Nitrogen fixation of the seagrass is very meaningful and important in the coastal ecosystem. However, seagrass varies from the spatial and temporal variations in the tropical areas, its  nitrogen fixation in leaf, roots and rhizome could be unclear. Here, we studied that the rates of nitrogen fixation in roots, rhizome and leaves of E. acoroides by principal component analysis, during southwest monsoon (July) and northeast period (October and January), separately. The results indicated that all of nitrogen fixation rates in the three parts of Enhalus acoroides were higher during southwest monsoon period than during northeast.. The rates of nitrogen fixation in leaves of Enhalus acoroides were higher in roots and rhizomes.. The difference of nitrogen fixation among the different parts of E. acoroides was very significant (p<0.01). Principal component analysis showed that temperature had an important influence on nitrogen fixation activity in E. acoroides. The seasonal changes in different parts of E. acoroides were driven by the temperature factor, while the spatial changes in different parts of E. acoroides was also controlled by environmental factors. The results clearly suggest that temperature may be an important cause for nitrogen fixation activity in E. acoroides.
 

Xincun Bay; Seagrass; Nitrogen fixation; Seasonal change; E. acoroides