What is a frequent growth pattern of filamentous algae?

Filamentous algae are known for their unique growth patterns, and one of the most characteristic features is their ability to form mat-like structures. These mats can create dense, tangled masses of algae that often accumulate at the surface or within the water column. Such growths can significantly affect water quality and aquatic ecosystems by blocking sunlight, disrupting aquatic life, and leading to increased organic matter as they die and decompose.

The option regarding floating on the surface does not accurately represent the typical growth of filamentous algae, as they often anchor themselves to substrates rather than simply float. Penetrating deep into sediments is more characteristic of certain rooted aquatic plants or other types of algae but does not apply to filamentous varieties, which typically thrive in less consolidated substrates. Growing as single cells is also not typical for filamentous algae, as they primarily exist in multi-cellular filamentous forms, further reinforcing that mat-like growth is their dominant pattern.