What type of growth is commonly observed with periphyton?

Periphyton is a complex community of microorganisms, primarily composed of algae, bacteria, and detritus, that adhere to submerged surfaces in aquatic environments. The correct answer reflects that periphyton typically grows as attached strands or mats that cling to rocks, sediments, and aquatic plants. This growth form is significant because it allows periphyton to efficiently access sunlight for photosynthesis and nutrients from the water, contributing to ecosystem productivity.

The other options describe growth forms that are not characteristic of periphyton. For instance, floating on the surface refers to phytoplankton or macrophytes rather than the benthic nature of periphyton. Piercing through the substrate suggests a penetrating growth that would be more typical of roots from terrestrial or submerged plants, and rapidly moving clusters do not produce the stationary and cohesive community structure associated with periphyton. Therefore, the attachment and formation of strands as described in the correct answer best exemplifies the unique growth style of periphyton in aquatic habitats.