What is the native small floating plant with overlapping fronds and roots hanging beneath?

The native small floating plant characterized by overlapping fronds and roots hanging beneath is indeed the mosquito fern. This plant, scientifically known as Azolla, is recognized for its distinctive appearance, where the fronds float on water, and the roots extend into the water below. Mosquito fern plays an important role in aquatic ecosystems, providing habitat for various small organisms and contributing to the nutrient cycling in water bodies.

The other options listed do not match the description. Southern (giant) bulrush and slender spikerush are both types of emergent wetland plants, which are rooted in the substrate of water bodies rather than floating. Maidencane is a grass-like plant found in wetland areas but does not exhibit the overlapping fronds or floating characteristics that define mosquito fern. Understanding these characteristics helps in identifying various aquatic plants and recognizing their roles in the ecosystem.