Submerged aquatic plants affect the priming effect of dissolved organic carbon degradation in shallow lakes

Aquatic plants have been widely used for lake ecological restoration. The effect of aquatic plants on lake biogeochemical cycling has been investigated intensively, however, plants' effect on biodegradation of dissolved organic carbon (DOC) is rarely studied. Here we designed an indoor incubation experiment to explore the priming effect (PE) of aquatic plant leaching solution on DOC in shallow lakes, referring to as the input of active dissolved organic matter (DOM) that would arouse changes in the degradation rate of original refractory DOM. Waters from 20 urban lakes of different tropic states were incubated to study their PE on DOC by adding leaching solutions from two submerged freshwater plants, Hydrilla (H) and Vallisneria (V). The study showed a clear influence of aquatic plants on PE with varying directions and intensities. The H incubation group showed a PE range of -6.19 %-9.79 %, with an average of 2.15 % ± 2.70 %, whereas the V incubation group exhibited a PE range of -10.03 % to 3.60 %, with an average of -0.65 % ± 3.11 %. The positive and negative PEs by the two plant species indicate a key role of plants over trophic states on organic carbon dynamics in freshwater lakes. From the perspective of plant leaching input, our results reveal that planting aquatic plants whose leaching solution can reduce PE like V could be used to enhance carbon storage and constrain carbon emission.