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Abstract: Coastal wetlands play critical roles in maintaining water quality; however, the impacts of predicted sea level rise on coastal wetlands is not well understood at this time. In this study, the relationship between soil properties and seed-spore bank was analyzed by CCA, which indicated that most cryptogam seeds (i.e. Xd1, Xd2, Xs1 and Xs2) were found far away from heavy metals zones. Emergence of environmentally sensitive cryptogam seeds were inhibited in soils with high levels of heavy metals in the Pearl River Estuary. Another significant result detected in CCA analysis is that salinity and heavy metal-Cd were the main influence factors to the seed-spore bank of the estuary wetland ecosystem. Two groups of detailed experiments with three replicates (untreated group and treated group) were conducted to further delve into the influence of salinity and heavy metal-Cd on seedling emergence. The treated group was incubated with three salinity gradients of 2000, 4000, 8000 mg/kg, and three Cd concentration levels of 3.5, 4.0, 4.5 mg/kg.. The results shows that higher salinity and Cd levels inhibit seed germination, but their suitable level ranges (i.e., [0, 200 0mg/kg] for salinity and [0, 4.0mg/kg] for Cd) can activate seedling emergence, such that more seedlings germinated under the intersectional levels at 2.1mg/kg Cd and 1200mg/kg salinity. If sea level rises quickly and permanently, salinity will act as the most important stressor of vegetation rehabilitation, and possibly result in salt-tolerant communities dominated in this area. This study has clear implications for the construction and function of treatment wetlands with predicted rises in sea level. |