海洋酸化条件下热带海草泰来藻对氮的利用机制研究

The efficient use of nitrogen (N) by the seagrass is critical in maintaining its high productivity. Moreover, N uptake by the seagrass is a key link in the material cycle of the seagrass ecosystem. Thus, it is of great scientific significance to study the N uptake of seagrass. The main mechanism of the N uptake in seagrass is the simultaneously sequestration of the various forms of dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON) via leaf and root. To our knowledge, no effort has been made so far to quantify the N uptake in seagrass under elevated carbon dioxide concentration. Under ocean acidification, this complicated process can be impacted by the changes of carbonate equilibrium in the sea water and the seagrass physiological status itself. In this proposal, uptake kinetics of DIN and DON by the tropic seagrass Thalassia hemprichii will be studied through laboratory incubation, using 15N as tracers under different carbon dioxide concentrations regimes. Relative enzymatic activities and root activity will be also measured. Furthermore, the N sources of the T. hemprichii in the typical tropical seagrass beds will be clarified. This study is expected to reveal the seagrass N uptake mechanism under the condition of future seawater carbon dioxide concentration. It will provide a scientific basis for forecasting the variation trend of N cycle in seagrass ecosystem and the role of the seagrass community in it under global change in the future.

海草对氮的高效利用是其维持高生产力的重要原因；从生态系统角度看，海草对氮的吸收是海草床中物质循环的关键过程。因此，研究海草对氮的利用机制有重要科学意义。海草对氮的吸收机制主要包括其叶片和根部两部分同时摄取不同溶解态的无机氮和有机氮。目前，尚未有研究报道海洋酸化如何影响海草对氮的吸收。海洋酸化的条件下，海水碳酸盐体系的变化以及海草生理状态的改变可能影响海草根、叶对不同形态氮的吸收特性及其比例，从而使海草的氮来源机制发生变化。本项目拟通过室内模拟实验，利用稳定同位素15N示踪技术，在不同的二氧化碳浓度条件下，研究我国典型热带海草泰来藻对不同形态氮的吸收动力学过程及相关酶活特性，探讨典型海草床中泰来藻氮的来源变化规律，以期揭示海洋酸化条件下海草对氮的利用机制。完成该研究，可为预测在全球变化的影响下，海草床生态系统的氮流动过程变化提供依据。

海草对氮的高效利用是其维持高生产力的重要原因；从生态系统角度看，海草对氮的吸收是海草床中物质循环的关键过程。因此，研究海草对氮的利用机制有重要科学意义。海草对氮的吸收机制主要包括其叶片和根部两部分同时摄取不同溶解态的无机氮和有机氮。目前，尚未有研究报道海洋酸化如何影响海草对氮的吸收。海洋酸化的条件下，海水碳酸盐体系的变化以及海草生理状态的改变可能影响海草根、叶对不同形态氮的吸收特性及其比例，从而使海草的氮来源机制发生变化。本项目拟通过室内模拟实验，利用稳定同位素15N示踪技术，在不同的二氧化碳浓度条件下，研究我国典型热带海草泰来藻对不同形态氮的吸收动力学过程及相关酶活特性，探讨典型海草床中泰来藻氮的来源变化规律，以期揭示海洋酸化条件下海草对氮的利用机制。完成该研究，可为预测在全球变化的影响下，海草床生态系统的氮流动过程变化提供依据。