Old BOW, deep in eutrophication process, lots of excess nutrients in water. This looks like a great candidate for the trash pump FA removal tool someone posted from youtube a while back. If you chemically treat it will die and decompose and only add more nutrients. Harvesting FA through a trash pump would be the way I'd attack this on such a large scale with a pontoon boat and barge. FA makes great fertilizer and soil amendment - you may even be able to sell it if you employ a little marketing ingenuity. 100% organic garden kelp!