How do grazer food chains differ from detrital food chains in inland waters?

In inland water ecosystems, energy flows through the trophic levels primarily via two distinct pathways: the grazer food chain and the detrital food chain.1

Grazer Food Chains

The grazer food chain is based on living primary producers, such as algae and macrophytes, which convert solar energy into biochemical energy through photosynthesis. In this pathway, energy is transferred from these living plants to herbivores (primary consumers) and subsequently to higher-level predators.21

Detrital Food Chains

In contrast, the detrital food chain is based on detritus—dead organic matter, including plant parts, animal remains, and waste products. Instead of living plants, this pathway begins with microorganisms (such as bacteria and fungi) that break down the organic debris. This microorganism-rich material is then consumed by invertebrates, which serve as food for vertebrates.31

While many ecosystems rely on both, some inland waters, such as certain freshwater streams, derive their energy base primarily from detritus rather than living plants.3