Laboratory and in-situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyallela azteca and Chironomus dilutus M. P. Mendes1, B. Cupe-Flores1, & K. Liber 1,2 (1) Toxicology Centre, University of Saskatchewan, Canada (2) School of Environment and Sustainability, University of Saskatchewan, Canada

Abstract

Abstract Selenium (Se) bioaccumulation and toxicity in aquatic vertebrates have been thoroughly investigated over the past two decades. Limited information is available on Se bioaccumulation at the base of aquatic food webs. In this study, we selected two laboratory-reared benthic macroinvertebrates (BMI), Hyalella azteca and Chironomus dilutus, to investigate Se bioaccumulation potential in a Canadian boreal lake (McClean Lake) receiving continuous Se input from a Saskatchewan uranium mill. Laboratory and in-situ experiments were conducted in summer 2019 to assess the potential effects of biological competition on Se uptake and transfer in co-exposed H. azteca and C. dilutus. In 2021, additional experiments were included to examine the use of lab-reared H. azteca as an indicator of on-site Se exposure (native population vs lab-reared) and the major source of Se (surface water, top 1 cm and top 2-3 cm sediment layers) contributing to Se bioaccumulation in H. azteca. Except for one site (9), comparable Se bioaccumulation and trophic transfer factors (TTFs) were observed in co-exposed H. azteca (whole-body Se 0.9 to 3.1 µg /g d.w; TTFs 0.6 to 6.3) and C. dilutus (whole-body Se at 0.7 to 3.2 µg Se/g d.w.; TTFs 0.7 to 3.4). Similar non-linear dietary Se uptake and bioaccumulation were observed between lab-reared and native H. azteca (NLR, p=0.003; 4.1 ± 0.8 µg Se/g d.w) until day 14 of the experiment. Results from this study corroborate the importance of the sediment-detrital pathway relative to waterborne Se exposure, with the former leading to greater Se bioaccumulation potential to higher trophic levels via BMI.