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E-M:/ personal water craft & sediment disturbance

Enviro-Mich message from John Rebers <jrebers@nmu.edu>

I am on the Citizens Advisory Committee for the Deer Lake Area of Concern
(AOC) near Ishpeming, which was listed as an AOC because of mercury in the
sediments which has resulted in mercury levels in the fish above
consumption advisory levels. Because of the extent of contamination,
dredging out all of the lake basin to eliminate the mercury is not a likely
option. However, mercury levels in the fish are dropping steadily over the
last 10 years - the most likely explanation is that fresh sediment is
covering up the mercury-contaminated sediments so it is no longer available
biologically. The lake is designated as catch and release only by the DNR,
and the local sports fishing community generally supports keeping that
designation even if mercury levels drop to the point below the consumption
advisory level.

Although this is not an ideal solution, it does seem to take care of one of
the main concerns, which is the level of mercury in fish and other
organisms. One possible concern is future activities that could disturb the
sediment, and one person I spoke to suggested that personal water craft
(aka jet skis) and water skiing could disturb the sediment and bring
mercury back to a zone where it is biologically available. However, the
chair of the AOC Advisory Committee expressed skepticism about this and is
opposed to restrictions on these activities. Does anyone know if there have
been published studies testing the idea that personal water craft, water
skiing, or similar activities disturb sediments in lakes? It would be
particularly useful if these studies addressed heavy metals, but any study
would be useful. What I really need to make an argument here are documented
studies, rather than anecdotal evidence.


John Rebers
Central Upper Peninsula Group, Sierra Club
338 West Crescent Street
Marquette, MI  49855
906-227-1585 (office)
906-228-3617 (home)
e-mail address: jrebers@nmu.edu

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