Food chain transfer and exposure effects of selenium in salmonid fish communities in two watersheds in the Canadian Rocky Mountains

Selenium (Se) concentrations and fish biomass were examined in streams in two mined watersheds to determine if juvenile salmonids reflect local Se exposure concentrations downstream of surface coal mines and to investigate the relationship between Se exposure and toxicity effects at the fish community level. Se concentrations were measured in water, biofilm, macroinvertebrates, and muscle tissues from juvenile westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis) in mine-affected and reference streams. Significant positive Se transfer relationships were found at each measured level of the lotic food chain. Se accumulation from macroinvertebrates to juvenile fish muscle tissue was not significantly different among fish species, but indicated a significant positive relationship between juvenile fish muscle tissue and dietary Se at capture sites. Mean muscle Se concentrations in some stream reaches exceeded proposed individual-level toxic effective concentrations (EC 10 ) in rainbow trout (3.14 ± 0.38 to 15.07 ± 2.24 mg·kg –1 dry mass) and westslope cutthroat trout (3.31 ± 0.32 to 13.79 ± 1.27 mg·kg –1 dry mass), but fish biomass at the reach scale was only significantly negatively related to mean fish muscle tissue Se concentrations for rainbow trout.