There is a wide array of wetlands, ranging from larger marshes along the St. Lawrence river, to smaller marshes and bogs along water courses, and large numbers of beaver ponds. The cycles in vegetation in beaver ponds contribute to further wetland diversity; depending upon the amount of beaver activity, there may be open water, marsh, wet meadows or shrub thickets. Some lakes in the area, such as Bob's Lake, also support uncommon species of turtles, such as the map turtles and Blanding's turtles. Where there is marble bedrock, or other sources of calcium, fens may arise. These often have unusual calcium dependent wetland plants.