Unhealthy mercury levels found in 25 percent of U.S. streams

“Understanding the source of mercury, and how mercury is transported and transformed within stream ecosystems, can help water resource managers identify which watersheds are most vulnerable to mercury contamination. They can then prioritize monitoring and management actions,” said William Werkheiser, USGS associate director for water.
Some of the highest fish mercury levels were found in southeastern U.S. streams draining forested watersheds containing abundant wetlands.
http://summitcountyvoice.com/2014/10/16/unhealthy-mercury-levels-found-in-25-percent-of-u-s-streams/