Mercury concentrations in landlocked Arctic char (Salvelinus alpinus) from the Canadian Arctic. Part I: Insights from trophic relationships in 18 lakes

Abstract

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to delta(13)C and delta(15)N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The delta(13)C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 +/- 1.1 to 64.3 +/- 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

“…Mercury levels in Arctic char from 19 lakes were positively correlated with watershed-to-lake area ratios, which explained approximately one-quarter of the variation in length-adjusted Hg concentrations in fish. [206,207] MeHg concentrations in fresh water aquatic invertebrates (Diptera, Chironomidae) from 22 lakes and ponds were found to be only weakly correlated with measures of Hg supply (i.e. watershed-to-lake area ratios, MeHg concentrations in water and sediment).…”

“…DOC) and stratification produce an environment favouring photoreduction to Hg 0 , which then evades to the atmosphere. [29] Landlocked Arctic char Lakes in the Canadian Arctic Archipelago have simple food webs in which Arctic char are often the only species of fish present, feeding primarily on the dominant benthic invertebrate, chironomids, or as cannibals on other char [206,225] while some adults exhibit cannibalistic feeding behaviour on juveniles. [166,226] Between 2005 and 2007, Hg biomagnification was investigated in the food webs supporting landlocked Arctic char populations in 18 lakes on: Ellesmere Island (n ¼ 4), Cornwallis Island (n ¼ 9), Victoria Island (n ¼ 1), Kent Peninsula (n ¼ 3) and Ungava Peninsula (n ¼ 1).…”

“…[166,226] Between 2005 and 2007, Hg biomagnification was investigated in the food webs supporting landlocked Arctic char populations in 18 lakes on: Ellesmere Island (n ¼ 4), Cornwallis Island (n ¼ 9), Victoria Island (n ¼ 1), Kent Peninsula (n ¼ 3) and Ungava Peninsula (n ¼ 1). [206] The sites covered a latitudinal gradient from 618 to 828N. The study included full food web sampling of Arctic char, periphyton, zooplankton, benthic invertebrates and ninespine stickleback (Pungitius pungitius) at each lake, as well as sediment and surface water samples.…”

“…[227] Of 212 char investigated in this survey, the majority consumed larvae (82 %) whereas pupae and adult chironomids were consumed in lesser amounts (52 and 11 %). However, on Cornwallis Island, adult chironomids were generally not present in char stomachs in the past [227] or recently, [206] although they were consumed in Char Lake. [226] Recent d 15 N data on insectivorous char show low variability in THg and d 15 N among Cornwallis Island lakes.…”

“…[226] Recent d 15 N data on insectivorous char show low variability in THg and d 15 N among Cornwallis Island lakes. [206,207] On Ellesmere Island, larger char fed selectively on pupae at the lake surface during the period of emergence, whereas smaller char (,20 cm) inhabited very shallow areas and fed mostly on chironomid larvae. [228] Life stage-related differences in habitat use and diet of the fish, which exposed them to different stable N isotope ratios and MeHg concentrations among larval, pupal and adult chironomids, [208] could explain some of the variability in d 15 N and Hg concentrations of char, particularly the differences between juvenile and adult fish.…”