title: Metamorphosis alters contaminants and chemical tracers in insects: implications for food webs.
abstract: Insects are integral to most freshwater and terrestrial food webs, but due to their accumulation of environmental pollutants they are also contaminant vectors that threaten reproduction, development, and survival of consumers. Metamorphosis from larvae to adult can cause large chemical changes in insects, altering contaminant concentrations and fractionation of chemical tracers used to establish contaminant biomagnification in food webs, but no framework exists for predicting and managing these effects. We analyzed data from 39 studies of 68 analytes (stable isotopes and contaminants), and found that metamorphosis effects varied greatly. δ(15)N, widely used to estimate relative trophic position in biomagnification studies, was enriched by ∼ 1‰ during metamorphosis, while δ(13)C used to estimate diet, was similar in larvae and adults. Metals and polycyclic aromatic hydrocarbons (PAHs) were predominantly lost during metamorphosis leading to ∼ 2 to 125-fold higher larval concentrations and higher exposure risks for predators of larvae compared to predators of adults. In contrast, manufactured organic contaminants (such as polychlorinated biphenyls) were retained and concentrated in adults, causing up to ∼ 3-fold higher adult concentrations and higher exposure risks to predators of adult insects. Both food web studies and contaminant management and mitigation strategies need to consider how metamorphosis affects the movement of materials between habitats and ecosystems, with special regard for aquatic-terrestrial linkages.
authors.affiliation: U.S. Geological Survey (USGS) Crustal Geophysics and Geochemistry Science Center, MS Denver Federal Center, Denver, Colorado 80225, United States.
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Kraus
authors.forename: David M
authors.initials: DM
authors.lastname: Walters
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Wesner
authors.forename: Craig A
authors.initials: CA
authors.lastname: Stricker
authors.forename: Travis S
authors.initials: TS
authors.lastname: Schmidt
authors.forename: Robert E
authors.initials: RE
authors.lastname: Zuellig
mesh_terms: D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis / Q000493:pharmacokinetics; D004785:Environmental Pollutants / Q000032:analysis / Q000493:pharmacokinetics*; D020387:Food Chain; D007313:Insecta / Q000737:chemistry* / Q000502:physiology; D007553:Isotope Labeling; D019216:Metals, Heavy / Q000032:analysis / Q000493:pharmacokinetics; D008675:Metamorphosis, Biological / Q000502:physiology*; D009587:Nitrogen Isotopes / Q000032:analysis / Q000493:pharmacokinetics; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000493:pharmacokinetics; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000493:pharmacokinetics; D012044:Regression Analysis
chemical_list: D002247:Carbon Isotopes; D004785:Environmental Pollutants; D019216:Metals, Heavy; D009587:Nitrogen Isotopes; D011084:Polycyclic Aromatic Hydrocarbons; D011078:Polychlorinated Biphenyls