Selenium speciation and localization in chironomids from lakes receiving treated metal mine effluent Justin J. Tse a,1 , Mercedes Gallego-Gallegos b , Eric D. Franz b,2 , Karsten Liber b , Ingrid J. Pickering a,⇑ a Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada b Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada highlights " Chironomid larvae are important vectors for selenium bioaccumulation. " Chironomids exposed to waterborne selenium species were compared to field chironomids. " Higher selenium levels led to a selenomethionine-like major form in tissues. " Selenium primarily localized in the head capsule, brain, salivary glands and gut lining. " Suggests selenomethionine is most readily accumulated, whether from food or water. article info Article history: Received 18 October 2011 Received in revised form 9 April 2012 Accepted 16 April 2012 Available online 17 May 2012 Keywords: Selenium Speciation X-ray absorption spectroscopy X-ray fluorescence imaging Chironomidae abstract A lake system in northern Saskatchewan receiving treated metal mine and mill effluent contains elevated levels of selenium (Se). An important step in the trophic transfer of Se is the bioaccumulation of Se by benthic invertebrates, especially primary consumers serving as a food source for higher trophic level organisms. Chironomids, ubiquitous components of many northern aquatic ecosystems, were sampled at lakes downstream of the milling operation and were found to contain Se concentrations ranging from 7 to 80 mg kg À1 dry weight. For comparison, laboratory-reared Chironomus dilutus were exposed to waterborne selenate, selenite, or seleno-DL-methionine under laboratory conditions at the average total Se concentrations found in lakes near the operation. Similarities in Se localization and speciation in lab- oratory and field chironomids were observed using synchrotron-based X-ray fluorescence (XRF) imaging and X-ray absorption spectroscopy (XAS). Selenium localized primarily in the head capsule, brain, sali- vary glands and gut lining, with organic Se species modeled as selenocystine and selenomethionine being the most abundant. Similarities between field chironomids and C. dilutus exposed in the laboratory to waterborne selenomethionine suggest that selenomethionine-like species are most readily accumulated, whether from diet or water. Ó 2012 Published by Elsevier Ltd. 1. Introduction Selenium (Se), an important micronutrient required by most organisms, is toxic above a rather narrow beneficial range. Sele- nium has a tendency to biomagnify through the food chain, such that even relatively low levels in surface waters can lead to significantly higher levels in top predators (Hymer and Caruso, 2006). High Se exposure to oviparous animals has been shown to cause teratogenic effects (Lemly, 1993; Muscatello et al., 2006). The present study involved a small lake system in northern Sas- katchewan that has been receiving treated metal mine effluent for over 25 years (Wiramanaden et al., 2010a, 2010b). Mean surface water Se levels of 10.3 and 4.0 lgL À1 in lakes downstream of the effluent source (Wiramanaden et al., 2010a) exceeded the Cana- dian water quality guideline for protection of aquatic life of 1 lgL À1 (CCREM, 1987). Previous research has shown increased deformities in laboratory-raised juvenile northern pike from moth- ers collected downstream of the effluent source (Muscatello et al., 2006). Additional research by Muscatello and Janz (2009) studied Se concentrations within the food web of the same study area, finding that Se interactions are complex and not yet fully understood. 0045-6535/$ - see front matter Ó 2012 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.chemosphere.2012.04.036 ⇑ Corresponding author. Address: Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK, Canada S7N 5E2. Tel.: +1 306 966 5706; fax: +1 306 966 8593. E-mail addresses: tse.jjp@gmail.com (J.J. Tse), mekigallego@yahoo.com (M. Gallego-Gallegos), eric.franz@cannorth.com (E.D. Franz), karsten.liber@usask.ca (K. Liber), ingrid.pickering@usask.ca (I.J. Pickering). 1 Present address: Robarts Research Institute, University of Western Ontario, London, Ontario, Canada. 2 Present address: Canada North Environmental Services, Saskatoon, Saskatchewan, Canada. Chemosphere 89 (2012) 274–279 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere