Use of a Food Web Bioaccumulation Model to Uncover Spatially Integrated Polychlorinated Biphenyl Exposures in Detroit River Sport Fish

We applied and tested a bioenergetic-based, steady-state food web bioaccumulation model to predict polychlorinated biphenyl (PCB) exposures in sport fish of the Detroit River (USA-Canada), which is a Great Lakes area of concern. The PCB concentrations in the sediment and water of the river were found to exhibit high spatial variation. The previously contained areas of high contamination may have spread to adjacent food webs as a result of fish movements. This process may cause biased predictions in single-compartment bioaccumulation models. We performed multiple simulations and contrasted model predictions against a database of 1152 fish sample records comprising 19 sport fish species. The simulations evaluated 4 spatial scales (river-wide, 2-nation, 4-zone, and 6-zone models) to reveal how the spatial heterogeneity of contamination and species-specific movements contribute to variation in fish PCB exposures. The model testing demonstrated that the 2-nation model provided the most accurate global prediction of fish contamination. However, these improvements were not equally observed across all species. The model was subsequently calibrated for poorly performing species, by allowing cross-zone exposures, demonstrating the importance of accounting for specific ecological factors, such as fish movement, to improve PCB bioaccumulation prediction, especially in highly heterogeneous water systems. Environ Toxicol Chem 2019;38:2771-2784. © 2019 SETAC.

Microbial metatranscriptomic investigations across contaminant gradients of the Detroit River

Microbial community function in freshwater sediments is influenced by the presence and persistence of anthropogenic pollutants, yet simultaneously imposes significant control on their transformation. Thus, microbes provide valuable ecosystem services in terms of biodegradation and bioindicators of compromised habitats. From a remediation perspective it is valuable to leverage the suite of microbial genes at the transcriptional level that are active in either natural versus stressed environments to provide insight into the cycling and fate of contaminants. Metatranscriptomic analysis of total bacterial and archaeal messenger RNA (mRNA) is a useful tool in this facet and was applied to sediments sampled from the Detroit River; a binational Area of Concern (AOC) in the Great Lakes. Previously established sediment surveys and modelling delineated the river into contaminant gradients based on concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals. Differential expression analysis through DESeq2 revealed that microbial transcripts associated with nitrate reduction, methanogenesis, and beta-oxidation were significant in legacy polluted sediments and linked with energetic pathways key in the generation of cellular currencies (acetyl-CoA, succinyl-CoA). Gluconeogenesis and polyester synthesis also showed high abundance in contaminated regions, along with increased expression of stress response genes and transposons, despite decreases in community α-diversity. Aromatic cleavage genes were detected, but in low abundance across the contaminant gradient. These results suggest that microbial communities within the Detroit River exploit unique anabolic and catabolic pathways to derive and store energy from legacy organic contaminants while simultaneously recruiting stress-response and gene transfer mechanisms to cope with xenobiotic pressures. By coupling well-resolved chemical datasets with metatranscriptomics, this study adds to the spatial understanding of in-situ microbial activities in pristine and perturbed freshwater sediments.

Distinguishing point and non-point sources of dissolved nutrients, metals, and legacy contaminants in the Detroit River

Water quality impacts to the Laurentian Great Lakes create bi-national issues that have been subject of investigation since the 1970s. However, distinguishing upgradient sources of nutrients, metals and legacy contaminants in rivers remains a challenge, as they are derived from multiple sources and flows typically vary throughout the region. These complications are especially pertinent in the Lake Huron to Lake Erie corridor and Detroit River. The Detroit River supplies 90% of the water to the western basin of Lake Erie (5300 m³/s) and is subject to a variety of co-occurring potential sources (e.g., agriculture, urbanization, and upgradient water bodies) of water quality indicators that limit source disaggregation. To find the source signal in the noise we used an integrative interpretation of dissolved chemical and isotopic parameters with sediment chemical, isotopic, and contaminant indicators. The approach combines archival data to distinguish point and non-point sources, and upgradient water bodies as sources of nutrients, metals and contaminants to the Detroit River and ultimately the western basin of Lake Erie. Persistent organic pollutants and metals cluster together as an urban group. Regional dissolved orthro-phosphate (PO₄) in the water column also groups with urban point sources rather than agricultural sources. Urbanization as the primary source of PO₄ in the Detroit River highlights the need for continued research on urban impacts and assessments of broader best management practices protecting Lake Erie.

Temporal trends, lake-to-lake variation, and climate effects on Arctic char (Salvelinus alpinus) mercury concentrations from six High Arctic lakes in Nunavut, Canada

Climate warming and mercury (Hg) are concurrently influencing Arctic ecosystems, altering their functioning and threatening food security. Non-anadromous Arctic char (Salvelinus alpinus) in small lakes were used to biomonitor these two anthropogenic stressors, because this iconic Arctic species is a long-lived top predator in relatively simple food webs, and yet population characteristics vary greatly, reflecting differences between lake systems. Mercury concentrations in six landlocked Arctic char populations on Cornwallis Island, Nunavut have been monitored as early as 1989, providing a novel dataset to examine differences in muscle [Hg] among char populations, temporal trends, and the relationship between climate patterns and Arctic char [Hg]. We found significant lake-to-lake differences in length-adjusted Arctic char muscle [Hg], which varied by up to 9-fold. Arctic char muscle [Hg] was significantly correlated to dissolved and particulate organic carbon concentrations in water; neither watershed area or vegetation cover explained differences. Three lakes exhibited significant temporal declines in length-adjusted [Hg] in Arctic char; the other three lakes had no significant trends. Though precipitation, temperature, wind speed, and sea ice duration were tested, no single climate variable was significantly correlated to length-adjusted [Hg] across populations. However, Arctic char Hg in Resolute Lake exhibited a significant correlation with sea ice duration, which is likely closely linked to lake ice duration, and which may impact Hg processing in lakes. Additionally, Arctic char [Hg] in Amituk Lake was significantly correlated to snow fall, which may be linked to Hg deposition. The lack of consistent temporal trends in neighboring char populations indicates that currently, within lake processes are the strongest drivers of [Hg] in char in the study lakes and potentially in other Arctic lakes, and that the influence of climate change will likely vary from lake to lake.

Characterizing polychlorinated biphenyl exposure pathways from sediment and water in aquatic life using a food web bioaccumulation model

Contaminant remediation decisions often focus on sediment-organism relationships, omitting the partitioning between sediment and water that exists across a given site. The present study highlights the importance of incorporating nonsedimentary routes of exposure into a nonequilibrium, steady-state food web bioaccumulation model for predicting polychlorinated biphenyl (PCB) concentrations in benthic invertebrates. Specifically, we examined the proportion of overlying water relative to the sediment porewater respired by benthic invertebrates, which has been used in previous studies to examine contaminant bioaccumulation. We evaluated the model accuracy using paired benthos-sediment samples and an extensive fish contamination database to ensure realistic predictions at the base of the Detroit River (Ontario, Canada, and Michigan, USA) food web. The results demonstrate that, compared with empirical regression analyses, the food web bioaccumulation model provided satisfactory estimates of PCB bioaccumulation for benthos simulations and better estimates for fish simulations. Our results showed that PCB bioaccumulation measurements are significantly affected by variations in pollutant uptake and elimination routes via the overlying water, which in turn are affected by the degree of disequilibrium of PCBs between sediments and water. Interestingly, we obtained contrasting results regarding the effectiveness of remediation strategies for reducing the contaminant burden of the aquatic biota based on different proportions of overlying water relative to porewater. These differences could consequently impact decisions about the approaches for source control and strategic sediment remediation. This study suggests that bioaccumulation assessments could be improved through better identification of chemical uptake-elimination routes in benthos and by accounting for chemical bioavailability in sediment and water components in areas with disequilibrium.Integr Environ Assess Manag 2019;00:000-000. © 2019 SETAC.

Polybrominated Diphenyl Ethers (PBDEs) in Sediments of the Huron-Erie Corridor

Polybrominated diphenyl ethers (PBDEs) were measured in 182 sediments from the Huron-Erie Corridor, North America. The median (5-95 percentile) Corridor ∑PBDE concentration was 1.03 ng/g dry wt (0.25-13.48 ng/g dry wt). Dry weight ∑PBDEs were elevated in U.S. waters of the Detroit River (US DR) and lowest in Canadian waters of Lake St. Clair (CA LSC). Sediment total organic carbon (TOC) explained some of the variation in ∑PBDEs, particularly in upstream waterbodies except for the Detroit River where local sources were apparent in the US DR and TOC-dilution occurred in CA DR. Canadian Federal Sediment Quality guidelines were exceeded at 19 stations, 14 occurring in the US DR. ∑Hazard Quotients (∑HQ) had a median (5-95 percentile) Corridor value of 0.46 (ND to 2.27). By strata, 43.2% of US DR stations had ∑HQ's greater than 1 while 21.3% of US SCR stations exceeded a value of 1.

Possible Ballast Water Transfer of Lionfish to the Eastern Pacific Ocean

The Indo-Pacific Red Lionfish was first reported off the Florida coast in 1985, following which it has spread across much of the SE USA, Gulf of Mexico, and Caribbean Sea. Lionfish negatively impact fish and invertebrate assemblages and abundances, thus further spread is cause for concern. To date, the fish has not been reported on the Pacific coast of North or Central America. Here we examine the possibility of ballast water transfer of lionfish from colonized areas in the Atlantic Ocean to USA ports on the Pacific coast. Over an eight-year period, we documented 27 commercial vessel-trips in which ballast water was loaded in colonized sites and later discharged untreated into Pacific coast ports in the USA. California had the highest number of discharges including San Francisco Bay and Los Angeles-Long Beach. A species distribution model suggests that the probability of lionfish establishment is low for the western USA, Colombia and Panama, low to medium for Costa Rica, Nicaragua, El Salvador and Guatemala, medium to high for mainland Ecuador, and very high for western Mexico, Peru and the Galapagos Islands. Given the species’ intolerance of freshwater conditions, we propose that ballast water exchange be conducted in Gatún Lake, Panama for western-bound vessels carrying ‘risky’ ballast water to prevent invasion of the eastern Pacific Ocean.

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.

Variable δ(15)N diet-tissue discrimination factors among sharks: implications for trophic position, diet and food web models

The application of stable isotopes to characterize the complexities of a species foraging behavior and trophic relationships is dependent on assumptions of δ¹⁵N diet-tissue discrimination factors (∆¹⁵N). As ∆¹⁵N values have been experimentally shown to vary amongst consumers, tissues and diet composition, resolving appropriate species-specific ∆¹⁵N values can be complex. Given the logistical and ethical challenges of controlled feeding experiments for determining ∆¹⁵N values for large and/or endangered species, our objective was to conduct an assessment of a range of reported ∆¹⁵N values that can hypothetically serve as surrogates for describing the predator-prey relationships of four shark species that feed on prey from different trophic levels (i.e., different mean δ¹⁵N dietary values). Overall, the most suitable species-specific ∆¹⁵N values decreased with increasing dietary-δ¹⁵N values based on stable isotope Bayesian ellipse overlap estimates of shark and the principal prey functional groups contributing to the diet determined from stomach content analyses. Thus, a single ∆¹⁵N value was not supported for this speciose group of marine predatory fishes. For example, the ∆¹⁵N value of 3.7‰ provided the highest percent overlap between prey and predator isotope ellipses for the bonnethead shark (mean diet δ¹⁵N = 9‰) whereas a ∆¹⁵N value < 2.3‰ provided the highest percent overlap between prey and predator isotope ellipses for the white shark (mean diet δ¹⁵N = 15‰). These data corroborate the previously reported inverse ∆¹⁵N-dietary δ¹⁵N relationship when both isotope ellipses of principal prey functional groups and the broader identified diet of each species were considered supporting the adoption of different ∆¹⁵N values that reflect the predators’ δ¹⁵N-dietary value. These findings are critical for refining the application of stable isotope modeling approaches as inferences regarding a species’ ecological role in their community will be influenced with consequences for conservation and management actions.

Development of temporally refined land-use regression models predicting daily household-level air pollution in a panel study of lung function among asthmatic children

Regulatory monitoring data and land-use regression (LUR) models have been widely used for estimating individual exposure to ambient air pollution in epidemiologic studies. However, LUR models lack fine-scale temporal resolution for predicting acute exposure and regulatory monitoring provides daily concentrations, but fails to capture spatial variability within urban areas. This study coupled LUR models with continuous regulatory monitoring to predict daily ambient nitrogen dioxide (NO(2)) and particulate matter (PM(2.5)) at 50 homes in Windsor, Ontario. We compared predicted versus measured daily outdoor concentrations for 5 days in winter and 5 days in summer at each home. We also examined the implications of using modeled versus measured daily pollutant concentrations to predict daily lung function among asthmatic children living in those homes. Mixed effect analysis suggested that temporally refined LUR models explained a greater proportion of the spatial and temporal variance in daily household-level outdoor NO(2) measurements compared with daily concentrations based on regulatory monitoring. Temporally refined LUR models captured 40% (summer) and 10% (winter) more of the spatial variance compared with regulatory monitoring data. Ambient PM(2.5) showed little spatial variation; therefore, daily PM(2.5) models were similar to regulatory monitoring data in the proportion of variance explained. Furthermore, effect estimates for forced expiratory volume in 1 s (FEV(1)) and peak expiratory flow (PEF) based on modeled pollutant concentrations were consistent with effects based on household-level measurements for NO(2) and PM(2.5). These results suggest that LUR modeling can be combined with continuous regulatory monitoring data to predict daily household-level exposure to ambient air pollution. Temporally refined LUR models provided a modest improvement in estimating daily household-level NO(2) compared with regulatory monitoring data alone, suggesting that this approach could potentially improve exposure estimation for spatially heterogeneous pollutants. These findings have important implications for epidemiologic studies - in particular, for research focused on short-term exposure and health effects.

The influence of neighborhood traffic density on the respiratory health of elementary schoolchildren

BACKGROUND

Several studies have found that living near major roadways is associated with an increase in respiratory illness but few studies have measured the volume and type of traffic.

OBJECTIVE

We investigated the relation between traffic volume and respiratory health of 2328 children 9 to 11 years old in the city of Windsor, Canada.

METHODS

We identified the roadways within a 200 meter radius of the child's neighborhood using the latitude and longitude of the residential postal code. Traffic exposure was defined as the sum of the annual volume of vehicles on all of these roadways. Volume was calculated using sensors to detect passing vehicles (simple traffic counts), and by counts and direction of traffic at intersections (turning movement counts). Ventilatory lung function was measured by spirometry and airway inflammation by exhaled nitric oxide (eNO).

RESULTS

The odds ratio between an interquartile increase in truck turning movement counts and chest congestion was 1.20 (1.06-1.35). The percentage of predicted FVC declined 0.68%, (95% CI 1.32, 0.03) for an interquartile increase in simple traffic counts (33,787 vehicles daily). Among those with self-reported asthma, effect sizes were larger. Percentage predicted FEV(1) declined 1.84% (95% CI 0.07, 3.61) associated with an interquartile range increase in turning movement counts. No statistically significant change was detected between traffic measures and exhaled nitric oxide.

CONCLUSIONS

Our findings provide further support for the hypothesis that neighborhood exposure to traffic-related air pollution increases respiratory symptoms and reduces ventilatory function in children, especially those with self-reported asthma.

Spatial variability and application of ratios between BTEX in two Canadian cities

Spatial monitoring campaigns of volatile organic compounds were carried out in two similarly sized urban industrial cities, Windsor and Sarnia, ON, Canada. For Windsor, data were obtained for all four seasons at approximately 50 sites in each season (winter, spring, summer, and fall) over a three-year period (2004, 2005, and 2006) for a total of 12 sampling sessions. Sampling in Sarnia took place at 37 monitoring sites in fall 2005. In both cities, passive sampling was done using 3M 3500 organic vapor samplers. This paper characterizes benzene, toluene, ethylbenzene, o, and (m + p)-xylene (BTEX) concentrations and relationships among BTEX species in the two cities during the fall sampling periods. BTEX concentration levels and rank order among the species were similar between the two cities. In Sarnia, the relationships between the BTEX species varied depending on location. Correlation analysis between land use and concentration ratios showed a strong influence from local industries. Use one of the ratios between the BTEX species to diagnose photochemical age may be biased due to point source emissions, for example, 53 tonnes of benzene and 86 tonnes of toluene in Sarnia. However, considering multiple ratios leads to better conclusions regarding photochemical aging. Ratios obtained in the sampling campaigns showed significant deviation from those obtained at central monitoring stations, with less difference in the (m + p)/E ratio but better overall agreement in Windsor than in Sarnia.