title: Acute and sub-lethal response to mercury in Arctic and boreal calanoid copepods.
abstract: Acute lethal toxicity, expressed as LC50 values, is a widely used parameter in risk assessment of chemicals, and has been proposed as a tool to assess differences in species sensitivities to chemicals between climatic regions. Arctic Calanus glacialis and boreal Calanus finmarchicus were exposed to mercury (Hg(2+)) under natural environmental conditions including sea temperatures of 2° and 10°C, respectively. Acute lethal toxicity (96 h LC50) and sub-lethal molecular response (GST expression; in this article gene expression is used as a synonym of gene transcription, although it is acknowledged that gene expression is also regulated, e.g., at translation and protein stability level) were studied. The acute lethal toxicity was monitored for 96 h using seven different Hg concentrations. The sub-lethal experiment was set up on the basis of nominal LC50 values for each species using concentrations equivalent to 50, 5 and 0.5% of their 96 h LC50 value. No significant differences were found in acute lethal toxicity between the two species. The sub-lethal molecular response revealed large differences both in response time and the fold induction of GST, where the Arctic species responded both faster and with higher mRNA levels of GST after 48 h exposure. Under the natural exposure conditions applied in the present study, the Arctic species C. glacialis may potentially be more susceptible to mercury exposure on the sub-lethal level.
authors.affiliation: Norwegian University of Science and Technology, Department of Biology, N-7491 Trondheim, Norway; SINTEF Materials and Chemistry, Environmental Technology, N-7465 Trondheim, Norway. Electronic address: ida.beathe.overjordet@sintef.no.
authors.forename: Ida Beathe
authors.initials: IB
authors.lastname: Overjordet
authors.affiliation: BioTrix, N-7022 Trondheim, Norway.
authors.forename: Dag
authors.initials: D
authors.lastname: Altin
authors.affiliation: Norwegian University of Science and Technology, Department of Chemistry, N-7491 Trondheim, Norway.
authors.forename: Torunn
authors.initials: T
authors.lastname: Berg
authors.affiliation: Norwegian University of Science and Technology, Department of Biology, N-7491 Trondheim, Norway.
authors.forename: Bjørn Munro
authors.initials: BM
authors.lastname: Jenssen
authors.affiliation: Norwegian Polar Institute, N-9296 Tromsø, Norway.
authors.forename: Geir Wing
authors.initials: GW
authors.lastname: Gabrielsen
authors.affiliation: SINTEF Materials and Chemistry, Environmental Technology, N-7465 Trondheim, Norway.
authors.forename: Bjørn Henrik
authors.initials: BH
authors.lastname: Hansen
mesh_terms: D000818:Animals; D001110:Arctic Regions; D033342:Copepoda / Q000187:drug effects*; D007928:Lethal Dose 50; D008628:Mercury / Q000633:toxicity*; D009792:Oceans and Seas; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Calanus finmarchicus; Calanus glacialis; Comparative ecotoxicology; Glutathione S-transferase; Polar; Stress gene transcription