珠江口老鼠簕稳定性碳氮同位素组成分析

Analysis of stable carbon and nitrogen isotope compositions of Acanthus ilicifolius in the Pearl River estuary

植物体内稳定性碳氮同位素组成能在一定程度上反映环境因子的变化。本研究对自然分布于珠江口(珠海淇澳和广州南沙)的红树植物老鼠簕(Acanthus ilicifolius)及其底泥的碳氮含量、稳定同位素δ^(13)C、δ^(15)N进行分析。结果表明:两地底泥和老鼠簕根的C、N含量差异不显著,但茎(P<0.05)、叶(P<005)中的N含量及C/N(P<0.01)有显著差异;老鼠簕为C3植物,两地老鼠簕植物根茎叶δ^(13)C值有逐渐下降趋势,且淇澳的δ^(13)C值均高于南沙的相应值,这可能与底泥盐度有关;两地老鼠簕根茎叶δ^(15)N值则有逐渐上升趋势,且淇澳的δ^(15)N值均高于南沙的相应值;两地的底泥、老鼠簕茎叶的δ^(15)N值差异明显,但根中的差异不显著,这与根茎叶中N含量的变化规律较一致;整体上,植物体中δ^(13)C、δ^(15)N值与底泥中的值无明显相关性。

Compositions of stable carbon and nitrogen in plants to some degree can reflect habitat changes. Stable carbon and nitrogen isotope ratios and carbon and nitrogen contents in mangrove plant Acanthus ilicifolius and in sediment from the Pearl River estuary （ Qi＇ ao of Zhuhai, and Nansha of Guangzhou） were measured. The results showed that there were no significant differ- ences in the contents of carbon and nitrogen in both sediment and plant root from the two sam- piing sites; however, there were significant differences in nitrogen content and carbon to nitrogen ratio （P〈0.01） in stem （P〈0.05） and leaf （P〈0.05）. The δ13C values detected in root, stem and leaf of A. ilicifolius, a C3 plant, from both sampling sites showed a decrease, and the δ13C values of samples from Qi＇ ao were significantly higher than that of Nansha, which may be due to the higher salinity of the sediment at Qi＇ ao. The δ15N values of root, stem and leaf from both sites showed some increase, with the δ15N values of all samples from Qi＇ ao being higher than that of Nansha. There were significant differences in δ15N values of sediment, stem, and leaf between the two sampling sites, but no significant difference in δ15N values of root from the two sampling sites, which was in accordance to the variations of nitrogen content in root, stern and leaf. Overall, there was no significant correlation between the δ3C, and δ15N values in plant and those in sediment.