PARENT SESSION
Organized Oral Session 5: Mercury cycles: Sources, mass balances, bioaccumulation, and options to manage affected systems
Organizer(s): EPH Best, JG Wiener, and D Planas
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal
Food chain transfer and toxicity of methylmercury in piscivorous avian wildlife.
Scheuhammer, Tony*,1, Burgess, Neil2, Evers, Dave3, Weech, Shari4, Elliott, John5, 1 Environment Canada, Ottawa, ON, Canada2 Environment Canada, Mount Pearl, NL, Canada3 BioDiversity Research Institute, Gorham, ME, USA4 UMA Group, Victoria, BC, Canada5 Environment Canada, Delta, BC, Canada
ABSTRACT- Mobilization of Hg through human industrial activities has resulted in environmental Hg concentrations that are several-fold higher than pre-industrial levels. Some proportion of Hg originating from both natural and anthropogenic sources is subsequently methylated and accumulates in aquatic invertebrates, fish, and ultimately in piscivorous wild birds and mammals. The sources of mercury that caused past instances of Hg poisoning of wildlife (e.g., decreased reproductive success of common loons breeding near a chloralkali plant) have largely been discontinued or greatly reduced. However, other regionally and globally significant sources of anthropogenic Hg remain; methylation of Hg and biomagnification of methylHg through food webs continues. Consequently, piscivorous wildlife continue to experience elevated methylHg exposure in at risk aquatic and wetland environments. Hg exposure in North American wildlife generally follows patterns of atmospheric deposition. For example, there is a clear west-to-east trend in Hg concentrations in blood, eggs, and feathers of common loons. Adult loons breeding in Kejimkujik National Park, Nova Scotia, have among the highest blood-Hg concentrations in North America (mean = 5.5 ug/g ww), experience low productivity, and their chicks exhibit altered behaviour. Low pH-low alkalinity-high DOC waters often contain fish with elevated Hg concentrations sufficiently high to be toxic to consumers; these environments are thus exceedingly sensitive to even small increases in Hg input. Also, fish-eating wildlife associated with ecosystems contaminated with Hg may experience elevated exposure to methyHg long after inputs of Hg have ceased. For example, Hg in organisms at various trophic levels from Hg-contaminated Pinchi Lake, BC, averaged about twice those of the same species from nearby reference lakes, even in the absence of substantial new inputs of Hg to Pinchi Lake over the past 60 years.
Key words: mercury, wildlife