eDNA-based detection reveals invasion risks of a biofouling bivalve in the world's largest water diversion project

Environmental DNA (eDNA) has increasingly been used to detect rare species (e.g., newly introduced nonindigenous species) in both terrestrial and aquatic ecosystems, often with distinct advantages over traditional methods. However, whether water eDNA signals can be used to inform invasion risks remains debatable owing to inherent uncertainties associated with the methods used and the varying conditions among study systems. Here, we sampled eDNA from canals of the central route of the South-to-North Water Diversion Project (hereafter SNWDP) in China to investigate eDNA distribution and efficacy to inform invasion risks in a unique lotic system. We first conducted a total of 16 monthly surveys in this system (two sites in the source reservoir and four sites in the main canal) to test if eDNA could be applied to detect an invasive, biofouling bivalve, the golden mussel Limnoperna fortunei. Second, we initiated a one-time survey in a sub-canal of the SNWDP using refined sampling (12 sites in ~22 km canal) and considered a few environmental predictors. We found that detection of target eDNA in the main canal was achieved up to 1100 km from the putative source population but was restricted to the warmer months (May-November). Detection probability exhibited a significant positive relationship with average daily minimum air temperature and with water temperature, consistent with the expected spawning season. eDNA concentration in the main canal generally fluctuated across months and sites and was generally higher in warmer months. Golden mussel eDNA concentration in the sub-canal decreased significantly with distance from the source and with increasing water temperature and became almost undetectable at ~22 km distance. Given the enormity of the SNWDP, golden mussels may eventually expand their distribution in the main canal, with established "bridgehead" populations facilitating further spread. Our findings suggest an elevated invasion risk of golden mussels in the SNWDP in warm months, highlighting the critical period for spread and, possibly, management.

Microbial community day-to-day dynamics during a spring algal bloom event in a tributary of Three Gorges Reservoir

The microbial food-loop is critical to energy flow in aquatic food webs. We tested the hypothesis that species composition and relative abundance in a microbial community would be modified by the development of toxic algal blooms either by enhanced carbon production or toxicity. This study tracked the response of the microbial community with respect to composition and relative abundance during a 7-day algal bloom event in the Three Gorges Reservoir in May 2018. Chlorophyll a biomass, microscopic identification and cell counting of algae and algal abundance (ind. L^-1) and carbon, nutrient concentrations (total phosphorus and nitrogen, dissolved total phosphorus and nitrogen), and DNA high throughput sequencing were measured daily. Algal density (1.2 × 10⁹ ind. L^-1) and Chlorophyll a (219 μg L^-1) peaked on May 20th-21st, when the phytoplankton community was dominated by Chlorella spp. and Microcystis spp. The concentrations of both dissolved total nitrogen and phosphorus declined during the bloom period. Based on DNA high throughput sequencing data, the relative abundance of eukaryotic phytoplankton, microzooplankton (20-200 μm), mesozooplankton (>200 μm), and fungal communities varied day by day while the prokaryotic community revealed a more consistent structure. Enhanced carbon production during the bloom was closely associated with increased heterotrophic microbial composition in both the prokaryotic and eukaryotic communities. A storm event, however, that caused surface cooling and deep mixing of the water column greatly modified the composition and relative abundance of species in the microbial loop. The high temporal variability and dynamics observed in this study suggest that many factors, and not just algal blooms, were interacting to determine the composition and relative abundance of species of the microbial loop.

Influence of Feeding Ecology on Legacy Organochlorine Contaminants in Freshwater Fishes of Lake Erie

Persistent organic pollutants (POPs) in biota are influenced by ecological, physiological, and physicochemical properties; however, there is a need for a better understanding about the interplay of these parameters on POP dynamics and fate. To address this, POPs in three Lake Erie freshwater fishes (freshwater drum, Aplodinotus grunniens; walleye, Sander vitreus; and white perch, Morone americana) with different feeding ecologies were assessed using life history characteristics and three stable isotopes (δ¹³ C, δ¹⁵ N, and δ³⁴ S). Lipid normalized POP concentrations were in the range of past studies and were generally similar among the three species when all ages were combined. Principal component analysis (PCA) found the two significant PCs (explaining 59% and 10% of the variation), with all POPs loading significantly onto PC1, which indicated a common source of contamination, likely legacy sediment loads. Loadings on both PCs were correlated with POP log K_OW . Age, habitat use (δ¹³ C and δ³⁴ S), trophic position (δ¹⁵ N) and interactions between age and δ¹⁵ N, age and species, and δ¹⁵ N and δ³⁴ S were significant predictors of POP concentration based on PC1 scores, whereas δ¹³ C and species were significant predictors of PC2 scores. The similar concentrations among the species, yet variation related to the ecology (age and trophic position) across individuals demonstrates the complexity of contaminant dynamics in freshwater fish in a large lake system and the need to consider variation across individuals within species. Environ Toxicol Chem 2021;40:3421-3433. © 2021 SETAC.

Multiple factors regulate filtration by invasive mussels: Implications for whole-lake ecosystems

The quagga mussel (Dreissena rostriformis bugensis) is a filter-feeding invasive species that has re-engineered many freshwater ecosystems worldwide. High clearance rates (CRs) and dense populations underpin their ecological impacts. CRs, however, are highly variable, as are environmental factors that regulate them. Despite their widespread distribution in Europe and North America, knowledge of how multiple environmental factors regulate CRs of quagga mussels remains limited. We investigated quagga mussel CRs under varying conditions including water temperature, food availability, habitat depth, flow velocity, and duration of incubation in chambers with both static and flowing water. We found that CR was positively related to water temperature and initial food concentration in static chambers. When coupled with limited food concentration, cold water (7.5 °C), due to a deep-water upwelling event, produced very low CR (~ 10× lower) compared to warmer water (12-24 °C) (0.47 vs. 3.12-5.84 L g^-1 DW h^-1). Mussels from deeper water (20 m) had CRs that were ~ 3.5× higher than from shallower depths (2-10 m) and CRs were inversely affected by total mussel dry weight. Flow rates from 1 to 22 cm s^-1 generated a unimodal pattern of CR with an optimal flow velocity of 6-12 cm s^-1 (~ 2× higher than suboptimal CRs). Enhanced flow velocity (22 cm s^-1), reflective of storm conditions in shallow waters, significantly increased the closing/reopening activity of mussel valves relative to lower velocities (1-12 cm s^-1). Incubation time had a strong negative effect (~ 2-4× reduction) on CRs likely reflecting refiltration in static chambers versus food saturation of mussels in flowing chambers, respectively. Our findings highlight how multiple factors can influence quagga mussel CRs by factors of 2-10. Given widespread habitat heterogeneity in large aquatic ecosystems, whole-lake estimates of mussel impacts should include multiple regulatory factors that affect mussel filtration.

Basin-Specific Pollutant Bioaccumulation Patterns Define Lake Huron Forage Fish

The Lake Huron ecosystem is unique among the Laurentian Great Lakes (USA/Canada) in that its surface area encompasses 3 distinct basins. This ecosystem recently experienced significant ecological restructuring characterized by changes in primary production, species dominance and abundances, and top predator energy dynamics. However, much of the evidence for this restructuring has been largely derived from biomonitoring data obtained from long-term sampling of the lake's Main Basin. We examined polychlorinated biphenyl (PCB) concentrations and the stable isotopes of carbon (δ¹³ C) and nitrogen (δ¹⁵ N) in rainbow smelt (Osmerus mordax), bloater (Coregonus hoyi), and round goby (Neogobius melanostomus) to determine spatial variability in these environmental markers as indicators of the ubiquity of trophic restructuring throughout Lake Huron. Stable isotopes indicated that North Channel fish occupied trophic positions between 0.5 and 1.0 lower relative to Main Basin and Georgian Bay conspecifics, respectively. Sum PCB concentrations for 41 congeners were highest for fish from the Main Basin (27.5 ± 3.0 ng g^-1 wet wt) and Georgian Bay (26.3 ± 3.4 ng g^-1 wet wt) relative to North Channel (13.6 ± 1.2 ng g^-1 wet wt) fish. Discriminant functions analysis demonstrated basin-specific PCB congener profiles with individual species also having distinct profiles dependent on their basin of collection. These bioaccumulation patterns among Lake Huron forage fish mirror those reported for lake trout in this lake and indicate that the degree of food-web ecological restructuring in Lake Huron is not equivalent across the basins. Specifically, basin-specific PCB congener profiles demonstrated that differences among Lake Huron secondary and top predator consumer species are likely dictated by cross-basin differences in zooplankton community ecology and trophodynamics that can regulate the efficiencies of prey energy transfer and PCB congener bioaccumulation patterns in aquatic food webs. Environ Toxicol Chem 2020;39:1712-1723. © 2020 SETAC.

Functional response and size-selective clearance of suspended matter by an invasive mussel

Filter feeding activities link suspension feeders with their environment and underpin their impact on aquatic ecosystems. Despite their ecological and economic impacts, the functional response and size-selective capture of suspended particulates have not been well documented for the golden mussel Limnoperna fortunei. Here we demonstrated that golden mussels had a type I functional response, with an attack rate a = 0.085 and negligible handling time (h). Clearance rate ranged between 72.6 ± 27.0 and 305.5 ± 105.9 mL ind.^-1h^-1 (Mean ± S.E.), depending on food concentrations, which exhibited an inverse relationship with clearance rate. Presence of golden mussels suppressed chlorophyll a concentration in experimental mesocosms, the extent of which was dependent on mussel abundance. Concentration of suspended particles in experimental mesocosms experienced a sharp initial decline across all size categories (≤1->50 μm), though with increased final concentration of large particles (>25 μm), indicating packaging and egestion by golden mussels of fine particles (down to ≤1 μm). Capture efficiency of quantitatively-dominant suspended matter (≤1-50 μm) by golden mussels was inversely related to particle size. Animal abundance, particle size, and their interaction (abundance × particle size) determined the extent to which matter was removed from the water column. Presently L. fortunei occurs primarily in the southern end of the central route of South to North Water Diversion Project (China), but the species is spreading north; we anticipate that impacts associated with filtering of L. fortunei will correspond with local population abundance along this gradient.

A Multitracer Approach to Quantifying Resource Utilization Strategies in Lake Trout Populations in Lake Huron

Lake ecosystems are threatened by an array of stressors. An understanding of how food webs and bioaccumulation dynamics respond to these challenges requires the quantification of energy flow. We present a combined, multitracer approach using both polychlorinated biphenyls (PCBs) and stable isotopes to trace energy flow, and to quantify how lake trout feeding strategies have adapted to changes in food web structure in 3 basins of Lake Huron (ON, Canada). This combined tracer approach allows the quantification of dietary proportions (using stable isotopes), which are then integrated using a novel PCB tracer approach that employs knowledge of PCB bioaccumulation pathways, to estimate consumption and quantify energy flow between age cohorts of individual fish across Lake Huron. We observed basin-specific differences in ultimate energy sources for lake trout, with Georgian Bay lake trout deriving almost 70% of their energy from benthic resources compared with 16 and 33% for Main Basin and North Channel lake trout, respectively. These differences in resource utilization are further magnified when they are contrasted with age. The dependency on pelagic energy sources in the Main Basin and North Channel suggests that these populations will be the most negatively affected by the ongoing trophic collapse in Lake Huron. Our study demonstrates the utility of a multitracer approach to quantify the consequences of food web adaptations to changes in aquatic ecosystems. Environ Toxicol Chem 2019;38:1245-1255. © 2019 SETAC.

Protein and lipid growth rates regulate bioaccumulation of PCBs and Hg in Bighead Carp (Hypophthalmichthys nobilis) and Silver Carp (Hypophthalmichthys molitrix) from the Three Gorges Reservoir, China

This study evaluated the effect of growth of different tissue compartments on the bioaccumulation of mercury (Hg) and polychlorinated biphenyls (PCBs) in Silver Carp (Hypophthalmichthys molitrix) and Bighead Carp (Hypophthalmichthys nobilis) from the Three Gorges Reservoir (TGR), China. A non-steady state bioenergetics/toxicokinetic model was developed to simulate PCB and Hg concentrations in these two species and compared with field data. Simulations using constant whole body growth rate and constant tissue to whole body weight ratios were contrasted against simulations adopting age specific whole body and tissue/age specific growth rates for their goodness of fit to field data. The simulations using age/tissue specific growth rates demonstrated better fit to field data for PCBs compared to the constant growth rate models (22% improved R²), while both models explained similar variation in Hg concentration data. Both species demonstrated higher growth rates of lipids (on a daily basis) relative to whole body and protein contributing to higher growth dilution of PCBs compared to Hg. Although stable isotope data indicated some degree of diet and/or habitat shift, simulations assuming a constant diet concentration explained between 36 and 40% of the variation in fish concentrations for both contaminants and fish species. This study demonstrates that differences in the bioaccumulation rate of PCBs and Hg by Asian carp can be partially explained by differences in the growth rates of key tissue storage compartments associated with each contaminant. These differences in chemical-specific growth dilution subsequently contribute to differences in chemical retention and bioaccumulation patterns of Hg and PCBs by fish.

Importance of growth rate on mercury and polychlorinated biphenyl bioaccumulation in fish

To evaluate the effect of fish growth on mercury (Hg) and polychlorinated biphenyl (PCB) bioaccumulation, a non-steady-state toxicokinetic model, combined with a Wisconsin bioenergetics model, was developed to simulate Hg and PCB bioaccumulation in bluegill (Lepomis macrochirus). The model was validated by comparing observed with predicted Hg and PCB 180 concentrations across 5 age classes from 5 different waterbodies across North America. The non-steady-state model generated accurate predictions for Hg and PCB bioaccumulation in 3 of 5 waterbodies: Apsey Lake (ON, Canada), Sharbot Lake (ON, Canada), and Stonelick Lake (OH, USA). The poor performance of the model for the Detroit River (MI, USA/ON, Canada) and Lake Hartwell (GA/SC, USA), which are 2 well-known contaminated sites with possibly high heterogeneity in spatial contamination, was attributed to changes in feeding behavior and/or prey contamination. Model simulations indicate that growth dilution is a major component of contaminant bioaccumulation patterns in fish, especially during early life stages, and was predicted to be more important for hydrophobic PCBs than for Hg. Simulations that considered tissue-specific growth provided some improvement in model performance particularly for PCBs in fish populations that exhibited changes in their whole-body lipid content with age. Higher variation in lipid growth compared with that of lean dry protein was also observed between different bluegill populations, which partially explains the greater variation in PCB bioaccumulation slopes compared with Hg across sampling sites. Environ Toxicol Chem 2018;37:1655-1667. © 2018 SETAC.

Effects of Long-Term Anthropogenic Disturbance on the Benthic Episammic Diatom Community of an Ancient, Tropical Lake

Habitat homogenization, nutrient enrichment and loss of biodiversity are broadly recognized as the consequences of human activity in aquatic systems. Diatoms (Bacillariophyceae) are frequently used in aquatic environmental assessment and impact monitoring, but in unique habitats dominated by endemic taxa, traditional approaches may not be appropriate. We examined the impacts of long term anthropogenic impacts upon the littoral episammic diatom community around the town of Soroako, located on Lake Matano, an ancient tropical lake. Lake Matano is located on central Sulawesi Island, Indonesia, and socio-economic conditions are typical of developing nations. Although differences in nutrient concentrations were undetectable with field-based spectroscopy approaches, mean Shannon diversity was decreased in association with proximity the town-site. However, mean ß-diversity was maintained despite several decades of shoreline modification at Soroako. Elevated abundances of early-successional diatom taxa in the disturbed area drove differences between areas immediately offshore of Soroako and those farther away. These findings suggest that increased physical disturbance and TSS loads around Soroako, rather than increased nutrient loading, influenced shifts in the diatom community. These results suggest that microscopy-based biomonitoring approaches are sensitive indicators of environmental modification that could be useful in areas where access to cutting-edge analytical equipment is limited.

Assessment of hazard metrics for predicting field benthic invertebrate toxicity in the Detroit River, Ontario, Canada

Numerical sediment quality guidelines (SQGs) are frequently used to interpret site-specific sediment chemistry and predict potential toxicity to benthic communities. These SQGs are useful for a screening line of evidence (LOE) that can be combined with other LOEs in a full weight of evidence (WOE) assessment of impacted sites. Three common multichemical hazard quotient methods (probable effect concentration [PEC]-Q_avg , PEC-Q_met , and PEC-Q_sum ) and a novel (hazard score [HZD]) approach were used in conjunction with a consensus-based set of SQGs to evaluate the ability of different scoring metrics to predict the biological effects of sediment contamination under field conditions. Multivariate analyses were first used to categorize river sediments into distinct habitats based on a set of physicochemical parameters to include gravel, low and high flow sand, and silt. For high flow sand and gravel, no significant dose-response relationships between numerically dominant species and various toxicity metric scores were observed. Significant dose-response relationships were observed for chironomid abundances and toxicity scores in low flow sand and silt habitats. For silt habitats, the HZD scoring metric provided the best predictor of chironomid abundances compared to various PEC-Q methods according to goodness-of-fit tests. For low flow sand habitats, PEC-Q_sum followed by HZD, provided the best predictors of chironomid abundance. Differences in apparent chironomid toxicity between the 2 habitats suggest habitat-specific differences in chemical bioavailability and indicator taxa sensitivity. Using an IBI method, the HZD, PEC-Q_avg , and PEC-Q_met approaches provided reasonable correlations with calculated IBI values in both silt and low flow sand habitats but not for gravel or high flow sands. Computation differences between the various multi-chemical toxicity scoring metrics and how this contributes to bias in different estimates of chemical mixture toxicity scores are discussed and compared. Integr Environ Assess Manag 2017;13:410-422. © 2016 SETAC.

Quantitative Biomonitoring in the Detroit River Using Elliptio complanata: Verification of Steady State Correction Factors and Temporal Trends of PCBs in Water Between 1998 and 2015

Quantitative biomonitoring methods were applied to determine PCB concentrations in water from the Detroit River over a 17 year period. During 2014, mussels were deployed for and extended duration (21-364 days) and time dependent PCB concentrations were fit to a bioaccumulation model to estimate elimination coefficients (k_tot) and provide site specific calibration of mussel toxicokinetics. The site specific calibration and different k_tot versus K_OW relationships from the literature were used to correct for steady state. ∑PCB concentrations in water were not significantly dependent on the k_tot values used indicating that individual variation exceeds error contributed by steady state correction factors. The model was then applied to estimate ∑PCB concentrations in water using the long term (1998-2015) data. ∑PCBs concentrations in water exhibited a significant decreasing trend with a half life of 9.12 years resulting in a drop in yearly geometric mean residues from 198.1 to 43.6 pg/L.

Ecological Implications of Steady State and Nonsteady State Bioaccumulation Models

Accurate predictions on the bioaccumulation of persistent organic pollutants (POPs) are critical for hazard and ecosystem health assessments. Aquatic systems are influenced by multiple stressors including climate change and species invasions and it is important to be able to predict variability in POP concentrations in changing environments. Current steady state bioaccumulation models simplify POP bioaccumulation dynamics, assuming that pollutant uptake and elimination processes become balanced over an organism's lifespan. These models do not consider the complexity of dynamic variables such as temperature and growth rates which are known to have the potential to regulate bioaccumulation in aquatic organisms. We contrast a steady state (SS) bioaccumulation model with a dynamic nonsteady state (NSS) model and a no elimination (NE) model. We demonstrate that both the NSS and the NE models are superior at predicting both average concentrations as well as variation in POPs among individuals. This comparison demonstrates that temporal drivers, such as environmental fluctuations in temperature, growth dynamics, and modified food-web structure strongly determine contaminant concentrations and variability in a changing environment. These results support the recommendation of the future development of more dynamic, nonsteady state bioaccumulation models to predict hazard and risk assessments in the Anthropocene.

PCB Food Web Dynamics Quantify Nutrient and Energy Flow in Aquatic Ecosystems

Measuring in situ nutrient and energy flows in spatially and temporally complex aquatic ecosystems represents a major ecological challenge. Food web structure, energy and nutrient budgets are difficult to measure, and it is becoming more important to quantify both energy and nutrient flow to determine how food web processes and structure are being modified by multiple stressors. We propose that polychlorinated biphenyl (PCB) congeners represent an ideal tracer to quantify in situ energy and nutrient flow between trophic levels. Here, we demonstrate how an understanding of PCB congener bioaccumulation dynamics provides multiple direct measurements of energy and nutrient flow in aquatic food webs. To demonstrate this novel approach, we quantified nitrogen (N), phosphorus (P) and caloric turnover rates for Lake Huron lake trout, and reveal how these processes are regulated by both growth rate and fish life history. Although minimal nutrient recycling was observed in young growing fish, slow growing, older lake trout (>5 yr) recycled an average of 482 Tonnes·yr(-1) of N, 45 Tonnes·yr(-1) of P and assimilated 22 TJ yr(-1) of energy. Compared to total P loading rates of 590 Tonnes·yr(-1), the recycling of primarily bioavailable nutrients by fish plays an important role regulating the nutrient states of oligotrophic lakes.

Comparison of the Toxicokinetics and Bioaccumulation Potential of Mercury and Polychlorinated Biphenyls in Goldfish (Carassius auratus)

Both mercury (Hg) and polychlorinated biphenyls (PCBs) demonstrate food web biomagnification in aquatic ecosystems, yet their toxicokinetics have not been simultaneously contrasted within a common fish species. This study quantifies uptake and elimination rates of Hg and PCBs in goldfish. Fish were exposed to contaminated food containing PCBs and Hg to determine dietary chemical assimilation efficiencies (AEs) and elimination coefficients (ktot). To test first-order kinetics, three exposure regimes were established by varying the proportion of contaminated fish incorporated into the food. Dietary AEs were 98 ± 10, 75 ± 12, and 40 ± 9% for MeHg, THg, and PCBs, respectively. The ktot values were 0.010 ± 0.003 and 0.010 ± 0.002 day(-1) for THg and MeHg, respectively. No significant differences were found in ktot among the dosing levels for either THg or MeHg, confirming that Hg elimination is a first-order process. For PCB, ktot ranged from 0.007 to 0.022 day(-1) and decreased with an increase in hydrophobicity. This study revealed that Hg had an AE higher than that of PCBs, while the ktot of Hg was similar to those measured for the most hydrophobic PCBs. We conclude that Hg has a bioaccumulation potential in goldfish 118% higher than the highest PCB BMF observed for congeners with a log KOW of >7.

Hexabromocyclododecane Flame Retardant Isomers in Sediments from Detroit River and Lake Erie of the Laurentian Great Lakes of North America

Sediments collected in 2004 from along the Detroit River (n = 19) and across all of Lake Erie (n = 18) were analyzed for isomers of the flame retardant chemical, hexabromocyclododecane (HBCD), using liquid chromatography-tandem mass spectrometry. Sediment samples had ΣHBCD concentrations ranging from not detected to 1.6 ng/g d.w. γ-HBCD (56 %-100 % of ΣHBCDs) was the predominate isomer, observed in 7 of 19 samples from the Detroit River and 6 of 18 samples from Lake Erie (all within the western basin). α-HBCD was found in 4 Detroit River and 2 Lake Erie western basin sites, while β-HBCD was only in two Detroit River samples. High ΣHBCD concentrations (>100 ng/g d.w.) were found in two sludge samples from two Windsor, ON, wastewater treatment plants that feed into the Detroit River upstream. HBCD contamination into the Detroit River is a major input vector into Lake Erie and with an apparent sediment dilution effect moving towards the eastern basin.

Ecological factors contributing to variability of persistent organic pollutant bioaccumulation within forage fish communities of the Detroit River, Ontario, Canada

Understanding variability of contaminant bioaccumulation within and among fish populations is critical for distinguishing between the chemical and biological mechanisms that contribute to food web biomagnification and quantifying contaminant exposure risks in aquatic ecosystems. The present study examined the relative contributions of chemical hydrophobicity (octanol-water partition coefficient [KOW ]) and habitat use as factors regulating variability in polychlorinated biphenyl (PCB) congener bioaccumulation in 3 lower trophic level cyprinid species across spatial and temporal scales. Bluntnose minnows (Pimephales notatus), spottail shiners (Notropis hudsonius), and emerald shiners (Notropis atherinoides) were sampled at 3 locations in the Detroit River, Ontario, Canada. Variability in PCB concentration was evaluated with respect to several factors, including chemical hydrophobicity, site, season, species, and weight using sum of squares and Levene's test of homogeneity of variance. Individual variability in bioaccumulated congener-specific residues depended on chemical hydrophobicity with mid- and high-range KOW congeners (log KOW  >6.0), demonstrating the highest amount of variance compared with low KOW congeners. Different feeding strategies also contributed to the variance observed for mid-range KOW congeners among species. In the present study, benthic feeding specialists exhibited lower variance in PCB concentrations compared with the 2 generalist species. The results indicate that chemical hydrophobicity and feeding ecology not only contribute to differences in the biomagnification potentials of fish, but also regulate between-individual variation in PCB concentrations both across and within fish species.

Effect of season and habitat on PCB bioaccumulation by caged bluegill sunfish deployed in a Great Lakes area of concern

Bluegill sunfish were caged in the Detroit River, Ontario, Canada, for 64 days to determine bioaccumulation rates of PCBs. Deployments involved placing fish in cages suspended in the water (suspended cages) compared to cages partially buried in sediments. Deployments were performed in the summer and winter months. During summer, fish exhibited significant increases in body weight and lipid content (sediment associated cages only), whereas in winter, body weights did not change. Lipid normalized PCB concentrations and PCB mass in fish increased significantly with time in summer deployments, but not in winter. Fish continued to accumulate PCBs over the 64 days caging duration except for PCBs 33, 49, and 52 in sediment associated cages. There were no significant differences in the bioaccumulation of PCBs between cage types. This study confirms that biomonitoring studies using caged fish should ensure chemical toxicokinetics are consistent when comparing bioaccumulation results among sites and/or time points.

Assessment of decadal changes in sediment contamination in a large connecting channel (Detroit River, North America)

Concentrations of selected heavy metals (Cd, Cu, Hg, Pb, Zn) and organic contaminants (PCBs, PAHs) were investigated in samples from the Detroit River (Great Lakes, North America) in 1999 and 2008/09 collected using a stratified random sampling design. Getis-Ord geospatial analysis was used to further establish locations of areas demonstrating significantly high and low contaminant concentrations in the river. Based on the stratified random sampling design, a majority of the examined metals and organic contaminants demonstrated little or no trends with respect to regional sediment concentrations and river-wide mass balances over the investigated time interval. The Getis-Ord analysis revealed local scales of contaminated and clean areas which did not conform to the original strata used in the geostatistical sampling design. It is suggested that geospatial analyses such as Getis-Ord be used in the design of future sediment quality surveys to refine locations of strata that can simultaneously address sediment recovery over system-wide, regional and local spatial scales.

Speciation patterns and processes in the zooplankton of the ancient lakes of Sulawesi Island, Indonesia

Although studies of ancient lake fauna have provided important insights about speciation patterns and processes of organisms in heterogeneous benthic environments, evolutionary forces responsible for speciation in the relatively homogenous planktonic environment remain largely unexplored. In this study, we investigate possible mechanisms of speciation in zooplankton using the freshwater diaptomids of the ancient lakes of Sulawesi, Indonesia, as a model system. We integrate phylogenetic and population genetic analyses of mitochondrial and nuclear genes with morphological and genome size data. Overall, our results support the conclusion that colonization order and local adaptation are dominant at the large, island scale, whereas at local and intralacustrine scales, speciation processes are regulated by gene flow among genetically differentiated and locally adapted populations. In the Malili lakes, the diaptomid populations are homogenous at nuclear loci, but show two highly divergent mitochondrial clades that are geographically restricted to single lakes despite the interconnectivity of the lake systems. Our study, based on coalescent simulations and population genetic analyses, indicates that unidirectional hybridization allows gene flow across the nuclear genome, but prevents the introgression of mitochondria into downstream populations. We suggest that hybridization and introgression between young lineages is a significant evolutionary force in freshwater plankton.

Spatial and temporal variability of PCBs in Detroit River water assessed using a long term biomonitoring program

An assessment of polychlorinated biphenyls (PCBs) in water of the Detroit River, North America, was performed using mussel biomonitoring data generated between 1996 and 2010. The study included a temporal monitoring program at six locations and an enhanced spatial survey performed during 2002. Mussels were transplanted at biomonitoring stations and collected after 21-226 d. A toxicokinetic model was used to perform steady state and control corrections followed by an equilibrium partitioning model to estimate bioavailable water concentrations of PCBs. Bioavailable water concentrations of PCBs were similar in magnitude and trends to dissolved water concentrations reported in previous studies using direct sampling approaches. PCB concentrations exhibited complex temporal patterns at the six biomonitoring stations with multi-year declines in PCB trajectories between 1996 and 2002 and less consistent trends occurring across stations in later years. Spatial patterns of PCBs during 2002 revealed significantly higher water contamination on the US side of the river (seasonal average mean ± standard error (SE) sum PCB concentration of 0.63 ± 0.11 ng L(-1)) compared to the Canadian side (mean ± SE sum PCB concentration of 0.09 ± 0.01 ng L(-1)). Spatial/temporal variability of bioavailable PCB concentrations was greatest between countries, followed by moderate variation across years and by river reach (upstream, midstream and downstream sections within a country) and lowest when comparing intra-seasonal variation.

Calibration of the gastrointestinal magnification model to predict maximum biomagnification potentials of polychlorinated biphenyls in a bird and fish

The gastrointestinal magnification (GI-magnification) model was calibrated in ring doves and Japanese koi using matched data on dietary assimilation and fecal depuration of polychlorinated biphenyls (PCBs). Mass transport parameters describing PCB flux from gut contents to organism (D(go)′; mol d(-1) Pa(-1)) and organism to gut contents (D(og); mol d(-1) Pa(-1)) were quantified to test the hypothesis that the ratio of these two terms approached unity. For birds, D(go)′/D(og) ranged from 2.9 to 6.3 and for fish the ratios ranged from 0.7 to 3.1. In both species, the ratio commonly exceeded 1. The GI-magnification model was used to predict maximum PCB biomagnification factors (BMF(max)) for each species which ranged from 18.5 to 33.8 for ring doves and 7.9 to 14.8 for Japanese koi. Chemical losses via respiration reduced steady state biomagnification factor (BMF(ss)) estimates by a negligible amount in birds, whereas for fish, predicted BMF(ss) decreased to values from 0.5 to 7.2. This study demonstrated that chemical transfer efficiency during assimilation exceeds organism/feces transfer which contributes to elevated PCB biomagnification potentials in birds and fish. Combined with reduced losses of chemical across respiratory surfaces, higher D(go)′/D(og) ratios of birds contribute to elevated biomagnification in birds over fish.

The methane cycle in ferruginous Lake Matano

In Lake Matano, Indonesia, the world's largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr)oxides in the lake sediments. Biogenic CH₄ accumulates to high concentrations (up to 1.4 mmol L⁻¹) in the anoxic bottom waters, which contain a total of 7.4 × 10⁵ tons of CH₄. Profiles of dissolved inorganic carbon (ΣCO₂) and carbon isotopes (δ¹³C) show that CH₄ is oxidized in the vicinity of the persistent pycnocline and that some of this CH₄ is likely oxidized anaerobically. The dearth of NO₃⁻ and SO₄²⁻ in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn) (hydr)oxides. Thermodynamic considerations reveal that CH₄ oxidation coupled to Fe(III) or Mn(III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH₄. 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe-rich environment. Such Fe-rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem.

Contribution of fecal egestion to the whole body elimination of polychlorinated biphenyls by Japanese koi (Cyprinus carpio)

This research investigated dose-dependent whole body and fecal elimination of 39 polychlorinated biphenyl (PCB) congeners spanning a range of chemical hydrophobicities (log Kow) by the Japanese koi (Cyprinus carpio). Both whole body (ktot) and fecal (keg) PCB congener elimination rate coefficients were negatively correlated with log Kow and observed to be dose independent. PCB congener ktot values determined for koi were representative of those generated for fish species of similar size and reared at near optimal temperatures. For persistent and metabolized-type PCB congeners, no significant difference was observed between the regressions describing the relationships between ktot and log Kow for these congeners. Individual PCB congener keg coefficient estimates ranged between 1% and 20% of their respective ktot values but averaged only 5% of the magnitude of ktot over a log Kow range of 5.7-7.8. These results verify first-order kinetics of PCB elimination by a fish species and demonstrate that the relative contribution of keg to ktot is negligible, even for highly hydrophobic (log Kow>6.5) compounds. It was concluded that gill elimination is the primary mechanism of elimination for persistent organic pollutants such as PCBs by Japanese koi.

Polychlorinated biphenyl elimination rates and changes in chemical activity in hibernating amphibians

The present study examined polychlorinated biphenyl (PCB) elimination rates in overwintering green frogs (Rana clamitans) to determine if changes in chemical activity occurred during hibernation. Adult green frogs were dosed with a 1:1:1 ratio of Aroclors 1248:1254:1260 in sunflower oil and allowed to enter into hibernation. Frogs were collected at four time points over the course of 85 days. Significant PCB elimination rates ranged from 0.0027 to 0.0376 d(-1). A negative correlation was found between K(OW) and elimination rate. Over the course of the present study, a decrease in total body percent lipid was measured. There was an overall increase in fugacity of higher K(OW) compounds corresponding to the relatively rapid decrease in lipid content. Congeners in metabolic group 2 (meta-para vicinal hydrogen atoms) were preferentially eliminated over those in metabolic group 3 (ortho-meta vicinal hydrogen atoms), suggesting that biotransformation was occurring during hibernation. It was concluded that metabolic activity during hibernation, associated with water temperature, was sufficiently high to reduce lipid concentrations and increase chemical activity in emerging adults.

The influence of diet on the assimilation efficiency of 47 polychlorinated biphenyl congeners in Japanese koi (Cyprinus carpio)

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 (K(OW)) 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.

No barriers to gene flow among sympatric polychromatic 'small' Telmatherina antoniae from Lake Matano, Indonesia

Genetic divergence, assortative courtship and intermale aggression were assessed between sympatric colour morphs of the sailfin silverside Telmatherina antoniae, endemic to Lake Matano, Indonesia. Genetic analysis using microsatellite markers showed no barriers to gene flow among T. antoniae primary colour morphs (blue and yellow) within sampling sites, sympatric populations or at the lake-wide level. Low but significant genetic differentiation was found between yellow morphs and mixed (blue-yellow) morphs. Behavioural surveys indicated assortative courtship does occur along primary colour lines; however, intermale aggression among paired and intruding male morphs appeared equal with respect to male colour. These observations support the hypothesis that males view other males as threats to their courtship regardless of their colour. This study supports recent work suggesting that assortative mating is present in T. antoniae despite a lack of reproductive isolation among colour morphs.

A combined food web toxicokinetic and species bioenergetic model for predicting seasonal PCB elimination by yellow perch (Perca flavescens)

A commonly used toxicokinetic model was coupled to a bioenergetic submodel optimized for yellow perch and an empirical growth submodel to predict daily PCB elimination flux in three size classes of fish under seasonally variable temperatures. Across seasons, the bioenergetic model predicted highly variable gill ventilation and fecal egestion rates which varied by 74.2-111.2 fold and 35-65 fold, respectively, over the annual cycle. The empirical growth model accounted for seasonal trends in overwintering lipid losses evident for all fish size classes and growth, evident only for the small fish size class, during warm water periods. The toxicokinetic model described seasonal trends in congener specific PCB mass balance of fish, but tended to overestimate PCB elimination for less hydrophobic congeners when the recommended gill transfer efficiency term (Ew) of 0.54 was used. Downward adjustment of Ew to an average value of 0.14 produced the strongest model fit for several low Kow PCBs but had less effect on model performance for mid- to high Kow congeners. The toxicokinetic model was less sensitive to parameters involved in fecal elimination of PCBs when applied to low and mid-Kow PCBs. This study demonstrates the importance of seasonal trends in metabolic rate, growth, and overwintering weight loss as factors that modify PCB toxicokinetics in temperate fish.

Photoferrotrophs thrive in an Archean Ocean analogue

Considerable discussion surrounds the potential role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce (<20 micromol x liter(-1)), and it is completely removed by sulfate reduction within the deep, Fe(II)-rich chemocline. The sulfide produced is efficiently scavenged by the formation and precipitation of FeS, thereby maintaining very low sulfide concentrations within the chemocline and the deep ferruginous bottom waters. Low productivity in the surface water allows sunlight to penetrate to the >100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lake's euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity.

Elimination of 10 polybrominated diphenyl ether (PBDE) congeners and selected polychlorinated biphenyls (PCBs) from the freshwater mussel, Elliptio complanata

Mussel biomonitors are widely used as screening tools for polybrominated diphenyl ethers (PBDEs) in marine and aquatic environments. This study determined elimination rate coefficients (k(tot)) for eight PBDE and five PCB congeners in the freshwater mussel, Elliptio complanata, over a 120d depuration period. Elimination of BDE 15, 28, 47, 75 and 100 was similar to PCBs of equivalent hydrophobicity and negatively related to chemical K(OW). Rapid elimination of BDE 190 and an inferred rapid elimination of BDE 183 indicate mussels are capable of biotransformation of certain highly brominated PBDEs. Time to 90% steady state ranged from 48 to 66d for di- and tribromoDE congeners and from 91 to >250d for tetra- to hexabromoDE congeners. Given the long time periods required for steady state, mussel accumulated PBDE residues should be interpreted in the context of calibrated bioaccumulation models.

Dietary exposure to low pesticide doses causes long-term immunosuppression in the leopard frog (Rana pipiens)

This study examines the relationship between dietary exposure of pesticides, DDT, and dieldrin and immunosuppression in the northern leopard frog (Rana pipiens). Immune function was measured before, during, and after a 10-week exposure period with the use of both adaptive and innate immunity responses. Exposure to low doses (75 ng/g body wt DDT or 2.1 ng/g dieldrin total dose over the 10 weeks) resulted in significant suppressive effects on antibody production and secondary delayed-type hypersensitivity (DTH). The high doses (750 ng/g DDT and 21 ng/g dieldrin), however, did not affect antibody production, DTH, or oxidative burst in a predictable dose-response manner. The differences in magnitude and direction of the effects of the two dosing regimes were likely due to differences in chemical exposure on the basis of feeding and effectiveness of chemical uptake. The low dose results demonstrated that moderate concentrations of pesticides, frequently observed in the environment, are able to weaken the immune response of R. pipiens.

Body shape vs. colour associated initial divergence in the Telmatherina radiation in Lake Matano, Sulawesi, Indonesia

Highly polymorphic colouration patterns are often associated with sexual selection in fish and can be the initial cause of divergence among closely related taxa. Here we use genetic, body colour and geometric morphometric data collected on 118 fish from Lake Matano, Sulawesi, Indonesia to test if colouration is the initial cause of divergence in the radiating Telmatherina genus. Results reveal that all Telmatherina previously described in this system can be categorized into three mitochondrial lineages and that colouration is only weakly associated with early divergence. Clade-specific body shapes, however, likely adapted to microenvironments are key to the initial divergence in this system. Data also show that although colourations were not likely instrumental in seeding divergence in these fish, they appear to have developed in parallel within each clade. Our results are consistent with an emerging pattern repeated in many vertebrate radiations, whereby divergence by colouration or other display traits is preceded by specialization to environmental adaptive peaks.

Resource-based adaptive divergence in the freshwater fish Telmatherina from Lake Matano, Indonesia

Adaptive radiations are an important source of biodiversity, but resolving which ecological pressures seed these processes in natural systems remains difficult. Here the adaptive radiation among Telmatherina, a genus of freshwater fish endemic to an ancient lake in central Sulawesi, Indonesia, was examined to determine its causal root. We demonstrate that all Telmatherina in this lake can be categorized into three lineages each possessing specialized skull shapes and pharyngeal jaw bones allowing them to exploit different resources. These data demonstrate a natural example of how resource partitioning has likely initiated adaptive radiation in a resource limited environment.

PCB elimination by yellow perch (Perca flavescens) during an annual temperature cycle

The significance of temperature on aquatic species ecology and physiology is well recognized yet its effects on chemical bioaccumulation kinetics are less well understood under natural conditions. In this study, yellow perch were dosed with a polychlorinated biphenyl (PCB) mixture and allowed to depurate the chemicals over 1 year under an ambient temperature cycle characteristic of northern temperate latitudes. PCB elimination kinetics during the summer months at optimal water temperature for perch (23 degrees C) were similar to those observed in lab studies with other species reared at their optimal temperature. During the fall and winter seasons, however, elimination of only 11 PCB congeners of log K(ow) < or = 5.7 was observed and half-lives averaged > 1000 d for these PCBs. PCB elimination was again observed with the onset of spring temperatures but elimination rates averaged 2.6 times slower for readily metabolized congeners and 7.5 times slower for more persistent PCBs than observed during the summer. Bioenergetics modeling efforts predicted maximum values for respiration, fecal egestion, and growth rates during summer months but also predicted rapid declines in these chemical dilution processes during the fall and winter concurrent with changes in temperature. As temperature increased into the spring, bioenergetic rates were predicted to increase but only achieved approximately 85% of maximum rates predicted for summer peak temperatures. These results indicate that minimal chemical elimination occurs in perch when metabolic functioning falls to low maintenance levels during the fall and winter. These seasons encompass approximately 8 months of the year at northern temperate latitudes and therefore these patterns have significant consequences for understanding mechanisms of food-web biomagnification of hydrophobic organic chemicals in aquatic systems.

Dacthal and chlorophenoxy herbicides and chlorothalonil fungicide in eggs of osprey (Pandion haliaetus) from the Duwamish-Lake Washington-Puget Sound area of Washington state, USA

Current-use chlorophenoxy herbicides including 2,4-dichlorophenoxyacetic acid, dicamba, triclopyr, dicamba, dimethyl tetrachloroterephthalate (DCPA or dacthal), and the metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and the fungicide, chlorothalonil, were investigated in the eggs of osprey (Pandion haliaetus) that were collected from 15 sites from five study areas Puget Sound/Seattle area of Washington State, USA. DCPA differs from acidic chlorophenoxy herbicides, and is not readily hydrolyzed to free acid or acid metabolites, and thus we developed a new method. Of the 12 chlorophenoxy herbicides and chlorothalonil analyzed only DCPA could be quantified at six of these sites (2.0 to 10.3 pg/g fresh weight). However, higher levels (6.9 to 85.5 pg/g fresh weight) of the unexpected DCPA structural isomer, dimethyl tetrachlorophthalate (diMe-TCP) were quantified in eggs from all sites. diMe-TCP concentrations tended to be higher in eggs from the Everett Harbor area. As diMe-TCP is not an industrial product, and not commercially available, the source of diMe-TCP is unclear. Regardless, these findings indicate that DCPA and diMe-TCP can be accumulated in the food chain of fish-eating osprey, and transferred in ovo to eggs, and thus may be of concern to the health of the developing chick and the general reproductive health of this osprey population.

Metamorphosis increases biotransformation of polychlorinated biphenyls: a comparative study of polychlorinated biphenyl metabolism in green frogs (Rana clamitans) and leopard frogs (Rana pipiens) at various life stages

Polychlorinated biphenyl (PCB) elimination rates were used to determine whether green frogs (Rana clamitans) and leopard frogs (Rana pipiens) at three life stages (tadpole, metamorph, and adult) were capable of metabolic biotransformation of PCBs. Polychlorinated biphenyls were grouped according to their structural properties to determine whether congeners with specific structures were eliminated more rapidly than others, which would suggest the occurrence of metabolic biotransformation. For both species and at all life stages studied, PCBs with adjacent unsubstituted meta-para sites (group-2 PCBs) were eliminated significantly faster than PCBs with adjacent unsubstituted ortho-meta sites (group-3 PCBs). Because these groups of PCBs span similar hydrophobicity ranges, it was concluded that green and leopard frogs can selectively metabolize group-2 PCBs. Metabolic activity was more pronounced in the metamorph stage than in any other life stage. In green frog metamorphs, the average elimination rate of the group-2 PCBs was 4.9-fold greater than that of the group-3 PCBs. By contrast, in green frog tadpoles, group-2 PCBs were eliminated 1.9-fold faster than group-3 PCBs, and in green frog adults, group-2 PCBs were eliminated 1.5-fold faster than group-3 PDBs.

Determination of polychlorinated biphenyl and polycyclic aromatic hydrocarbon elimination rates in adult green and leopard frogs

The purpose of the present study was to quantify elimination kinetics of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in adult green frogs (Rana clamitans) and leopard frogs (Rana pipiens). Three experiments were conducted: PCB elimination rate constants were determined for both frog species, and PAH elimination rate constants were determined for leopard frogs only. In green frogs, significant PCB elimination rate constants ranged from 0.013 to 0.04 d(-1) (time for frogs to achieve 90% steady state with water [t90] = 57.8-178.2 d). In leopard frogs, significant PCB elimination rate constants ranged from 0.004 to 0.047 d(-1) (t90 = 48.8-657.9 d). Polycyclic aromatic hydrocarbon elimination in leopard frogs was faster than PCB elimination in either frog species: Significant PAH rate constants ranged from 0.069 to 0.188 d(-1) (t90 = 12.2-33.5 d). In both species, and for both PCBs and PAHs, a significant inverse relationship was found between the chemical elimination rate constant and Kow. These results show that adult anurans have relatively low elimination rates of PCBs but exhibit a small capacity for metabolic biotransformation of PAHs that is comparable to that of invertebrates but lower than that of fish. These findings suggest that adult amphibians have the potential to be used as biomonitors for persistent organic chemicals.

Does metamorphosis increase the susceptibility of frogs to highly hydrophobic contaminants?

The purpose of this study was to determine whether the process of metamorphosis in amphibians increases the chemical activity of hydrophobic contaminants such as polychlorinated biphenyls (PCBs). We conducted an experiment in which green frog tadpoles were orally dosed with a PCB mixture; then placed into clean water to eliminate the chemicals as metamorphosis occurred. On several sampling dates before and during metamorphosis, organisms were sacrificed and analyzed to determine lipid contents and concentrations of individual PCB congeners. The majority of the PCBs studied in this experiment showed increases in chemical activity (fugacity) as a result of the physical changes that occurred during amphibian metamorphosis. A positive relationship was observed between PCB hydrophobicity and the magnitude of the fugacity increase. We determined that the fugacity of a persistent PCB congener will increase during green frog metamorphosis if its log K(ow) value is greater than 5.85. The fugacity of some of the more highly hydrophobic PCBs increased during metamorphosis by up to a factor of 4. Because of the rapid increases in chemical activity that were observed during metamorphosis, we conclude that toxicity tests involving hydrophobic organic contaminants should be conducted not only on tadpoles or adult frogs, but also on metamorphosing amphibians.

Simultaneous determination of tetrabromobisphenol A, tetrachlorobisphenol A, bisphenol A and other halogenated analogues in sediment and sludge by high performance liquid chromatography-electrospray tandem mass spectrometry

A high performance liquid chromatography-electrospray (negative) ionization-tandem mass spectrometry (HPLC-ESI(-)-MS-MS) based method has been developed for simultaneous determination of bisphenol A (BPA), tetrachlorobisphenol A (TCBPA), and tetrabromobisphenol A (TBBPA), as well as lower brominated BPA analogues in sediment and sludge samples. Samples were extracted with MTBE, target compounds were partitioned by aqueous solution of sodium hydroxide. The solution was subsequently acidified, and the enrichment and desalting were performed via solid phase extraction (SPE). After cleanup the target compounds were determined by HPLC-ESI(-)-MS-MS. The method limits of quantification (MLOQs) from sediment and sludge for BPA, monobromo-bisphenol A (mono-BBPA), dibromo-bisphenol A (di-BBPA), tribromo-bisphenol A (tri-BBPA), TBBPA and TCBPA were 0.15, 0.02, 0.02, 0.04, 0.05, and 0.03 ng/g (dry weight), respectively. Mean recovery of the analytes from spiked samples ranged from 70 to 105%, and the relative standard deviation ranged from 4.9 to 13.1%. The method was successfully applied to sediment and sludge samples analysis.

Genetic and morphological data supporting the hypothesis of adaptive radiation in the endemic fish of Lake Matano

Adaptive radiation resulting from differential selection acting on functional features is believed to be an important source of biodiversity. In this study, morphometric measures and mitochondrial DNA are used to test for adaptive radiation within four fish genera (Glossogobius, Oryzias, Dermogenys and Telmatherina) endemic to an ancient island lake (Lake Matano, Sulawesi, Indonesia), using the framework proposed by Schluter (The Ecology of Adaptive Radiation, Oxford University Press, 2000). We demonstrate common ancestry and rapid divergence in one genus (Telmatherina) based on 560 bp of 16S sequence data. We found higher levels of variation in feeding-related traits (N = 8) for Telmatherina relative to the other genera, while no differences were found for sexual display traits (N = 8) or neutral morphological traits (N = 8). Telmatherina also had the highest number of distinct colouration patterns among the four genera. These data, combined with the very low productivity of the lake, are indicative of selection driving adaptive radiation. The morphometric divergence in the Telmatherina likely results from selection acting on feeding traits in this low productivity lake, leading to trophic specialization among closely related morphotypes. These results provide indirect but compelling data supporting the adaptive radiation of Telmatherina in this system.

Determination of laboratory and field elimination rates of polychlorinated biphenyls (Pcbs) in the freshwater mussel, Elliptio complanata

Chemical elimination rate constants (k2) were determined for 41 polychlorinated biphenyl (PCB) congeners in dosed freshwater mussels, Elliptio complanta, following a 150-day laboratory depuration period. Congener-specific elimination rates were inversely dependent on the n-octanol/water partition coefficient (K(ow)) of the chemical according to the regression equation: logk2 = (-0.59 +/- 0.05) logK(ow) + (2.05 +/- 0.28) (R2 = 0.80, p < 0.001). PCB elimination rate constants in E. complanta were lower than reported for zebra mussels and green-lipped mussels but similar in magnitude and K(ow) dependence to data reported for American oysters. In order to validate the laboratory-derived PCB elimination rate constants, mussels dosed with [13C]PCB153 were allowed to depurate at one of the biomonitoring stations utilized in the Detroit River Biomonitoring Program and sampled at the same time intervals as laboratory animals. The field elimination rate constant for [13C]PCB153 was significantly greater than, but within a factor of 3 of, the laboratory elimination rate constant determined for unlabeled PCB153. This similarity in estimates of k2 for labeled and unlabeled PCB153 indicates that there is relatively little error introduced by using laboratory PCB elimination rate constants to estimate PCB153 toxicokinetics in mussels deployed at this field station. Elimination rate constants determined for PCBs in this species were lower and exhibited a stronger K(ow) dependence than elimination rate constants reported for selected PAHs. This suggests that E. complanata may possess some capability for PAH biotransformation.

Evaluation of chloroform/methanol and dichloromethane/hexane extractable lipids as surrogate measures of sample partition capacity for organochlorines in fish tissues

Organic contaminant concentration data are often lipid normalized to provide an indication of the chemical fugacity in the sample or to compare the relative equilibrium status of samples from the same environment. This study compared lipid normalized PCB and organochlorine concentration data for tissues of individual fish when lipids were measured using chloroform/methanol (CM) or dichloromethane/hexane (DH) extractions. The CM extraction produced higher lipid yields for dorsal muscle (8-fold difference) and carcass (1.7-fold difference) compared to DH extractions, while both methods yielded comparable lipid contents for liver and adipose tissue. Lipid normalized tissue/carcass PCB and organochlorine concentration ratios were variable across tissue types when lipid contents from the CM technique were used, whereas, tissue/carcass concentration ratios approached the expected value of unity for each tissue when DH-derived lipids were used. These data suggest that the tissue lipid content as derived using the DH extraction provided a better surrogate measure of sample partition capacity than tissue lipids determined using the CM technique.

Plasma-associated halogenated phenolic contaminants in benthic and pelagic fish species from the Detroit River

Halogenated phenolic contaminants (HPCs), polychlorinated biphenyls (PCBs), and other organochlorine (OC) contaminants (DDTs, chlordanes, HCH, and octachlorostyrene (OCS)) were determined (ng/g, wet wt basis) in the blood plasma of 6 piscivorous/pelagic- and 7 benthic-feeding fish species from the Detroit River. Seven to twelve hydroxylated (OH) PCB congeners with pentachloro- to nonachloro-substitution, pentachlorophenol (PCP) and 4-OH-heptachlorostyrene (4-OH-HpCS), as well as a number of other unidentified HPCs, were detected in all the fish species studied. The concentrations of sigma-OH-PCB (0.57-129.5 ng/ g), 4-OH-HpCS (0.02-0.31 ng/g), and PCP (0.05-3.42 ng/ g) in comparison to other major polychlorinated contaminants (sigma-PCB (10.4-909.0 ng/g), sigma-chlordane (0.72-8.68 ng/g), sigma-DDT (2.10-66.57 ng/g), and sigma-HCH (0.04-0.84 ng/g)) demonstrate the importance of HPCs, especially OH-PCBs, as plasma-associated contaminants. OH-PCBs are most likely metabolites of PCBs, and 4-OH-HpCS is a likely metabolite of OCS. Our findings indicate that metabolic biotransformation is a factor in the bioaccumulation, pharmacokinetics, and fate of OCS and highly chlorinated PCB congeners that are generally more recalcitrant in fish. Target tissue exposure to circulating OH-PCBs was variable, and thus potential OH-PCB-mediated toxicological activity and effects (e.g., endocrine-related) and health risks are different among the fish species.

Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure

An injection study and a field study were used to investigate the hypothesis that environmental xenobiotics have the potential to alter the immune function of northern leopard frogs (Rana pipiens). Three assays, IgM-specific antibody response to keyhole limpet hemocyanin linked to dinitrophenyl (KLH-DNP), zymozan induced chemiluminescence (CL) of whole blood and the delayed-type hypersensitivity (DTH), were used to assay humoral, innate and cell-mediated immune endpoints. Sublethal doses of DDT (923 ng/g wet wt), malathion (990 ng/g wet wt), and dieldrin (50 ng/g wet wt) were used in the injection study. In all pesticide-injected groups, antibody response was dramatically suppressed, DTH reactions were enhanced, and respiratory burst was lower. When the order of administration of pesticides and antigens was reversed, no differences in immune function between the control and dosed groups were apparent, indicating that frogs exposed to pathogens prior to pesticide exposure can still respond. A field study found significant differences in immune function between frog populations in pesticide-exposed and pesticide-free locations. The antibody response and CL were suppressed and the DTH enhanced in frogs from Essex County (ON, Canada). Overall, the results suggest that exposure to these pesticides can cause both stimulatory and suppressive immune changes in adult frogs and is doing so in wild populations.

Quantitative biomonitoring of PAHs using the Barnes mussel (Elliptio complanata)

The elimination rate constants (k(2)) of nine polycyclic aromatic hydrocarbons (PAHs) were examined for the freshwater mussel Elliptio complanata. The concentrations of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[ a]anthracene, chrysene, benzo[ b]fluoranthene, and indeno[1,2,3-c,d]pyrene revealed a significant inverse relationship with time and their k(2) values ranged from 0.10 to 0.22 day(-1). The k(2) values of these significantly cleared PAHs were similar to k(2) values observed for nonmetabolized organochlorines in mussels previously reported in the literature. The inverse relationship between k(2) and K(ow) provides evidence that the nine PAHs were being passively eliminated from the mussels and that they can be used to calibrate the mussel as a quantitative biomonitor. A general expression relating elimination rate constants and chemical K(ow) is derived for hydrophobic contaminants in E. complanata. The k(2) versus log K(ow) regression equation for mussels developed herein was similar to other studies documenting the elimination of PCBs and PAHs in a number of bivalve species.

A comparison of the transport and fate of polychlorinated biphenyl congeners in three Great Lakes food webs

A food web bioaccumulation model was used to compare transport and fate of polychorinated biphenyls (PCB) congeners in three food webs in the Laurentian Great Lakes of North America. The model was used to quantify the contribution of sediment-derived and freely dissolved PCBs to the body burden of aquatic biota. In eastern Lake Erie (OH, USA), almost 100% of the chemical body burden of biota originates from sediment. In western Lake Erie, benthic invertebrates accumulated slightly more than half of their PCB body burden from sediment while fish accumulated less than half of their chemical body burden from sediment. Fish from Lake Ontario, Canada, accumulated less than 30% of their body burden of PCB congeners with log Kow < 6.4 from sediment and approximately half of their body burden of PCB congeners with log Kow > or = 6.4 from sediment. Field data and the model were also used to determine the effects of declining concentrations of PCBs in water and sediment on concentrations of PCBs in aquatic biota. Results indicate that, as concentrations of PCB congeners in the ecosystem decline, the role of sediment as the source of contaminant to aquatic biota increases. Furthermore, as sediment becomes the predominant source of contaminant to aquatic biota. the concentration of PCB congeners in biota tends to equilibrium with bottom sediment.

Roles of DT diaphorase in the genotoxicity of nitroaromatic compounds in human and fish cell lines

The genotoxicity of nitroaromatic compounds was examined in two cultured cell lines, namely, a human hepatoma cell line, HepG2, and a brown bullhead fibroblast cell line, BB. Furthermore, the role of the quinone-reducing enzyme DT diaphorase [NAD(P)H:(quinone acceptor) oxidoreductase] was examined with respect to its influence on the genotoxic effects of model nitroaromatic pollutants. The nitroreductive characteristics of these two cell lines were examined using an acetylated cytochrome c reduction assay for enzymatic nitroreductase activity. Subsequently, the influence of DT diaphorase on the genotoxicity of two model nitroaromatics, 4-nitroquinoline 1-oxide (4NQ) and nitrofurantoin (NF), revealed that DT diaphorase was the predominant 4NQ reductase in cytosols of both cell lines, but played a lesser role in NF reduction in both species. Despite these interspecific similarities, results revealed marked qualitative differences between the two species in terms of the influence of DT diaphorase on quinone-mediated genotoxicity. When pretreated with the DT diaphorase inhibitor dicoumarol, HepG2 cells exhibited an exacerbation of genotoxicity in the presence of 4NQ, indicating a protective influence of the enzyme. In contrast, 4NQ genotoxicity in BB cells was reduced in the presence of dicoumarol, indicating a deleterious effect of DT diaphorase activity. Conversely, dicoumarol pretreatment was moderately protective against NF-mediated genotoxicity in HepG2 cells but exacerbated NF toxicity in BB cells. This study illustrates the manner in which functionally analogous enzymes may have markedly distinct influences on xenobiotic toxicity in different cellular systems.

In vitro toxicological methods for environmental health testing

Increasing public interest in environmental health issues has created a demand for alternatives to using animals for assessing the toxic effects of chemical mixtures on humans. This review focuses on applications of in vitro toxicological screening methods developed for human health biomonitoring using cultured clonal cell lines, which have the which have the following advantages: genetic variation between samples and experiments is minimal; the cultivation of cell lines is rapid and consistent conditions for culture are easily maintained; most of the phenotypic variation that is encountered with use of cell donors is eliminated; and radiolabeled precursors can be used for labeling and quantifying protein and DNA. We describe the current state of development of in vitro toxicity testing methods, present detailed procedures for the test methods optimized in our laboratory, and compare these techniques with other approaches. Toxicity testing using cell lines provides a mechanism to quantify the risks associated with environmental exposure to chemical mixtures.

Influence of DT diaphorase on quinone-mediated genotoxicity in human and fish cell lines

The influence of the quinone-reducing enzyme, DT diaphorase [NAD(P)H: (quinone acceptor) oxidoreductase], on the genotoxicity of quinones was examined in two cell lines, namely a human hepatoma cell line, HepG2 and a brown bullhead fibroblast cell line, BB. The quinone-reductive characteristics of these two cell lines were examined using an acetylated cytochrome c reduction assay for enzymatic reductase activity. Subsequently, the influence of DT diaphorase on the genotoxicity of two model quinones, menadione (MND) and 9,10-phenanthrenequinone (PQ) was examined in an alkaline unwinding assay for DNA single-strand breaks. Results revealed that DT diaphorase was the predominant quinone reductase in cytosols of both cell lines, and that levels of specific DT diaphorase activity were generally equivalent in the two species. Despite these similarities, results revealed marked qualitative differences between the two species in terms of the influence of DT diaphorase on quinone-mediated genotoxicity. When pretreated with the DT diaphorase inhibitor, dicoumarol, HepG2 cells exhibited a marked exacerbation of genotoxicity in the presence of either MND or PQ, indicating protective influence of the enzyme. In contrast, quinone genotoxicity in BB cells was not affected by DT diaphorase inhibition, indicating the lack of a protective effect of DT diaphorase. This study illustrates the manner in which functionally analogous enzymes may have markedly distinct influences on xenobiotic toxicity in different cellular systems.