不同形态磷对沉积物-水界面浮游植物增殖及群落结构演替的影响

探讨了不同磷形态对沉积物-水界面浮游植物增殖及群落结构演替的影响,以九龙江北溪西陂水库沉积物-上覆水体(水体藻类丰度为7.2×10~4cells·L~(-1),以硅藻、绿藻、蓝藻为主,分别占藻类丰度的49.16%、32.40%、17.32%)为研究对象,磷源包括:无机磷(NaH_2PO_4·2H_2O)、有机磷(单磷酸腺苷,AMP)、SMT方法提取沉积物总无机磷(SMT-TP)、鲜沉积物(Sediment)和野外原水(OW).结果表明,无机磷和有机磷(N∶P=20∶1)培养组对藻类增殖有明显促进作用.其中,无机磷组中浮游植物群落结构演替为以蓝藻和绿藻为主,分别占藻类丰度的76.67%和23.34%;有机磷组中浮游植物群落则演替为以绿藻为主,占藻类丰度的92.51%.在低磷组(N∶P=25∶1)、野外原水(N∶P=17∶1)、SMT-TP组(N∶P=10∶1)中,浮游植物群落结构从硅藻、绿藻和蓝藻演替为以蓝藻和绿藻为主,与无机磷组结果趋于一致.而鲜沉积物(N∶P=10∶1,含有无机磷和有机磷)组群落结构演变为蓝藻占优势,所占比例为71.80%.该结果表明,磷的形态对浮游植物群落结构具有重要的影响.模拟环境无机磷组、有机磷组和SMT-TP培养组中,浮游植物群落多样性具有降低的趋向,硅藻逐渐消失;而野外原水和鲜沉积物组中浮游植物群落多样性稳定,硅藻仍然存在,表明自然环境中其他元素调控水体中浮游植物群落多样性.鲜沉积物组中浮游植物群落结构逐渐演替为以蓝藻为主,暗示沉积物对蓝藻水华暴发具有重要贡献.

Effect of the different phosphorus forms on the succession of phytoplankton community at sediment-water interface

To reveal the effects of different phosphorus forms on the growth and succession of phytoplankton community, we investigated the phytoplankton community change at sediment-water interface in Xipi Reservoir, Jiulong River, with different phosphorus sources, as inorganic phosphate (IP, NaH₂PO₄·2H₂O), organic phosphorus (adenosine monophosphate, AMP), sediment phosphorus extracted by SMT methods (SMT-TP), fresh sediment (Sediment) and original water (OW). The phytoplankton abundance in Xipi Reservoir is 7.2×10⁴ cells·L^-1, dominated by Diatom (49.16%), Chlorophyta (32.40%) and Cyanobacteria (17.32%). Our results show a significant higher growth rate of phytoplankton in IP and AMP treatments (N:P=20:1), where the dominant phyla in phytoplankton community changed to Cyanobacteria and Chlorophyta, accounting for 76.67% and 23.34% of total population, respectively. The phytoplankton community in AMP treatment was dominated by Chlorophyta (92.51%). In treatments of low phosphorus (N:P=25:1), OW (N:P=17:1) and SMT-TP (N:P=10:1), the dominant phyla in phytoplankton community were Diatoms, Chlorophyta and Cyanobacteria, consistent with the results in IP treatment. However in Sediment treatment (N:P=10:1, contain both inorganic and organic phosphorus), the dominant phyla changed to Cyanobacteria, accounting for 71.80% of total population. The results indicate the significant impacts of phosphorus forms on phytoplankton community structure. In all the IP, AMP and SMT-TP treatments, the diversity of phytoplankton community declined and Diatom gradually became rare phylum. On the contrast, the diversity of phytoplankton community remained stable in Sediment and OW treatments, and Diatom was still the major phylum. It implied that natural sediment can maintain and regulate phytoplankton community structure. The dominancy of Cyanobacteria in Sediment treatment suggested that the release of phosphorus from sediment has an important contribution to the cyanobacteria bloom.