长江口潮滩生态系统氮微循环过程中大型底栖动物效应实验模拟

依据长江口滨岸潮滩大型底栖动物的自然分布特征,选取了两段典型的研究区域——崇明东部潮滩和浒浦岸段边滩,运用实验模拟和对比分析方法,定量地研究了大型底栖动物谭氏泥蟹和河蚬对潮滩生态系统中氮营养盐的界面扩散及其早期成岩变化的影响。研究表明,谭氏泥蟹主要通过掘穴活动增加沉积物-水-气三相接触界面,促进沉积物中的无机氮(NH 4- N、NO- 2 -N和NO- 3- N)向上覆水体中扩散,并且也加快了沉积物中氮的氨化作用和硝化作用速率,而河蚬则主要通过生理活动机制影响潮滩生态系统内氮素的迁移转化过程。研究结果深刻揭示了大型底栖动物通过生物扰动和生理活动作用机制,促进了长江口潮滩生态系统内氮素的生物地球化学循环过程速率。

Experimental simulation of the effects of macrobenthos on the microcycling of nitrogen in the Yangtze estuarine and tidal flat ecosystem

Based on the natural distribution of macrobenthos, two sections typical of the eastern tidal flat of Chongming Island and Xupu tidal flats were chosen as the study area in the Yangtze estuarine and coastal zone. Using a comparative and simulative approach, this study quantitatively explored the effects of macrobenthos (Ilyoplax deschampsin and Corbicula fluminea) on the exchange of nitrogen across the sediment-water interface and the early diagenesis of nitrogen in tidal sediments from the Yangtze Estuary. It was found that Ilyoplax deschampsin and Corbicula fluminea affected the exchange of nitrogen across the sediment-water interface by different biological mechanisms. Ilyoplax deschampsin enhanced the exposed area of sediment to water and air by its bioturbation. It therefore accelerated the exchange of nitrogen at the sediment-water interface. Compared with Ilyoplax deschampsin, Corbicula fluminea, however, influenced the exchange of nitrogen across the sediment-water interface mainly by the physiological mechanisms such as excretion. Crabs such as Ilyoplax deschampsin changed the physical structure of the tidal sediments through intense bioturbation, and increased the content of dissolved oxygen in the sediments by increasing the exposure of these sediments to air. As a consequence, the processes of biogeochemical cycling of nitrogen (e.g. ammonification and nitrification) were markedly accelerated in the estuarine and tidal sediments. Corbicula fluminea is mainly round in tidal surface sediment. It affected nitrogen cycling in the surface sediments mainly by physiological activities such as the excretion. In addition, it was also found that the burrowing of Corbicula fluminea, to some extent, had a potential influence on the nitrogen cycling.