Abstract: 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 differences in the contents of carbon and nitrogen in both sediment and plant root from the two sampling 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 δ¹³C 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 δ¹⁵N 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 δ¹⁵N 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, stem and leaf. Overall, there was no significant correlation between the δ¹³C, and δ¹⁵N values in plant and those in sediment.

Key words: multi-scale effects, pollinators diversity, landscape heterogeneity, pan traps, the lower reaches of the Yellow River.