氮磷形态与浓度对铜绿微囊藻和斜生栅藻生长的影响

以铜绿微囊藻（Microcystis aeruginosa）和斜生栅藻（Scendesmus obliquus）为研究对象，分别以硝酸钠、氯化铵和尿素为氮源，以磷酸氢二钾、甘油磷酸钠和三磷酸腺苷为磷源，配置不同浓度的氮磷培养基（氮浓度1.00，4.00，8.00mg/L，磷浓度0.20，2.00mg/L），通过一次性培养实验研究2种藻氮、磷饥饿时对不同形态和不同浓度氮磷的生长响应.结果表明，2种藻对氮、磷的形态和浓度响应均不同，且藻种之间也有明显的响应差异.铜绿微囊藻在3种浓度硝酸钠培养下比生长速率无显著差异，而斜生栅藻的比生长速率在硝酸钠4.00mg/L时达到最高，说明1.00mg/L的硝酸钠已满足铜绿微囊藻对氮的生长需求，斜生栅藻对氮的需求高于铜绿微囊藻.铜绿微囊藻在1.00，4.00mg/L氯化铵和尿素培养下的比生长速率相同，且比生长速率和现存量均高于同浓度硝酸钠培养组，说明相比于硝酸钠，铜绿微囊藻更喜欢利用还原态的氯化铵和尿素.但当氯化铵浓度高达8.00mg/L时，铜绿微囊藻比生长速率低于相同浓度尿素和硝酸钠培养组，也低于低浓度氯化铵培养组，说明高浓度氯化铵不利于铜绿微囊藻的生长.然而，斜生栅藻在8.00mg/L氯化铵培养下比生长速率和现存量与尿素培养时无显著差异，而且均高于硝酸钠培养组，说明斜生栅藻对氯化铵的耐受能力比铜绿微囊藻高.3种形态的磷均能被铜绿微囊藻和斜生栅藻利用，但铜绿微囊藻用高浓度有机磷培养时的现存量更高，斜生栅藻则在高浓度无机磷培养下生长更好，说明铜绿微囊藻比斜生栅藻能更好的利用有机磷，高浓度的无机磷不利于铜绿微囊藻生长.太湖目前铵氮浓度降低显著，水体无机磷占比很低，溶解态有机磷浓度占比较高，这些都更有利于蓝藻形成优势.

Effects of nitrogen and phosphorus forms and concentrations on the growth of Microcystis aeruginosa and Scenedesmus obliquus

The growth of Microcystis aeruginosa and Scenedesmus obliquus was investigated using sodium nitrate, ammonium chloride and urea as nitrogen (N) source; dipotassium hydrogen phosphate, sodium glycerophosphate and adenosine triphosphate as phosphorus (P) source. The N concentrations of culture media were 1.00, 4.00, 8.00mg/L, respectively, and the P concentrations were 0.20, 2.00mg/L, respectively. Bulk culture experiment was conducted to investigate the growth response of Microcystis aeruginosa and Scenedesmus obliquus to different forms and concentrations of N and P under N and P starvation. The results showed that different forms of N and P can stimulate the growth of two species of algae, but there was a bit difference. There was no significant difference in growth rates of M. aeruginosa between different concentrations of sodium nitrate, while the growth rates of S. obliquus reached the highest growth rate when N concentration of sodium nitrate increased to 4.00mg/L. It indicated that 1.00mg/L sodium nitrate has saturated the N requirement of M. aeruginosa, and the nitrogen demand of S. obliquus was higher than that of M. aeruginosa. The growth rates of M. aeruginosa was same when cultured with 1.00 and 4.00mg/L of ammonium chloride and urea, and the growth rates and maximal cell densities were higher than that cultured with same concentration of sodium nitrate. Compares with sodium nitrate, indicating M. aeruginosa prefers to use ammonium chloride and urea. However, the growth rates of M. aeruginosa cultured by 8.00mg/L ammonium chloride was lower than that cultured with same concentrations of urea and sodium nitrate, and also lower than that cultured with low concentration ammonium chloride, indicating high concentration of ammonium chloride was harmful to the growth of M. aeruginosa. There was no significant difference in growth rate and maximal cell densities of S. obliquus between 8.00mg/L of ammonium chloride and 8.00mg/L of urea. And both were higher than that using sodium nitrate to culture. It indicated that the tolerance of S. obliquus to ammonium chloride was higher than that of M. aeruginosa. All three forms of P can be utilized by M. aeruginosa and S. obliquus. However, the maximal cell densities of M. aeruginosa was higher with high concentration of organic phosphorus, and S. obliquus grew better under high concentration of inorganic phosphorus, indicating that availability of different forms of P were different among different algae. The ammonium concentration declined significantly, and inorganic phosphorus concentration was lower than organic phosphorus in recent years in Lake Taihu, which will benefit dominance of cyanobacteria. At present, the concentration of ammonium nitrogen in Taihu Lake is significantly reduced, the proportion of inorganic phosphorus in water is very low, and the concentration of dissolved organic phosphorus is relatively high, which is more favorable to the formation of cyanobacteria.