Leaf Nutrient Resorption of Seagrass Zostera Japonica Aschers, Et Graebn, in Beihai, Guangxi, China

摘要

Resorption of nutrients (C, N, P, Ca, Mg, Fe and Mn) from senescent leaves of Zostera japonica and the concentration of nutrients (C, N, P, Ca, Mg, Fe and Mn) in the sediment from three subtropical seagrass meadows (Guchenling, Zhulin and Ronggenshan) in Beihai, Guangxi, China were studied. Resorption efficiencies were quantitatively assessed by comparing nutrient content between the leaf with the highest content and the senescent leaves. In addition, the relationship between nutrient resorption efficiencies and nutrient sources (the sediment and the adult leaf) were evaluated. During the course of leaf development in Z. japonica (young leaf - adult leaf - senescent leaf), C content first rose and then declined; N and P contents gradually declined; but Ca, Mg, Fe and Mn gradually rose. During leaf senescence, resorption efficiencies of C, N, P, Ca, Mg, Fe and Mn were 2.1%, 19.5%, 45.1%, -61.1%, -12.0%, -27.1% and -72.3%, respectively. For Z. japonica, C, N and P contributed to new leaf growth, whereas Ca, Mg, Fe and Mn was not. The nutrient contents of the sediment and adult leaf were not significantly correlated to leaf nutrient resorption efficiencies. It was calculated that for Z. japonica approximately 13.8% of total N demand and 31% of total P demand could be met by internal resorption.