Effect of colonial breeding of Chinese Egret (Egretta eulophotes) on the heavy metal accumulation in heronry soil

We measured the concentrations of heavy metal elements, i.e., V, Cr, Mn, Ni, Cu, Zn, Cd, Se and Pb and the semi-metal element As in feces of Chinese Egret (Egretta eulophotes) on Caiyu Island in Zhangpu County, Fujian Province, China using inductively coupled plasma-mass spectrometry (ICP-MS) and compared the differences between the topsoil of their nesting and non-nesting areas before and after breeding. The results show that no Se and Cd was detected in any of the samples, including feces and soil, while heavy metal concentrations in the non-nesting soil were not significantly different before and after breeding (p > 0.05), but the differences in concentrations of Zn and Pb in the nesting soil were highly significant before and after breeding (p < 0.01). A comparison of the concentrations of the elements in the nesting and non-nesting soils also reveals that before breeding, the concentration of Zn in these two soils were significantly different (p < 0.01). After breeding, concentrations of Cu, Zn, As and Pb in the nesting and nonnesting soil were significantly different (p < 0.01) while V and Ni concentrations showed merely significant differences (p < 0.05). These findings indicate that the colonial breeding activities of E. eulophotes play an important role in the transfer of heavy metals between wetland and island ecosystems and that such activities may, over time, result in heavy metal contamination of the heronry soil on the island.