title: Environmental, geographic and trophic influences on methylmercury concentrations in macroinvertebrates from lakes and wetlands across Canada.
abstract: Macroinvertebrates are a key vector in the transfer of methylmercury (MeHg) to fish. However, the factors that affect MeHg concentrations and bioaccumulation in these organisms are not as well understood as for fish, and studies on a broad geographic scale are lacking. In this study, we gathered published and unpublished MeHg and carbon (δ(13)C) and nitrogen (δ(15)N) stable isotope data for freshwater macroinvertebrates from 119 lakes and wetlands across seven Canadian provinces, along with selected physical, chemical and biological characteristics of these systems. Overall, water pH was the most important determinant of MeHg concentrations in both predatory and non-predatory invertebrates [[Formula: see text] = 0.32, p < 0.001; multivariate canonical redundancy analysis (RDA)]. The location of lakes explained additional variation in invertebrate MeHg (partial R(2) = 0.08 and 0.06 for latitude and longitude, respectively; RDA), with higher concentrations in more easterly and southerly regions. Both invertebrate foraging behaviour and trophic position (indicated by functional feeding groups and δ(15)N values, respectively) also predicted MeHg concentrations in the organisms. Collectively, results indicate that in addition to their feeding ecology, invertebrates accumulate more MeHg in acidic systems where the supply of MeHg to the food web is typically high. MeHg concentrations in macroinvertebrates may also be influenced by larger-scale geographic differences in atmospheric mercury deposition among regions.
authors.affiliation: Biology Department, Canadian Rivers Institute, University of New Brunswick, 100 Tucker Park Road, Saint John, NB, E2L 4L5, Canada.
authors.forename: Meredith G
authors.initials: MG
authors.lastname: Clayden
authors.forename: Karen A
authors.initials: KA
authors.lastname: Kidd
authors.forename: John
authors.initials: J
authors.lastname: Chételat
authors.forename: Britt D
authors.initials: BD
authors.lastname: Hall
authors.forename: Edenise
authors.initials: E
authors.lastname: Garcia
mesh_terms: D000818:Animals; D002170:Canada; D002244:Carbon / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods; D005399:Fishes; D020387:Food Chain; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D007448:Invertebrates / Q000737:chemistry*; D060106:Lakes / Q000737:chemistry*; D008767:Methylmercury Compounds / Q000633:toxicity*; D009584:Nitrogen / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D053833:Wetlands
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D002244:Carbon; D009584:Nitrogen