6.3 Research Question Paper

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6.3 Research question #3
How do mercury stable isotopes ratio change in mercury bio-uptake and bio-magnification in an Arctic marine ecosystem?
There is still debate in the scientific community about Hg trophic transfer and/or in vivo transformations lead to MDF and MIF of Hg isotopes (Bergquist and Blum, 2007; Perrot et al., 2012; Senn et al., 2010; Kwon et al., 2012; Das et al., 2009). The MDF and MIF signatures of food webs may help to identify major sources and processes leading to significant bioaccumulation of MeHg (Perrot et al., 2012). To the best of my knowledge, there is no feeding experiment mimicking high Arctic marine ecosystem to study Hg transport, transformation and change in isotopic (both MDF and MIF) composition in food webs.
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Three Artemia tanks will be constructed from 20 L PET plastic carboys. The open top of the tank will be covered with an acrylic plastic sheet to minimize evaporative loss. Tanks will be kept at 4 to 5⁰C in a temperature controlled chamber. Each tank will be filled with 16 L of sterilized seawater and are continuously bubble with Hg free air as described in the Artemia protocol. Before hatching, the Artemia’s cysts will be sterilized by immersing 200 ppm sodium hypochlorite for 20 minutes. The sterilized cysts will be poured into a fine steel mesh coffee filter and rinsed 3 times with seawater. Then cyst will be transferred to the prepared Artemia tank whereupon they will be hatched after 12 to 24 hours. This tank will be used exclusively as nauplii nursery and will maintain throughout the food chain experiment as a food source for juvenile Artemia for the 3 treatment tanks. Once the nauplii reach approximately 1 mm in length (about 3 to 4 days), water will be drained out using filters and about 100 ml of the concentrated nauplii will be collected and feed with appropriate algae source in 2 tanks. Feeding will be repeated once the Artemia has cleared the tank of motile, suspended algae, typically 2 to 4 days depending on the density and size of the Artemia. During the six-week spiking experiment, HgT and isotopic ratios will be measured in Artemia samples every week (protocol, Trent

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