查看文章

The growth dynamics of a residual Ruppia cirrhosa meadow of the eutrophic Valle Smarlacca lagoon, Italy, were monitored over an annual cycle and related to the cycling of iron, sulphur and phosphorus in the rhizosphere sediments. The Ruppia biomass and rates of gross primary production increased during spring and early summer, but declined rapidly thereafter. This biomass decline was particularly evident for the below-ground biomass. Microelectrode profiling demonstrated a clear seasonal trend in sediment redox potential, with the sediments becoming increasingly reduced during spring and summer. In addition, high concentrations of toxic free sulphides (up to 7mM) were detected in the porewater during summer and autumn. Radial oxygen release by the seagrass roots rather than iron precipitation appears to be the principal detoxification mechanism for sulphides in the rhizosphere. However, in summer …