T7 AM Metals in the Environment: Dietary Concerns in Aquatic Systems
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 327-329

(RIC-1117-837472) Assessing effects of metal mining effluent on fathead minnow (Pimephales promelas) reproduction in a trophic-transfer system.

Rickwood, C^{1, 2}, Dubé, M^{1, 2}, Weber, L¹, Driedger, K¹, Janz, D¹, ¹ University of Saskatchewan, Saskatoon, SK, Canada² National Water Research Institute, Saskatoon, SK, Canada

ABSTRACT- Assessment 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. Studies investigating the relative importance of trophic-transfer of metals in aquatic environments have highlighted that dietary uptake can be a significant route of exposure in fish. The effects of MME on creek chub and fathead minnow (Pimephales promelas) (FHM) have been reported downstream of numerous metal mine discharges in the Junction Creek system, Sudbury, ON, Canada, 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 not only water-borne (FHM-only) but also food- and water-borne (trophic-transfer) exposure to MME on FHM reproduction. Reproductive performance of FHM were assessed for 21 d under controlled laboratory conditions to obtain baseline data of various endpoints including egg production, hatching success and occurrence of deformed larvae. At the end of the pre-exposure, breeding pairs were selected for either the trophic-transfer system or the FHM-only standard bioassay. Exposure to 45% v/v MME and control treatments for both systems was then conducted for a further 21 d after which time measures of condition, gonad size, liver size, testosterone, 17b-estradiol, vitellogenin and metal body burdens were taken. It was evident that the number of spawning events and egg production in both the FHM-only and the trophic-transfer system were reduced compared to controls. Hatching success was not affected in the FHM-only treatment. In the trophic-transfer system, however, a severe reduction in larval hatching and a substantial increase in deformities including scoliosis and yolk sac edema occurred after exposure to MME. This would suggest that contaminated food was a major route of exposure causing effects on larval survival.

Key words: Fathead Minnow, Metal Mine effluent, Trophic-transfer, Reproduction