What is the main activity of grazers in aquatic systems?

Grazers in aquatic systems primarily consume algae and biofilms that grow on surfaces such as rocks, plants, and other substrates. This feeding activity plays a crucial role in nutrient cycling within the ecosystem. By grazing on these organisms, they help regulate algal populations, which can otherwise lead to water quality issues if left unchecked. Additionally, the removal of biofilms and algae promotes the growth of new phytoplankton and can influence the overall primary production in the water body.

The other activities mentioned, such as feeding on sediment or gathering nutrients from the water column, are more characteristic of different functional groups within the aquatic food web. Fragmenting organic matter is typically associated with detritivores or decomposers, which break down dead organic material rather than actively grazing on living algae and biofilms. This distinction is vital to understanding the roles different organisms play in nutrient cycling and aquatic ecosystem health.