Lentic, lotic, and sulfate-dependent waterborne selenium screening guidelines for freshwater systems.

There is consensus that fish are the most sensitive aquatic organisms to selenium (Se) and that Se concentrations in fish tissue are the most reliable indicators of potential toxicity. Differences in Se speciation, biological productivity, Se concentration, and parameters that affect Se bioavailability (e.g., sulfate) may influence the relationship between Se concentrations in water and fish tissue. It is desirable to identify environmentally protective waterborne Se guidelines that, if not exceeded, reduce the need to directly measure Se concentrations in fish tissue. Three factors that should currently be considered in developing waterborne Se screening guidelines are 1) differences between lotic and lentic sites, 2) the influence of exposure concentration on Se partitioning among compartments, and 3) the influence of sulfate on selenate bioavailability. Colocated data sets of Se concentrations in 1) water and particulates, 2) particulates and invertebrates, and 3) invertebrates and fish tissue were compiled; and a quantile regression approach was used to derive waterborne Se screening guidelines. Use of a regression-based approach for describing relationships in Se concentrations between compartments reduces uncertainty associated with selection of partitioning factors that are generally not constant over ranges of exposure concentrations. Waterborne Se screening guidelines of 6.5 and 3.0 µg/L for lotic and lentic water bodies were derived, and a sulfate-based waterborne Se guideline equation for selenate-dominated lotic waters was also developed. Environ Toxicol Chem 2017;36:2503-2513. © 2017 SETAC.

Dietary selenium disrupts hepatic triglyceride stores and transcriptional networks associated with growth and Notch signaling in juvenile rainbow trout.

Dietary Se has been shown to adversely affect adult fish by altering growth rates and metabolism. To determine the underlying mechanisms associated with these observations, we measured biochemical and transcriptomic endpoints in rainbow trout following dietary Se exposures. Treatment groups of juvenile rainbow trout were fed either control Lumbriculus variegatus worms or worms cultured on selenized yeast. Selenized yeast was cultured at four nominal doses of 5, 10, 20 or 40mg/kg Se dry weight (measured dose in the worms of 7.1, 10.7, 19.5, and 31.8mg/kgSedw respectively) and fish were fed for 60days. At 60 d, hepatic triglycerides, glycogen, total glutathione, 8-isoprostane and the transcriptome response in the liver (n=8/group) were measured. Fish fed the nominal dose of 20 and 40mg/kg Se dry weight had lower body weight and a shorter length, as well as lower triglyceride in the liver compared to controls. Evidence was lacking for an oxidative stress response and there was no change in total glutathione, 8-isoprostane levels, nor relative mRNA levels for glutathione peroxidase isoforms among groups. Microarray analysis revealed that molecular networks for long-chain fatty acid transport, lipid transport, and low density lipid oxidation were increased in the liver of fish fed 40mg/kg, and this is hypothesized to be associated with the lower triglyceride levels in these fish. In addition, up-regulated gene networks in the liver of 40mg/kg Se treated fish included epidermal growth factor receptor signaling, growth hormone receptor, and insulin growth factor receptor 1 signaling pathways. These molecular changes are hypothesized to be compensatory and related to impaired growth. A gene network related to Notch signaling, which is involved in cell-cell communication and gene transcription regulation, was also increased in the liver following dietary treatments with both 20 and 40mg/kg Se. Transcriptomic data support the hypothesis that dietary Se increases the expression of networks for growth-related signaling cascades in addition to those related to fatty acid synthesis and metabolism. We propose that the disruption of metabolites related to triglyceride processing and storage, as well as gene networks for epidermal growth factor and Notch signaling in the liver, represent key molecular initiating events for adverse outcomes related to growth and Se toxicity in fish.

Relationship between mRNA biomarker candidates and location near a marine municipal wastewater outfall in the benthic indicator species Modiolus modiolus (L.).

The deep-sea horse mussel Modiolus modiolus (L.) is a sentinel bivalve species used for the assessment of potential biological exposure to anthropogenic contaminants in benthic environments. Using a combination of endpoints that included gross biological metrics, reproductive status, tissue contaminant load, and mRNA abundance profiles, we characterized variation in the local M. modiolus population situated in different spatial zones relative to a municipal wastewater outfall. Significant differences were observed in reproductive indicators, growth parameters, and abundance of four specific mRNA transcripts representative of stress response or membrane transport (CAT, NET/SCF6, ABCA4 and HSP70) in adductor muscle tissue of animals adjacent to the wastewater outfall. Concentrations of metals and organic chemicals in M. modiolus tissue were generally highest directly at the outfall site with much lower levels at 100-800 m from the outfall. This general pattern did not match the mRNA profiles. HSP70 and ABCA4 mRNA showed increased abundance in all regions adjacent to the municipal outfall compared to the reference site. One site group located within 100-200 m south/south-easterly of the outfall had increased levels of all four transcripts. Some mRNAs showed significant correlations with nickel, arsenic, lead, selenium, copper, and one of thirteen polycyclic aromatic hydrocarbons measured (dibenzo(a,h)-anthracene). Three mRNAs (CAT, NET/SCF6, and ABCA4) were negatively correlated with bis(2-ethylhexyl)phthalate. The data suggest that these benthic organisms are exhibiting biological responses to the outfall and support an alternate interpretation regarding dispersal of contaminants. The potential effects of emerging chemicals of concern entering the receiving environment merits further assessment.

Developmental toxicity of selenium to Dolly Varden char (Salvelinus malma).

Gametes were collected from Dolly Varden char (Salvelinus malma) from waterbodies in a region exposed to mining-related selenium (Se) releases in British Columbia, Canada. Fertilized eggs were incubated in a laboratory and deformities were assessed on newly-hatched alevins using a graduated severity index. No effects were observed on egg or alevin survival or larval weight across the studied exposure range of 5.4 to 66 mg/kg dry weight in egg. Length of some larvae was reduced at the highest egg Se concentrations and a clear residue-response relationship was observed for larval deformity. The egg concentration corresponding to a 10% increase in the frequency of deformity (EC10) was 54 mg/kg dry weight, which is substantially higher than reported for other cold-water fish species.

Patterns of bioaccumulation of polybrominated diphenyl ether and polychlorinated biphenyl congeners in marine mussels.

Marine mussels (Modiolus modiolus) and sediment from 14 stations near a municipal outfall and three reference locations were analyzed for polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) to evaluate and compare patterns of bioaccumulation of individual congeners between these two groups of chemicals. Of the 47 PBDEs and 209 PCBs analyzed, 34 PBDE and 153 PCB congeners or coeluting groups of congeners were detected in one or more matrices. The predominant PBDE congeners were BDEs 47, 99, 100, and 209, accounting for 80-90% of the total PBDEs in all matrices. PCBs and PBDEs exhibited a parabolic relationship of the biota-sediment accumulation factor (BSAF) versus the log octanol-water partition coefficient(Kow). Below Kow 10(5.5), BSAFs ranged between 1 and 3, reflecting approximate equilibrium between mussels and sedimentforthese relatively water soluble congeners. BSAFs increased with increasing Kow to maximum values of approximately 30-100 for congeners with Kow approximately 10(7) and then declined at higher Kow to a value of approximately 1 for BDE 209. BSAFs for PBDEs were generally 2- to 3-fold higher than those for PCBs of a similar Kow. The calculated BSAFs for PBDE congeners indicate that PBDEs have a pattern of bioaccumulative behavior in mussels similar to that of the PCBs, and that some PBDE congeners may be more bioaccumulative in mussels than PCBs.

Effects of an oil spill on the regrowth of emergent vegetation in a northern Alberta Lake.

Following a train derailment in August 2005, Wabamun Lake (Alberta, Canada) was exposed to approximately 149,500 L of bunker "C" oil, much of which became entrained in the abundant Schoenoplectus tabernaemontani (= Scirpus validus) beds in the eastern basin of the lake. We assessed the regrowth of emergent macrophytes during the subsequent two growing seasons. Postspill measures of productivity, including transect length, total cover, and biomass were within the variability of prespill data collected in 2001, with the exception of a few specific areas in which biomass appeared to be affected. We conclude that exposure to oil during the late growing season in August 2005 and through the winter senescent period and regrowth in the summers of 2006 and 2007 did not cause large-scale changes to S. tabernaemontani communities. Physical factors such as cleanup activities and vegetation management appeared to be responsible for the reduced regrowth observed at some locations. Few previous studies have been published on the effects of oil spilled into freshwater on macrophyte communities; thus, the results of this study are expected to provide useful information for the assessment of future freshwater oil spills.

Assessing exposure of sediment biota to organic contaminants by thin-film solid phase extraction.

Differences in bioavailability among sediments are a source of variability and uncertainty in sediment quality assessment. We present three sets of studies designed to test a thin-film solid phase extraction technique for characterizing the bioavailability of organic chemicals in sediments. Laboratory studies with spiked natural sediments reveal highly reproducible thin-film extractions for chemicals with octanol-water partition coefficients between 10(4.5) and 10(8.5), with 95% equilibration times between 1 and 600 h. Studies with field-collected sediments illustrate that method detection limits are sufficiently low for field application at contaminated sites. Bioaccumulation studies with clams (Macoma balthica) show excellent correlations between thin-film and animal tissue concentrations. We conclude that thin-film extraction provides an ecologically relevant, fugacity-based measure of chemical exposure that can be expected to improve sediment quality assessments.

The importance of benthos in weight of evidence sediment assessments--a case study.

Sediment quality in a Texas reservoir subject to point and non-point sources of contaminants was assessed using the Sediment Quality Triad weight of evidence approach. Fifteen stations were sampled plus a reference station which, unfortunately, comprised a different habitat type than the other 15 stations. Accordingly, standard comparisons between reference and exposed stations were inappropriate. Interpretation of potential relationships between benthic community structure and sediment-associated contaminants was also confounded by differences in habitat-related characteristics (e.g., water depth and total organic carbon) within the reservoir. Multivariate analyses of the benthic community identified two station groupings separated primarily by habitat-related differences rather than contaminant-related toxicity. Laboratory toxicity tests and chemical analyses, including measures of bioavailability, did not differ consistently between the two community-based station groupings, indicating that toxicity resulting from chemical contamination was not the primary factor in observed community structure in the reservoir, although alterations to the benthos due to chemical contamination could not be ruled out in the absence of an appropriate reference comparison. Appropriately giving highest weight to resident benthic community structure, followed by the results of laboratory toxicity tests, then chemical analyses, provided the best possible assessment of chemical pollution in the absence of a suitable reference comparison. The alternative approach of relying on only sediment toxicity and chemistry data, without considering the full weight of evidence, would have provided misleading information.

Design and application of a transparent and scalable weight-of-evidence framework: an example from Wabamun Lake, Alberta, Canada.

A weight-of-evidence (WOE) framework was developed to evaluate potential effects on the aquatic ecosystem of Wabamun Lake (Alberta, Canada) associated with the release of Bunker "C" oil after a train derailment. The wide variety of stakeholders and interested regulatory agencies made it necessary to develop a consistent and transparent approach to assessing ecological effects on multiple ecosystem components within the lake with the use of a large number of lines of evidence (LOEs). Consequently, a scalable WOE framework was necessary to integrate the findings of 38 different LOEs. A priori and a posteriori weighting factors were applied to each individual LOE, and a combination of numeric and nonnumeric rating systems was used to integrate LOEs into an overall WOE conclusion for 5 different ecosystem components. We provide guidance regarding the development of a WOE framework and emphasize techniques that enhance the application of best professional judgement during the WOE process.

In situ experimental assessment of lake whitefish development following a freshwater oil spill.

Wabamun Lake (Alberta, Canada) has been subject to ongoing contamination with polycyclic aromatic hydrocarbons (PAHs) from multiple sources for decades and in August 2005 was exposed to ca. 149 500 L of bunker C oil following a train derailment. We compared the pattern, frequency, and severity of deformity in larvae of lake whitefish (Coregonus clupeaformis) incubated in situ in areas of Wabamun Lake exposed only to "background" PAH contamination and in areas additionally exposed to PAHs from the oil. All sites in the lake (including reference areas) showed incidences of deformity higher than are typically observed in laboratory studies. A small number of oil-exposed sites showed higher incidences of some teratogenic deformities and a tendency to exhibit deformities of higher severity than sites not exposed to oil. The frequency of moderate to severe deformities in 8 of 16 classes was correlated with PAH exposure. Nonmetric multivariate ordination of deformity data revealed a general pattern of increasing incidence and severity of several skeletal (lordosis, scoliosis) and craniofacial (ocular, jaw) deformities at sites with relatively high exposure to oil-derived PAHs. A simultaneous consideration of incidence, severity, and pattern of deformity enabled us to detect a consistent (overall approximately 5% above background) response to the oil despite high variability and high background deformity rates in this historically contaminated environment.

A control chart approach to monitoring and communicating trends in tissue selenium concentrations.

A primary aim of monitoring programs is to determine changes relative to background conditions, which typically represent a distribution of values, not a single value, and which may be elevated naturally. Graphical inspection of the statistical distribution of background and subsequent data provides the best means to determine changes over time and the relative significance of those changes based on both their magnitude and trajectory. The control chart approach commonly used in laboratory and product testing is a useful tool that allows for such determinations in a manner that is transparent to both scientists and nonscientists. This approach can be used both with true baseline (i.e., pre-development) data and with operational baseline (i.e., post-development) data and is particularly relevant for monitoring selenium (Se) tissue concentrations.

The sorptive capacity of animal protein.

Partition coefficients that are used to predict concentrations of hydrophobic organic chemicals in biota (e.g., the bioconcentration factor) often assume that the sorptive capacity of an organism or tissue is adequately represented by its lipid content. In lean organisms and tissues, however, theory suggests that partitioning may be strongly influenced by the sorptive capacity of nonlipid materials, such as protein. Little is known about the sorptive capacity of proteins for hydrophobic organic chemicals, and methods to include proteins in bioaccumulation models do not exist. Here, we present a compilation and meta-analysis of published data to estimate the relative sorptive capacities of animal proteins and lipids for neutral organic chemicals. We found that the estimated sorptive capacity of protein in solid animal tissues ranged from around 1 to 10% that of lipid for compounds with a log octanol/water partition coefficient (K(OW)) of greater than two. The sorptive capacity of blood protein (albumin) appeared to be substantially higher than this, especially for low-K(OW) chemicals. For modeling purposes, we recommend estimating the sorptive capacity of animal protein as 5% that of lipid. According to this estimate, the sorptive capacity of an animal or tissue will be dominated by the contribution from protein if the lipid content makes up less than 5% of the dry-weight organic content. In such situations, a consideration of the sorptive capacity of nonlipid constituents, such as protein, will permit more accurate predictions of chemical accumulation and distribution.

Selenium toxicity to invertebrates: will proposed thresholds for toxicity to fish and birds also protect their prey?

Efforts to manage the environmental risks of selenium (Se) in freshwater ecosystems have focused primarily on fish and birds, with invertebrates most often considered only as dietary sources of Se to higher trophic levels. Relatively little attention has been given to the risk of Se toxicity to invertebrates. Based on a review of 156 aqueous, dietary, or internal Se concentrations associated with toxic effects in 29 macroinvertebrate species, we found that water concentrations associated with acute lethality varied > 1000-fold among taxa, whereas toxic dietary concentrations varied approximately 100-fold and toxic internal concentrations varied about 30-fold. Sublethal effects occurred at approximately 10-fold lower concentrations than lethality. Sublethal effects occurred at 1-30 microg Se/g dry weight in invertebrate tissue, a range that encompasses proposed dietary thresholds for toxicity to fish and water birds, suggesting that Se may cause toxic effects in some invertebrate species at concentrations considered to be "safe" for the organisms consuming them.

Ion-trap tandem mass spectrometry-based analytical methodology for the determination of polychlorinated biphenyls in fish and shellfish. Performance comparison against electron-capture detection and high-resolution mass spectrometry detection.

Optimization of the Varian Saturn 2200 ion-trap tandem mass spectrometry (IT-MS/MS) system and comparison of its data quality with two other detection methods [electron-capture detection (ECD) and high-resolution mass spectrometry (HRMS)] was pursued by measuring polychlorinated biphenyls (PCBs) levels in fish and shellfish samples. IT-MS/MS methodology provided limits of detection (LOD) comparable to those obtained by ECD but superior specificity for the detection of a selected number of 39 PCB native congeners and 9 (13)C-labelled PCB standards. The method detection limits (MDLs) established for IT-MS/MS ranged between 1.0 and 5.0 pg/g on a wet weight basis while those obtained by ECD and HRMS were 1.0-4.0 pg/g and 0.1-2.0 pg/g, respectively. Overall, the results obtained in the study demonstrate that gas chromatography (GC) combined with IT-MS/MS provide higher data quality than those achievable by GC-ECD. For this particular set of target analytes the specificity achievable with IT-MS/MS was comparable to that obtained by HRMS and both techniques provided comparable data in terms of accuracy and precision.

Ecosystemic effects of salmon farming increase mercury contamination in wild fish.

Net-pen salmon aquaculture has well-known effects on coastal ecosystems: farm waste increases sediment organic content and the incidence of sediment anoxia, supports increased production of deposit-feeding invertebrates, and attracts higher densities of demersal fish and other mobile carnivores. These impacts are widely considered to be localized and transitory, and are commonly managed by imposing a period of fallowing between cycles of production. The implications of these ecosystemic effects for contaminant cycling, however, have not previously been considered. We found elevated levels of mercury in demersal rockfishes near salmon farms in coastal British Columbia, Canada, attributable to a combination of higher rockfish trophic position and higher mercury levels in prey near farms. Mercury concentrations in long-lived species such as rockfishes change over a longer time scale than cycles of production and fallowing, and thus at least some important effects of fish farms may not be considered transitory.

A bioenergetic biomagnification model for the animal kingdom.

Species vary greatly in the degree to which they accumulate dietary contaminants. Bioenergetic processes play a key role in chemical uptake and elimination, and interspecific variation in bioaccumulation can be attributed in large part to variation in how species feed, digest, and allocate energy. We present a quantitative treatment of this relationship for the entire animal kingdom. We derive a model to predict the biomagnification factor for nonmetabolizable, slowly eliminated chemicals, BMF(max). We test the model with observed biomagnification factors and independently derived bioenergetic parameters for a diverse suite of species, including herbivores and carnivores, heterotherms and homeotherms, vertebrates and invertebrates, adults and juveniles, domestic/laboratory animals and wild individuals from freshwater, marine, and terrestrial environments. The model successfully predicts species-specific BMF(max) values across this range of taxa, with values ranging from less than 1 in caterpillars to nearly 100 in some carnivores. In addition, we make novel predictions of BMF(max) for several taxa for which no measured bioaccumulation data are available. Our analysis provides new insights into the role of ecology in chemical dynamics across the animal kingdom, providing a general framework for understanding how characteristics of an organism and its ecological context influence the degree to which that organism accumulates chemicals present in its diet.

Magnification and toxicity of PCBs, PCDDs, and PCDFs in upriver-migrating Pacific salmon.

The depletion of lipids associated with pre-spawning migration of Pacific salmon has the potential to magnify concentrations of hydrophobic organic contaminants (HOCs), which elevates risk of toxic effects. We present data from a field study of sockeye salmon (Oncorhynchus nerka) migrating to spawn in Great Central Lake, BC, which demonstrate that pre-spawning migration causes a magnification of PCB, PCDD, and PCDF concentrations in female gonads (1.9-2.5-fold), female soma (3.4-5.6-fold), and male soma (5.6-9.7-fold). We further develop a model of prespawning migration chemical magnification for sockeye salmon stocks as a function of migration distance. This model is shown to be consistent with available empirical data on pre-spawning magnification and predicts magnification factors ranging between 1.4 and 7.9 in gonad and between 1.6 and 10.4 in soma in seven Pacific salmon stocks in British Columbia. Post-migration (prespawning) toxic equivalent dioxin concentrations in roe were measured to be approximately 3 pg/g lipid in salmon from the Great Central Lake sockeye stock and estimated to range between 1.5 pg/g lipid for the shortest-migrating stocks and 7 pg/g lipid for the longest-migrating stocks. Concentrations in certain stocks approach or exceed the concentration of 3 pg/g lipid associated with 30% egg mortality in Oncorhynchus mykiss. This indicates the potential for population-level effects of current contaminant levels. It also suggests that historic contaminant concentrations, which were greater than current concentrations, may have contributed significantly to the decline of certain Pacific salmon stocks in British Columbia.