Responding to your point below. Im hoping its northern milfoil, I have underwater footage of this lake from 4 years ago at the end of July and it appears there is that same milfoil in the lake but not in a prolific way - just he odd one here and there and some shallower spots with more present. All the weeds present today seem to be the same as were there 4 years ago. Fingers crossed.
The possible Potamogeton Foliosus in my older footage seems to have grown and then by mid summer fallen to the bottom and lose it's color so probably dying. In the footage there is an abundance of plankton of sorts.
Here is the video, the underwater footage starts at about 4:15 mark - before that we are eating hotdogs....as one does.
That is a type of milfoil, possibly Eurasian Water Milfoil. Bad for the pond, it will completely take over and is an extremely invasive species. To kill that plant and not any of the others, a 10 PPB dosage of Fluridone will kill it. It has to stay around 7-10 PPB for close to 30 days for it to be effective, so if you have water flowing through the pond it will be hard to keep that dosage rate. If there is no flow through I really like using Fluridone (Sonar A.S. or it's generic equivalent) as it only affects some invasive species at low dosage rates and does not affect native plants. I don't know of another systemic herbicide that will do that.
