Program

The production, transport and export of organic matter in mangrove wetland ecosystem play a significant role on the coastal carbon cycle. In recent years, strong anthropogenic perturbation (e.g. aquaculture, sewage discharge) occurred in many Chinese mangrove ecosystems. However, little is known about the influence of such perturbation on the dynamics of dissolved organic matter (DOM) in these wetland systems.

Many tidal mangrove creeks along the Zhangjiang Estuary, southeast China were influenced by frequent discharge of aquaculture wastewater and pulse input of upstream polluted rivers, providing an ideal place to study such scientific issues. A 48h (including four tidal cycles) hourly time-series observation was taken in two fix station of a creek in this area in July 18-20, 2016. Two field investigations were also taken along the whole creek and the adjacent Zhangjiang Estuary in June 19 and July 19, 2016. The quality and quantity of DOM was characterized using absorption spectroscopy, fluorescence excitation-emission matrices-parallel factor analysis (EEM-PARAFAC) and dissolved organic carbon analysis.Laboratory incubations were performed to evaluate the contribution of DOM to the creek DOM pool from the leaching process of mangrove leaf litter.

The DOM abundances of the freshwater end member from the tidal creeks were higher than those from the Zhangjiang Estuary, indicating much stronger DOM sources for the tidal creeks. The DOM concentration and composition showed great variation during and between the tidal cycles. Generally, the abundance of colored DOM (CDOM) and fluorescent DOM (FDOM) showed decrease during the flood period while increase during the ebb period for the mixing process. However, the DOM abundances and composition of the freshwater end member changed greatly due to the discharge of aquaculture wastewater and upstream polluted rivers during the low tide period. Mangrove input may be another source of DOM as significant DOM release was observed in the leaching experiment of the leaf litter. This study reveals the necessity of anthropogenic influence in the DOM dynamics analysis of the tidal mangrove creek.