Aquatic organisms play a crucial role in nutrient cycling within ecosystems by participating in the decomposition and transformation of organic matter. Through processes like feeding, excretion, and decomposition, these organisms facilitate the redistribution of nutrients such as nitrogen and phosphorus back into the ecosystem, promoting primary productivity. This cycling is vital for maintaining healthy aquatic systems, supporting food webs, and ensuring the overall resilience of the ecosystem. Their activities help sustain fish populations and contribute to water quality.