Understanding the Factors Driving Intra-Specific Variations of Contaminants in Urban-Adapted Birds and their Endocrine and Metabolic Impacts

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A growing number of new organic contaminants of potential environmental concern are constantly discharged into terrestrial and aquatic ecosystems in highly urbanized environments, and have the potential to bioaccumulate and be toxic to the most susceptible wildlife species such as birds. This may be the case for the numerous emerging halogenated flame retardants (HFRs) for which no national or international regulations exist despite their massive (and growing) usage worldwide in a wide range of consumer and industrial products to achieve fire safety standards, that is, to slow down the spread of fire. A recent study conducted by my lab reported unexpectedly high concentrations of the HFR class polybrominated diphenyl ethers (PBDEs) as well as several as yet undetected emerging HFRs in tissues of an abundant urban-adapted avian species, the ring-billed gull (Larus delawarensis), breeding in the Montreal area. Evidence from my lab suggests that the endocrine system (e.g., thyroid axis) and certain related endpoints (e.g., energetic metabolism) may be adversely affected in the most HFR-exposed ring-billed gulls. The short-term objectives of the proposed NSERC DG research program will be to investigate: 1) the biological factors governing the bioaccumulation and maternal transfer in ring-billed gulls of novel and emerging HFRs of greatest health concern for wildlife; 2) the in vitro biotransformation capacity in ring-billed gulls towards selected emerging HFRs; and 3) the exposure-related effects and underlying mechanisms of toxicity of selected emerging HFRs on two endocrine axes in ring-billed gulls and chicken via analysis of thyroid hormone and corticosterone levels, mRNA transcription of genes involved in their regulation as well as lipid composition (lipidomics) and field metabolic rate (FMR; measures an animal's total energy expenditure). The novelty and expected significance of the proposed research is that the bioaccumulation, biotransformation, and exposure-related health impacts (e.g., endocrine, metabolic rate, lipid metabolism) on animals exposed to currently used contaminants including HFRs are understudied fields of research. One other significant aspect of this work is the comparative approach, that is, the examination of differences in chemically-induced effects among naturally-exposed bird populations (gull) and an avian model (chicken). This proposed research program will thus provide new knowledge on the dynamics and bioactivity of novel chemical stressors in the Canadian environment. Furthermore, it will represent a unique HQP training opportunity for one Ph.D. and three M.Sc. students as well as five B.Sc. honour students in novel aspects of animal bioenergetics, ecotoxicology, bioenergetics, endocrinology, analytical chemistry, and lipidomics.