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John McCall 
MS Student
Biological Sciences
Michigan Technological University 

Epi- and population genomic assessments of stamp sand toxicity to salmonids and consequences for Lake Superior fisheries

Abstract: The Keweenaw Peninsula in Michigan historically had significant native copper deposits which made the region the second largest global producer of copper between 1850 and 1930 (Murdoch 1943).  Two mines deposited over 22 million metrics tonnes/50 billion lbs of mine tailing wastes (“stamp sands”) along the shore of Lake Superior’s Big Traverse Bay (Pepin 2017).  Erosion of this pile has resulted in stamp sands being distributed over 35% of Buffalo Reef, a natural spawning reef for lake trout (Salvelinus namaycush) and whitefish (Coregonus clupeaformis) that is estimated to produce almost 1/3 of the regional catch of these species in Lake Superior.  We used reduced representation bisulfite sequencing and genotyped fish from Buffalo Reef and Lake Superior to quantify adverse developmental or toxic effects associated with stamp sand dispersal onto spawning habitat and potential consequences for the fishery.  Bisulfite sequencing identified over 22k loci in lake trout that were screened for unusual DNA methylation at cytosine and guanine dinucleotides, which is a conserved epigenetic marker in vertebrates shown to modulate gene expression due to environmental stress.  Buffalo Reef lake trout were hypomethylated and had an aberrant methylation pattern compared to a Lake Huron outgroup, suggesting acute or chronic toxicity from legacy stamp sand exposure.  Genotype data showed Buffalo Reef lake trout had more heterozygosity than allopatric fish in Lake Superior and a gradient of genetic differentiation across a large spatial scale. Individual fish were also genetically admixed across sites suggesting high gene flow between populations and potential loss of genetic diversity or demographic consequences for fishes due to continuing stamp sand inundation at Buffalo Reef.