Which term refers to dead or decaying organic matter?

The term that refers to dead or decaying organic matter is detritus. In aquatic ecosystems, detritus consists of decomposing plant and animal material that plays a crucial role in nutrient cycling. It serves as an important food source for various organisms, including bacteria and detritivores, which break down this organic matter and recycle nutrients back into the ecosystem.

Understanding detritus is key in water quality studies as it can significantly influence the health of aquatic environments. When organic matter decomposes, it can impact oxygen levels and nutrient concentrations in the water, affecting the overall ecology of the habitat. In contrast, the other terms listed refer to different concepts: plankton includes small organisms drifting in water, biomass refers to the total mass of living matter in an area, and fossils are preserved remains of ancient organisms. Each of these plays a distinct role in ecology and science, but they do not specifically denote decaying organic matter like detritus does.