care and skill. A new fully automatic sorting and dispensing machine for H. azteca based on image analysis has recently been developed by the company Life Science Methods. Nevertheless, an anesthesia step is necessary prior to the automatic selection. In the present study, we show that a single-pulse of 90 min of tricaine at the concentration of 1 g/L can be used and is recommended to select H. azteca males manually or automatically using the sorting machine. In the second part, we demonstrate that the machine has the ability to select, sort, and disperse the males of a culture batch of H. azteca as efficiently as manual procedures. In the last part of the study, BCFs of two organic substances were evaluated using the H. azteca bioconcentration test (HYBIT) protocol, with an anesthetizing step and robotic selection compared with manual selection without an anesthetizing step. The different BCF values obtained were in accordance with those indicated in the literature and showed that an anesthetizing step had no effect on the BCF values. Therefore, these data validated the interest in this sorting machine for selecting males to perform bioconcentrations studies with H. azteca. Environ Toxicol Chem 2023;00:1-10. © 2023 SETAC.

Mechanistic modeling of the bioconcentration of (super)hydrophobic compounds in Hyalella azteca

Bioconcentration tests using the freshwater amphipod Hyalella azteca as an alternative to conventional fish tests have recently received much attention. An appropriate computational model of H. azteca could help in understanding the mechanisms behind bioconcentration, in comparison to the fish as test organism. We here present the first mechanistic model for H. azteca that considers the single diffusive processes in the gills and gut. The model matches with the experimental data from the literature quite well when appropriate physiological information is used. The implementation of facilitated transport was essential for modeling. Application of the model for superhydrophobic compounds revealed binding to organic matter and the resulting decrease in bioavailable fraction as the main reason for the observed counterintuitive decrease in uptake rate constants with increasing octanol/water partition coefficient. Furthermore, estimations of the time needed to reach steady state indicated that durations of more than a month could be needed for compounds with a log Kow > 8, limiting the experimental applicability of the test. In those cases, model-based bioconcentration predictions could be a preferable approach, which could be combined with in vitro biotransformation measurements. However, our sensitivity analysis showed that the uncertainty in determining the octanol/water partition coefficients is a strong source of error for superhydrophobic compounds.

Realistic environmental exposure to secondary PET microplastics induces biochemical responses in freshwater amphipod Hyalella azteca

ABSTRACT Freshwater environments are especially susceptible to microplastic contamination due to their proximity to urbanised and industrial areas. Also, there is a lack of information about the effects of this pollutant on freshwaters making it difficult the conservation of these environments. Benthic species, such as the freshwater amphipod Hyalella azteca, have been superficially studied so far for evaluation of microplastic pollution. In the present study, we analyzed whether polyethylene terephthalate (PET) microplastics could lead to reduced survival of H. azteca or changes in biochemical markers (SOD, CAT, MDA, and GST) at environmentally relevant concentrations (60 and 600 particles) after 7 d of exposure. The results showed that there was no significant mortality at any of the concentrations tested. The enzyme CAT showed no variation compared to the control group at any of the concentrations. SOD, MDA, and GST were statistically different (p < 0.05). Our study demonstrated that PET MP did not affect the survival of H. azteca at environmentally relevant concentrations. However, changes in biomarkers of oxidative stress may be detected at low level of exposure (60 particles). Although survival is not affected, the macrobenthic invertebrate community may be under threat in environments where there is PET microplastic pollution.

Invertebrate Species for the Bioavailability and Accumulation Assessment of Manufactured Polymer-Based Nano- and Microplastics.

Bioaccumulation tests with invertebrates have recently been discussed as a suitable alternative to bioaccumulation tests with metal- or metal oxide-based nanoparticles in fish for regulatory assessment. In the present study, as a first step, we investigated the suitability of three invertebrate species for bioaccumulation tests with nano- and microplastics. In a laboratory approach the freshwater bivalve Corbicula fluminea, the freshwater amphipod Hyalella azteca, and the terrestrial isopod Porcellio scaber were exposed to fluorescently labeled nano- and microplastics to evaluate their suitability to estimate the bioavailability and bioaccumulation of these test items. No bioaccumulation was observed in H. azteca or P. scaber. In contrast, the measurement of the relative fluorescence of the test items in the soft tissue and the feces of the filter-feeding bivalve allowed us to derive data that may be useful for the regulatory bioaccumulation assessment of manufactured nano- and microplastics. The developed measurement method using fluorescence represents a time-efficient and cost-effective analytical method for manufactured nano- and microplastics in laboratory studies for regulatory assessment. Environ Toxicol Chem 2022;41:961-974. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Spatiotemporal Distribution of Hydrophobic Organic Contaminants in Spiked-Sediment Toxicity Tests: Measuring Total and Freely Dissolved Concentrations in Porewater and Overlying Water.

The sediment–water interface of spiked‐sediment toxicity tests is a complex exposure system, where multiple uptake pathways exist for benthic organisms. The freely dissolved concentration (C free) in sediment porewater has been proposed as a relevant exposure metric to hydrophobic organic contaminants (HOCs) in this system. However, C free has rarely been measured in spiked‐sediment toxicity tests. We first developed a direct immersion solid‐phase microextraction method for measuring C free in overlying water and porewater in a sediment test using polydimethylsiloxane‐coated glass fibers, resulting in sensitive and repeatable in situ measurements of HOCs. Then, we measured C free and total dissolved concentrations (C diss) in the sediment test systems with the freshwater amphipod Hyalella azteca and thoroughly evaluated the temporal and spatial profiles of four HOCs (phenanthrene, pyrene, benzo[a]pyrene, and chlorpyrifos). Furthermore, we examined the relationship between the measured concentrations and the lethality of H. azteca. We found that the test system was far from an equilibrium state for all four chemicals tested, where C diss in overlying water changed over the test duration and a vertical C free gradient existed at the sediment–water interface. In porewater C diss was larger than C free by a factor of 170 to 220 for benzo[a]pyrene because of the strong binding to dissolved organic carbon. Comparison of the median lethal concentrations of chlorpyrifos in the sediment test and those in water‐only tests indicates that C free in porewater was the most representative indicator for toxicity of this chemical. The method and findings presented in the present study warrant further research on the chemical transport mechanisms and the actual exposure in sediment tests using different chemicals, sediments, and test species. Environ Toxicol Chem 2021;40:3148–3158. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Testing the bioaccumulation potential of manufactured nanomaterials in the freshwater amphipod Hyalella azteca

Standardized experimental approaches for the quantification of the bioaccumulation potential of nanomaterials in general and in (benthic) invertebrates in particular are currently lacking. We examined the suitability of the benthic freshwater amphipod Hyalella azteca for the examination of the bioaccumulation potential of nanomaterials. A flow-through test system that allows the generation of bioconcentration and biomagnification factors was applied. The feasibility of the system was confirmed in a 2-lab comparison study. By carrying out bioconcentration and biomagnification studies with gold, titanium dioxide and silver nanoparticles as well as dissolved silver (AgNO3) we were able to assess the bioaccumulation potential of different types of nanomaterials and their exposure pathways. For this, the animals were examined for their total metal body burden using inductively coupled mass spectroscopy (ICP-MS) and for the presence of nanoparticulate burdens using single-particle ICP-MS. The role of released ions was highlighted as being very important for the bioavailability and bioaccumulation of metals from nanoparticles for both examined uptake paths examined (bioconcentration and biomagnification). In 2018 a tiered testing strategy for engineered nanomaterials was proposed by Handy et al. that may allow a waiver of bioaccumulation fish studies using inter alia invertebrates. Data gained in studies carried out with invertebrates like the developed Hyalella azteca test may be included in this proposed tiered testing strategy.

Unravelling the uptake pathway and accumulation of silver from manufactured silver nanoparticles in the freshwater amphipod Hyalella azteca using correlative microscopy

Silver nanoparticles (AgNPs) are known to enter the aquatic environment via leachates from landfills or by the effluent or sludge of sewage treatment plants.Even if the AgNPs are sulfidized, Ag from these particles was shown to still be available to several species like the benthic freshwater amphipod Hyalella azteca. However, it is still unknown if the primary uptake of Ag from these particles occurs mainly by Ag ions, or if the main uptake of Ag is by ingestion of AgNPs and if they can be found in the animal tissues or just in the gut content without any tissue transfer.To elucidate the main uptake pathway and localization of AgNPs potentially taken up by H. azteca, we exposed the amphipods to Ag using AgNP containing sewage sludge or dissolved Ag from AgNO3.Further, we seperated the exposed animals into two groups. One had direct contact to the AgNPs enriched sludge, allowing them to feed on it, the second group seperated from the sludge by a strainer allowing only indirect contact by potentially released AgNPs or ions.The animals exposed for 7 days were examined for their total and nano particulate Ag content using (single-particle) inductively coupled plasma mass spectrometry as well as using methods of correlative microscopy. Thus we were able to show, that low amounts of AgNPs were present exclusively in animals with direct contact to the AgNP enriched sludge and only in the region of the gut. No transfer of AgNPs from the gut into the animals tissue was observed by correlative microscopy. However, measurable Ag body burdens in animals from all treatments and groups indicated that ionic uptake is the main uptake pathway for (bio)accumulation of Ag from AgNPs.

Toxicity of dinonylnaphthalene sulfonates to Pimephales promelas and epibenthic invertebrates

Dinonylnaphthalene sulfonic acids (NSAs) are high production volume chemicals that are used primarily as additives in a wide range of industrial products (i.e., coatings, sealants, fuels, metal-extractants, paints, rubber materials). This study examined the effect of three NSA congeners on freshwater organisms: barium dinonylnaphthalene sulfonate (BaDNS), calcium dinonylnaphthalene sulfonate (CaDNS), and dinonylnaphthalene disulfonic acid (DNDS). Chronic effects were characterized by exposing fertilized fathead minnow eggs to sediment-associated NSAs and measuring various developmental and growth endpoints for 21 d. No effects in hatch success and larval growth were observed when fathead minnow eggs were exposed to CaDNS and DNDS concentrations up to 246 and 798 μg/g dry weight, respectively, in spiked sediment (~2% organic carbon). However, when NSAs were associated with substrate containing no organic carbon (sand), EC50s for fathead minnow hatch success, larval growth, biomass production, and overall survival were 58.3, 18.8, 15.5, and 13.8 μg/L, respectively, for CaDNS. Acute effect characterization was also conducted in water-only exposures for the three NSA congeners using the freshwater amphipod Hyalella azteca, the pulmonate snail Planorbella pilsbryi, and larval freshwater mussels Lampsilis cardium and Lampsilis siliquoidea. The sulfonate salts (BaDNS and CaDNS) were significantly more acutely toxic to all tested invertebrates in the water-only exposures, with LC50s ranging from 0.47 to 12.1 μg/L, compared to DNDS (LC50s ≥ 98.2 μg/L). This is the first study to provide empirical data on the aquatic toxicity of three NSA congeners.

Acute and chronic toxicity of neonicotinoid and butenolide insecticides to the freshwater amphipod, Hyalella azteca

Neonicotinoids are the most widely used insecticides in the world. They are preferentially toxic to insects while displaying a low toxicity toward vertebrates, and this selective toxicity has resulted in the rapid and ubiquitous use of these compounds. However, neonicotinoids have been detected in agricultural surface waters and are known to cause adverse effects in non-target aquatic organisms. A wide range of toxicity has been reported for aquatic crustaceans, but most of the studies focus on the acute effects of imidacloprid, and few data are available regarding chronic effects of other neonicotinoids or neonicotinoid replacements (e.g., butenolides). The objective of this study was to assess the acute and chronic toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to the freshwater amphipod Hyalella azteca. Chronic (28-d), water-only, static-renewal tests were conducted. Survival was assessed weekly, and growth was measured at the end of the exposure. Effects of neonicotinoids varied depending on the compound. Acute (7-d) LC50s were 4.0, 4.7, 60, 68, 230, and 290 μg/L for clothianidin, acetamiprid, dinotefuran, thiacloprid, imidacloprid, and thiamethoxam, respectively. Chronic (28-d) survival and growth were reduced at similar concentrations to acute (7-d) survival for thiamethoxam, acetamiprid, clothianidin, and dinotefuran. However, chronic survival and growth of amphipods exposed to imidacloprid and thiacloprid were reduced at lower concentrations than acute survival, with respective 28-d LC50s of 90 and 44 μg/L, and EC50s of 4 and 3 μg/L. Flupyradifurone was intermediate in toxicity compared to the neonicotinoids: 7-d LC50, 28-d LC50, and 28-d EC50 were 26, 20, and 16 μg/L, respectively. The concentrations of imidacloprid and clothianidin reported for North American surface waters fall within the effect ranges observed in this study, indicating the potential for these compounds to cause adverse effects to indigenous populations of H. azteca.

Derivation of combined species sensitivity distributions for acute toxicity of pyrethroids to aquatic animals

The aquatic toxicity profiles of synthetic pyrethroid insecticides are remarkably similar, and results for a large number of species can be combined across compounds in Species Sensitivity Distributions (SSDs). Normalizing acute toxicity values (median lethal concentrations, LC50s) for each species and each pyrethroid to the LC50 of the same pyrethroid to the freshwater amphipod Hyalella azteca (the most sensitive species to all pyrethroids tested) enabled expression of LC50s as Hyalella equivalents that can be pooled across pyrethroids. The resulting normalized LC50s (geometric means for each species across pyrethroids) were analyzed using SSDs. Based on tests with measured exposure concentrations, the fifth percentiles (Hazard Concentrations, HC5s) of the SSDs were 4.8 Hyalella equivalents for arthropods (36 species) and 256 Hyalella equivalents for fish (24 species). HC5 values are useful as effects metrics for screening-level risk assessments, and the full SSDs can be integrated with estimated exposure distributions for higher-level risk characterization. The combined pyrethroid SSDs provide a more taxonomically representative and statistically robust basis for risk characterization than data for the most sensitive single species or SSDs based on data for a single pyrethroid alone, and are especially useful for pyrethroids that have been tested with smaller numbers of species.

Bioconcentration studies with the freshwater amphipod Hyalella azteca: are the results predictive of bioconcentration in fish?

Bioconcentration factors (BCF) for regulatory purposes are usually determined by fish flow-through tests according to technical guidance document OECD 305. Fish bioconcentration studies are time consuming, expensive, and use many laboratory animals. The aim of this study was to investigate whether the freshwater amphipod Hyalella azteca can be used as an alternative test organism for bioconcentration studies. Fourteen substances of different hydrophobicity (log Kow 2.4–7.6) were tested under flow-through conditions to determine steady state and kinetic bioconcentration factors (BCFss and BCFk). The results were compared with fish BCF estimates for the same substances described in the literature to show the relationship between both values. Bioconcentration studies with the freshwater amphipod H. azteca resulted in BCF estimates which show a strong correlation with fish BCF values (r2 = 0.69). Hyalella BCF values can be assessed in accordance with the regulatory B criterion (BCF > 2000, i.e., REACH) and thereby enable the prediction of B or non-B classification in the standard fish test. Therefore, H. azteca has a high potential to be used as alternative test organism to fish for bioconcentration studies.

Silver nanoparticles in sewage treatment plant effluents: chronic effects and accumulation of silver in the freshwater amphipod Hyalella azteca

BackgroundIncreasing amounts of engineered nanoparticles (NPs) in wastewater can reach the aquatic environment by passing through the sewage treatment plant (STP). NPs can induce ecotoxicological effects due to their specific chemical properties. However, their bioavailability and toxicity are potentially influenced by transformation processes caused by substances present in the STP, e.g., humic acids or sulfides. Due to the lack of a test system allowing to test NPs under realistic environmental conditions, we coupled two existing test systems, the activated sludge simulation test (OECD TG 303A 2001) and the chronic exposure test with the freshwater amphipod Hyalella azteca (Environment Canada 2013), to gain a test scenario that allows to consider the altered behavior and fate of NPs induced by the STP process. This should improve the environmental realism of the chronic exposure test with Hyalella. In the first study, we tested the STP effluent containing AgNPs. In the second and third study, tap water and control STP effluent were spiked with AgNPs and used as test media.ResultsThe chronic exposure studies with the freshwater amphipod H. azteca showed that the investigated AgNPs lose most of their toxicity while passing through the STP. Over all studies with total Ag concentrations ranging from 0.85 to 68.70 µg/L, significant effects of the AgNPs were only observed in the survival of test animals exposed to tap water containing the highest Ag concentration (62.59 µg/L). Accumulation of silver in the body of test animals was clearly dependent on the pretreatment of the AgNPs. Silver ions (Ag+) released from AgNPs are supposed to be the major pathway leading to body burden following exposure to test media containing AgNPs.ConclusionThe coupled test system is suitable for testing substances that can reach the environment via the STP effluent. The investigated AgNPs lose most of their toxicity while passing through the STP. Accumulation of silver in the animals exposed to the different treatments was apparent, whereby silver ions (Ag+) released from AgNPs were supposed to be the major pathway leading to body burden.

Individual and Combined Effects of Petroleum Hydrocarbons Phenanthrene and Dibenzothiophene on Reproductive Behavior in the Amphipod Hyalella azteca

Predicting impacts of oil spills on the environment requires a better understanding of the effects on aquatic organisms, both for single hydrocarbons and for their interactions. In this study, the individual and combined effects of the petroleum hydrocarbons phenanthrene and dibenzothiophene (DBT) were assessed on the reproductive behavior of the freshwater amphipod Hyalella azteca. Following a 24-h exposure to single polycyclic aromatic hydrocarbons (PAHs), or an equimolar mixture of phenanthrene–dibenzothiophene (Phen–DBT), mate-guarding behavior was assessed. This consisted of an assessment of the incidence of mate guarding right at the end of the exposure period and quantification of the “time taken to initiate mate guarding” (TIMG) and “proportion of time spent mate guarding” (PTMG) during a subsequent 10-min observation period in clean water. Both Phen and DBT reduced the incidence of mate guarding at the end of the exposure. TIMG and PTMG during the observation period were not affected by the PAHs other than indirectly by their effect on mate guarding status at the end of the exposure. The interaction between Phen and DBT varied among the mate guarding measures. For mate guarding status at the end of the exposure period and for TIMG, the interaction did not deviate statistically from an additive effect. For PTMG, the overall interaction was a synergistic one. This study’s findings point out that assessments of hydrocarbon toxicity need to take into account that subtle reproductive behaviors (that may be important for population persistence) may be negatively affected. The results also show that the general assumption of additive effects among PAHs may be an oversimplification.

Interlaboratory validation of organism recovery for use in 42-day sediment toxicity tests with Hyalella azteca.

Environment and Climate Change Canada has developed a 42-d sediment toxicity test that includes a reproduction endpoint with the freshwater amphipod Hyalella azteca. The new methodology conducts the entire exposure in sediment, in contrast to existing standardized methods whereby adults are transferred to a water-only exposure before release of their first brood at day 28. This midtest transfer to clean water was because of the results of a juvenile H. azteca recovery trial conducted in the 1990s concluding that reproductive endpoints could be biased because of low recovery of young amphipods from sediment. Using a new procedure and reduced volume of sediment, an interlaboratory recovery trial was conducted using 2-d to 5-d old H. azteca added to control sediment. A total of 29 technicians from 8 laboratories participated in the present study. The average recovery for all laboratories and all technicians was 76% (coefficient of variation [CV] = 30%). Based on an initial target recovery of at least 80%, 19 of 29 (66%) technicians met this criterion, with an average recovery for this group of 88% (CV = 8.3%). Factors that reduced recovery success included: not using a light table, technicians with minimal sediment testing experience, and the use of imported young amphipods with limited acclimation. Excluding those results, the overall average recovery, which included 17 participating technicians, increased from 76% to 88% and lowered the CV from 30% to 8.6%. Based on these results, Environment and Climate Change Canada will recommend ≥85% average recovery of young in control sediment and require ≥80% as a technician performance criterion in its new test design for the reproduction methodology. Environ Toxicol Chem 2017;36:1085-1089. © 2016 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Validation of a new standardized test method for the freshwater amphipod Hyalella azteca: Determining the chronic effects of silver in sediment.

Environment Canada has developed a new 42-d sediment toxicity test method that includes a reproduction test endpoint with the freshwater amphipod Hyalella azteca. Because of concerns that existing standard methodologies, whereby adults are transferred to a water-only exposure before release of their first brood at day 28, will lead to internal contaminant depuration and loss of sensitivity, the Environment Canada methodology conducts the entire exposure in sediment. To demonstrate applicability of the method for assessing the toxicity of chemical-spiked sediment, H. azteca were exposed for 42 d to sediment amended with silver nitrate (AgNO3 ). Mortality was significantly higher at the highest sediment concentration of Ag (2088 mg/kg dry wt); however, there was no significant reduction in biomass or reproduction as a result of Ag exposure despite significant bioaccumulation. Based on Ag measurements and speciation modeling, the principle route of Ag exposure was likely through the ingestion of complexed colloidal or particulate Ag. The techniques used to recover young amphipods from sediment were critical, and although this effort can be labor intensive (20-45 min/replicate), the technicians demonstrated 91% recovery in blind trials. For the first time, Environment Canada will require laboratories to report their recovery proficiency for the 42-d test-without this information, data will not be accepted. Overall, the reproduction test will be more applicable when only a few chemical concentrations need to be evaluated in laboratory-amended sediments or for field-collected contaminated site assessments (i.e., contaminated site vs reference site comparisons). Environ Toxicol Chem 2016;35:2430-2438. © 2016 SETAC.

Navigating the tmdl process: sediment toxicity

A key step in the development of Total Maximum Daily Load (TMDL) allocations for water bodies impaired due to sediment toxicity is the identification of chemicals responsible for toxicity. Sediment toxicity identification evaluation procedures (TIEs) are one of the primary tools used in this process. This project evaluated standardized and recently developed sediment TIE methods developed by the US EPA and others, to determine their utility for identifying chemicals responsible for toxicity. In this study, formulated sediments were spiked with five chemicals: copper, fluoranthene, tetrachlorobenzene, nonylphenol and ammonia. Experiments were conducted using sediments spiked with single chemicals and chemical mixtures. Toxicity tests used the estuarine amphipod Eohaustorius estuarius and the freshwater amphipod Hyalella azteca. TIEs were conducted using solid-phase (whole sediment) and sediment interstitial waters. Our results indicate that the TIE methods are sufficient to characterize and identify toxicity due to single and multiple chemicals using spiked sediments. One key finding from the spiked sediment experiments is that methods to elute chemicals from extraction media used in solid-phase and interstitial water TIEs require further refinement to ensure complete and consistent elution of sorbed chemicals. An additional finding is that both solid-phase and interstitial water TIE procedures provide useful lines of evidence and that both approaches should be used in a weight-of-evidence approach in the sediment TIE process. In the final phase of this project, we evaluated the TIE procedures using ambient samples collected from three marine sites and three freshwater sites. Marine sediments were collected from Switzer Creek in San Diego Bay, Upper Newport Bay in Newport Beach, and Consolidated Slip, in Long Beach Harbor, all of which are sites in southern California. Freshwater sediments were collected from two additional sites in California: San Diego Creek, in Newport Beach, and Alisal Slough, in Salinas. The final freshwater sediment was collected from a site in Indiana Harbor. Multiple solid-phase and interstitial water TIEs were conducted on each sediment and results of these were combined with chemical analyses and other lines-of-evidence to evaluate the methods. The results indicate that sediment TIE methods are sufficiently developed to characterize toxicity due to general classes of chemicals such as cationic metals, organic chemicals, and ammonia. Methods to improve extraction and elution of metal and organic chemicals in highly toxic sediments require further refinement in order to allow identification of specific chemicals responsible for toxicity as part of the Phase II TIE process. These refinements include determining the appropriate masses of solid-phase extraction media to allow complete removal of toxic chemicals from sediments and interstitial waters. In addition, we recommend that additional studies be designed to determine optimal equilibration periods to maximize removal of toxic chemicals using resin amendments in solid-phase sediment TIEs. As in the spiked-sediment TIEs, we observed inconsistent elution of toxic chemicals from extraction media used in solid-phase and interstitial water Phase II TIEs with the ambient samples. These procedures require additional work to ensure that chemicals responsible for toxicity are completely eluted from extraction media. Improvement of the Phase II TIE elution and solvent handling steps should facilitate better identification of chemicals responsible for toxicity, particularly in situations where toxicity is due to highly insoluble chemicals. When these considerations are satisfactorily addressed, the methods evaluated are capable of providing useful lines of evidence that can be combined to successfully identify sediment toxicants. This title belongs to WERF Research Report Series ISBN: 9781843397663 (Print) ISBN: 9781780403786 (eBook)

Description of two new species of Hyalella(Amphipoda: Hyalellidae) from Eastern North America with a revised key to North American members of the genus

Since the 1990s, it has been presumed that different populations/size classes of the freshwater amphipod Hyalella azteca (Saussure, 1858) were different species, and a multitude of genetic evidence was later produced to confirm that it is in fact a cryptic species complex. However, no new species of Hyalella have been described from the eastern United States or Canada since then. Herein we describe two new species, Hyalella ( Hyalella ) spinicauda and Hyalella ( Hyalella ) wellborni , collected from Illinois, Indiana, Michigan, Wisconsin, and Texas, USA, and Ontario, Canada, based on morphological characters but informed by genetic analyses. In addition, we provide an updated key to the described species of Hyalella in North America and the Caribbean.

Predicting toxicity to Hyalella azteca in pyrogenic-impacted sediments-Do we need to analyze for all 34 PAHs?

Polycyclic aromatic hydrocarbons (PAHs) are major drivers of risk at many urban and/or industrialized sediment sites. The US Environmental Protection Agency (USEPA) currently recommends using measurements of 18 parent + 16 groups of alkylated PAHs (PAH-34) to assess the potential for sediment-bound PAHs to impact benthic organisms at these sites. ASTM Method D7363-13 was developed to directly measure low-level sediment porewater PAH concentrations. These concentrations are then compared to ambient water criteria (final chronic values [FCVs]) to assess the potential for impact to benthic organisms. The interlaboratory validation study that was used to finalize ASTM D7363-13 was developed using 24 of the 2-, 3-, and 4-ring PAHs (PAH-24) that are included in the USEPA PAH-34 analyte list. However, it is the responsibility of the user of ASTM Method D7363 to establish a test method to quantify the remaining 10 higher molecular weight PAHs that make up PAH-34. These higher molecular weight PAHs exhibit extremely low saturation solubilities that make their detection difficult in porewater, which has proven difficult to implement in a contract laboratory setting. As a result, commercial laboratories are hesitant to conduct the method on the entire PAH-34 analyte list. This article presents a statistical comparison of the ability of the PAH-24 and PAH-34 porewater results to predict survival of the freshwater amphipod Hyalella azteca, using the original 269 sediment samples used to gain ASTM D7363 Method approval. The statistical analysis shows that the PAH-24 are statistically indistinguishable from the PAH-34 for predicting toxicity. These results indicate that the analysis of freely dissolved porewater PAH-24 is sufficient for making risk-based decisions based on benthic invertebrate toxicity (survival and growth). This reduced target analyte list should result in a cost-saving for stakeholders and broader implementation of the method at PAH-impacted sediment sites. Integr Environ Assess Manag 2016;12:493-499. © 2015 SETAC.

Temporal and spatial trends in sediment contaminants associated with toxicity in California watersheds

California's Stream Pollution Trends program (SPoT) assesses long-term water quality trends, using 100 base-of-the-watershed sampling sites. Annual statewide sediment surveys from 2008 to 2012 identified consistent levels of statewide toxicity (19%), using the freshwater amphipod Hyalella azteca. Significant contaminant trends included a decrease in PCBs, stable concentrations of metals and PAHs, and a statewide increase in detections and concentrations of pyrethroid pesticides. The pyrethroid pesticide bifenthrin was detected in 69% of samples (n = 410). Detection of toxicity increased in a subset of samples tested at a more environmentally relevant test temperature (15 °C), and the magnitude of toxicity was much greater, indicating pyrethroid pesticides as a probable cause. Pyrethroid toxicity thresholds (LC50) were exceeded in 83% of samples with high toxicity. Principal components analysis related pyrethroids, metals and total organic carbon to urban land use.