Abstract Trophic transfer efficiency (TTE) represents the proportion of energy transferred between consecutive trophic levels within a food web. Though it is a fundamental property that shapes energy flow across all ecosystem types, a comprehensive understanding of TTE in freshwater ecosystems is still lacking. This review evaluated common estimation methods, identified key influencing factors, and outlined future research priorities based on a global freshwater TTE dataset. Methods to estimate TTE include production estimates, carbon‐transfer measurements, model‐based approaches, and predator–prey mass‐ratio estimates; mixed‐effects analyses indicate that method choice significantly structures reported TTE, yet each method has limitations in accuracy and consistency. Trophic transfer efficiency also varies across ecosystem types, consistent with systematic differences in the environmental and biological controls on energy transfer among systems. Light, nutrients, and organic matter affect TTE by altering the abundance and composition of primary producers, whereas food quality, temperature, and dissolved oxygen impact TTE by modulating consumer growth and metabolism of individual consumers. At the community and ecosystem levels, predation pressure, competition, species richness, the presence of non‐native species, and cross‐ecosystem interactions shape community structure, thus affecting TTE. Better understanding of TTE in freshwater ecosystems will depend on refined estimation methods and integration of new techniques, such as remote sensing and stable‐isotope labeling, to improve TTE estimates. Research priorities include understanding the synergistic effects of anthropogenic pressures and climate change on TTE, investigating how food quality and individual‐level metabolic processes govern TTE, and examining the influence of cross‐ecosystem energy fluxes on TTE dynamics. It is essential to recognize that TTE varies among trophic levels and cannot be represented by a single value along the entire food chain. Our synthesis reveals that more research is needed in the tropics and the southern hemisphere to expand our understanding of global variability in TTE. This would facilitate greater use of TTE as an indicator of ecological change or the restoration of efficient energy transfer through freshwater food webs.
Song et al. (Sun,) studied this question.