Changes in functional traits and stoichiometry of Aegiceras corniculatum propagule in three shrimp aquaculture effluent regions

Shrimp aquaculture has caused broadscale shifts in mangrove ecosystems worldwide, including changes in habitats and functional traits of mangroves, to the point of widespread destruction in some countries. The propagule is an important stage in mangrove life history, reflecting the resource investment of parents and the ability of offspring to build a population. However, the impacts of shrimp aquaculture effluent on propagule functional traits and stoichiometry are poorly understood. Here, we comparatively investigated the functional traits and stoichiometry of Aegiceras corniculatum propagules in different shrimp aquaculture effluent-affected habitats on the coast of the South China Sea, including a control plot with no effluent discharge, a direct discharge area, and a landfill restoration area. We found that shrimp aquaculture effluent was associated with substantial impacts on the functional traits and stoichiometry of A. corniculatum propagules. In functional traits, both propagule morphology and biomass traits decreased in habitats affected by shrimp aquaculture effluent; in stoichiometry, the discharge of shrimp aquaculture effluent increased N and P contents, and after stopping the discharge, N and P in propagules remained at high concentration; propagule C/N and C/P ratios in all habitats were consistent with those of soils in that both were reduced and exhibited consistent N limits. Our findings highlight the effects of shrimp aquaculture effluent on functional traits and stoichiometric characteristics of A. corniculatum propagules, which may help improve our understanding of the underlying mechanisms of mangrove propagule adaptability. It also provides a scientific basis for assessing its impact on mangrove reproduction potential and population renewal and applies to mangrove management and restoration.