Reproductive strategies and seasonal changes in the somatic indices of seven small-bodied fishes in Atlantic Canada in relation to study design for environmental effects monitoring

Guidance on assessing the potential impacts of selenium in freshwater ecosystems

Despite decades of fate and effects studies, environmental selenium (Se) contamination and management remain an issue for many freshwater systems in North America. Several regulatory bodies have promulgated updated targets or management levels for Se; however, additional guidance on best practices for monitoring Se to protect freshwater aquatic life is warranted. In this article, we describe current approaches to assessing the ecological risks of Se in impaired freshwater systems and outline recommended methods for collecting and analyzing biological and abiotic samples and interpreting data. Because reproductive impairment of fish populations is most commonly used to determine the potential impacts of Se, several biological factors that could affect Se toxicity are explored, including diet, trophic positions, reproductive biology, body size and maturity, migratory movements, and use of seasonal habitats. Measuring Se concentrations in mature eggs is the most reliable metric for estimating potential reproductive impairment in fish populations because the range of toxicity thresholds is relatively narrow for all but a few tolerant fish species. In situations where collecting mature eggs is not feasible, we review the use of alternative fish tissue for estimating potential effects. Factors affecting Se uptake from freshwater are also considered with guidance on collecting abiotic (e.g., water and sediment) and biotic components of aquatic food webs (e.g., macroinvertebrates, biofilm). Integr Environ Assess Manag 2024;00:1-16. © 2024 SETAC.

Thermal Stress Induces Metabolic Responses in Juvenile Qingtian Paddy Field Carp Cyprinus carpio var qingtianensis

Extreme fluctuations in water temperature lead to significant economic losses for the aquaculture industry. Cyprinus carpio var qingtianensis (locally called Qingtian paddy field carp), is a local variety commonly found in Zhejiang province, China. Unlike traditional aquaculture environments, the water temperature range between day and night in the rice field environment is much larger, and the high temperature in summer may exceed the growth threshold of fish because there is no manual intervention; therefore, the study of how the Qingtian paddy field carp (PF carp) adapts to high-temperature conditions can shed light how the species adapt to the rice field environment. To investigate the molecular mechanisms of this fish under thermal stress, the liver metabolomics of Qiangtian paddy field carp (PF carp) were analyzed. In this study, metabolomics was used to examine the metabolic reaction of PF carp (102 days old, 104.69 ± 3.08 g in weight, 14.65 ± 0.46 cm in length) at water temperatures of 28 °C (control group, CG), 34 °C (experimental group (EG) 34), and 38 °C (EG38). The results show that 175 expression profile metabolites (DEMs), including 115 upregulated and 60 downregulated metabolites, were found in the CG vs. EG34. A total of 354 DEMs were inspected in CG vs. EG38, with 85 metabolites downregulated and 269 metabolites upregulated. According to the pathway enrichment study, various pathways were altered by thermal stress, including those of lipid, amino-acid, and carbohydrate metabolism. Our study presents a potential metabolic profile for PF carp under thermal stress. It also demonstrates how the host responds to thermal stress on a metabolic and molecular level.

Assessing reproductive effects on fish populations: an evaluation of methods to predict the reproductive strategy of fishes

Many environmental monitoring programs include an assessment of the health of fish populations using a sentinel species and include an indicator of reproductive potential. Knowledge of the reproductive strategy of the fish species is critical for data interpretation but is not always known. The reproductive strategy of a species can be determined from detailed histological analyses of ovaries throughout the reproductive cycle; however, these studies can be costly and can delay the implementation of a monitoring program. Three quick and cost-effective methods of predicting the reproductive strategy (annual single spawning or annual multiple spawning) are evaluated in this study using predicted probabilities from binary logistic regression models as a means of classifying the reproductive strategies of 18 different fish species in Atlantic Canada. The first method was based on the hypothesis that the variability in the ovary weight-body weight relationship in prespawning females is higher in multiple spawners. This method did not have a good classification rate due to some multiple spawners having low variability. The other two methods involved predictor variables representing the proportion of oocytes in different stages of development and predictor variables representing the distribution of oocyte sizes during the prespawning season for 111 fish (25 different samples for species). Predicted probabilities from these regression models could be used to correctly classify the reproductive strategies of all 25 samples (development stage model) and all but one sample (oocyte size distribution model). These models can be used to estimate the reproductive strategy of a species from a single sample of fish collected during the prespawning period to support species selection and data interpretation in environmental monitoring programs.

The biology and ecology of slimy sculpin: A recipe for effective environmental monitoring

Recently, the use of small-bodied fish in environmental monitoring has increased, particularly within the Canadian environmental effects monitoring (EEM) and other adaptive programs. Although it is possible to measure changes with many small-bodied species, interpretation is often complicated by the absence of information on the biology and ecology of fish not of commercial, recreational, or traditional interest. Knowing and understanding the basic biology of these fishes aids in the sensitivity of study designs (i.e., ability to detect change) and the interpretation of all biological levels of responses (e.g., cellular to community). The increased use of slimy sculpin ( Cottus cognatus Richardson, 1836) in impact assessment studies in North America provides a considerable amount of information on life history aspects. The slimy sculpin has the most ubiquitous North American distribution among cottids but yet has a very small home range, thus integrating environmental conditions of localized areas. This paper describes aspects of slimy sculpin life cycle that affect collection efficiency and timing, and describes and provides data collected over more than 10 years of studies at more than 20 reference study sites. This overview provides a functional and informative compilation to support adaptive environmental monitoring and provide a baseline for comparative ecological study.

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.