Metagenomics Reveals Trophic Transfer of Hg in Songbirds in Acadia National Park

Abstract

Mercury is a toxic pollutant which is spread around the earth through both natural and anthropogenic dispersion. Further investigation into the flow of mercury through riparian ecosystems is needed. Studies show that adult breeding songbirds are effective indicators of mercury in terrestrial ecosystems. The objective of this study was to investigate the trophic transfer of mercury through songbird diet analysis using DNA meta-barcoding paired with songbird blood mercury. We collected songbird fecal and blood samples in June and July of 2018 from two sites on Mount Desert Island in Acadia National Park, Maine. At Hunter's Brook (n = 8), Hg concentrations in songbird blood ranged from 149 - 297 ppb wet weight. At Marshall Brook (n = 8), Hg concentrations in songbird blood ranged from 29 - 336 ppb wet weight. Data show a correlation between a diet of insects and songbird blood mercury levels. Next generation sequencing of songbird fecal samples revealed that songbird diets consisted mostly of the order Coleoptera at both Marshall Brook and Hunter's Brook sites.