水丝蚓对太湖沉积物有机磷组成及垂向分布的影响

Abstract

Bioturbation is an important dynamic process in lake sediment.Tubificid worms,widely distributed in Taihu Lake,were selected to study the potential effects of bioturbation on organic phosphorus(P) components and their vertical distribution in sediments.The experiments were performed with the field sediment column under a constant-flow incubation condition in laboratory,while the contents and components of organic P in sediments were analyzed by phosphorus-31 nuclear magnetic resonance spectroscopy(31P-NMR) which is currently a more direct and powerful tool in characterization of organic P forms at the molecular level.The obtained results demonstrated orthophosphate monoesters,phospholipids,DNA,pyrophosphate and phosphonates were the main organic P components.Compared with the control group(no bioturbation of tubificid worms),organic P components in sediments had no significant difference after the bioturbation of tubificid worms,while their vertical distribution changed obviously.The maximum concentration of total P and organic P appeared in the 0—0.5 cm sediment layer,and then decreased sharply downwards in control group,however,the maximum concentration of total P and organic P in sediments with the bioturbation of tubificid worms appeared in the 0.5—1cm sediment layer,their concentration in the 0—0.5 cm sediment layer were lower than that in control group.Based on 31P NMR analysis,the concentration of labile organic P in 0.5—1cm sediment layer with the bioturbation of tubificid worms was reduced significantly,such as DNA,which content was reduced from 11.2 mg/kg to 6.1 mg/kg.In addition,some physical and chemical indexes in sediments were also changed with the bioturbation of tubificid worms,water content,porosity in the 0—4cm sediment layer and alkaline phosphatase activity in the 0—1.5 cm sediment layer were increased significantly.Some research had found that the increase of water content and porosity in sediments can effect the substance release from sediments.In this research,alkaline phosphatase activity was found to be negatively correlated with the concentration of DNA and phospholipids,this indicated that the increasing of alkaline phosphatase activity can accelerate the decomposition of labile organic P,resulting in the decrease of DNA and phospholipids in the upper sediment.