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This BUI will be considered to be ‘not impaired’ when….
Incidence rates of bird and animal reproductive problems in sentinel wildlife species do not exceed background levels at suitable reference sites elsewhere in the Great Lakes basin or suitable inland control populations for a minimum of three years; AND
…when scientifically defensible wildlife bioassays of indicator species confirm that there are no reproductive problem and no significant toxicity from the water column or sediment contaminants or bioaccumulation.
What was done?
- Using wildlife that feed from the aquatic environment, researchers assessed contaminant concentrations and hatching success of Northern leopard frogs (2008 to 2013), Black-crowned night herons (2009 and 2011), Snapping turtles (2014 to 2016), Colonial waterbirds (2015 to 2019) and Tree swallows (2016 to 2019).
- Northern leopard frogs: Hatching success for Northern leopard frog eggs following exposure to water and water and sediment were also high and similar to hatching success of sites outside the AOC.
- Black-crowned night herons & Tree swallows: Tree swallow and Black-crowned night heron hatching success at Detroit River sites were similar to upstream reference sites; with one exception in 2009 when lower hatching success was due to predation.
- Snapping turtles & Colonial waterbirds: High hatching success (HS) that was similar between the Detroit River and reference sites for both Cormorant and Snapping turtle eggs. Also, productivity estimates for Herring gulls at downstream surrogate Detroit River colonies were sufficiently high to maintain a stable population.
- In the majority of egg/tissue samples collected, the concentrations of PCBs and mercury in Northern leopard frogs (whole bodies), Snapping turtles (eggs) and birds (eggs and nestling livers) were below levels associated with adverse effects on reproduction. Three of the egg samples had mercury exceedances, however these were not found to reduce hatching success.
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