Abstract:

Stamp sand, a residual byproduct of early 20th-century copper mining in Michigan’s Keweenaw Peninsula, poses an escalating threat to aquatic ecosystems and food security for Indigenous communities. In particular, the continued encroachment of stamp sand into Buffalo Reef - a critical spawning ground for Lake Whitefish - has coincided with a concerning decline in fish reproduction. However, the specific impacts of stamp sand on early developmental stages of aquatic species remain poorly understood. To address this gap, we used zebrafish (Danio rerio) as a model organism to evaluate the developmental toxicity of stamp sand exposure. Zebrafish embryos were exposed to three concentrations of stamp sand (0%, 50%, and 100%) to assess its effects on key survival parameters: cardiac function, and sensory organ development. Preliminary data revealed significant disruption in neuromast development, with a notable reduction in sensory hair cells. Immunofluorescence analysis indicated that prolonged exposure to stamp sand leads to a substantial loss of claudin B-expressing support cells, essential for neuromast regeneration. We hypothesize that this damage results from diminished cellular proliferation and elevated apoptotic activity in neuromast support cells. While cardiovascular function remained largely unaffected, the loss of sensory integrity within the lateral line system, suggests profound alternative consequences. These findings highlight the potential for long-term ecological damage and underscore the urgent need for environmental remediation and policy action.