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Selenium (Se) is a contaminant of concern in Canada mainly due to its teratogenic effects on fish and birds. However, few studies have assessed the effects of Se on invertebrates in a field setting. The objective of this experiment was to assess potential community‐level impacts of Se additions on zooplankton and benthic macroinvertebrates in a boreal lake ecosystem. From June to August 2018, Se (as selenite) was added to six limnocorrals in Lake 239 at the International Institute for Sustainable Development–Experimental Lakes Area, Northwestern Ontario, Canada, to achieve mean measured aqueous concentrations of 0.4, 0.8, 1.6, 3.4, 5.6 and 7.9 µg Se/L, with three untreated limnocorrals serving as controls (background Se = 0.08–0.09 µg/L). Periphyton, phytoplankton, and invertebrates (zooplankton and benthos) were monitored for 63 days. Zooplankton community composition shifted as a function of Se exposure, with Cladocera biomass and density decreasing with increasing Se concentrations. Similarly, cumulative abundance and biomass of Heptageniidae decreased with increasing Se treatment throughout the experimental period. The present study demonstrated that Se can have impacts on aquatic invertebrates at environmentally relevant exposure levels, and that future ecological risk assessments should consider the impacts of Se on both vertebrates and invertebrates. Environ Toxicol Chem 2022;41:95–107. © 2021 SETAC [ABSTRACT FROM AUTHOR]

To fully assess the long‐term impacts of oil spills like the 2010 Deepwater Horizon incident in the northern Gulf of Mexico, the potential for organisms other than microbes to affect the fate and distribution of the oil may have to be considered. This influence could be substantial for abundant bioturbating benthic animals like the ghost shrimp Lepidophthalmus louisianensis. An assessment of the influence of these ghost shrimp on petroleum hydrocarbons was conducted in laboratory micro‐ and mesocosms containing coastal Gulf of Mexico sediment, seawater, and oil or the polynuclear aromatic hydrocarbon (PAH) pyrene. In an experiment with pyrene added to the water column, the ghost shrimp presence lowered water‐column pyrene concentrations. In an experiment with oil added to the sediment surface, the ghost shrimp presence decreased PAH concentrations in the sediment surface layer but increased these in the water column and subsurface sediment. A companion study and a mass‐balance analysis indicated a net loss of PAHs through an enhancement of microbial degradation. In an experiment in which oil was added as a narrow subsurface layer in the sediment, the ghost shrimp presence appeared to broaden the oil's depth distribution. Taken together, these results demonstrate that ghost shrimp can significantly influence the biodegradation and distribution of spilled oil in coastal ecosystems. Environ Toxicol Chem 2020;39:637–647. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Sediments from the Upper Columbia River, Washington, USA, are contaminated with metals from smelting operations. We conducted short‐term and long‐term tests with the midge Chironomus dilutus and the amphipod Hyalella azteca and short‐term tests with the freshwater mussel Lampsilis siliquoidea with 54 sediments from the Upper Columbia River to characterize thresholds for toxicity of metals to benthic invertebrates. Test sediments were screened for toxicity by comparisons with low‐metal reference sediments. Toxic effects on amphipods occurred primarily in sediments from the upstream (riverine) reach, and toxic effects on midges occurred in sediments from both the upstream reach and the downstream (reservoir) reach. Little toxicity was observed in mussel tests. Toxicity thresholds (20% effect concentrations [EC20s]) for metals in sediment and porewater were estimated from logistic concentration–response models. Copper (Cu) concentrations in the simultaneously extracted metal fraction of sediments and bioavailable Cu in porewater, as characterized by biotic ligand models, had consistent associations with toxicity endpoints. Concentration–response models for sediment Cu produced EC20s for 6 endpoints, with long‐term amphipod survival and reproduction being the most sensitive. A logistic regression model fitted to an endpoint sensitivity distribution for sediment Cu predicted that approximately one‐half of the sediments tested would be toxic to at least one endpoint and that approximately 20% of test sediments would be toxic to more than half of the endpoints. These results indicate that sediments from the upstream reach of the Upper Columbia River, which contain high concentrations of metals associated with slags, cause a wide range of toxic effects in laboratory tests and are likely to have adverse effects on benthic invertebrate communities. Environ Toxicol Chem 2018;37:3102–3114. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America. [ABSTRACT FROM AUTHOR]

The importance of pyrethroids as potential stressors to benthic organisms has gradually become evident in urban creeks; however, the occurrence and toxicity of sediment-associated pyrethroids are rarely studied in large rivers. In this context, 10 sediments from a large urban river (Guangzhou reach of the Pearl River in China) were assessed for pyrethroid occurrence and sediment toxicity to the benthic invertebrate Chironomus dilutus. One half of the sediments exhibited lethality to C. dilutus in a 10-d exposure and all surviving midges showed significant change of enzymatic activity. Moreover, mortality occurred during a 20-d exposure for all the sediments, in accordance with the high hazard quotients to benthic species estimated from pyrethroid residues in sediment. Pyrethroids were detectable in all sediments with the concentrations ranging from 2.43 to 61.2 ng/g dry weight, and permethrin and cypermethrin dominated pyrethroid composition. Acute toxic units for pyrethroids ranged from 0.03 to 0.56 (cypermethrin accounted for 13-81%) and showed a direct relationship with sediment mortality among the midges. This is consistent with the studies on small creeks in Guangzhou in which sediment-bound cypermethrin was found as a main stressor to benthic invertebrates. Comparatively, sediment toxicity and pyrethroid residues in large rivers were significantly lower than those in nearby creeks (urban tributaries). The difference may be partially explained by differing flow rates and water-carrying capacity among waterbodies at different scales; further validation is required. Overall, extensive use of pyrethroids has caused a threat to benthic species not only in small creeks but also in large rivers. Environ Toxicol Chem 2017;36:3367-3375. © 2017 SETAC [ABSTRACT FROM AUTHOR]

Biomarkers are widely used in ecotoxicology as indicators of exposure to toxicants. However, their ability to provide ecologically relevant information remains controversial. One of the major problems is understanding whether the measured responses are determined by stress factors or lie within the natural variability range. In a previous work, the natural variability of enzymatic levels in invertebrates sampled in pristine rivers was proven to be relevant across both space and time. In the present study, the experimental design was improved by considering different life stages of the selected taxa and by measuring more environmental parameters. The experimental design considered sampling sites in 2 different rivers, 8 sampling dates covering the whole seasonal cycle, 4 species from 3 different taxonomic groups (Plecoptera, Perla grandis; Ephemeroptera, Baetis alpinus and Epeorus alpicula; Tricoptera, Hydropsyche pellucidula), different life stages for each species, and 4 enzymes (acetylcholinesterase, glutathione S-transferase, alkaline phosphatase, and catalase). Biomarker levels were related to environmental (physicochemical) parameters to verify any kind of dependence. Data were statistically elaborated using hierarchical multilevel Bayesian models. Natural variability was found to be relevant across both space and time. The results of the present study proved that care should be paid when interpreting biomarker results. Further research is needed to better understand the dependence of the natural variability on environmental parameters. Environ Toxicol Chem 2017;36:3158-3167. © 2017 SETAC [ABSTRACT FROM AUTHOR]

Greenwich Bay is an urbanized embayment of Narragansett Bay potentially impacted by multiple stressors. The present study identified the important stressors affecting Greenwich Bay benthic fauna. First, existing data and information were used to confirm that the waterbody was impaired. Second, the presence of source, stressor, and effect were established. Then linkages between source, stressor, and effect were developed. This allows identification of probable stressors adversely affecting the waterbody. Three pollutant categories were assessed: chemicals, nutrients, and suspended sediments. This weight of evidence approach indicated that Greenwich Bay was primarily impacted by eutrophication-related stressors. The sediments of Greenwich Bay were carbon enriched and low dissolved oxygen concentrations were commonly seen, especially in the western portions of Greenwich Bay. The benthic community was depauperate, as would be expected under oxygen stress. Although our analysis indicated that contaminant loads in Greenwich Bay were at concentrations where adverse effects might be expected, no toxicity was observed, as a result of high levels of organic carbon in these sediments reducing contaminant bioavailability. Our analysis also indicated that suspended sediment impacts were likely nonexistent for much of the Bay. This analysis demonstrates that the diagnostic procedure was useful to organize and assess the potential stressors impacting the ecological well-being of Greenwich Bay. This diagnostic procedure is useful for management of waterbodies impacted by multiple stressors. Environ Toxicol Chem 2017;36:449-462. © 2016 SETAC [ABSTRACT FROM AUTHOR]

In 2007, approximately 420 500 cubic meters of contaminated sediment were removed from the Ashtabula River by dredging. The primary objective of the present study was to monitor contaminant exposure in fish and macroinvertebrates before, during, and after dredging. This was done by measuring tissue concentrations of polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH) in brown bullhead catfish ( Ameriurus nebulosa) and in benthic macroinvertebrates, assessing changes in DNA damage in fish liver and blood, and scoring external and histopathological lesions and anomalies in the fish. In surficial sediment PCBs and PAHs were also quantified in conjunction with the biological sampling. The results show a significant reduction in contaminant levels in both fish and macroinvertebrates following dredging, indicating the effectiveness of the remediation in reducing exposure of biota to the primary contaminants of concern. Similarly, DNA damage levels in fish collected from the Ashtabula River significantly declined following dredging; however, a similar reduction in DNA damage over time was seen in fish collected from a reference site (Conneaut Creek), making interpretation difficult. Macroinvertebrate PCB concentrations were reflective of the sediment concentrations in the areas where Hester-Dendy samplers were deployed for macroinvertebrate collection. The present study demonstrates that these methods can be used to evaluate and assess the effectiveness of remediation techniques at contaminated sediment sites. Environ Toxicol Chem 2015;34:1267-1276. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Sediment quality values (SQV) are commonly used-and misused-to characterize the need for investigation, understand causes of observed effects, and derive management strategies to protect benthic invertebrates from direct toxic effects. The authors compiled more than 40 SQVs for mercury, nearly all of which are 'co-occurrence' SQVs derived from databases of paired chemistry and benthic invertebrate effects data obtained from field-collected sediment. Co-occurrence SQVs are not derived in a manner that reflects cause-effect, concentration-response relationships for individual chemicals such as mercury, because multiple potential stressors often co-occur in the data sets used to derive SQVs. The authors assembled alternative data to characterize mercury-specific effect thresholds, including results of 7 laboratory studies with mercury-spiked sediments and 23 studies at mercury-contaminated sites (e.g., chloralkali facilities, mercury mines). The median (± interquartile range) co-occurrence SQVs associated with a lack of effects (0.16 mg/kg [0.13-0.20 mg/kg]) or a potential for effects (0.88 mg/kg [0.50-1.4 mg/kg]) were orders of magnitude lower than no-observed-effect concentrations reported in mercury-spiked toxicity studies (3.3 mg/kg [1.1-9.4 mg/kg]) and mercury site investigations (22 mg/kg [3.8-66 mg/kg]). Additionally, there was a high degree of overlap between co-occurrence SQVs and background mercury levels. Although SQVs are appropriate only for initial screening, they are commonly misused for characterizing or managing risks at mercury-contaminated sites. Spiked sediment and site data provide more appropriate and useful alternative information for characterization and management purposes. Further research is recommended to refine mercury effect thresholds for sediment that address the bioavailability and causal effects of mercury exposure. Environ Toxicol Chem 2015;34:6-21. © 2014 SETAC [ABSTRACT FROM AUTHOR]

Laboratory and mesocosm experiments have demonstrated that some glyphosate-based herbicides can have negative effects on benthic invertebrate species. Although these herbicides are among the most widely used in agriculture, there have been few multiple-stressor, natural system-based investigations of the impacts of glyphosate-based herbicides in combination with fertilizers on the emergence patterns of chironomids from wetlands. Using a replicated, split-wetland experiment, the authors examined the effects of 2 nominal concentrations (2.88 mg acid equivalents/L and 0.21 mg acid equivalents/L) of the glyphosate herbicide Roundup WeatherMax, alone or in combination with nutrient additions, on the emergence of Chironomidae (Diptera) before and after herbicide-induced damage to macrophytes. There were no direct effects of treatment on the structure of the Chironomidae community or on the overall emergence rates. However, after macrophyte cover declined as a result of herbicide application, there were statistically significant increases in emergence in all but the highest herbicide treatment, which had also received no nutrients. There was a negative relationship between chironomid abundance and macrophyte cover on the treated sides of wetlands. Fertilizer application did not appear to compound the effects of the herbicide treatments. Although direct toxicity of Roundup WeatherMax was not apparent, the authors observed longer-term impacts, suggesting that the indirect effects of this herbicide deserve more consideration when assessing the ecological risk of using herbicides in proximity to wetlands. Environ Toxicol Chem 2014; 33:2076-2085. © 2014 SETAC [ABSTRACT FROM AUTHOR]

An in situ caging study was conducted downstream of a metal mine in northern Canada to determine the significance of surface water versus sediment exposure on selenium (Se) bioaccumulation in the benthic invertebrate Chironomus dilutus. Laboratory-reared C. dilutus larvae were exposed to either site-specific whole-sediment and surface water or surface water only for 10 d at sites with differing sediment and Se characteristics. Results showed elevated whole-body Se concentrations in C. dilutus larvae when exposed to sediment and water, compared with larvae exposed to Se in the surface water only at concentrations ranging from <1 µg Se/L to 12 µg Se/L. In response to these findings, a second in situ experiment was conducted to investigate the importance of dietary Se (biofilm and detritus) versus whole-sediment-exposure pathways. Larvae exposed to sediment detritus had the highest Se concentrations after 10 d of exposure (15.6 ± 1.9 µg/g dry wt) compared with larvae exposed to whole-sediment (12.9 ± 1.7 µg/g dry wt) or biofilm (9.9 ± 1.6 µg/g dry wt). Detritus and biofilm appear to be enriched sources of organic Se, which are more bioaccumulative than inorganic Se. Midge larvae from the reference treatment contained elevated concentrations of diselenides (i.e., selenocystine), while larvae from the biofilm treatment had the highest concentrations of selenomethionine-like compounds, which may be a biomarker of elevated Se exposures derived from anthropogenic sources. Whenever possible, Se concentrations in the organic fraction of sediment should be measured separately from whole-sediment Se and used for more accurate ecological risk assessments of potential Se impacts on aquatic ecosystems. Environ Toxicol Chem 2013;32:2836-2848. © 2013 SETAC [ABSTRACT FROM AUTHOR]

Amendment of activated carbon to sediments has been shown to effectively reduce the bioavailability of hydrophobic organic contaminants, but concerns have been raised about the potential toxicological impacts of administering a strong sorbent into sediments. The present study provides a summary of several investigations carried out as part of a pilot-scale study in a river to understand the secondary effects of activated carbon added to reduce the bioavailability of sediment-associated polychlorinated biphenyls. While some previous laboratory amendment studies have found reduced lipid content in freshwater worms exposed to activated carbon-treated sediments, the authors did not observe an impact with fine-granular activated carbon-amended sediments aged in the field. Benthic community studies did not find differences between control and activated carbon-treated field sites over 3 yr of postapplication monitoring. Laboratory studies with submerged aquatic plants indicated reduced growth in sediments amended with ≥5% activated carbon, which was attributed to volume dilution of nutritional sediment or bulk density changes and was also observed when the sediment was amended with biochar and inert perlite. Since in situ sorbent amendment is likely to be implemented in depositional sediment environments, potential negative impacts will likely be short-term if the treated site is slowly covered with new sediment over time. Overall suitability of activated carbon amendment for a site will depend on balancing ecosystem and human health benefits from contaminant bioavailability reduction with any potential negative impacts expected under field conditions. Environ Toxicol Chem 2013;32:1504-1515. © 2013 SETAC [ABSTRACT FROM AUTHOR]

As the use of single-walled carbon nanotubes (SWNTs) increases over time, so does the potential for environmental release. This research aimed to determine the toxicity, bioavailability, and bioaccumulation of SWNTs in marine benthic organisms at the base of the food chain. The toxicity of SWNTs was tested in a whole sediment exposure with the amphipod Ampelisca abdita and the mysid Americamysis bahia. In addition, SWNTs were amended to sediment and/or food matrices to determine their bioavailability and bioaccumulation through these routes in A. abdita, A. bahia, and the estuarine amphipod Leptocheirus plumulosus. No significant mortality to any species via sediment or food matrices was observed at concentrations up to 100 ppm. A novel near-infrared fluorescence spectroscopic method was utilized to measure and characterize the body burdens of pristine SWNTs in nondepurated and depurated organisms. We did not detect SWNTs in depurated organisms but quantified them in nondepurated A. abdita fed SWNT-amended algae. After a 28-d exposure to [14C]SWNT-amended sediment (100 µg/g) and algae (100 µg/g), [14C]SWNT was detected in depurated and nondepurated L. plumulosus amphipods at 0.50 µg/g and 5.38 µg/g, respectively. The results indicate that SWNTs are bioaccessible to marine benthic organisms but do not appear to accumulate or cause toxicity. Environ Toxicol Chem 2013;32:1270-1277. © 2013 SETAC [ABSTRACT FROM AUTHOR]

Species sensitivity distributions (SSDs) quantify fractions of species potentially affected in contaminated environmental compartments using test species sensitivity data. The present study quantitatively describes associations between predicted and observed ecological impacts of contaminant mixtures, based on monitoring data of benthic macroinvertebrates. Local mixture toxic pressures (multisubstance potentially affected fraction of species [msPAF]) were quantified based on measured concentrations of 45 compounds (eight metals, 16 chlorinated organics, mineral oil, 16 polycyclic aromatic hydrocarbons, four polychlorinated biphenyls), using acute as well as chronic 50%-effective concentration-based SSD-modeling combined with bioavailability and mixture modeling. Acute and chronic toxic pressures were closely related. Generalized linear models (GLMs) were derived to describe taxon abundances as functions of environmental variables (including acute toxic pressure). Acute toxic pressure ranged from 0 to 42% and was related to abundance for 74% of the taxa. Habitat-abundance curves were generated using the GLMs and Monte Carlo simulation. Predicted abundances for the taxa were associated with acute mixture toxic pressure in various ways: negative, positive, and optimum abundance changes occurred. Acute toxic pressure (msPAF) was associated almost 1:1 with the observed fraction of taxa exhibiting an abundance reduction of 50% or more. The findings imply that an increase of mixture toxic pressure associates to increased ecological impacts in the field. This finding is important, given the societal relevance of SSD model outputs in environmental policies. Environ. Toxicol. Chem. 2012; 31: 2175-2188. © 2012 SETAC [ABSTRACT FROM AUTHOR]

The use of sediment quality guidelines to predict the toxicity of metals in sediments is limited by an inadequate understanding of exposure pathways and by poor causal links between exposure and effects. For a 10-d exposure to Cu-spiked sediments, toxicity to the amphipod Melita plumulosa was demonstrated to occur through a combination of dissolved and dietary Cu exposure pathways, but for the bivalves Spisula trigonella and Tellina deltoidalis, toxicity occurred primarily by exposure to dissolved Cu. For relatively oxidized sediments that had moderate amounts of organic carbon (2.6-8.3% OC), silt (20-100% <63-µm particles) but low acid-volatile sulfide (AVS), acute toxicity thresholds for the three species were derived based on the OC-normalized Cu concentration of the less than 63-µm sediment fraction. For all three species, no effects were observed at concentrations below 10 µg/L dissolved Cu (in pore water and overlying water) or below 12 mg Cu/g OC (for <63 µm sediment). For sediments with silt/OC properties of 20/0.5, 50/1, or 70/4%, the particulate Cu-based threshold equated to 60, 120, or 480 mg Cu/kg, respectively. For oxic/suboxic sediments in which AVS is not limiting metal availability, sediment quality guidelines of this form will provide adequate protection against toxicity and improve the prediction of effects for sediments with varying properties. Environ. Toxicol. Chem. 2011; 30:1599-1610. © 2011 SETAC [ABSTRACT FROM AUTHOR]

A field experiment was performed in four freshwater systems to assess the effects of Ni on the benthic macroinvertebrate communities. Sediments were collected from the sites (in Belgium, Germany, and Italy), spiked with Ni, and returned to the respective field sites. The colonization process of the benthic communities was monitored during a nine-month period. Nickel effect on the benthos was also assessed in the context of equilibrium partitioning model based on acid volatile sulfides (AVS) and simultaneously extracted metals (SEM). Benthic communities were not affected at (SEM − AVS) ≤ 0.4 µmol/g, (SEM − AVS)/fraction of organic carbon ( f) < 21 µmol/g organic carbon (OC). Sediments with (SEM − AVS) > 2 µmol/g, (SEM − AVS)/ f > 700 µmol/g OC resulted in clear adverse effects. Uncertainty about the presence and absence of Ni toxicity occurred at (SEM − AVS) and (SEM − AVS)/ f between 0.4 to 2 µmol/g and 21 to 700 µmol/g OC, respectively. The results of our study also indicate that when applying the SEM:AVS concept for predicting metal toxicity in the field study, stressors other than sediment characteristics (e.g., sorption capacity), such as environmental disturbances, should be considered, and the results should be carefully interpreted. Environ. Toxicol. Chem. 2011;30:162-172. © 2010 SETAC [ABSTRACT FROM AUTHOR]

High altitude creates unique challenging conditions to biota that limit the diversity of benthic communities. Because environmental pollution may add further stress to life at high altitude, the present study explored the effect of metal pollution on the macroinvertebrate community composition in Andean streams between 3,500 to 4,500 meters above sea level (masl) during wet and dry seasons. At polluted sites, showing a high conductivity and a low pH, metal concentrations (e.g., Al, 13.07 mg/L; As, 3.49 mg/L; Mn, 19.65 mg/L; Pb, 0.876 mg/L; Zn, 16.08 mg/L) ranged from 8-fold up to 3,500-fold higher than at reference sites. The cumulative criterion unit allowed quantifying the potential toxicity of metal mixtures at the contaminated sites. Principal component analysis of physical chemical variables showed that reference sites were more likely to be structured by transparency, water discharge, and current velocity, while polluted sites appeared to be determined by metals and conductivity. Canonical correspondence analysis indicated a strong influence of highly correlated metals in structuring invertebrate communities, which were dominated by dipterans, coleopterans, collembolans, and mites at polluted sites. At reference sites crustaceans, ephemeropterans, plecopterans, and trichopterans were the most representative taxa. We concluded that severe metal pollution induced changes in macroinvertebrate community composition in high-altitude Andean streams, with a replacement of sensitive taxa by more tolerant taxa. Yet relatively species-rich communities persisted under harsh conditions. Environ. Toxicol. Chem. 2010;29:2761-2768. © 2010 SETAC [ABSTRACT FROM AUTHOR]

The present study evaluated sorbent amendments for in situ remediation of sediments contaminated with two divalent metals. A literature review screening was performed to identify low-cost natural mineral-based metal sorbents and high-performance commercial sorbents that were carried forward into laboratory experiments. Aqueous phase metal sorptivity of the selected sorbents was evaluated because dissolved metals in sediment porewater constitute an important route of exposure to benthic organisms. Based on pH-edge sorption test results, natural sorbents were eliminated due to inferior performance. The potential as in situ sediment amendment was explored by comparing the sorption properties of the engineered amendments in freshwater and saltwater (10 PPT salinity estuarine water) matrices. Self-assembled monolayers on mesoporous supports with thiols (Thiol-SAMMS™) and a titanosilicate mineral (ATS™) demonstrated the highest sorption capacity for cadmium (Cd) and lead (Pb), respectively. Sequential extraction tests conducted after mixing engineered sorbents with contaminated sediment demonstrated transfer of metal contaminants from a weakly bound state to a more strongly bound state. Biouptake of Cd in a freshwater oligochaete was reduced by 98% after 5-d contact of sediment with 4% Thiol-SAMMS and sorbed Cd was not bioavailable. While treatment with ATS reduced the small easily extractable portion of Pb in the sediment, the change in biouptake of Pb was not significant because most of the native lead was strongly bound. The selected sorbents added to sediments at a dose of 5% were mostly nontoxic to a range of sensitive freshwater and estuarine benthic organisms. Metal sorbent amendments in conjunction with activated carbon have the potential to simultaneously reduce metal and hydrophobic contaminant bioavailability in sediments. Environ. Toxicol. Chem. 2010;29:1883–1892. © 2010 SETAC [ABSTRACT FROM AUTHOR]

The present study examined the ability of three chemical estimation methods to predict toxicity and nontoxicity of polycyclic aromatic hydrocarbon (PAH) -contaminated sediment to the freshwater benthic amphipod Hyalella azteca for 192 sediment samples from 12 field sites. The first method used bulk sediment concentrations of 34 PAH compounds (PAH34), and fraction of total organic carbon, coupled with equilibrium partitioning theory to predict pore-water concentrations (KOC method). The second method used bulk sediment PAH34 concentrations and the fraction of anthropogenic (black carbon) and natural organic carbon coupled with literature-based black carbon–water and organic carbon–water partition coefficients to estimate pore-water concentrations (KOCKBC method). The final method directly measured pore-water concentrations (pore-water method). The U.S. Environmental Protection Agency's hydrocarbon narcosis model was used to predict sediment toxicity for all three methods using the modeled or measured pore-water concentration as input. The KOC method was unable to predict nontoxicity (83% of nontoxic samples were predicted to be toxic). The KOCKBC method was not able to predict toxicity (57% of toxic samples were predicted to be nontoxic) and, therefore, was not protective of the environment. The pore-water method was able to predict toxicity (correctly predicted 100% of the toxic samples were toxic) and nontoxicity (correctly predicted 71% of the nontoxic samples were nontoxic). This analysis clearly shows that direct pore-water measurement is the most accurate chemical method currently available to estimate PAH-contaminated sediment toxicity to H. azteca. Environ. Toxicol. Chem. 2010;29:1545–1550. © 2010 SETAC [ABSTRACT FROM AUTHOR]

The influence of diet on polychlorinated biphenyl (PCB) assimilation was investigated by measuring dietary assimilation efficiencies (AEs) for 47 PCB congeners in juvenile koi (Cyprinus carpio) fed five experimental diets. Two of the diets were naturally contaminated and were obtained by collecting mayflies from Lake Erie (ON, Canada) and emerald shiners from the Detroit River (MI, USA). The remaining diets consisted of commercial fish pellets (lipid contents from 6.7 to 24%) that were contaminated by spiking with a PCB mixture. Experimental fish were held individually to quantify the amount of food consumed per fish and, following a 48-h fasting period to facilitate food digestion and assimilation; AEs were determined by mass balance. Fish fed the benthic invertebrate food exhibited the highest PCB AEs (70–101%) and were significantly elevated compared to the other diet treatments (AEs ranging from 23 to 87%). The PCB AEs for fish fed emerald shiners did not differ from those fed pellet formulations. Variation among PCB AEs was not related to diet lipid content. For all diet treatments, PCB AEs were significantly related to chemical hydrophobicity. The relationship between chemical AE and n-octanol/water partition coefficient (KOW) was best explained by a linear model compared to a two-phase resistance model. Overall, PCB AEs were observed to be dependent on both diet type and chemical hydrophobicity, with both factors contributing nearly equally to the variation measured in this toxicokinetic parameter. Environ. Toxicol. Chem. 2010;29:401–409. © 2009 SETAC [ABSTRACT FROM AUTHOR]

A wide range of human pharmaceuticals are present at low concentrations in freshwater systems, particularly in sections of polluted river. These compounds show high biological activity, often associated with a high stability. These characteristics imply a potential impact of these substances on aquatic biota even when present at low environmental concentrations. Low flow conditions in Mediterranean rivers, most of which flow through densely populated areas and are subjected to intensive water use, increase the environmental risk of these emergent compounds. Here, we studied whether pharmaceuticals in river water affect the local benthic community structure (diatoms and invertebrates). For this purpose, we analyzed the occurrence of pharmaceuticals along the Llobregat River and examined the benthic community structure (diatoms and invertebrates) of this system. Some pharmaceutical products in the Llobregat River registered concentrations greater than those cited in the literature. Multivariate analyses revealed a potential causal association between the concentrations of some anti-inflammatories and b-blockers and the abundance and biomass of several benthic invertebrates (Chironomus spp. and Tubifex tubifex). Further interpretation in terms of cause-and-effect relationships is discussed; however, it must be always taken with caution because other pollutants also may have significant contributions. Combined with further community experiments in the laboratory, our approach could be a desirable way to proceed in future risk management decisions. [ABSTRACT FROM AUTHOR]

A bioassay was developed to assess the toxic effects of ingested prey contaminated by polycyclic aromatic hydrocarbons (PAHs) using the teleost Fundulus heteroclitus as a predator and the polychaete Nereis virens as a benthic vector. Ten groups of nine male adult Fundulus were exposed for 21 d to 10 different diets of Nereis contaminated with benzo[a]pyrene (BaP) by spiking dead Nereis with BaP (spiked Nereis [SN] diets, 0-26 μg of BaP per gram dry wt) or by exposing living Nereis to a diet, to sediments, or to both contaminated with BaP (exposed Nereis [EN] diets, 0-16 μg/g dry wt). Another group was exposed to commercial fish food, used as reference diet. Condition and prevalence of histopathological changes were not affected. Exposure to the SN diets containing at least 3.5 μg of BaP per gram dry weight caused an induction of ethoxyresorufin-O-deethylase activity in the intestine but not in the liver. In contrast, fish exposed to the highest doses (≥13.4 μg of BaP per gram dry wt) had increased cellular proliferation rate in the liver but not in the intestine. Quantifiable levels of free BaP tetrol-like metabolites were detected in the bile of fish exposed to diets containing more than 6.8 μg/g dry weight of BaP, and exhibited a dose-response relationship in fish exposed to SN diets. For a similar dose of BaP, EN and SN diets had similar effects. Thus, the BaP metabolic products that could have been produced in Nereis apparently did not contribute to the biomarkers responses. This bioassay can be applied to a variety of prey contaminated naturally or experimentally with PAHs. The present study supports the use of intestinal biomarkers, in addition to hepatic biomarkers, in environmental monitoring to assess the impact of dietary exposure to PAHs. [ABSTRACT FROM AUTHOR]

We examined the influence of heavy metal pollution from an abandoned mine on benthic macroinvertebrates, at population and community levels, and the potential amount of food available for drift-feeding fish in northern Japanese streams. We studied multiple polluted and unpolluted sites with similar longitudinal positions to avoid problems caused by upstream-downstream comparisons. The ranges of zinc, copper, cadmium, and lead concentrations among the study sites were 5 to 812 μg/L, less than 0.12 to 5.2 μg/L, less than 0.0026 to 4.9 μg/L, and 0.1 to 18.6 μg/L, respectively. The abundance of several populations and community metrics showed a significant negative response to heavy metal pollution. Mayfly diversity and abundance was relatively sensitive to heavy metal pollution. In addition, the biomass of groups of macroinvertebrate taxa that are highly available for salmonids were significantly reduced at metal-polluted sites; this decrease in the most highly available group was noticeable (99% at the heavily polluted upper sites and 69% at the moderately polluted lower sites in spring). These results suggest that we should consider the indirect effect of pollution on food availability for the conservation of fish populations that depend on drifting macroinvertebrates. [ABSTRACT FROM AUTHOR]

The global spread of invasive species is changing the structure of aquatic food webs worldwide. The North American Great Lakes have proved particularly vulnerable to this threat. In nearshore areas, invasive benthic species such as dreissenid mussels and round gobies (Neogobius melanostomus) have gained dominance in recent years. Such species are driving the flow of energy and material from the water column to the benthic zone, with dramatic effect on nutrient and contaminant cycling. Here, we develop a stage-structured model of a benthified food web in Lake Michigan with seasonal resolution and show how its bioaccumulation patterns differ from expected ones. Our model suggests that contaminant recycling through the consumption of lipid-rich fish eggs and mussel detritus is responsible for these differences. In southern Lake Michigan's Calumet Harbor (Chicago, IL, USA), round gobies have nitrogen isotope signatures with considerable spread, with some values higher than their predators and others lower than their prey. Contrary to patterns observed in linear pelagic systems, we predict that polychlorinated biphenyl (PCB) concentrations in these fish decrease with increasing size due to the lipid- and benthos-enriched diets of smaller fish. We also present here round goby PCB concentrations measured in 2005 after an invasional succession in Calumet Harbor and demonstrate how the change from one invasive mussel species to another may have led to a decrease in round goby PCB accumulation. Our results suggest that benthic-dominated systems differ from pelagic ones chiefly due to the influence of detritus and that these effects are exacerbated in systems with low species diversity and high biomass. [ABSTRACT FROM AUTHOR]

In artificial streams (pilot rivers) supplied with the river water of Gave de Pau (France), we studied the effects of methyl methacrylate (MMA) on the autochthonous bivalve Unio tumidus transferred into the streams and on natural freshwater communities colonizing the channels. Unio tumidus and freshwater communities were exposed to MMA for 15 and 30 d, respectively, at measured concentrations ranging from 0.6 to 122 mg/L. Biomarkers studied in the digestive gland and gills of U. tumidus comprised detoxication systems (namely, antioxidant enzyme activities and glutathione status) and lipid peroxidation as a marker of cytotoxicity. Biocoenotic indicators were used to evaluate effects on benthic invertebrates and diatoms. In bivalves, a decrease in antioxidant levels was found at the lowest concentrations tested (0.6 and 6 mg/L), whereas an increase in lipid peroxidation and mortality was registered at 30 mg/L after 15 d of exposure. Disturbances in freshwater communities occurred after 30 d at MMA concentrations of greater than 30 mg/L. Antioxidant responses in bivalves were recorded at the lowest MMA concentration tested, which was close to the predicted no-effect concentration (0.74 mg/L), and cytotoxicity was registered at a concentration corresponding to the 21-d no-observed-effect concentration for Daphnia magna. On the basis of the criteria studied, antioxidant biomarkers of bivalves appeared to be more sensitive than biocoenotic indicators to MMA. [ABSTRACT FROM AUTHOR]

Pyrethroid insecticides are widely used in both agricultural and urban environments. Pyrethroids have been frequently detected in California, USA, stream bed sediments. Pyrethroids are strongly hydrophobic so their bioavailability is determined by their sorption to sediment. In the present study, we used disposable polydimethylsiloxane (PDMS) fibers to sample from the freely dissolved (effective) permethrin concentration that governs bioaccumulation and toxicity, and tested the correlation of those measurements with uptake by Chironomus tentans. In sediments that were incrementally diluted with silica sand, both PDMS fiber and organic carbon (OC) normalized sediment concentrations were highly correlated with C. tentans permethrin uptake. However, for multiple sediments with OC ranging from 1.4 to 27%, C. tentans permethrin uptake showed a better correlation with PDMS fiber concentrations than sediment OC-normalized concentrations. We conclude that the qualitative properties of sediment OC influence permethrin phase distribution and therefore the bioavailability of permethrin in sediment-water systems. Consequently selective methods such as PDMS fibers yield improved estimates of bioaccumulation and toxicity as such methods detect freely dissolved permethrin concentrations in the sediment. [ABSTRACT FROM AUTHOR]

Despite concerns about potential risks associated with the presence of pharmaceuticals and personal care products (PPCPs) in the environment, few toxicological data address the effects of these compounds. In aquatic systems, which often represent the final repository for PPCPs, increasing toxicological information regarding aquatic biota is improving our capacity to assess potential risks. However, responses of key biota, such as benthic invertebrates, have not been investigated as widely. In the present study, we examined the toxicity of four PPCPs—the lipid regulator atorvastatin (ATO), the antiepileptic drug carbamazepine (CBZ), the synthetic hormone 17α-ethinylestradiol (EE2), and the antimicrobial triclosan (TCS)—to the midge Chironomus tentans and the freshwater amphipod Hyalella azteca in 10-d waterborne exposures. The toxicity of the four compounds varied between 0.20 and 47.3 mg/L (median lethal concentration), with a relative toxicity ranking of TCS > EE2 > ATO > CBZ. Hyalella azteca was more sensitive than C. tentans to these compounds. The toxicity data were used in a hazard quotient approach to evaluate the risk posed by the four PPCPs to benthic invertebrates and other aquatic organisms. For each compound, a hazard quotient was calculated by dividing the lowest toxicity value by the highest exposure value found in the literature, to which an uncertainty factor was applied. With hazard quotients of 3.55 to 11.5, we conclude that potential risks exist toward benthic invertebrates for the toxicity of TCS and CBZ and that further investigations of these compounds are required to characterize more completely the risks to benthic organisms. In contrast, our data also indicate that considering the low concentrations currently detected in the environment, ATO and EE2 pose negligible risks to benthic invertebrates. [ABSTRACT FROM AUTHOR]

We measured stable isotope ratios (δ13C and δ15N) of particulate organic matter (POM) sources and benthic organic matter compartments as well as sediment C to N ratios from the coastal area of the southern end of the Southern California Bight (SCB). We used the isotopic values to evaluate the relative importance of the major POM sources to the sediment and two benthic macroinvertebrates. Application of a simple model to sediment δ13C values suggested that sewage-derived POM (SDPOM) supplies an average of 48% of the organic C to study area sediments. Application of a similar model to Spiophanes duplex δ13C values suggested that SDPOM from wastewater treatment plants discharging into the SCB could supply up to 57% of the C assimilated by this important benthic macroinvertebrate in areas as far away as 26 km from SDPOM inputs. The stable isotope data for Amphiodia urtica were more difficult to interpret because of the complex feeding habits of this organism. [ABSTRACT FROM AUTHOR]

A mass-balance model for the uptake of organic contaminants in the opposum shrimp (Mysis relicta) is developed. The model describes the concentration in the mysid as a function of time as it grows and its lipid content changes over a two-year life span. The model can describe uptake in varying proportions from pelagic and benthic sources. Four mysid scenarios are considered: entirely pelagic, entirely benthic, half-pelagic and half-benthic, and following the observed seasonal behavior patterns. The seasonal-scenario mysid yields results consistent with levels of total polychlorinated biphenyls reported for Lake Ontario (Canada/USA). The relative sediment and water fugacities are shown to play a critical role in determining the contamination level in mysids. Inclusion of mysids in a simple food-web model demonstrates higher concentrations in upper-trophic-level organisms by two effects: introduction of another trophic level in the food web, and increased benthic-pelagic coupling. [ABSTRACT FROM AUTHOR]

The immediate response and recovery of the macrobenthic communities of nonisolated and isolated freshwater outdoor 9 m3 mesocosms following an acute stress caused by the addition of deltamethrin were studied over a 14-month period. To discriminate between internal and external recovery mechanisms, half of the treated ponds were covered by 1-mm mesh lids that restricted aerial recolonization. Both structural (abundance of the different taxonomic groups) and functional (litter breakdown) parameters were monitored. Insects were broadly reduced in numbers by deltamethrin addition. In general, noninsect groups were not affected or increased in abundance in deltamethrin-treated ponds, probably because of relative insensitivity to deltamethrin, reduced predation, and lower competition for food. No major change in litter breakdown rates were seen, probably because of functional redundancy among the macrobenthic community. Chironominae larvae recovered in open, treated mesocosms 62 d after deltamethrin addition and most insect groups recovered 84 d after the treatment date. However, the presence of lids significantly reduced insect recovery rate, suggesting that it largely depends on the immigration of winged forms (i.e., external recovery) from surrounding non- or less affected systems. These results indicate that the recovery time of macrobenthic communities in an affected natural pond would depend on spatial characteristics of the landscape and also the season that exposure occurs. Isolated ecosystems would display posttreatment insect recovery dynamics very different from highly connected ones, evolving toward alternate pseudoequilibrium states, possibly with lower biodiversity but with preserved functionality. Consequences for higher tier risk assessment of pesticides are discussed. [ABSTRACT FROM AUTHOR]

Cause-effect sediment-quality benchmarks for the protection of benthic invertebrates are needed for polychlorinated biphenyls (PCBs) to support predictive risk assessments and retrospective evaluations of the causes of observed sediment toxicity. An in-depth evaluation of PCB aquatic toxicity and organic carbon partitioning was conducted to predict sediment effect concentrations using the equilibrium partitioning (EqP) approach. This evaluation was limited to invertebrate toxicity data, because PCBs may exert toxicity to invertebrates and fish via different toxicological mechanisms. As a result of differences in organic carbon partitioning among PCBs of differing levels of chlorination, the estimated EqP benchmarks increase with increasing degree of chlorination for various commercial and environmental PCB mixtures. Studies of spiked sediment toxicity using PCBs were reviewed, and their results generally were consistent with EqP predictions. Additionally, toxicity and benthic community data were reviewed for eight PCB-contaminated sites; these data also showed agreement with EqP predictions. None of these lines of evidence supports previously proposed, empirical sediment-quality guidelines for PCBs. Reasons for the lack of agreement between cause-effect and association-based benchmarks are discussed, and areas of future research to further refine EqP predictions for PCBs are identified. [ABSTRACT FROM AUTHOR]

In 2002, we developed an in situ life-cycle bioassay with Chironomus tentans in artificial streams to evaluate the effects of a complex metal mine effluent under ambient environmental conditions. The bioassay was tested in the field using effluent from the Copper Cliff Waste Water Treatment Plant at INCO (Sudbury, ON, Canada). Chironomus tentans were exposed throughout the life cycle to 45% Copper Cliff effluent, which is the average effluent concentration measured in Junction Creek (ON, Canada), the natural receiving environment. Chironomus tentans in the effluent treatment exhibited reduced survival (p = 0.001), reduced total emergence (p = 0.001), increased time-to-emergence (p = 0.001), and reduced hatching success (p = 0.001) relative to animals in the reference water treatment. Chironomus tentans in the effluent treatment were not significantly different from the reference in terms of growth, sex ratio, number of egg cases/female, and number of eggs/egg case. This research showed how a life-cycle bioassay could be used in situ to assess metal mine effluent effects on a benthic invertebrate. [ABSTRACT FROM AUTHOR]

The sorption of polycyclic aromatic hydrocarbons (PAHs) to soot carbon in marine sediments has been hypothesized to reduce PAH bioavailability. This hypothesis was tested for eight species of marine benthic invertebrates (four polychaete worms, Clymenella torquata, Nereis virens, Cirriformia grandis, and Pectinaria gouldii, and four bivalve mollusks, Macoma balthica, Mulinia lateralis, Yoldia limatula, and Mya arenaria) that span a wide range of feeding behavior, ability to metabolize PAHs, and gut chemistry. Organisms were exposed for 20 d to two PAH-spiked sediments, one with soot and one without soot. The soot treatment generally resulted in lower bioaccumulation than the no soot treatment, though the differences between treatments were not significant for all species. All but one species accumulated significant PAH concentrations in their tissues from the soot treatment, indicating that soot-bound PAH cannot be dismissed as unavailable to infaunal benthic biota. Bioaccumulation factors were correlated negatively to both the organisms' ability to metabolize PAHs and the gut fluid contact angle, supporting the hypotheses that high PAH metabolism results in lower bioaccumulation factors and bioavailability of PAHs may be limited partially by PAH solubilization in the gut lumen. The variability in bioaccumulation due to the soot treatment was much less than the variability between species and between PAH analytes. Comparatively low bioaccumulation was observed in Nereis virens, a species commonly used in bioaccumulation tests. These results suggest that more effort is needed in understanding the salient characteristics of species present in a threatened environment, rather than focusing solely on the sediment geochemistry (e.g., soot and organic carbon content) and contaminant characteristics when predicting ecological risk of PAH-contaminated sediments. [ABSTRACT FROM AUTHOR]

The bioavailability of polycyclic aromatic hydrocarbons (PAHs) to benthic organisms is complicated by the variety of ways that they are introduced to coastal waters (dissolved, as nonaqueous phase liquids, and tightly bound to soot, coal, tire rubber, and eroded shale). In order to better understand the controlling variables that affect chemical and biological availability of PAHs, a study was conducted in which three deposit-feeding infaunal benthic invertebrate species (Cirriformia grandis, Clymenella torquata, and Macoma balthica) were exposed to sediments amended with PAH-rich materials (coal dust, tire rubber, diesel soot, creosote, crude oil, and fuel oil). Lipid and organic carbon normalized bioaccumulation factors (BAFlocs) were calculated after 20 d of exposure and PAH bioavailability from the different treatments was assessed. Bioaccumulation of coal-derived PAHs usually was too low to be measured, though PAHs associated with soot and tire rubber showed significant accumulation in organism tissues. Polycyclic aromatic hydrocarbons from the fuel oil, creosote, and crude oil treatments were more bioavailable than PAHs bound in solid carbonaceous matrices (soot, coal, and tire rubber). Desorption of PAHs from the amended sediments into seawater also was measured using XAD resin. As was observed with bioaccumulation, PAHs in coal were desorbed the least; tire rubber and diesel soot were intermediate; and creosote, fuel oil, and crude oil desorbed to the greatest extent. In only one out of the three species evaluated was PAH bioaccumulation related to extent of desorption after 20 d. Decoupling between biological and chemical availability may be due to species-specific factors such as surfactant-mediated solubilization in the guts of some deposit-feeding organisms. A significant finding of this work was the demonstration that PAHs associated with soot and tire rubber in their native state (rather than experimentally added) are available to some benthic biota. [ABSTRACT FROM AUTHOR]

A multimetric benthic assessment method was developed for two benthic assemblages in the San Francisco Estuary (USA) using data from several monitoring programs collected over five years. Assessment indicators used were total number of taxa, total abundances, oligochaete abundances, number of molluscan taxa, number of amphipod taxa, and Capitella capitata and Streblospio benedicti abundances. Exceedances of the maximum or minimum indicator values in reference samples were used to assess test samples using a weight-of-evidence to obtain an assessment value. Only 2.5% of the samples from the deeper, offshore sites had benthic impacts, 14.3% of the samples from near wastewater discharges had impacts, and 78.3% of the samples from the estuary margins and channels were impacted. Impacted samples from both assemblages had significantly higher mean effects range-median quotient values (mERMq) than reference samples, total organic carbon (TOC) was significantly higher in the impacted samples from the mesohaline assemblage, and percent fines was significantly higher in the impacted samples from the polyhaline assemblage, reflecting the close associations of contaminants with fine sediments and organic material. In samples with mERMq below 0.050, there were no benthic impacts. The incidence of impacts remained low (9.4%) at mERMq below 0.146, but when mERMq was above 0.146, 68.2% of the samples had benthic impacts, and samples with mERMq above 0.740 were always impacted. [ABSTRACT FROM AUTHOR]

A 28-d partial life-cycle test with the estuarine amphipod Leptocheirus plumulosus was developed in response to the need for an assay to mimic chronic exposure to sediment-associated contaminants. To ensure that toxicity tests have environmental relevance, it is essential to evaluate the relationship between laboratory responses and field measures of contamination. Consequently, one objective of the study was to compare the results of the chronic sediment toxicity test with L. plumulosus to gradients of sediment contamination and the in situ benthic community in its native Chesapeake Bay. Chronic tests were conducted by two laboratories, the Army Corps of Engineers Waterways Experiment Station ([WES]; Vicksburg, MS, USA) and the University of Maryland ([UM] College Park, MD, USA) using different feeding regimes, providing the opportunity to evaluate the effect of this variable on response sensitivity. A second objective was to compare the relative sensitivity of acute and chronic tests with L. plumulosus with field-collected sediments. Overall, there was good agreement between the toxicological response of acute and chronic tests with L. plumulosus and field measures of contamination. Survival in the acute test and chronic test conducted by WES was negatively correlated with concentrations of sediment-associated contaminants. Survival in acute exposures was significantly reduced in sediments from 8 of 11 stations. Indigenous L. plumulosus were found only at two of the three stations that did not exhibit acute toxicity. An unexpected finding was the difference in responsiveness of the two chronic tests. Survival in tests conducted by UM and WES was significantly reduced in sediments from 4 and 6 of 11 stations, respectively. No additional sublethal toxicity was detected in the UM chronic test, but the WES test detected reproductive effects at two additional stations. We believe the observed differences were related to the test diet used. Partly as a result of our... [ABSTRACT FROM AUTHOR]

Effects of contaminants on communities are difficult to assess and poorly understood. We analyzed in situ effects of trace metals and common environmental variables on benthic macroinvertebrate communities in floodplain lakes. Alternative measures of trace metal availability were evaluated, including total metals, metals normalized on organic carbon (OC) or clay, simultaneously extracted metals (SEM), combinations of SEM and acid-volatile sulfide (AVS), and metals accumulated by detritivore invertebrates (Oligochaeta). Accumulated metal concentrations correlated positively with sediment trace metals and negatively with surface water dissolved OC. Sixty-eight percent of the variation in benthic community composition was explained by a combination of 11 environmental variables, including sediment, water, and morphological characteristics with trace metals. Metals explained 2 to 6% of the community composition when SEM -- AVS or individual SEM concentrations were regarded. In contrast, total, normalized, and accumulated metals were not significantly linked to community composition. We conclude that examination of SEM or SEM -- AVS concentrations is useful for risk assessment of trace metals on the community level. [ABSTRACT FROM AUTHOR]

Polybrominated diphenylethers (PBDEs) are ubiquitous environmental contaminants showing rapid temporal increase in some sample types. The compounds are known to biomagnify in aquatic food webs and are assumed to archive into sediments and soils. Currently, no direct evidence indicates whether sediment-associated PBDEs are available for biota. The aim of the present study was to explore the uptake and elimination of two common congeners (47 and 99) in sediment-inhabiting invertebrates to shed light on possible bioavailability of sediment-associated PBDEs. Two clean lake sediments were spiked with environmentally relevant concentrations of 14C-labeled tetra- and pentabromo diphenylether, and oligochaetes (Lumbriculus variegatus) were exposed for three or four weeks to allow kinetic accumulation calculations. Subsequent depuration tests were performed after three weeks of exposure to obtain depuration rates. Both congeners were clearly bioavailable, and only slight differences in steady-state tissue concentrations were found between the four sediment-ingesting oligochaete treatments (biota sediment accumulation factors [BSAFs], 3.0-3.7). The tetrabromo diphenylether-exposed oligochaetes that did not ingest sediment had clearly lower influx rates (0.1 vs 1-3 nmol h-1) than sediment-ingesting worms. Also, the estimated BSAF (1.8) was statistically different from that of the sedimentingesting oligochaetes. These findings support the significance of feeding behavior in bioaccumulation of very hydrophobic organic contaminants. Depuration of both congeners was biphasic, indicating two kinetically different compartments in L. variegatus. Compartment A made up 73 to 92% of total radioactivity in tissues and had relatively fast depuration rates (half-lives, 10.5-47.5 h); the smaller compartment B had very slow depuration rates. No significant biotransformation of PBDEs was evident. The present study clearly demonstrates that the sediment-associated PBDEs, like... [ABSTRACT FROM AUTHOR]

We used mesocosms to examine the impact of different concentrations of pulp mill effluent (PME) on structural and functional endpoints of a benthic assemblage in the Saint John River (NB, Canada) during 1999 and 2000. Previous studies on this effluent's effects produced conflicting results, with field surveys suggesting a pattern of mild nutrient enrichment, while laboratory toxicity tests linked effluent exposure to moderate contaminant effects. Experimental treatments included three concentrations of sulfite pulp mill effluent (0, 5, 10% v/v PME). Endpoints for the assessment included algal biomass and taxonomic composition, benthic invertebrate abundance and composition, and insect emergence. Low concentrations of PME increased periphyton biomass and caused changes in community structure within the diatom-dominated community. Pulp mill effluent addition had little effect on several structural endpoints measured for benthic invertebrates, including abundance and taxonomic richness, but significantly changed community composition. For both periphyton and benthic invertebrates, community composition endpoints were more sensitive indicators of PME exposure. Insect emergence was a highly relevant functional endpoint. When benthic and emerged insects were combined, total abundance increased with PME addition. Results from two trophic levels, which provided multiple lines of evidence, indicated that the main impact of these PME concentrations is nutrient enrichment rather than effluent toxicity. Our findings also suggest that benthic invertebrate and periphyton assemblages, algal biomass production, and insect emergence are sensitive response measures. Future studies may confirm this observation. The consideration of both functional and structural endpoints at different trophic levels can greatly improve our understanding the effects of discharges to rivers. Such an understanding could not have been obtained using standard assessment techniques and illustrates the value of mesocosms and the benthic community assemblage approach in environmental assessment. [ABSTRACT FROM AUTHOR]

The relative sensitivity of four benthic invertebrates (Hyalella azteca, Chironomus riparius, Hexagenia spp., and Tubifex tubifex) was determined for Cd, Cu, and Ni in water-only and in spiked-sediment exposures. Survival (median lethal concentrations [LC50s] and the concentrations estimated to be lethal to 25% of test organisms [LC25s]), and endpoints for growth and reproduction (mean inhibitory concentrations [IC25s]) were compared. The sensitivities differed depending on the species and metal, although some trends emerged. In water-only exposures, H. azteca is the most sensitive species to cadmium and nickel, with mean LC50s of 0.013 and 3.6 mg/L, respectively; C. riparius is the most sensitive species to copper, with a mean LC50 of 0.043 mg/L. In the spiked-sediment exposures, the order in decreasing sensitivity to copper is Hyalella = Hexagenia > Chironomus > Tubifex for survival and growth/reproduction. For cadmium, the order in decreasing sensitivity is Hyalella = Chironomus > Hexagenia > Tubifex, and for nickel is Hyalella « Hexagenia > Chironomus > Tubifex. Chironomus riparius and Hexagenia spp. survival can be used to distinguish between toxicity caused by different metals. Species test responses in field-collected sediment (Collingwood Harbour, ON, Canada) were examined in an attempt to determine the causative agent of toxicity throughout, using the established species sensitivities. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Test responses in the field-collected sediment do not support causality by Cu, a suspected toxicant based on comparison of sediment chemistry with sediment quality guidelines. [ABSTRACT FROM AUTHOR]

This study investigated the effect of long-term sediment aging on the toxicokinetics of benzo[a]pyrene (BaP) and hexachlorobiphenyl (HCBP) using three freshwater benthic invertebrates. Hyalella azteca, Chironomus tentans, and Lumbriculus variegatus were exposed to BaP- and HCBP-spiked sediments that were aged for 7 d or 1.5 years. The toxicokinetics of the two compounds were determined for each test organism using a two-compartment model. The modeling of BaP was more complex because biotransformation was included within the model. The results of this study showed that the HCBP uptake clearance rates (ks) for each species were generally an order of magnitude greater than those determined for BaP and this difference was most likely due to preferential and rapid binding of BaP to sediment particles. Overall, the bioavailability of HCBP in spiked sediments tended to decrease with duration of aging, based on ks values and bioaccumulation factors (BAFs). However, the decreases in bioavailability appear to be species specific. Benzo[a]pyrene did not decline in bioavailability for the species tested because it may resist movement into the micropores of the sediment due to its large size. In addition to the bioassays, this article outlines a method for toxicokinetic modeling of biotransformed compounds and methods for statistical comparisons of kinetic parameters (i.e., ks, kd . . . ) and BAF values. [ABSTRACT FROM AUTHOR]

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

Benthic macroinvertebrate communities of the North Fork Powell River (NFP), southwest Virginia, USA, appear to be impacted by aluminum (Al) and iron (Fe) from acid mine drainage (AMD) beyond the zone of pH depression. As part of a watershed restoration project, we used integrative techniques, including water column, sediment, and in situ toxicity tests; sediment and water column chemistry; and habitat assessments, to detect AMD impacts. An analysis of variance, least significant difference post hoc test, and Spearman correlations were used to test the sensitivity of these integrative techniques to detect various (acidic or neutralized) levels of AMD input and to determine the mode of impairment (metal-contaminated sediments or water) to the benthic macroinvertebrate community. Benthic macroinvertebrate indices were the most sensitive endpoint to AMD inputs and were significantly correlated (p ≤ 0.05) with water column metal concentrations in in situ and water column toxicity tests. Sediment chemistry and toxicity did not detect AMD impacts and were not significantly correlated with benthic macroinvertebrate indices. These results suggest that the primary mode of impairment to the benthic macroinvertebrate communities beyond the zone of pH depression were waterborne Al and Fe. [ABSTRACT FROM AUTHOR]

Benthic communities in floodplain lake ecosystems are often exposed to varying levels of both food and toxicants. Inhibition through toxicants of sensitive species and stimulation through increased amounts of food of opportunistic species have been observed in separate studies. The aim of this study was therefore to assess the responses of benthic invertebrates to combined food and contamination input. Hence, seven floodplain lakes located along the River Waal, The Netherlands, with different levels of food (being either phytoplankton or macrophyte dominated) and toxicants were selected. The responses of the sensitive mayfly Ephoron virgo and the opportunistic midge Chironomus riparius to these sediments were assessed in 10-d growth bioassays with both species and a 28-d emergence experiment with C. riparius. A decrease in both survival and growth of E. virgo was observed with increasing contaminant levels. In contrast, C. riparius responded to the food quantity and quality in the sediments in spite of the toxicants present. Therefore, we conclude that the midge C. riparius is not a suitable test organism for the assessment of sediment toxicity. Alternatively, it proved to be an appropriate test organism to determine the nutritional value of sediments. The mayfly E. virgo turned out to be a much more appropriate test organism for sediment toxicity bioassays because it responds to the toxicant levels in the sediments rather than to the nutritional value. Our results demonstrate that the trophic state of an ecosystem (macrophyte or plankton dominated) influences the ecological risk of toxicants to benthic invertebrates in a species-specific way. It is concluded that not the toxicant load but the combination of food and contaminants determines the persistence of benthic invertebrates and therewith the benthic invertebrate composition in complexly polluted ecosystems. [ABSTRACT FROM AUTHOR]

Ten-day acute mortality of the benthic amphipod Ampelisca abdita is used in a number of regulatory, research, and monitoring programs to evaluate chemical contamination of marine sediments. Although this endpoint has proven to be valuable for characterizing the relative toxicities of sediments, the significance of acute mortality with respect to population viability has not yet been established. In this study, population modeling along with empirical extrapolation were used to describe a relationship between acute mortality and population-level response of A. abdita. The research involved the performance of a standard 10-d sediment toxicity bioassay and a 70-d full life-cycle chronic population (including reproduction) bioassay exposing A. abdita to sediments spiked with concentrations of the divalent metal cadmium (normalized to acid volatile sulfide) expected to produce a range of biological effects. These data provided age-specific schedules of survival and fecundity that were used to parameterize an age-classified projection matrix model for A. abdita. Measured exposure data and population growth rate estimates, obtained using the demographic information collected during the 70-d assay, were used to develop exposure--response models. These data were also used to develop an empirical relationship between population growth rate (Α) and acute mortality. This relationship describes how acute data may be used to predict concentrations that produce population-level effects. Model manipulations permit extrapolation of early life-stage mortality (the acute endpoint) to changes in population growth rate. These relationships were used to evaluate a range of ecologically acceptable acute mortality for A. abdita. [ABSTRACT FROM AUTHOR]

The distribution patterns of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in four benthic invertebrate species of western Lake Erie, USA, to assess and compare the processes governing the exposure dynamics of these two classes of contaminants. Significant differences in the sum of 17 PAH compounds were observed among the four species, with mayflies containing the highest PAH body burden, followed by dreissenid mussels, amphipods, and crayfish. For PCBs, mayflies contained significantly higher concentrations of the sum of 39 PCB congeners than the other organisms, and dreissenids had higher levels than crayfish. No significant differences were found in the σPCB levels between dreissenids and amphipods or between amphipods and crayfish. For PCBs, the relationship between biota-sediment accumulation factors (BSAFs) and log Kow followed a parabolic pattern indicative of selective bioaccumulation. In contrast, BSAFs for PAHs were inversely related to log Kow, suggesting that metabolism of the higher Kow compounds was occurring. These results support the conclusion that mayflies and dreissenids play major roles in the transfer of PAHs and PCBs to upper trophic levels, and they demonstrate that the exposure dynamics of PAHs and PCBs are different in the benthic components of aquatic food webs. [ABSTRACT FROM AUTHOR]

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available for assessing risks to benthic invertebrates due to VOCs in sediment. More strongly hydrophobic organic chemicals are frequently assessed by using the equilibrium partitioning (EqP) approach, which predicts the bioavailable fraction of chemical (the concentration dissolved in pore water) from the sediment-sorbed fraction, assuming that partitioning is at equilibrium. As typically applied, the EqP approach is ineffective for assessing VOCs in sediment, because the standard EqP equation fails to account for the contribution of dissolved chemical to the total chemical concentration in sediment. For chemicals with low organic carbon--water partition coefficients (KOCs), this results in nonsensical sediment-quality benchmarks that are more conservative (i.e., lower) than benchmarks calculated by assuming 100% bioavailability. A modified EqP equation is presented that accounts for the dissolved fraction of total chemical concentrations in sediment. Results of the standard and modified EqP equations converge with increasing KOC and are essentially identical at log KOC values exceeding approximately 3.5. [ABSTRACT FROM AUTHOR]

Organic matter (OM) input to marine sediments varies seasonally both in quantity and quality. Because sedimentary OM (SOM) constitutes food for many benthic organisms, its properties should affect the dietary uptake of sediment-associated contaminants. We explored the effect of SOM quality/food value on short- and long-term pyrene accumulation in the mud snail (Hydrobia ulvae) and performed dual-tracer pulse-chase experiments to investigate the feeding mechanisms driving dietary pyrene uptake. The quality of the SOM was manipulated by enriching sediments either with high-quality microalgae or low-quality lignin, adding equal amounts of total organic carbon. Long- and short-term bioaccumulation increased with increasing SOM quality, as did pyrene ingestion rate (IRpyr), which also was affected by feeding history. By feeding selectively, snails concentrated pyrene 10-fold in ingested compared to ambient sediment, independent of SOM quality. Average pyrene absorption efficiency (AEpyr: 65%) varied inversely with SOM quality and IRpyr. Both AEpyr and gut passage time (α 1/IRpyr) agreed with theoretical models incorporating the time-dependence of absorption efficiency. Thus, SOM quality moderates dietary contaminant uptake in deposit feeders, and in H. ulvae, this occurs via OM-induced alterations of ingestion rate. Consequently, enhanced sediment-associated contaminant uptake is predicted for deposit feeders following phytoplankton blooms, principally because of OM quality-driven increases in the ingestion rate. [ABSTRACT FROM AUTHOR]

Rasgão Reservoir, located close to the Metropolitan region of São Paulo, Brazil, has been analyzed previously, and its sediment was found to be highly toxic, with high levels of metals and polycyclic aromatic hydrocarbons and a complete absence of benthic life. Polychlorinated biphenyls also were present, as was mutagenic activity, detected with the Salmonella/microsome assay. Because of the extremely complex mixture of contaminants in these sediments, a toxicity identification evaluation was performed on the pore water and elutriate using Ceriodaphnia dubia and Vibrio fischeri. Toxicity characterization, identification, and confirmation procedures were performed in one representative sample of the reservoir, and the results indicated that ammonia was the main cause of the toxicity detected with C. dubia in both sediment pore water and elutriate. Chemical analysis corroborated this observation by revealing un-ionized ammonia concentrations as high as 5.14 mg/L in pore water and 2.06 mg/L in elutriate. These high ammonia levels masked possible toxicity caused by other classes of compounds. The toxicity detected with V. fischeri decreased with the time of sample storage and was related to the organic fraction of the pore water and the elutriate, in which compounds such as benzothiazole and nonylphenol were detected. [ABSTRACT FROM AUTHOR]

The U.S. Environmental Protection Agency's (U.S. EPA) narcosis model requires the measurement of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) (so-called 34 PAHs) in sediments to calculate the number of PAH toxic units (TU) available to benthic organisms. If data for the 34 PAHs are not available, the U.S. EPA proposes estimating the risk by multiplying the TU for 13 parent PAHs by 11.5 (95% confidence interval) based on data from 488 sediments. This estimate is overly conservative for PAHs from pyrogenic manufactured gas plant (MGP) processes based on the analysis of 45 sediments from six sites. Parent PAHs contributed approximately 40% of the total concentrations and TU for MGP sediments. In contrast, parent PAHs from diesel fuel and petroleum crude oil contributed only 2 and 1%, respectively, of the PAH concentrations and TU, compared to approximately 98 to 99% contributed by the alkyl PAHs. Statistical comparison of the TU based on the measured 34 alkyl and parent PAHs and those based on only 13 parent PAHs demonstrated that a factor of 4.2 (rather than 11.5) is sufficient to estimate total TU within a 95% confidence level for MGP sites. Similarly, measurement of parent PAHs is sufficient to accurately estimate the total 34 alkyl and parent PAH concentrations for MGP-impacted sediments. [ABSTRACT FROM AUTHOR]

An empirical screening level approach was developed to assess the probability of toxicity to benthic organisms associated with contaminated sediment exposure. The study was based on simple logistic regression models (LRMs) of matching sediment chemistry and toxicity data retrieved from a large database of field-collected sediment samples contaminated with multiple chemicals. Three decisions were made to simplify the application of LRMs to sediment samples contaminated with multiple chemicals. First, percent mortality information associated with each sediment sample was condensed into a dichotomous response (i.e., toxic or nontoxic). Second, each LRM assumed that toxicity was attributable to a single contaminant. Third, individual contaminants present at low concentrations were excluded from toxic sediment samples. Based on an analysis of the National Sediment Inventory database, the LRM approach classified 55% of nontoxic sediments as toxic (i.e., false-positives). Because this approach has been used to assess the probability of benthic toxicity as reported by the U.S. Environmental Protection Agency (U.S. EPA), the resultant estimates of potential toxicity convey a misleading impression of the increased hazard that sediments pose to the health of aquatic organisms at many sites in the United States. This could result in important resources needlessly being diverted from truly contaminated sites to evaluate and possibly remediate sediments at uncontaminated sites. [ABSTRACT FROM AUTHOR]