Rock Snot or Didymo algae, about which we previously posted, seems to be becoming more of a problem in our local waters. Roanoke.com's Field reporter Bill Cochran reports that the Tennessee Valley Authority has confirmed its presence in Watauga, South Holston, and Tennessee rivers. (link to article) Rock Snot forms thick brown mats on river beds that can choke out insects and foul fly fishermen's hooks. Here is another link to the TVA's article.
One rather ironic solution for this problem is the New Zealand Mud Snail. Talk about a catch 22.