Which organism type is primarily responsible for decomposition in aquatic ecosystems?

In aquatic ecosystems, bacteria play a crucial role in the decomposition process. They break down organic matter, such as dead plants and animals, as well as waste materials, converting them into simpler compounds. This microbial digestion is essential for nutrient cycling, as it helps release nutrients back into the water, making them available for primary producers like phytoplankton. Bacteria are incredibly efficient decomposers, able to thrive in various environmental conditions and rapidly reproduce, enabling them to effectively manage organic waste.

The other organisms listed, while they have important roles, do not primarily focus on decomposition. Fish are generally considered consumers and can influence the food web dynamics, but they do not decompose organic matter at the same level. Zooplankton feed on microorganisms and organic particles but are not the main agents of decomposition. Phytoflagellates, primarily photosynthetic, contribute to primary production rather than decomposition, making them important for energy input into the ecosystem but not for breaking down organic materials.