INVESTIGATING THE STOICHIOMETRIC COUPLING BETWEEN MESOZOOPLANKTON ASSEMBLAGE AND SESTON IN FRESHWATERS

Food quality can significantly affect the phosphorus content, growth, reproduction, as well as physiological behavior of zooplankton, leading to regulate the energy transfer efficiency at the primary producer-consumer interface. However, the elemental coupling between zooplankton and food is scarcely observed at the community level. In this study, the elemental coupling and the elemental imbalances between seston and mesozooplankton assemblage in addition to the ecological impacts of such imbalances on zooplankton-phytoplankton interaction were detailed by analyzing the compositions of carbon, nitrogen, and phosphorus in seston and mesozooplankton assemblage derived from 13 samples containing water bodies in the Hubei province, China. The achieved results showed that both C﹕N and C﹕P ratios in mesozooplankton were positively correlated with the corresponding ratios in seston. Besides, the elemental imbalances between seston and mesozooplankton were positively correlated with the corresponding seston ratio (C﹕N,r=0.97, P<0.001; C﹕P,r=0.81, P=0.001). Further analysis also revealed that the energy transfer efficiency between zooplankton and phytoplankton declined with the increase of elemental imbalance in C﹕P ratio (r= –0.58, P=0.037). Moreover, a similar decline in zooplankton biomass was found as well as increase of imbalance in C﹕P ratio (r= –0.59, P=0.033). These results indicated that seston stoichiometry could remarkably impact the elemental stoichiometry of mesozooplankton assemblage, and the elemental imbalances tended to be greater with the increase of seston stoichiometry; consequently, the energy transferred to mesozooplankton was decreased as well.