桑沟湾养殖海域柱状沉积物中磷的赋存形态和生物有效性

Forms and bioavailability of phosphorus in sediment cores of culture zones in Sanggou Bay

关键词:  桑沟湾  柱状沉积物  磷形态  年代序列  生物有效性

Key words:  Sanggou Bay  Core sediment  Phosphorus forms  Chronosequence  Bioavailability

摘要:

以桑沟湾扇贝和海带两个养殖海区的柱状沉积物为研究对象，采用连续提取法将沉积物中磷的赋存形态分为交换态磷（Ex-P）、铁结合态磷（Fe-P）、自生磷（Au-P）、碎屑磷（De-P）和有机磷（Or-P），并分析了各形态磷的垂直分布特征；利用沉积物年代序列测定的结果，结合桑沟湾水产养殖历史，探讨了近200年来桑沟湾养殖海域沉积物中磷形态的含量变化情况，并进一步分析了该区域的生物有效磷。结果表明，柱状沉积物中上层各形态磷的含量高于底层，表明养殖活动使桑沟湾表层沉积物中的磷含量增大。各形态磷的含量在贝壳沉积区内变化幅度均较大，Or-P是沉积物中磷的主要形态；扇贝养殖区沉积物中的总磷（TP）、Or-P和海带养殖区沉积物中的TP、Or-P在沉积时间序列上分布基本一致，其含量变化与各时期工业生产和海水养殖活动密切相关；两个区域柱状沉积物中潜在生物有效性磷占总磷的百分比为61.2%和71.0%。沉积物中Ex-P的含量对该海域的初级生产力的影响较大。

Abstract:

Phosphorus is the most important limiting factor in nutrient cycling, and it is also the key element controlling primary production in aquatic environment. Sediments act as both a sink and a source of phosphorus due to continuous transport of chemical species across the sediment-water interface. Phosphorus is actively involved in both terrestrial and marine biogeochemical cycles. However, not all fractions of phosphorus in sediment are released to the overlying water. Therefore, the effects of phosphorus fractions in sediments for promoting aquatic environment eutrophication can be more efficiently evaluated based on phosphorus fractions, rather than total phosphorus. In this work, forms and bioavailability of phosphorus in the columnar sediments of two sampling sites in Sanggou Bay were analyzed by means of sequential extraction method (SEDEX). According to this method, there are five types of phosphorous:iron-phosphorous (Fe-P), organic-phosphorous (Or-P), detritus-phosphorous (De-P), exchangeable-phosphorous (Ex-P) and autologous-phosphorous (Au-P); The ages of sediment were also used to explore the content change of phosphorous forms in about two hundred years.The results showed that, for two sites, the contents of total phosphorus and phosphorus forms in the core sediments obviously decreased with depth.The main form of total phosphorus (TP) in sediments was organic phosphorus (Or-P) ,which accounted for 59.5 %, 57.6 % of TP in S1 and S2 sites, respectively ,and the percentage of Fe-P was less than 1 % ,which indicated that the environment of Sanggou Bay was less polluted. The contents of various forms in upper layer were all higher than those in bottom sediment and varied greatly in the shell deposition, which suggested that farming activity increased phosphorus sedimentation. In addition, the total phosphorus and contents of phosphorus forms had a tendency to decrease toward the bottom of the core, regardless of the phosphorus species;The distribution of TP and Or-P in time series was almost the same for both two sites;Bioavailable phosphorus in sediments occupied 61.2 % ,71.0 % of the total phosphorus pool,respectively;The content of Ex-P in sediment imposed a greater impact on the primary productivity in culture zones of Sanggou Bay.