Returning to normal? Assessing transcriptome recovery over time in male rainbow darter (Etheostoma caeruleum) liver in response to wastewater-treatment plant upgrades

Identifying transcriptomic indicators of tertiary treated municipal effluent in longnose dace (Rhinichthys cataractae) caged under semi-controlled conditions in experimental raceways

To evaluate effects of tertiary treated wastewater treatment plant effluent (MWWE) on transcriptomic responses in longnose dace (Rhinichthys cataractae; LND) we conducted a semi-controlled study in experimental raceways (Advancing Canadian Water Assets facility) imbedded in the Pine Creek treatment plant (Calgary, AB). LND collected from a reference site in the Bow River (REF) were caged in raceways containing either 5 % Pine Creek effluent (PC) or Bow River water (BR; control) over 28 d. Liver transcriptomes were analyzed in males and females sampled on days 7, 14 and 28 from BR and PC, and compared to REF fish on day 0. Concurrent with the caging, selected environmental substances of concern were analyzed in the BR and PC. Significantly different unigenes (SDUs) in females (vs males) within both BR and PC raceways increased over time and compared to REF fish. Moreover, SDUs in females and males within the same treatment (i.e., BR, PC) showed a temporal increase as well as compared to REF fish. Time was the dominant factor affecting SDUs, whereas sex and treatment had less of an impact on the transcriptome profiling. Gene Set Enrichment Analysis of BR vs PC over time revealed effects on genes involved in growth, metabolism of carbohydrates and lipids, and immune system on day 7; however, by day 28, 80-100 % of the transcripts localized to enriched biomarkers were associated with tissue immune responses in both sexes. Exposure to 5 % effluent had significant effects on female liver somatic index but no effects were observed on other phenotypic health indices in either sex. BR was used as the source of reference water, but analyses showed trace amounts of ESOCs. Analyses did not point towards definitive response patterns that could be used in field-based ecotoxicogenomic studies on the impacts of well-treated MWWE but suggested compromised adaptive immune responses.

Changes in chemical occurrence, concentration, and bioactivity in the Colorado River before and after replacement of the Moab, Utah wastewater treatment plant

Long-term (2010-19) water-quality monitoring on the Colorado River downstream from Moab Utah indicated the persistent presence of Bioactive Chemicals (BC), such as pesticides and pharmaceuticals. This stream reach near Canyonlands National Park provides critical habitat for federally endangered species. The Moab wastewater treatment plant (WWTP) outfall discharges to the Colorado River and is the nearest potential point-source to this reach. The original WWTP was replaced in 2018. In 2016-19, a study was completed to determine if the new plant reduced BC input to the Colorado River at, and downstream from, the outfall. Water samples were collected before and after the plant replacement at sites upstream and downstream from the outfall. Samples were analyzed for as many as 243 pesticides, 109 pharmaceuticals, 20 hormones, 51 wastewater indicator chemicals, 20 metals, and 8 nutrients. BC concentrations, hazard quotients (HQs), and exposure activity ratios (EARs) were used to identify and prioritize contaminants for their potential to have adverse biological effects on the health of native and endangered wildlife. There were 22 BC with HQs >1, mostly metals and hormones; and 23 BC with EARs >0.1, mostly hormones and pharmaceuticals. Most high HQs or EARs were associated with samples collected at the WWTP outfall site prior to its replacement. Discharge from the new plant had reduced concentrations of nutrients, hormones, pharmaceuticals, and other BC. For example, all 16 of the hormones detected at the WWTP outfall site had maximum concentrations in samples collected prior to the WWTP replacement. The WWTP replacement had less effect on instream concentrations of metals and pesticides, BC whose sources are less directly tied to domestic wastewater. Study results indicate that improved WWTP technology can create substantial reductions in concentrations of non-regulated BC such as pharmaceuticals, in addition to regulated contaminants such as nutrients.

Wild fish responses to wastewater treatment plant upgrades in the Grand River, Ontario

Municipal wastewater treatment plant (WWTP) effluent is one of several point sources of contaminants (nutrients, pharmaceuticals, estrogens, etc.) which can lead to adverse responses in aquatic life. Studies of WWTP effluent impacts on rainbow darter (Etheostoma caeruleum) collected downstream of WWTPs in the Grand River, Ontario have reported disruption at multiple levels of biological organization, including altered vitellogenin gene expression, lower levels of in vitro steroid production, and high frequency of intersex. However, major upgrades have occurred at treatment plants in the central Grand River over the last decade. Treatment upgrades to the Waterloo WWTP were initiated in 2009 but due to construction delays, the upgrades came fully on-line in 2017/2018. Responses in rainbow darter have been followed at sites associated with the outfall consistently over this entire time period. The treatment plant upgrade resulted in nitrification of effluent, and once complete there was a major reduction in effluent ammonia, selected pharmaceuticals, and estrogenicity. This study compared several key responses in rainbow darter associated with the Waterloo WWTP outfall prior to and post upgrades. Stable isotopes signatures in fish were used to track exposure to effluent and changed dramatically over time, corresponding to the effluent quality. Disruptions in in vitro steroid production and intersex in the darters that had been identified prior to the upgrades were no longer statistically different from the upstream reference sites after the upgrades. Although annual variations in water temperature and flow can potentially mask or exacerbate the effects of the WWTP effluent, major capital investments in wastewater treatment targeted at improving effluent quality have corresponded with the reduction of adverse responses in fish in the receiving environment.

Changes to levels of microcontaminants and biological responses in rainbow trout exposed to extracts from wastewater treated by catalytic ozonation

Two separate pilot-scale studies were performed at two wastewater treatment plants comparing conventional ozonation and catalytic ozonation with an alumina-based catalyst supplied by BASF. The results of the first pilot study showed that catalytic ozonation achieved the same degree of disinfection as conventional ozonation with 30% lower applied ozone dose and enhanced the removal of several contaminants of emerging concern (CECs). The second pilot study conducted over 6 months of operation with the same batch of catalyst showed sustained enhanced removal of CECs relative to ozonation alone. The removals of CECs by catalytic ozonation was particularly effective for compounds with low reaction rates with ozone, indicating reactions with hydroxyl radicals formed in the presence of the catalyst. Analysis of plasma vitellogenin and total glutathione in liver tissues of juvenile rainbow trout (Oncorhynchus mykiss) injected with wastewater extracts indicated that catalytic ozonation removed the estrogenic activity and modulated oxidative stress caused by exposure to the organic compounds in wastewater extracts. Analysis of other biomarker responses indicated that no transformation products were formed that can cause lipid damage in the liver or affect levels of a brain neurotransmitter (i.e. serotonin). Catalytic ozonation is a promising technology to increase the efficiency of ozone treatment of municipal wastewater and to meet increasingly more stringent regulations for effluent quality.

Impacts on Metabolism and Gill Physiology of Darter Species (Etheostoma spp.) That Are Attributed to Wastewater Effluent in the Grand River

The effluent from municipal wastewater treatment plants is a major point source of contamination in Canadian waterways. The improvement of effluent quality to reduce contaminants, such as pharmaceuticals and personal care products, before being released into the environment is necessary to reduce the impacts on organisms that live in the river downstream. Here, we aimed to characterize the metabolic and gill physiological responses of rainbow (Etheostoma caeruleum), fantail (Etheostoma flabellare), and greenside (Etheostoma blennioides) darters to the effluent in the Grand River from the recently upgraded Waterloo municipal wastewater treatment plant. The routine metabolism of darters was not affected by effluent exposure, but some species had increased maximum metabolic rates, leading to an increased aerobic scope. The rainbow darter aerobic scope increased by 2.2 times and the fantail darter aerobic scope increased by 2.7 times compared to the reference site. Gill samples from effluent-exposed rainbow darters and greenside darters showed evidence of more pathologies and variations in morphology. These results suggest that darters can metabolically adjust to effluent-contaminated water and may also be adapting to the urban and agricultural inputs. The modification and damage to the gills provide a useful water quality indicator but does not necessarily reflect how well acclimated the species is to the environment due to a lack of evidence of poor fish health.

Disentangling of the ecotoxicological signal using "omics" analyses, a lesson from the survey of the impact of cyanobacterial proliferations on fishes

Omics technologies offer unprecedented perspectives for the rational investigation of complex biological systems. Indeed, omics present the ability of offering an extensive perception of the biochemistry and physiology of the cell and of any perturbing consequences of contaminants through the joint investigation of thousands of molecular responses simultaneously; then it has recently conducted to a fervent attention by research ecotoxicologists. Beyond the presentation of latest advances, exemplified here by omics investigation of cyanobacterial deleterious effects on various fishes (at various experimental and biological scales and with various analytical tools and pipeline), the present review paper re-explores the promising perspectives and also the pitfalls of such holistic investigations of the ecotoxicological response of organisms for environmental assessment.

Evaluating the potential role of bioactive chemicals on the distribution of invasive Asian carp upstream and downstream from river mile 278 in the Illinois waterway

Two non-native carp species have invaded the Illinois Waterway and are a threat to Great Lakes ecosystems. Poor water quality in the upper Illinois Waterway may be a factor contributing to the stalling of the carp population front near river mile 278. In 2015, the U.S. Geological Survey collected 4 sets of water samples from two sites upstream and 4 sites downstream from river mile 278, and one tributary. Each sample was analyzed for up to 649 unique constituents of which 287 were detected including 96 pesticides, 62 pharmaceuticals, 39 wastewater indicator chemicals, 29 metals, 19 volatile organic compounds (VOCs), 6 disinfection by-products (DBPs), 5 hormones, and 5 carboxylic acids. Potential for bioactivity was estimated by comparing chemical concentrations to aquatic life or human health criteria and to in-vitro bioactivity screening results in the U.S Environmental Protection Agency ToxCast™ database. The resulting hazard quotients and exposure-activity ratios (EARs) are toxicity indexes that can be used to rank potential bioactivity of individual chemicals and chemical mixtures. This analysis indicates that several bioactive chemicals (BCs) including: carbendazim, 2,4-D, metolachlor, terbuthylazine, and acetochlor (pesticides); 1,4-dioxane (VOC); metformin, diphenhydramine, sulfamethoxazole, tramadol, fexofenadine, and the anti-depressants (pharmaceuticals); bisphenol A, 4-nonylphenol, galaxolide, 4-tert-octylphenol (wastewater indicator chemical); lead and boron (metals); and estrone (hormone) all occur in the upper Illinois Waterway at concentrations that produce elevated EARs values and may be adversely affecting carp reproduction and health. The clear differences in water quality upstream and downstream from river mile 278 with higher contaminant concentrations and potential bioactivity upstream could represent a barrier to carp range expansion.

Cumulative effects of municipal effluent and parasite infection in yellow perch: A field study using high-throughput RNA-sequencing

Multiple metabolic, immune and reproductive effects have been reported in fish residing in effluent-impacted sites. Natural stressors such as parasites also have been shown to impact the responses of organisms to chronic exposure to municipal effluent in the St. Lawrence River (Quebec, Canada). In order to comprehensively evaluate the cumulative impacts of anthropogenic and natural stressors on the health of yellow perch, differential mRNA transcription profiles were examined in juvenile females collected from effluent-impacted and upstream sites with low or high infection levels of the larval trematode Apophallus brevis. Transcriptomics was used to identify biological pathways associated with environmental exposure. In total, 3463 isoforms were differentially transcribed between sites. Patterns reflecting the combined effects of stressors were numerically dominant, with a majority of downregulated transcripts (68%). The differentially expressed transcripts were associated with 27 molecular and cellular functions ranging from cellular development to xenobiotic metabolism and were involved in the development and function of 13 organ systems including hematological, hepatic, nervous, reproductive and endocrine systems. Based on RNA-seq results, sixteen genes were measured by qPCR. Significant differences were observed for six genes in fish exposed to both stressors combined, whereas parasites and effluent individually impacted the transcription of one gene. Lysozyme activity, lipid peroxidation, retinol-binding protein and glucose-6-phosphate dehydrogenase were selected as potential biomarkers of effects to study specific pathways of interest. Lipid peroxidation in perch liver was different between sites, parasite loads, and for combined stressors. Overall, results indicated that juvenile yellow perch responded strongly to combined parasite and effluent exposure, suggesting cumulative effects on immune responses, inflammation and lipid metabolism mediated by retinoid receptors. The present study highlight the importance of using a comprehensive approach combining transcriptomics and endpoints measured at higher levels of biological organization to better understand cumulative risks of contaminants and pathogens in aquatic ecosystems.

Modeling the exposure of wild fish to endocrine active chemicals: Potential linkages of total estrogenicity to field-observed intersex

Decades of studies on endocrine disruption have suggested the need to manage the release of key estrogens from municipal wastewater treatment plants (WWTP). However, the proposed thresholds are below the detection limits of most routine chemical analysis, thereby restricting the ability of watershed managers to assess the environmental exposure appropriately. In this study, we demonstrated the utility of a mechanistic model to address the data gaps on estrogen exposure. Concentrations of the prominent estrogenic contaminants in wastewaters (estrone, estradiol, and ethinylestradiol) were simulated in the Grand River in southern Ontario (Canada) for nine years, including a period when major WWTP upgrades occurred. The predicted concentrations expressed as total estrogenicity (E2 equivalent concentrations) were contrasted to a key estrogenic response (i.e., intersex) in rainbow darter (Etheostoma caeruleum), a wild sentinel fish species. A predicted total estrogenicity in the river of ≥10 ng/L E2 equivalents was associated with high intersex incidence and severity, whereas concentrations <0.1 ng/L E2 equivalents were associated with minimal intersex expression. Exposure to a predicted river concentration of 0.4 ng/L E2 equivalents, the environmental quality standard (EQS) proposed by the European Union for estradiol, was associated with 34% (95% CI:30-38) intersex incidence and a very low severity score of 0.6 (95% CI:0.5-0.7). This exposure is not predicted to cause adverse effects in rainbow darter. The analyses completed in this study were only based on the predicted presence of three major estrogens (E1, E2, EE2), so caution must be exercised when interpreting the results. Nevertheless, this study illustrates the use of models for exposure assessment, especially when measured data are not available.

Are we closer to the vision? A proposed framework for incorporating omics into environmental assessments

Environmental science has benefited a great deal from omics-based technologies. High-throughput toxicology has defined adverse outcome pathways (AOPs), prioritized chemicals of concern, and identified novel actions of environmental chemicals. While many of these approaches are conducted under rigorous laboratory conditions, a significant challenge has been the interpretation of omics data in "real-world" exposure scenarios. Clarity in the interpretation of these data limits their use in environmental monitoring programs. In recent years, one overarching objective of many has been to address fundamental questions concerning experimental design and the robustness of data collected under the broad umbrella of environmental genomics. These questions include: (1) the likelihood that molecular profiles return to a predefined baseline level following remediation efforts, (2) how reference site selection in an urban environment influences interpretation of omics data and (3) what is the most appropriate species to monitor in the environment from an omics point of view. In addition, inter-genomics studies have been conducted to assess transcriptome reproducibility in toxicology studies. One lesson learned from inter-genomics studies is that there are core molecular networks that can be identified by multiple laboratories using the same platform. This supports the idea that "omics-networks" defined a priori may be a viable approach moving forward for evaluating environmental impacts over time. Both spatial and temporal variability in ecosystem structure is expected to influence molecular responses to environmental stressors, and it is important to recognize how these variables, as well as individual factor (i.e. sex, age, maturation), may confound interpretation of network responses to chemicals. This mini-review synthesizes the progress made towards adopting these tools into environmental monitoring and identifies future challenges to be addressed, as we move into the next era of high throughput sequencing. A conceptual framework for validating and incorporating molecular networks into environmental monitoring programs is proposed. As AOPs become more defined and their potential in environmental monitoring assessments becomes more recognized, the AOP framework may prove to be the conduit between omics and penultimate ecological responses for environmental risk assessments.

Assessing recovery of in vitro steroid production in male rainbow darter (Etheostoma caeruleum) in response to municipal wastewater treatment plant infrastructure changes

The present study examined in vitro 11-ketotestosterone and testosterone production by the testes of rainbow darter (Etheostoma caeruleum) collected from selected reference sites and downstream of 2 municipal wastewater treatment plants (MWWTPs; Waterloo and Kitchener) on the central Grand River (Ontario, Canada), over a 6-yr period (2011-2016). The main objective was to investigate if infrastructure upgrades at the Kitchener MWWTP in 2012 resulted in a recovery of this response in the post-upgrade period (2013-2016). Two supporting studies showed that the fall season is appropriate for measuring in vitro sex steroid production because it provides stable detection of steroid patterns, and that the sample handling practiced in the present study did not introduce a bias. Infrastructure upgrades of the Kitchener MWWTP resulted in significant reductions in ammonia and estrogenicity. After the upgrades, 11-ketotestosterone production by MWWTP-exposed fish increased in 2013 and it continued to recover throughout the study period of 2014 through 2016, returning to levels measured in reference fish. Testosterone production was less sensitive and it lacked consistency. The Waterloo MWWTP underwent some minor upgrades but the level of ammonia and estrogenicity remained variable over time. The production of 11-ketotestosterone and testosterone in rainbow darter below the Waterloo MWWTP was variable and without a clear recovery pattern over the course of the present study. The results of the present study demonstrated that measuring production of sex steroids (especially 11-ketotestosterone) over multiple years can be relevant for assessing responses in fish to environmental changes such as those resulting from major infrastructure upgrades. Environ Toxicol Chem 2018;37:501-514. © 2017 SETAC.

Multi-year prediction of estrogenicity in municipal wastewater effluents

In this study, the estrogenicity of two major wastewater treatment plant (WWTP) effluents located in the central reaches of the Grand River watershed in southern Ontario was estimated using population demographics, excretion rates, and treatment plant-specific removals. Due to the lack of data on estrogen concentrations from direct measurements at WWTPs, the treatment efficiencies through the plants were estimated using the information obtained from an effects-directed analysis. The results show that this approach could effectively estimate the estrogenicity of WWTP effluents, both before and after major infrastructure upgrades were made at the Kitchener WWTP. The model was then applied to several possible future scenarios including population growth and river low flow conditions. The scenario analyses showed that post-upgrade operation of the Kitchener WWTP will not release highly estrogenic effluent under the 2041 projected population increase (36%) or summer low flows. Similarly, the Waterloo WWTP treatment operation is also expected to improve once the upgrades have been fully implemented and is expected to effectively treat estrogens even under extreme scenarios of population growth and river flows. The developed model may be employed to support decision making on wastewater management strategies designed for environmental protection, especially on reducing the endocrine effects in fish exposed to WWTP effluents.

How Does Reference Site Selection Influence Interpretation of Omics Data?: Evaluating Liver Transcriptome Responses in Male Rainbow Darter (Etheostoma caeruleum) across an Urban Environment

Studies quantifying the influence of reference site selection on transcriptomic profiles in aquatic organisms exposed to complex mixtures are lacking in the literature, despite the significant implications of such research for the interpretation of omics data sets. We measured hepatic transcriptomic responses in fish across an urban environment in the central Grand River watershed (Ontario, Canada). Adult male rainbow darter (RBD) (Etheostoma caeruleum) were collected from nine sites at varying distances from two major municipal wastewater treatment plants (MWWTPs) (Waterloo, Kitchener), including three upstream reference sites. The transcriptomic response in RBD was independently compared with that of fish from each of the three reference sites. Data collected in fish downstream of the Waterloo MWWTP (poorest effluent quality) suggested that ∼15.5% of the transcriptome response was influenced by reference site selection. In contrast, at sites where the impact of MWWTPs was less-pronounced and fish showed less of a transcriptome response, reference site selection had a greater influence (i.e., ∼56.9% of transcripts were different depending on the site used). This study highlights the importance of conducting transcriptomics studies that leverage more than one reference site, and it broadens our understanding of the molecular responses in fish in dynamic natural environments.