Mesozooplankton conduct the energy and material fluxes from unicellular primary producers to higher trophic levels. The community structure of mesozooplankton mediates secondary production, trophic transfer, and dynamics of marine food webs. Water-mass interactions and environmental variation are considered the major drivers of marine mesozooplankton community composition. Beyond these abiotic conditions, the mismatch between the elemental requirement of zooplankton and the elemental composition of their phytoplankton prey, which is known as stoichiometric imbalance, can critically influence competition among zooplankton taxa and consequently community structure. This mechanism has been observed in freshwater systems, but how stoichiometric imbalance regulates marine zooplankton communities remains elusive. The stoichiometric knife-edge framework predicts that the mismatch between prey stoichiometry and consumer requirements reduce consumer growth. Accordingly, strong stoichiometric imbalances, resulting from either deficiencies or excesses of nitrogen (N) or phosphorus (P) in prey relative to consumer requirements, may reduce the relative abundance of zooplankton families (Figure A).
To investigate how stoichiometric imbalance influences zooplankton competition and mesozooplankton community structure, Ph.D. student Wei Chen collaborated with the team of Assistant Professor Pei-Chi Ho and Distinguished Professor Chih-hao Hsieh at the Institute of Oceanography. They analyzed stoichiometric imbalances (N:PImbalance, C:PImbalance, C:NImbalance) between herbivorous mesozooplankton families and their picoplankton prey, together with the relative abundance of mesozooplankton families in the southern East China Sea. The results revealed significant differences in C:N:P ratios among herbivorous mesozooplankton families, indicating that different zooplankton families experience different degrees of stoichiometric imbalance when feeding on common picoplankton prey (Figure B). Most importantly, phosphorus deficiency relative to nitrogen in prey (when N:PImbalance is positive) is associated with lower relative abundance of the corresponding zooplankton family, whereas phosphorus in excess of zooplankton requirements was associated with higher relative abundance (when N:PImbalance is negative) (Figure C). These patterns were consistent across seasons, despite pronounced seasonal variation in water-mass interactions in the southern East China Sea (Figure D).
These findings highlight the role of stoichiometric imbalance in shaping mesozooplankton community structure, particularly the effects of phosphorus imbalance relative to consumer requirements. This study provides new insights into the ecological processes regulating zooplankton taxonomic composition and diversity in subtropical marine systems.
(Figure A) Schematics illustrating the relationship between relative abundance of zooplankton consumers (families A and B) and their stoichiometric imbalance with prey (P). Zooplankton family B experiences higher stoichiometric imbalance than family A, and thus its relative abundance is lower.
(Figure B) Molar N:P ratios of herbivorous mesozooplankton families.
(Figure C) Generalized linear model (GLM) regression of mesozooplankton relative abundance and consumer-prey N:P imbalance. Colors represent different stations and dot shapes represent the seasons.
(Figure D) GLM regressions of mesozooplankton relative abundance and consumer-prey N:P imbalance in three sampling seasons. Dot shapes represent the zooplankton families.
Source: Wei Chen, Chih-hao Hsieh, Chia-Ting Chen, Pei-Ling Wang, Pei-Chi Ho (2026) Stoichiometric imbalance affects competitive superiority in marine herbivorous zooplankton communities. Limnology and Oceanography, Volume 71, Issue 11, e70538.
