Environ. Sci. Technol. 2008, 42, 3109–3114
Reproductive Success, Early Life Stage Development, and Survival of Westslope Cutthroat Trout (Oncorhynchus clarki lewisi) Exposed to Elevated Selenium in an Area of Active Coal Mining BARRI-LYNN RUDOLPH, IISAK ANDRELLER, AND CHRISTOPHER J. KENNEDY* Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., Canada V5A 1S6
Received August 14, 2007. Revised manuscript received January 10, 2008. Accepted January 14, 2008.
The effects of accumulated Se on the reproductive success and larval development of cutthroat trout (Oncorhynchus clarki lewisi) collected from a site of active coal mining in British Columbia were assessed. Eggs from 12 fish from an exposed site (Clode Pond) and 16 from a reference site (O’Rourke Lake) were field-collected and reared in the laboratory. Egg Se concentrations ranged from 12.3 to 16.7 and 11.8 to 140.0 µg/g dry weight (dw) from fish collected at the reference and exposed sites, respectively. Other studies, including those with this species, have not shown Se to affect egg viability; however, in the present study, eggs with Se concentrations >86.3 µg/g dw were not successfully fertilized or were nonviable at fertilization, while eggs with concentrations >46.8 and 20.6 µg/g dw. The present data, in conjunction with the data from several other studies in temperate fish, suggest that current Se thresholds are conservative for cold-water fish.
Introduction Significant increases in environmental Se concentrations can occur through anthropogenic activities including coal mining (1–3). Se is an essential micronutrient; however, there is a narrow margin between “normal” and toxic concentrations in tissues. Research to date indicates that the most ecologically significant Se toxicity arises from maternally transferred Se that accumulates in egg yolks during vitellogenesis. Deformities and edema occur when developing larvae utilize the yolk sac (4). On the basis of studies with warm-water fish, Lemly (5) reported a rapid increase in larval deformities when egg Se concentrations exceed 10 µg/g dry weight (dw) * Corresponding author phone: 778-782-5640; fax: no. 778-7823496; e-mail:
[email protected]. 10.1021/es072034d CCC: $40.75
Published on Web 03/07/2008
2008 American Chemical Society
and therefore proposed Se effect thresholds of 10, 8, and 4 µg/g dw for eggs, skeletal muscle, and the whole body, respectively. These guidelines are lower than the whole-body chronic criterion recommended by the USEPA (6) of 7.91 µg/g dw (based on increased mortality in a laboratory study with bluegill sunfish [Lepomis macrochirus]). This value corresponds to approximately 17 µg/g Se (dw) in eggs using the whole body to egg concentration conversion equation provided by the USEPA (6). There is currently debate with respect to the applicability of toxicity thresholds and guidelines derived from warm-water fish to native cold-water fishes inhabiting north temperate aquatic systems (5, 7, 8). Studies on field-collected temperate fish have demonstrated that elevated Se body burdens do not appear to cause adverse effects in cold-water fish at concentrations that exceed thresholds proposed for warm-water species (9). Kennedy et al. (10) found that, despite elevated egg Se concentrations (8.7 to 81.3 µg/g dw) in wild cutthroat trout (Oncorhynchus clarki lewisi) from Se-exposed versus reference site fish, no significant effects on fertilization, time to hatch, percent hatch, deformities, or mortalities were found. Holm et al. (11) reported a deformity threshold in eggs between 32 to 40 µg/g dw (estimated from ww assuming 75% moisture) in rainbow trout (Oncorhynchus mykiss) and no increase in larval deformities in brook trout (Salvelinus fontinalis) collected from two sites with mean egg Se concentrations of 26.4 and 31.2 µg/g dw, (estimated from wet weight (ww) assuming 75% moisture). Similarly, Muscatello et al. (12) reported an EC20 (the concentration that resulted in a 20% increase in total deformities above background levels) of 33.6 µg/g dw in northern pike (Esox lucius) eggs. Finally, no correlation between deformities and Se was observed in white suckers with a mean Se egg concentration of 21 µg/g dw (estimated from ww assuming 93% moisture) (13). The objectives of the present study were to build on Kennedy et al. (10) and to further examine the effects of elevated Se concentrations on the reproductive and developmental success of westslope cutthroat trout (WCT; O. clarki lewisi) and to determine the effects threshold concentration of Se in eggs. This entailed a specific examination of the relationship between egg Se concentrations, egg viability, and development and survival of the embryo-larval stages.
Materials and Methods Study Area. In June 2005, WCT were collected from a reference site (O’Rourke Lake) and an exposed site (Clode Pond). Clode Pond is on the property of the Fording River Coal Operations (FRO, Elk Valley Coal Corporation) in southeast BC (Canada). WCT were confined to Clode Pond for 8 months prior to the start of the present study. O’Rourke Lake is located east of the mine site. O’Rourke Lake is an isolated water body into which WCT were stocked in 1985, 1989, and 1992. Water concentrations of Se were 0.093 and 90%; and water temperature, 4.0 ( 0.5 °C) at Simon Fraser University (SFU), Burnaby, BC, 46.8 and
