亚热带河口陆基养虾塘水体溶解性碳浓度及沉积物-水界面碳通量时空动态特征

以福建闽江和九龙江河口陆基养虾塘为研究对象,通过野外原位观测和室内模拟培养实验,开展了河口陆基养虾塘养殖期间水体溶解性有机碳(DOC)和溶解性无机碳(DIC)及养虾塘沉积物-水界面碳交换通量变化特征的研究。结果表明:时间变化上,养虾塘水体溶解性碳浓度及沉积物-水界面碳通量在闽江河口呈现8月中旬10月中旬6月中旬的特征,在九龙江河口表现为随养殖阶段推移而增加的趋势;空间变化上,闽江河口养虾塘水体溶解性碳浓度及沉积物-水界面碳通量显著高于九龙江河口;沉积物释放溶解性碳速率与水体溶解性碳浓度呈现显著正相关关系,沉积物碳释放过程是引起养虾塘水体溶解性碳浓度时空变化的重要因素。表明河口区水产养虾塘碳循环研究时需考虑不同形态碳生物地球化学循环的时空差异性。

Spatial-temporal variations of water column dissolved carbon concentrations and dissolved carbon flux at the sediment-water interface in the shrimp ponds from two subtropical estuaries

Aquaculture ponds play an important role in the global carbon cycle. In order to understand the dynamics of carbon in the shrimp ponds, dissolved carbon (dissolved organic carbonDOC] and dissolved inorganic carbonDIC]) concentrations in the pond water column, and the exchange fluxes of dissolved carbon across the sediment-water interface, were investigated in the Min River estuary (MRE) and Jiulong River estuary (JRE) on the southeast coast of China. Water and sediment samples were collected using a hydrophore and sediment sampler from three shrimp ponds in June, August, and October 2015, respectively. Meanwhile, water-quality indicators (water temperature, pH, dissolved oxygen, and salinity) were measured in situ using a portable instrument. The dissolved carbon concentration in water was analyzed using a SHIMADZU TOC-V_CPH/CPN analyzer. Sediment oxygen and nutrient exchange (SONE) incubation techniques were used to measure the rates of dissolved carbon fluxes. The results showed that dissolved carbon concentrations in the pond water, and fluxes across the sediment-water interface from the estuaries of shrimp ponds greatly varied in spatial and seasonal dynamics. Mean dissolved carbon concentrations and fluxes were significantly higher from the shrimp ponds in the Min River estuary than in the Jiulong River estuary (P < 0.05). Average seasonal dissolved carbon concentrations (or fluxes) in the Min River estuary and Jiulong River estuary followed the order:August > October > June and October > August > June, respectively. The variations in dissolved carbon concentrations in the water were significantly positively correlated with the dissolved carbon fluxes across the sediment-water interface, indicating that the process of dissolved carbon release in the sediment affects the dynamic variation of dissolved carbon concentrations in the water column. Overall, the dynamic variation of dissolved carbon concentrations and fluxes in the shrimp ponds could be due to the synthetic action of abiotic factors (e.g., temperature and salinity), the foraging and metabolic activity of shrimp, and feed supply. Our study highlights the need to consider the spatio-temporal difference of carbonic biogeochemical cycles to better understand the dynamic of carbon cycling from the aquaculture ecosystems in the estuaries.