铁对拟柱孢藻( Cylindrospermopsis raciborskii )和角星鼓藻( Staurastrum spp.)季节动态和生长的影响——以广东大沙河水库为例

Effect of iron on the seasonal dynamics and growth of Cylindrospermopsis raciborskii and Staurastrum spp.:A case study from Dashahe Reservoir,Guangdong Province

拟柱孢藻(Cylindrospermopsis raciborskii)和角星鼓藻(Staurastrum spp.)是热带亚热带浮游植物群落中的常见优势种类,为了解铁对2种浮游植物季节动态和生长的影响,本文通过对典型热带水库的野外调查,分析铁与2种藻生物量和相对生物量的季节动态的关系,并通过室内实验分别以无机磷(KH 2 PO 4)和有机磷(C 6 H 13 O 9 P)为磷源,比较3种铁浓度(0.029、0.29和0.689 mg/L)下拟柱孢藻(C.raciborskii,N8)和角星鼓藻(Staurastrum sp.,FACHB-1449)的比生长速率、铁载体产量和碱性磷酸酶活性的差异.结果显示,拟柱孢藻和角星鼓藻是浮游植物群落的主要优势种类,两者的生物量最大占到总生物量的82%以上;两者对环境变量响应的区别主要体现在对溶解性铁浓度变化的响应差异上,拟柱孢藻生物量与溶解性铁有显著的线性回归关系,但角星鼓藻的生物量与铁没有显著线性回归关系.室内实验中,拟柱孢藻N8的比生长速率在无机磷源铁浓度为0.689 mg/L条件下最大,为0.098±0.01 d-1,2种磷源条件下比生长速率均随铁浓度降低而显著降低,6个实验组均检到铁载体:6个实验组角星鼓藻FACHB-1449的比生长速率没有明显差异,平均为0.079±0.001 d-1,均未检出铁载体,磷源和铁浓度对其比生长速率的影响不显著;有机磷源条件下,拟柱孢藻N8实验组碱性磷酸酶活性均显著高于角星鼓藻FACHB-1449实验组,拟柱孢藻N8实验组酶活性随铁浓度降低而显著降低,但角星鼓藻FACHB-1449各实验组的碱性磷酸酶活性无明显差异.以上结果表明,水体中溶解性铁的供应对拟柱孢藻的种群动态和优势有重要作用,与角星鼓藻相比,拟柱孢藻的生长更易受到铁的限制,尤其在无机磷缺乏、磷源主要以有机磷形式供应时,铁对拟柱孢藻生长的限制作用增强.

Cylindrospermopsis raciborskii and Staurastrum spp.are the common dominant species in(sub)tropical reservoirs.To understand the effect of iron on seasonal dynamics and growth C.raciborskii and Staurastrum spp.,we investigated and analyzed the driving effect of iron on the biomass and the relative biomass of them,in a typical tropical reservoir.And we performed batch culture experiments with C.raciborskii N8 and Staurastrum sp.FACHB-1449 under three iron concentrations(0.029 mg/L,0.29 mg/L,0.689 mg/L)with two kinds of phosphorus source respectively,and we compared the difference of the specific growth rate,alkaline phosphatase activity and siderophore between the two species.The results showed that,C.raciborskii and Staurastrum spp.are the dominant genera in phytoplankton community,the highest proportion of the both was 82%in phytoplankton biomass;the different of the response to environmental conditions mainly reflected in the changes of biomass with iron concentration between the two genera,such as the significant linear regression was detected between C.raciborskii biomass and dissolved iron concentration,but not in Staurastrum spp.biomass.In culture experiments,the maximal specific growth rate of C.raciborskii N8 was 0.098 d-1±0.01 d-1 at iron concentration of 0.689 mg/L with inorganic phosphorus and it significantly decreased with the decrease of iron concentration in both phosphorus source condition,concurrently,siderophore was detected in all of the treatments with C.raciborskii N8;comparatively,the specific growth rate of Staurastrum sp.FACHB-1449 was no significant difference among the six treatments,which was 0.079 d-1±0.001 d-1 in all of the treatments,and no siderophore was detected in all of the treatments,which mean the phosphorus source and iron concentration did not significantly effect on the specific growth rate.In addition,the alkaline phosphatase activities was significantly higher in the treatments with C.raciborskii N8 than in the treatments with Staurastrum sp.FACHB-1449 under organic phosphorus source,and the alkaline phosphatase activities in the treatments with C.raciborskii N8 significantly decreased with the decrease of iron concentration,but not in the treatments with Staurastrum sp.FACHB-1449.It was concluded that the supply of dissolved iron was critical to the seasonal dynamics of biomass and dominance of C.raciborskii,the growth of C.raciborskii is more vulnerable than Staurastrum spp.to iron concentration decrease,and the limiting effect of iron on C.raciborskii will be enhanced under inorganic phosphorus deficiency condition.