Good point on the limited shallow zones with the pond. This pond has <10% of the shoreline with a relatively shallow slope before dropping into deeper water. Most of the limestone quarry ponds in the area lack shoreline vegetation with the exception of those surrounded by a tall water reed type of invasive plant (I don't know the name but I don't want them around my pond and actively work to keep them in check). The floating island concept is a good one to try. Dying the water is not an option for a number of reasons.

Was hoping to find a way to stimulate zooplankton growth with the existing phosphorous concentration. Perhaps aquatic plants harvest P at a lower concentration than zooplankton?