Scavenging Amphipods: Sentinels for Penetration of Mercury and Persistent Organic Chemicals into Food Webs of the Deep Arctic Ocean

Abstract

Archived specimens of the scavenging amphipod Eurythenes gryllus, collected from 2075 to 4250 m below the surface on five expeditions to the western and central Arctic Ocean between 1983 and 1998, were analyzed for total mercury (∑Hg), methyl mercury (MeHg), polychlorinated biphenyls (PCBs) and other industrial or byproduct organochlorines (chlorobenzenes, pentachloroanisole, octachlorostyrene), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). Median ∑Hg concentrations ranged from 70 to 366 ng g(-1) wet weight (ww). MeHg concentrations (3.55 to 23.5 ng g(-1) ww) accounted for 1.7 to 20.1% (median 3.7%) of ∑Hg. ∑Hg and MeHg were positively and significantly correlated with ww (∑Hg r(2) = 0.18, p = 0.0004, n = 63; MeHg r(2) = 0.42, p = 0.0004, n = 25), but not significantly with δ(13)C nor δ(15)N. Median concentrations of total persistent organic pollutants (POPs) ranged from 9750 to 156,000 ng g(-1) lipid weight, with order of abundance: ∑TOX (chlorobornanes quantified as technical toxaphene) > ∑PCBs > ∑DDTs > ∑chlordanes > ∑mirex compounds > ∑BDEs ∼ ∑chlorobenzenes ∼ octachlorostyrene > α-hexachlorocyclohexane ∼ hexachlorobenzene ∼ pentachloroanisole. Enantioselective accumulation was found for the chiral OCPs o,p'-DDT, cis- and trans-chlordane, nonachlor MC6 and oxychlordane. Lipid-normalized POPs concentrations were elevated in amphipods with lipid percentages ≤10%, suggesting that utilization of lipids resulted in concentration of POPs in the remaining lipid pool. Multidimensional Scaling (MDS) analysis using log-transformed physiological variables and lipid-normalized organochlorine concentrations distinguished amphipods from the central vs western arctic stations. This distinction was also seen for PCB homologues, whereas profiles of other compound classes were more related to specific stations rather than central-west differences.

Spatial and temporal distribution of chiral pesticides in Calanus spp. from three Arctic fjords

“…Hence, ice cover and water masses give a similar contribution to the enantiomeric signal of CC at these locations indicating EF patterns of CC are affected by other unknown factors. Benthic feeding amphipods have shown larger deviations from racemic compared to pelagic plankton (Bidleman et al, 2013b;Borgå and Bidleman, 2005). This helps supports our hypothesis that EFs observed in plankton species within this study are impacted by benthic e pelagic coupling in fjords and reflect enantiomer enriched signatures present within the sediment and/ or benthic dwelling organisms.…”

The influence of global climate change on the environmental fate of persistent organic pollutants: A review with emphasis on the Northern Hemisphere and the Arctic as a receptor

“…Given the strong partitioning of many contaminants to organic matter, the process of vertical flux ‗draws down' dissolved POPs concentrations in the surface layer much in the same way it draws down CO 2 and, likewise, forces net exchange of POPs from atmosphere to ocean to re-attain equilibration (Dachs et al, 1999). The process of transfer out of the upper ocean can be passive in the form of biological and inorganic detritus (e.g., Timothy et al, 2013), or larger dead animals (Bidleman et al, 2013), or the vertical migration of living zooplankton (Pućko et al 2013b). The general process of removing biological matter (C, N, P, Si) from the upper ocean in this way is termed the "biological pump‖.…”

“…For many POPs, the cold, dark regions beneath perennial sea ice, together with very low vertical particle flux (e.g., Honjo et al, 2010;Hwang et al, 2015), permits chemicals like HCH to persist long enough in near-surface waters to transport over decadal time periods to even the most remote locations (Macdonald et al, 2000). The small vertical particle flux and the occasional sinking of larger organisms do, however, permit further transport into basin waters and sediments for chemicals that partition strongly into organic particles or become concentrated in foodwebs (e.g., Sober and Gustafson, 2014; Bidleman et al, 2013) .…”

Organic matter transfer in Lake Superior's food web: Insights from bulk and molecular stable isotope and radiocarbon analyses

“…A third potential explanation for 15 N enrichment is the engagement of Limnocalanus in scavenging behavior, consuming flesh from deceased higher trophic position organisms. This is not a currently documented Limnocalanus behavior, however, scavenging has been suggested or observed for Antarctic marine copepod species (Bradford and Wells ), and, particularly in cold water locales, is also well documented in other zooplankton species, including Mysis (Johannsson et al ) and various amphipods (Fisk et al ; Bidleman et al ).…”