The important role of Turbidity Maximum Zone in sedimentary dynamic of estuarine mangrove swamp

Abstract

Sedimentation is a key process affecting wetland sustainability and carbon burial flux. In context of sea level rise, climate change and human activities, further understanding about the sedimentary dynamic in wetland is critical in predicting the landscape evolution or the change in carbon burial flux. In this study, based on the field hydrological observation in a mangrove system in the Nanliu River estuary, we found the net flux of suspended sediment to mangrove is 39–72 kg/m in tidal cycles with Turbidity Maximum Zone (TMZ) forming in surface layer and only is 9–18 kg/m in tidal cycles without TMZ. The higher net flux of suspended sediment to mangrove in tidal cycles with TMZ forming in surface layer is attributed to high SSC in rising tide and intense flocculation in mangrove. The significant discrepancy in sedimentation rate in the mangrove patches also can be explained by the probability of TMZ forming in the surface layer of estuary. In future, rapid sea level rising may lead to the change of TMZ pattern in estuary, which will result in non-negligible variation in sedimentation rate in wetlands. According to the present data of sedimentation rate in wetlands, the fragility of wetlands in river estuary may be miscalculated.