Growth and energy storage in juvenile fathead minnows exposed to metal mine waste water in simulated winter and summer conditions.

Juvenile fathead minnows (Pimephales promelas) were exposed from 10 to 100 days post-hatch (dph) to metal mining effluent under simulated summer (20 degrees C and 16/8 light/dark) or winter (4 degrees C and 8/16 light/dark) conditions in order to test the winter stress syndrome hypothesis. The condition factor of fish at 100 dph was similar between seasons, and was greater in the summer effluent exposure group compared to the summer control. Whole body triglycerides were lower in the effluent exposure group compared to control under winter conditions, but not summer. Whole body burdens of several trace metals, notably Cu, Rb and Se, were greater in the effluent exposed fish at 100 dph and displayed seasonal differences in bioaccumulation. Fathead minnows were also exposed from 10 to 100 dph to graded concentrations of ammonia (0.02-0.40 mg unionized NH(3)/L) under summer conditions in order to investigate potential effects of this component of the effluent. There was no effect of ammonia exposure on growth parameters, but an increase in whole body triglycerides was observed at the highest exposure. The seasonal differences in bioaccumulation and biological responses suggest that winter conditions may be an important modifying factor in aquatic toxicological studies.

Overwinter alterations in energy stores and growth in juvenile fishes inhabiting areas receiving metal mining and municipal wastewater effluents.

The winter stress syndrome hypothesis proposes that the combination of winter conditions and contaminant exposure reduces overwinter survival in juvenile fishes, mainly due to increased depletion of stored energy (lipids). To test this hypothesis in the field, juvenile fathead minnows (Pimephales promelas), creek chub (Semotilus atromaculatus), and white sucker (Catostomus commersoni) were collected from three exposure sites along Junction Creek, Sudbury, Ontario, Canada, representing cumulative inputs from metal mining and municipal wastewater. Overwinter survival potential was determined through measurements of growth (length, weight, muscle RNA/DNA ratio, muscle proteins) and energy stores (whole body triglycerides) in fish collected just prior to and following the overwinter period. We hypothesized that fish collected from exposure sites would exhibit reduced growth and energy storage compared to reference fish in both fall and spring, and that fish from all sites would exhibit reduced energy storage in spring compared to the previous fall. Whole body Se concentrations were elevated (11-42 microg/g dry wt) in juvenile fathead minnows and white sucker collected at two exposure sites in comparison to fish collected from the reference site (3-6 microg/g dry wt). In contrast to our hypothesis, fathead minnows were larger with greater triglyceride stores at exposure sites compared to the reference site. White suckers were smaller at exposure sites but did not differ in triglycerides among sites. Overall, the results in these fish species exposed to metal mining and municipal wastewaters do not support the winter stress syndrome hypothesis. It is recommended that future studies focus on relating growth and energy storage with other environmental factors such as habitat and food availability in addition to anthropogenic contamination.

Effects of multiple effluents on resident fish from Junction Creek, Sudbury, Ontario.

Junction Creek in Sudbury, Ontario, Canada receives effluent from three metal mining effluents (MMEs), as well as urban run-off and municipal sewage treatment plant (STP) discharges. The present study examined organismal and sub-organismal end-points in prespawning fathead minnow (FHM; Pimephales promelas) and creek chub (CC; Semotilus atromaculatus) collected in May 2004 from Junction Creek. Metal body burdens of Cd, Cu, Rb, Se, and Sr increased in a gradient down Junction Creek in both species. In general, male fish had lower body weights downstream of effluents, while females were unchanged or larger compared to reference fish. Livers were larger in FHM of both sexes downstream of STP and in CC downstream of two MMEs compared to reference fish, while gonad weight was unchanged. The most consistent finding was delayed development, increased cell death and increased eosinophilia in FHM testes collected downstream of all effluents, while female FHM and both sexes of CC gonads were relatively unaffected. In conclusion, the results of the current study in Junction Creek suggest that male FHM reproduction may be sensitive to multiple effluents, but failed to clearly establish whether MME or STP effluents were causative agents over urban inputs or historical contamination.

Assessing effects of metal mining effluent on fathead minnow (Pimephales promelas) reproduction in a trophic-transfer exposure system.

Assessment of effects of metal mine effluent (MME) on aquatic organisms in lab-based settings predominantly evaluates contaminant transfer through the water only with little emphasis on food-borne exposure. The effects of MME on fathead minnow (Pimephales promelas) (FHM) have been reported downstream of metal mine discharges in the Junction Creek system, Sudbury, ON, but to date, no study has investigated the significance of trophic transfer in this system. Our objective was to develop a self-sustaining trophic-transfer bioassay, using Chironomus tentans and FHM, that allowed assessment of the effects of not only water-borne (FHM-only) but also food- and water-borne (trophic-transfer) exposure to MME on FHM reproduction. Reproductive performance of FHM was assessed for 21 days under controlled laboratory conditions to obtain baseline data of various endpoints, including egg production and hatching success. Exposure to 45% (v/v) Copper Cliff mine effluent (CCME) and control treatments for both systems was then conducted for a further 21 days. It was evident that reproductive output in both the water-only and the trophic-transfer system was reduced compared to controls. It was only in the trophic-transfer system that a significant reduction in larval hatching and an increase in deformities occurred after exposure to CCME. This would suggest that contaminated food was a route of exposure causing effects on larval survival.