太湖草、藻型湖区沉积物-水界面厚度及环境效应研究

Study on the thickness and environmental effects of sediment-water interface of phytoplankton and macrophyte dominated zones in Lake Taihu

在太湖草、藻型湖区采样,分别测定了1,3,5,10,15cm 5层沉积物和沉积物表面以上5,20,35cm处及水表面以下20cm处4层水的多项指标.结果表明：草型湖泊水柱中SS总、SS有机、Chl-a、TN、TDN、TP和TDP等指标显著低于藻型湖区;草型湖区水柱中SS总、SS有机、TN、TDN和TP都呈现出越往下浓度越高的趋势,而藻型湖区各水层间差异不明显.两类湖区沉积物的TN、TP、TOC和粒径都在3~5cm处出现拐点;草型湖区沉积物溶解氧层厚度（〈1mm）小于藻型湖区（〈2.5mm）.可见在不同的生境类型以及不同的指标体系下,沉积物-水界面的厚度也相应不同.

To understand the difference of the properties of sediment-water interface between macrophytes-dominant region and phytoplankton-dominant region in large and shallow lakes,the sediment cores and the overlying water columns were sampled in phytoplankton and macrophyte dominated zones in Lake Taihu.Five layer of sediment cores,with depths of surface 1 cm,3cm,5cm,10 cm and 15cm were sliced for physicochemical analysis.At the same time,four layers of overlying water,with depth of 5 cm,20 cm,35cm above the sediment surface,and one layer of 20 cm below the water surface,were sample and analyzed for the comparative research.The results showed that,the concentrations of total suspended substance,organic suspended substance,chlorophyll-a,total nitrogen,total dissolved nitrogen,total phosphorus and total dissolved nitrogen in water column at macrophyte-dominant region were significant lower than those in phytoplankton dominated zone.Vertical profile of concentrations of total suspended substance,organic suspended substance,chlorophyll-a,total nitrogen and total dissolved nitrogen in water column at macrophyte-dominant region showed a increasing trend from surface to bottom,while these trends were not obvious in phytoplankton dominated region.The profile of contents of total nitrogen,total phosphorus,total organic carbon and mean value of grain size in sediment column showed a turning point at the depth of 3~5cm below the surface in both macrophyte-dominant and phytoplankton-dominant regions.But the oxygen penetration depths in the two regions were much different.The oxygen penetration depth in macrophyte-dominant region was less than 1mm,while it could be 2.5mm in phytoplankton-dominant region.The results suggested that the thickness of sediment-water interface in shallow lakes could be very different in different ecosystem or based on different parameters.