Integrating Omic Technologies into Aquatic Ecological Risk Assessment and Environmental Monitoring: Hurdles, Achievements, and Future Outlook

Background: In this commentary we present the findings from an international consortium on fish toxicogenomics sponsored by the U.K. Natural Environment Research Council (Fish Toxicogenomics—Moving into Regulation and Monitoring, held 21–23 April 2008 at the Pacific Environmental Science Centre, Vancouver, BC, Canada). Objectives: The consortium from government agencies, academia, and industry addressed three topics: progress in ecotoxicogenomics, regulatory perspectives on roadblocks for practical implementation of toxicogenomics into risk assessment, and dealing with variability in data sets. Discussion: Participants noted that examples of successful application of omic technologies have been identified, but critical studies are needed to relate molecular changes to ecological adverse outcome. Participants made recommendations for the management of technical and biological variation. They also stressed the need for enhanced interdisciplinary training and communication as well as considerable investment into the generation and curation of appropriate reference omic data. Conclusions: The participants concluded that, although there are hurdles to pass on the road to regulatory acceptance, omics technologies are already useful for elucidating modes of action of toxicants and can contribute to the risk assessment process as part of a weight-of-evidence approach

Toxicogenomics effects of sewage on juvenile Chinook salmon (Oncorhynchus tshawytscha)

As a part of an Environment Canada project, this research used microarrays and Quantitative Polymerase Chain Reaction to evaluate the effects of British Columbia, Canada, sewage on liver gene expression in exposed juvenile chinook (Oncorhynchus tshawytscha) salmon. The studies highlighted the effects of xenoestrogens on gene expression. Xenoestrogens can alter the expression of genes associated with adult fish reproductive processes, particularly those relating to egg production (female-specific): vitellogenin and the vitelline envelope proteins. Examination of genetic males and females indicated very few significant differences in the expression of female-specific genes between the sexes, indicating that gene expression alterations caused by sewage were unrelated to genetic sex in underyearling fish. Gene expression patterns were examined for trends across time and sewage concentrations. Trends found included U-shaped and linear dose response curves. All concentrations of sewage examined caused gene expression alterations, including the very low environmentally relevant concentrations: 0.05%, 0.1%, 0.7%

Xenoestrogen effects on fish: molecular to physiological approaches

Estrogen hormones, or compounds that mimic them (xenoestrogens), are found in surface waters worldwide mainly due to discharges to the environment from anthropogenic sources, such as sewage treatment plant (STP) effluents. Fish are adversely affected by these xenoestrogens in the areas of reproduction, growth, immune function and offspring fitness. To identify and explore the effects of xenoestrogens on salmonids, a series of toxicological studies were performed using comprehensive panels of assays evaluating immune, osmoregulatory, hematological, metabolic, reproductive and endocrine-related parameters in response to xenoestrogen- and STP effluent-exposures. Most studies included a post-treatment depuration phase to determine recovery timeframes of altered parameters. In male or juvenile fish, xenoestrogens are known to induce vitellogenesis, the mature female-related process of making eggs under estrogen receptor (ER) control that is initiated by the hepatic production of egg proteins, vitellogenin (VTG) and vitelline envelope proteins (VEPs). In three studies, induction of liver somatic index (LSI), plasma VTG protein or hepatic gene transcripts (ERs, VTG and VEPs) were found due to exposure to a tertiary-treated STP effluent, a synthetic wastewater, and estrogen hormones. In Rainbow trout exposed to xenoestrogens, LSI and transcripts recovered to baseline values after treatments ceased, while VTG protein concentrations remained elevated through recovery phases. Thus, gene expression alterations were only useful as indicators of existing exposure, while VTG protein levels were indicative of both present and prior exposure. Xenoestrogens affected several immune system functions, including reduced leukocyte counts, potentially increasing susceptibility to pathogens. Isolated leukocytes from head kidney and peripheral blood contained ERα and ERβ transcripts, although only ERα1 and ERα2 were altered by xenoestrogen exposure, providing a direct mechanistic pathway for xenoestrogen modulation of the immune system. Reductions in burst swimming performance were found in Rainbow trout exposed to xenoestrogens, with potential mechanisms suggested involving altered osmoregulation (evidenced by reduced chloride ions) and decreased blood oxygen carrying capacity via a reduction in red blood cell counts. Overall, most but not all altered parameters recovered from exposure to xenoestrogens, and the adverse effects of environmentally-relevant concentrations of xenoestrogens on many biological functions showed that xenoestrogens pose a hazard to wild juvenile fish

Microbiome Analysis Across a Natural Copper Gradient at a Proposed Northern Canadian Mine Site

Due to the environmental persistence, bioaccumulation, and toxicity of metals released by mining activities, mitigation methods are crucial to minimize impacts on aquatic environments. Bioremediation is one mitigation strategy used to reduce the potential for metal accumulation and toxicity in aquatic organisms. At a potential mine site in Yukon, Canada, elevated copper (Cu) concentrations and low pH are found in a water course near a naturally mineralized area; however, Cu concentrations and acidity are greatly reduced downstream. Physicochemical processes do not appear to explain this natural remediation and it is suggested that unique microbial communities may be responsible through Cu immobilization. To investigate the role of microbes in sequestering or transforming Cu in the water, biofilm samples were collected from 5 sites along a natural copper gradient: upstream of Cu introduction, on a Cu-rich tributary, 30 m downstream of Cu introduction where Cu levels were reduced, and 2 and 7 km further downstream where Cu concentrations were low. Taxonomic profiles of microbial communities (microbiomes) were compiled using DNA sequencing of 16S rRNA gene amplicons. Clear relationships between total Cu concentrations, pH and the microbiomes were evident. In the most Cu-affected samples, communities were dominated by bacteria from the Gallionellaceae family. Metagenomic sequencing profiled the genes present in microbiomes from the most Cu-contaminated sampling location and the area immediately upstream and showed that microbes in this area are well adapted to tolerate heavy metals. This study provides fundamental knowledge of microbial communities at a potential mine site and characterizes the genes likely involved in providing tolerance to an acidic and metals-rich environment. These results inform hypotheses for future experiments to support the development of bioremediation approaches that incorporate the use of native microorganisms at mining sites