Which of the following organisms play a crucial role as primary producers in freshwater systems?

Diatoms are a type of algae that are vital to freshwater ecosystems as primary producers. They photosynthesize, converting sunlight into energy and producing organic matter that serves as the foundation of the food web. This process not only provides energy for themselves but also for a variety of organisms that rely on them for sustenance, such as zooplankton and various fish species. Diatoms are particularly effective at thriving in a range of aquatic environments and contribute significantly to the overall productivity of freshwater systems.

In contrast, frogs and dragonflies serve as consumers in the food web, playing roles higher up by feeding on various organisms but not producing their own energy. Detritivores, while important for recycling nutrients by decomposing organic matter, do not perform photosynthesis and therefore are not considered primary producers. Thus, diatoms stand out as essential contributors to the energy base in freshwater ecosystems.