Response strategies of leaf vein traits and stomatal traits of Aegiceras corniculatum to shrimp aquaculture wastewater discharge

Sediments, waters and vegetation work together and cooperate mutually to maintain normal function of mangrove wetland ecosystem. To gained a comprehensive understanding of the response strategies existed by the leaf traits of Aegiceras corniculatum and to identity the key factors that drive leaf traits variation in the response to shrimp aquaculture wastewater, we sampled leaves of A. corniculatum, sediments and interstitial water from non-discharge area (CK), direct discharge area (DDA) and landfill restoration area (LRA) in Qinzhou Bay in southeast coast of China. We established a correlation between leaf vein traits and stomatal traits and abiotic conditions such as pH, nutrient content in sediment. In comparison to CK and LRA, leaf vein traits (primary vein diameter, secondary vein diameter, tertiary vein diameter, enclosed circular area, vein spacing, and tertiary vein density) exhibited a decrease in DDA. This observation suggests that the persistent discharge of shrimp aquaculture wastewater exerts a detrimental impact on the leaves’ mechanical support, nutrient, and water transport capacity. Furthermore, a marked negative correction emerges between stomatal density and length. In contrast, within LRA, an increase in stomatal density and a corresponding reduction in stomatal length indicate a heightened transpiration function of the leaves, thereby enhancing the efficiency of water and inorganic salt transport. Subsequently, the leaf vein traits in LRA are observed to be higher than in CK, suggesting that the leaf traits of A. corniculatum has undergone pre-adaptation to DDA and possesses high phenotypic plasticity. Through the analysis of leaf vein and stomatal traits in diverse shrimp aquaculture wastewater discharge habitats, this study demonstrates that such pre-adaptation and elevated phenotypic plasticity facilitates the adaptation of A. corniculatum to the challenging shrimp aquaculture wastewater environment.