Variation in stable isotope signatures of the submersed macrophyte Vallisneria natans collected from several shallow lakes in China

Abstract

We examined the stable carbon and nitrogen isotope variation in the submersed macrophyte Vallisneria natans in several shallow Chinese lakes relative to physicochemical parameters of the lake water and V. natans tissue. Of the parameters examined, the δ ¹⁵N values of V. natans were correlated only with different inorganic nitrogen concentrations in the water column, suggesting that V. natans could be a sensitive bioindicator for monitoring nitrogen input into lakes. The δ ¹³C of V. natans varied widely and was correlated only with the inorganic carbon concentration of the water, possibly reflecting complex photosynthetic fixation and adaptations of V. natans to utilize inorganic carbon sources of different types.

Keywords:

• stable isotope
• carbon strategy
• submersed macrophyte
• bioindicator
• eutrophic lake

Acknowledgements

We gratefully thank Aiping Wu, Shikai Wu, and Hong Yang of the Donghu Experimental Station of Lake Ecosystems, Chinese Academy of Sciences, for permission to use data on physiologic variables of V. natans and nitrogen, phosphorous, and carbon concentrations in the water of the studied lakes. This research was supported by the National Natural Science Foundation of China (Grant Nos 30870260 and 30870428), the Excellent Youth Foundation of Hubei Scientific Committee (Degradation mechanism and healthy evaluation of Lake Ecosystem), and the K.C. Wong Education Foundation (Hong Kong) and the Knowledge Innovation Program of the Chinese Academy of Sciences.