太湖浮游硅藻时空演化与环境因子的关系

利用1992年至2002年每月1次的监测资料,系统分析了太湖北部3个区域(河口、梅梁湾、湖心)浮游硅藻(Planktonic diatoms)生物量周年变化和空间分布情况.同时,水中磷酸盐(PO43--P)、氨氮(NH4+-N)、硝氮(NO3--N)和硅酸盐(SiO23--Si)含量等相关资料也被用于解释太湖浮游硅藻时空分布的原因.结果显示,直链硅藻(Aulacoseira sp.)是太湖浮游硅藻的优势种,其它常见种有小环藻(Cyclotella sp.)、针杆藻(Synedrasp.)等.硅藻总生物量占浮游藻类生物量百分比平均值约为20%.太湖浮游硅藻生物量在河口最大,梅梁湾其次,湖心最小,究其原因可能与河口的特殊生态环境(水流速度)有关,另外,河口丰富的营养盐,特别是磷酸盐和氨氮也是一个重要因素.温度可能是影响太湖浮游硅藻生物量季节变化的关键因素.Pearson相关分析证实,磷酸盐、氨氮和温度均与硅藻生物量显著相关(p<0.01),且蓝藻生物量百分比与硅藻生物量百分比呈显著负相关.研究结果说明,太湖浮游硅藻的生长分布受多种环境因子(磷酸盐、氨氮、温度)的影响限制,太湖浮游硅藻与蓝藻可能存在着竞争演替的趋势.

Long-term evolution of planktonic diatoms and their relationships with environmental factors in Lake Taihu

The variation of the abundance of planktonic diatoms was analyzed using monthly monitoring data covering the period 1992—2002 in the large shallow eutrophic Lake Taihu in China. The concentrations of PO3-4-P, NH+4-N, NO-3-N and SiO2-3-Si were used to explain the spatial and temporal distribution of planktonic diatoms at three stations in the lake (Meiliang Bay, Lake Centre and Lake Mouth). The most abundant planktonic diatom was Aulacoseira sp., with other main unicellular diatoms as Cyclotella sp. and Synedra sp. At the Lake Mouth, diatoms occurred more frequently and appeared at higher densities than in the Meiliang Bay and the Lake Centre. The higher water flow rate seemed to maintain a high abundance of diatoms at the Lake Mouth. In contrast, nutrients as PO3-4-P and NH+4-N played the critical role in shaping the spatial distribution of diatoms in Lake Taihu. Water temperature appeared to be important in the timing of the annual onset of diatom growth. Pearson correlations confirmed that PO3-4-P, NH+4-N and water temperature were the most significant parameters related to the diatom development in Taihu (p < 0.01). Further we found a high negative correlation between diatoms and cyanobacteria. In average diatoms contributed 20% of total phytoplankton and were hence less important building up biomass in Taihu than cyanobacteria.