Hexachlorocyclohexane (HCH) Isomers and Chiral Signatures of α-HCH in the Arctic Marine Food Web of the Northwater Polynya

Abstract

Concentrations of hexachlorocyclohexane (HCH) isomers (alpha, beta, and gamma) and enantiomer fractions (EFs) of alpha-HCH were determined in the Northwater Polynya Arctic marine food web. Relative food web structure was established using trophic level models based on organic delta 15N values. Concentrations of HCH in the samples collected, including water, sediment, benthic invertebrates (four species), pelagic zooplankton (six species), Arctic cod, seabirds (seven species), and ringed seal, were in the range previously reported for the Canadian Arctic. The relative proportion of the HCH isomers varied across the food web and appeared to be related to the biotransformation capacity of each species. For invertebrates and fish the biomagnification factors (BMFs) of the three isomers were > 1 and the proportion of each isomer and the EFs of alpha-HCH were similar to water, suggesting minimal biotransformation. Seabirds appear to readily metabolize gamma- and alpha-HCH based on low BMFs for these isomers, high proportions of beta-HCH (62-96%), and high EFs (0.65-0.97) for alpha-HCH. The alpha- and beta-HCH isomers appear to be recalcitrant in ringed seals based on BMFs > 1 and near racemic EFs for alpha-HCH. The beta isomer appears to be recalcitrant in all species examined and had an overall food web magnification factor of 3.9. EFs of alpha-HCH and the proportion of beta-HCH in sigma-HCH in the food web were highly correlated (r2 = 0.92) suggesting that EFs were a good indicator of a species capability to biotransform alpha-HCH.

Hexachlorocyclohexanes in Arctic and Antarctic Marine Ecosystems

“…Their decreasing trend were very significant (p = 0.001) during this time span; these Authors reported that α-HCH concentrations declined faster than those of δ-HCH, in agreement with observations for Arctic air and water (Li et al, 1998;Jantunen and Bidleman, 1995). The HCH isomer abundance were α-HCH > β-HCH > δ-HCH in Polar cod (Sinkkonen et al, 2000;Moisey et al, 2001) and δ-HCH > α-HCH > β-HCH in the Antarctic T. bernacchi (Corsolini et al, 2006). These patterns could be interpreted as an indication that the use of technical HCH (containing 60-70% of α-HCH) has decreased faster than that of pure lindane (Li et al, 1998).…”

“…Fish species collected in the Arctic region and analyzed for HCHs were mostly the Arctic cod (Arctogadus glacialis), the Polar cod (Boreogadus saida), the Greenland halibut (Reinhardtius hippoglossoides), and others. ΣHCH concentrations in Polar cod muscle from the Canadian Arctic were 90.2±13.7 ng/g lipid wt (Moisey et al, 2001), 40±3.2 ng/g lipid wt (Hoekstra et al, 2003), and 10 ng/g lipid wt (Kelly et al , 2008); concentrations in the Greenland halibut muscle were as 81 ng/g lipid wt in (Fisk et al, 2002), and 53 ng/g lipid wt in Greenland shark (Somniosus microcephalus) liver (Fisk et al, 2002). Levels in Polar cod were of the same order of magnitude, but a decreasing trend can be observed during 2000s.…”

“…Anyway, α-and δ-HCH were reported to be decreasing in the Arctic (Rigét et al, 2010). A study on the occurrence of HCH in several species of seabirds from the Northwater Polynia (NOW) reported ΣHCH concentrations in various species: 222±19.9 ng/g lipid wt in dovekie, 84.5±9.6 ng/g lipid wt in thick-billed murre, 285±46.7 ng/g lipid wt in black guillemot, 47.3±6.3 ng/g lipid wt in black-legged kittiwake, 442.7±51.9 ng/g lipid wt in glacous gull, 143.0±32.7 ng/g lipid wt in ivory gull, 65.1±5.8 ng/g lipid wt in northern fulmar (Moisey et al, 2001). These Authors reported the α, β and γ-isomer patterns of abundance was β-HCH > α-HCH > δ-HCH in all these species.…”

Comparing measured and predicted PCB concentrations in Arctic seawater and marine biota

“…Contaminant's half-lives were assumed long as invertebrates and fish have restricted or negligible biotransformation of PCBs (e.g. Moisey et al, 2001). (D) Diet composition: Copepods- Scott et al (1999), Euphausiids-Båmstedt and Karlson (1998), Amphipods-Scott et al (1999), Polar cod- Lønne and Gulliksen (1989).…”

“…Moisey et al, 2001), assuming that POP partition only into lipids and not other organic phases is debated (e.g. Swackhamer and Skoglund, 1993;Skoglund and Swackhamer, 1999).…”