title: Transformation of mercury at the bottom of the Arctic food web: an overlooked puzzle in the mercury exposure narrative.
abstract: We show 2008 seasonal trends of total and monomethyl mercury (THg and MeHg, respectively) in herbivorous (Calanus hyperboreus) and predatory (Chaetognaths, Paraeuchaeta glacialis, and Themisto abyssorum) zooplankton species from the Canadian High Arctic (Amundsen Gulf and the Canadian Beaufort Sea) in relation to ambient seawater and diet. It has recently been postulated that the Arctic marine environment may be exceptionally vulnerable to toxic MeHg contamination through postdepositional processes leading to mercury transformation and methylation. Here, we show that C. hyperboreus plays a hitherto unrecognized central role in mercury transformation while, itself, not manifesting inordinately high levels of THg compared to its prey (pelagic particulate organic matter (POM)). Calanus hyperboreus shifts Hg from mainly inorganic forms in pelagic POM (>99.5%) or ambient seawater (>90%) to primarily organic forms (>50%) in their tissue. We calculate that annual dietary intake of MeHg could supply only ∼30% of the MeHg body burden in C. hyperboreus and, thus, transformation within the species, perhaps mediated by gut microbial communities, or bioconcentration from ambient seawater likely play overriding roles. Seasonal THg trends in C. hyperboreus are variable and directly controlled by species-specific physiology, e.g., egg laying and grazing. Zooplankton that prey on species such as C. hyperboreus provide a further biomagnification of MeHg and reflect seasonal trends observed in their prey.
authors.affiliation: Centre for Earth Observation Science, University of Manitoba , 460 Wallace Building, 125 Dysart Road, Winnipeg, R3T 2N2, Canada.
authors.forename: Monika
authors.initials: M
authors.lastname: Pućko
authors.forename: A
authors.initials: A
authors.lastname: Burt
authors.forename: W
authors.initials: W
authors.lastname: Walkusz
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: R W
authors.initials: RW
authors.lastname: Macdonald
authors.forename: S
authors.initials: S
authors.lastname: Rysgaard
authors.forename: D G
authors.initials: DG
authors.lastname: Barber
authors.forename: J-É
authors.initials: JÉ
authors.lastname: Tremblay
authors.forename: G A
authors.initials: GA
authors.lastname: Stern
mesh_terms: D033304:Amphipoda / Q000378:metabolism; D000818:Animals; D001110:Arctic Regions; D001711:Biotransformation; D002170:Canada; D033342:Copepoda / Q000378:metabolism; D004781:Environmental Exposure / Q000032:analysis*; D004784:Environmental Monitoring; D005399:Fishes; D020387:Food Chain; D005843:Geography; D060434:Herbivory; D008628:Mercury / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D011235:Predatory Behavior; D012621:Seasons; D012623:Seawater / Q000737:chemistry; D012767:Ships; D014874:Water Pollutants, Chemical / Q000032:analysis; D015048:Zooplankton / Q000378:metabolism
chemical_list: D008767:Methylmercury Compounds; D009930:Organic Chemicals; D052638:Particulate Matter; D014874:Water Pollutants, Chemical; D008628:Mercury