互花米草入侵对河口盐沼湿地食物网的影响

The impact of invasion of Spartina alterniflora on the food webs of estuarine salt marshes

盐沼湿地因其在河口及沿岸水域生态系统中的重要地位而被普遍关注,近年来互花米草在长江口乃至整个东南沿海地区的入侵及迅速蔓延更是引起了广泛重视。由于对维系本区域湿地生态系统运转的食物网结构的了解仍很有限,从而难以准确评估互花米草入侵后对原有生态系统的影响。本研究通过基于碳、氮稳定同位素测定结果的IsoSource软件估算和聚类分析,对长江口盐沼湿地内不同初级生产者的相对营养贡献大小进行了初步评估。结果显示在该湿地食物网中,底栖微藻和本土陆源C3植物是主要的营养来源。入侵C4植物互花米草的营养贡献不显著,在本次研究中仅有堇拟沼螺这一腹足类消费者在夏季较为确定地表现出对源自互花米草的富δ13C的有机质的摄取。随着互花米草的迅速扩散,其在长江口湿地的有机质产出中所占比例还将不断增加,这将可能从营养基础的层面自下而上对该食物网的结构和功能造成影响。

Salt marsh has now been extensively concerned for its important role in estuarine and coastal ecosystems,and the rapid expanding of invaded Spartina alterniflora is also regarded as a serious problem in the Changjiang Estuary and even all the coastal region of southeast China.However,it is still difficult to evaluate the impact of the invasion of S.alterniflora on the native ecosystem for lacking of knowledge about the food web structures of salt marshes here.The relative trophic contributions of primary producers in the salt marshes of the Changjiang Estuary have been estimated by IsoSource and clustering analysis based on measurement of carbon and nitrogen stable isotopes of the dominate producers and consumers.The results indicate that the food web here is mostly supported by microphytobenthos（MPB） and native terrestrial C3 vascular plants,while the contribution of invaded C4 plants S.alterniflora is minor and its δ^13C enriched production can only be utilized specifically by one gastropod in summer.The proportion of S.alterniflora in the total production of salt marshes in the Changjiang Estuary will increase during its rapid expanding,so that influence the structure and function of food web here ＂bottom-up＂ from the trophic base.