Which two types of filamentous algae exist in aquatic environments?

The correct choice highlights the two primary forms of filamentous algae found in aquatic environments: attached and planktonic.

Attached filamentous algae, or benthic algae, grow on substrates like rocks, sediments, and plants. They play an essential role in the ecosystem by providing habitat and food for various aquatic organisms. These algae can form mats or filaments that create complex structures within the habitat.

Planktonic filamentous algae, on the other hand, exist suspended in the water column. While they can also form colonies, they are typically not anchored to a substrate and can move with the water currents. This form allows them to capture sunlight and nutrients more effectively from the open water.

Together, these two types represent the versatility of filamentous algae in different aquatic niches and their ability to thrive in a variety of environmental conditions. Understanding these forms is crucial for applying effective management practices in aquatic pest control and promoting healthy ecosystems.

The other options do not accurately describe the recognized classifications of filamentous algae. For example, free-floating algae aren't typically referred to in the context of filamentous types, and rooted and floating algae describe different types of macrophytes rather than filamentous algae.