Population‐level consequences for wild fish exposed to sublethal concentrations of chemicals – a critical review

Abstract

Concentrated chemical spills have been shown to impact adversely on fish populations and even cause localized population extinctions. Evaluating population-level impacts of sublethal exposure concentrations is, however, complex and confounded by other environmental pressures. Applying effect measures derived from laboratory-based chemical exposures to impacts in wild fish populations is constrained by uncertainty on how biochemical response measures (biomarkers) translate into health outcomes, lack of available data for chronic exposures and the many uncertainties in available fish population models. Furthermore, wild fish show phenotypic plasticity and local adaptations can occur that adds geographic and temporal variance on responses. Such population-level factors are rarely considered in the chemical risk assessment process and can probably be derived only from studies on wild fish. Molecular technologies, including microsatellite and SNP genotyping, and RNASeq for gene expression studies, are advancing our understanding of mechanisms of eco-toxicological response, tolerance, adaptation and selection in wild populations. We examine critically the application of such approaches with examples including using microsatellites that has identified roach (Rutilus rutilus) populations living in rivers contaminated with sewage effluents that are self-sustaining, and studies of stickleback (Gasterosteus aculeatus) and killifish (Fundulus heteroclitus) that have identified genomic regions under selection putatively related to pollution tolerance. Integrating data on biological effects between laboratory-based studies and wild populations, and building understanding on adaptive responses to sublethal exposure are some of the priority research areas for more effective evaluation of population risks and resilience to contaminant exposure.

Climate change–contaminant interactions in marine food webs: Toward a conceptual framework

“…While prior adaption of some groups of marine animals or populations to cope with climate change stress is likely to trigger more resilience and adaptation to such climatic changes (Moe et al., ; Parmesan, ), there has been little time for long‐lived species to develop adaptive mechanisms to cope with industrial PCBs developed in the 20th century (Hooper et al., ; Moe et al., ; Stahl et al., ). Conversely, for those species that have been able to adapt to contaminated habitats (Hamilton et al., ; Medina, Correa & Barata, ), it may be difficult to confront and adapt to a rapidly changing climate (Hooper et al., ; Moe et al., ; Stahl et al., ). The interactive effects of a combined climate change‐induced pollutant sensitivity and pollutant‐induced climate change susceptibility processes are unclear.…”

Histological and Transcriptomic Changes in Male Zebrafish Testes Due to Early Life Exposure to Low Level 2,3,7,8-Tetrachlorodibenzo-p-Dioxin

“…Such studies in wild fish populations are complicated by the complexity of aquatic environments. 1 Zebrafish are an excellent model system because they are vertebrates with short generation times, homogeneous genetic backgrounds, and modest housing needs that stabilize biotic and abiotic factors, thus facilitating single and multigenerational studies with minimal time, expense, and confounding variables.…”

“…For example, exposure to EDCs contributes to an array of reproductive disorders in both humans (e.g., reduced fertility, abnormal development and function of reproductive organs, poor sperm quality, and cancer) [5][6][7][8] and fish (e.g., testicular oocytes or ''intersex,'' reduced recruitment, and elevated vitellogenin concentrations). 1,6,[9][10][11] Furthermore, we have shown that reproductive endpoints are observed in offspring of TCDD-lineage F2 male and control female spawnings, 4 indicating that transgenerational inheritance of TCDD reproductive toxicity in zebrafish occurs through the male germ line.…”

“…1 Research that uncovers critical pathways and biomarkers of effect can inform novel therapies, future research needs, and prevention and conservation strategies.…”

Endocrine disruption in aquatic systems: up‐scaling research to address ecological consequences

“…Specifically, these differences include the nature of the EDC exposure regime, possible compounding environmental influences (e.g. multiple stressors), and the fact that multiple effect mechanisms may operate through trophic interactions across food webs at the macroscale (Hamilton et al ., ). There are several potential inconsistencies in findings about endocrine disruption from different biological, spatial and temporal scales.…”