[Effects of EDTA and iron on growth and competition of Microcystis aeruginosa and Scenedesmus quadricauda].

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 (> or = 13.5 micromol/L), and consequently, it favored the dominance of S. quadricauda. Moreover, increasing iron concentration from 3 micromol/L to 18 micromol/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.