Answer:
Step-by-step explanation:
C. Decomposing dead matter in bodies of water.
Free-living nematodes are important decomposers in aquatic ecosystems. They play a crucial role in the food web by breaking down dead matter and recycling nutrients. Their feeding activities help to release nutrients into the water that can be taken up by other organisms, such as algae and bacteria. This, in turn, provides a source of energy for higher trophic levels. Additionally, nematodes are also indicators of water quality and can be used as bioindicators of environmental stress. While nematodes may contribute to the cleaning of water in some ways, their primary ecological role is as decomposers.