An Assessment of the Spatial and Temporal Variability of Biological Responses to Municipal Wastewater Effluent in Rainbow Darter (Etheostoma caeruleum) Collected along an Urban Gradient.

Municipal wastewater effluent (MWWE) and its constituents, such as chemicals of emerging concern, pose a potential threat to the sustainability of fish populations by disrupting key endocrine functions in aquatic organisms. While studies have demonstrated changes in biological markers of exposure of aquatic organisms to groups of chemicals of emerging concern, the variability of these markers over time has not been sufficiently described in wild fish species. The aim of this study was to assess the spatial and temporal variability of biological markers in response to MWWE exposure and to test the consistency of these responses between seasons and among years. Rainbow darter (Etheostoma caeruleum) were collected in spring and fall seasons over a 5-year period in the Grand River, Ontario, Canada. In addition to surface water chemistry (nutrients and selected pharmaceuticals), measures were taken across levels of biological organization in rainbow darter. The measurements of hormone production, gonad development, and intersex severity were temporally consistent and suggested impaired reproduction in male fish collected downstream of MWWE outfalls. In contrast, ovarian development and hormone production in females appeared to be influenced more by urbanization than MWWE. Measures of gene expression and somatic indices were highly variable between sites and years, respectively, and were inconclusive in terms of the impacts of MWWE overall. Robust biomonitoring programs must consider these factors in both the design and interpretation of results, especially when spatial and temporal sampling of biological endpoints is limited. Assessing the effects of contaminants and other stressors on fish in watersheds would be greatly enhanced by an approach that considers natural variability in the endpoints being measured.

Optimization of effects-assessment of greenside darter (Etheostoma blennioides) exposed to tertiary treated municipal wastewater based on seasonal changes of reproductive endpoints.

The present study describes the seasonal changes in reproductive endpoints of the greenside darter (Etheostoma blennioides) and its implications for environmental monitoring. Fish collections conducted at the appropriate time for the site-specific sentinel fish species can provide a wide variety of population-level information including recruitment, reproduction, and energy storage. The objectives of the present study were to: 1) characterize seasonal changes in reproductive endpoints of the greenside darter (both sexes) to determine the appropriate period for monitoring of this sentinel species; and 2) evaluate the effect of exposure of this sentinel species to tertiary treated municipal effluent at the selected monitoring period. Based on the selected parameters (gonadosomatic index [GSI], liver somatic index [LSI], condition factor, and in vitro gonadal steroid production [testosterone (T) in both sexes; estradiol (E2) in females; and 11-ketotestosterone (11KT) in males]), the present study provides evidence for the value of collecting darters during recrudescence (late fall/early winter) to ensure temporal stability, minimum variability, and stable steroid production capacity. Darters exposed to tertiary treated municipal effluent tended to be larger and heavier relative to reference fish but did not demonstrate any consistent responses in terms of condition or relative liver size. No effect on gonadal development was observed, even though these tertiary-effluent-exposed fish demonstrated a significant reduction in the ability to produce hormones. The present study suggests that although fish exposed to tertiary treated effluent demonstrate no population-level effects, they are still responding at a physiological level. Documentation of the reproductive cycle of sentinel species allows for selection of the most appropriate sampling period to reduce variability and greatly enhances the reliability and interpretation of biological responses.

Assessment of status of white sucker (Catostomus commersoni) populations exposed to bleached kraft pulp mill effluent.

Credible ecological risk assessments often need to include analysis of population-level impacts. In the present study, a predictive model was developed to investigate population dynamics for white sucker (Catostomus commersoni) exposed to pulp mill effluent at a well-studied site in Jackfish Bay, Lake Superior, Canada. The model uniquely combines a Leslie population projection matrix and the logistic equation to translate changes in the fecundity and the age structure of a breeding population of white sucker exposed to pulp mill effluent to alterations in population growth rate. Application of this density-dependent population projection model requires construction of a life table for the organism of interest, a measure of carrying capacity, and an estimation of the effect of stressors on vital rates. A white sucker population existing at carrying capacity and subsequently exposed to pulp mill effluent equivalent to a documented exposure experienced during the period 1988 to 1994 in Jackfish Bay would be expected to exhibit a 34% to 51% annual decrease in recruitment during the first 5 yr of exposure and approach a population size of 71% of carrying capacity. The Jackfish Bay study site contains monitoring data for biochemical endpoints in white sucker, including circulating sex steroid concentrations, that could be combined with population modeling to utilize the model demonstrated at the Jackfish Bay study site for investigation of other white sucker populations at sites that are less data-rich.

Assessment of the health status of wild fish from the Wheatley Harbour Area of Concern, Ontario, Canada.

The overall health and endocrine function of wild brown bullhead (Ameiurus nebulosus) and goldfish (Carassius auratus) from the Wheatley Harbour Area of Concern (Lake Erie, Ontario, Canada) was assessed using a suite of physiological and biochemical endpoints. Smaller gonads were detected in female brown bullhead and goldfish from Wheatley Harbour compared with Hillman Marsh (Ontario, Canada) reference fish. Female brown bullhead exhibited decreased in vitro synthesis of 17ß-estradiol. Female goldfish had decreased plasma vitellogenin concentrations. Plasma testosterone and 11-ketotestosterone were significantly depressed in males of both species. Perturbations in the thyroid status were detected, but varied between sexes and species. Observed differences included lower plasma concentrations of thyroid hormones and/or elevated liver deiodinase activity. Histological evaluation of the thyroid tissue indicated that in the case of female goldfish, those perturbations stimulated the thyroid (as indicated by increased thyroid epithelial cell height) and partially depleted the thyroxine reserves, as indicated by decreased colloid and elevated thyroid activation index. Increased mixed-function oxygenase activity in brown bullhead from Wheatley Harbour was consistent with exposure to planar aromatic contaminants. A principal component analysis of selected variables showed the separation of fish by collection site. The endpoints most strongly associated with the separation were generally those exhibiting significant differences between sites. The results of the present study indicate that the health of fish populations within Wheatley Harbour warrants continued attention.