Redfield revisited: Insights into freshwater seston carbon : nitrogen : phosphorus stoichiometry

Abstract Seston carbon (C), nitrogen (N), and phosphorus (P) stoichiometry plays a fundamental role in aquatic ecosystems, influencing nutrient cycling, primary and secondary production, and trophic interactions. In freshwater systems such as lakes, P limitation is more common, whereas in marine environments, N more frequently limits primary production, reflecting different nutrient limitation patterns across aquatic ecosystems. The Redfield ratio (C 106 : N 16 : P 1 molar), developed from marine seston, has long been considered a benchmark for nutrient composition and a predictor of nutrient limitation across aquatic ecosystems. A later global freshwater and marine seston survey proposed the Sterner ratio (C 166 : N 20 : P 1 molar) as a broader global seston average. We present the results of a fully replicated, multi‐annual freshwater mesocosm experiment testing the effect of variable resource N : P stoichiometry on seston stoichiometry. We found that the seston C : N : P ratio aligned with the Redfield ratio under N‐limited conditions, while P‐limited conditions aligned with the Sterner global survey of freshwater ecosystems. Ternary plots offered visual insight into stoichiometric shifts, showing a trend toward P depletion relative to C and N as N : P supply increases. The average seston C : N : P ratio observed from our experimental data was C 141 : N 22 : P 1 (molar) and variation in seston C : N : P was small compared to the resource ratio gradient. Our mesocosm experiment showed that the Redfield ratio provides a useful description of seston stoichiometry in N‐limited freshwater ecosystems. These findings advance the understanding of bottom‐up controls on seston C : N : P stoichiometry and highlight the need to refine ecological theories regarding the application of the Redfield ratio in freshwater ecosystems.