There is more than one reason.
(1) The flood of 2008 washed into our waterway vegetation, which though native to North America, did not exist previously in our waterway: Elodea Canadensis is an example.
(2) The invasive filter-feeding zebra mussels, cleared the water at about the same time. At least in the Island View Bay region, zebra mussels reached a population peak in 2009; in 2010, after having cleared the water (thus diminishing their food supply), fewer remained. Clear water over a nutrient-rich muck bottom offer ideal conditions for aquatic plant growth. In some areas around our shoreline, the muck does not begin at the shore, but starts further out. Aquatic vegetation was observed to be more prolific on the muck, than on the sand and gravel bottom without the muck.