After a few more hours research my best guess is that they are Gloeotrichia, a form of blue-green algae which may or may not produce toxic compounds. Either way they are found throughout Lakeland PP and PRA, where backcountry travel (portage routes) necessitates drinking the water. Yikes. I wish I had a sample, might go get one, but it looks a heck of a lot like this:
https://www.google.com/search?q=Gloe...iouZGanJZ4Lc2M