EDTA和铁对铜绿微囊藻和四尾栅藻生长和竞争的影响

Effects of EDTA and Iron on Growth and Competition of Microcystis aeruginosa and Scenedesmus quadricauda

铁限制不但会影响浮游植物的种群密度,而且会影响浮游植物的群落结构.为了探讨有机配体和铁的作用对湖泊中浮游植物的种群竞争,采用批量培养的方法,研究了不同EDTA及Fe浓度下,太湖蓝藻铜绿微囊藻和绿藻四尾栅藻的生长和竞争.结果表明,较高浓度的EDTA（≥13.5μmol/L）可以抑制铜绿微囊藻的生长,但不抑制四尾栅藻,因而有利于四尾栅藻占据优势;铁的浓度由3μmol/L增大至18μmol/L时,可缓解较高浓度EDTA（13.5~27μmol/L）对铜绿微囊藻的抑制作用,而增大其它微量元素浓度（B、Mn、Zn、Cu、Mo等）则无此作用;说明高浓度EDTA与铁的螯合作用能抑制铜绿微囊藻而不抑制四尾栅藻.高浓度EDTA对2种藻具有不同影响的原因可能是2种藻对铁的吸收机制不同.

Not only population density of phytoplankton but also its community structure were influenced by iron limitation. The growth and competition of a cyanobacterium Microcystis aeruginosa and a green alga Scenedesmus quadricauda at different iron and EDTA concentrations were investigated using batch cultures. The results showed that the growth of M. aeruginosa was significantly inhibited whereas S. quadricauda wasn＇t when EDTA at high concentrations （≥13.5μmol/L）, and consequently, it favored the dominance of S. quadricauda. Moreover, increasing iron concentration from 3 μmol/L to 18μmol/L could greatly alleviate the growth inhibition of M. aeruginosa while increasing concentration of other microelements e.g. B, Mn, Zn, Cu, Mo didn＇ t. These results suggest that high EDTA concentration decreases iron availability for M. aeruginosa, but not for S. quadricauda. The reason that the two algae respond to high EDTA concentrations differently is that their adsorption strategies for iron should be different.