Effects Of Fe And La And Chelating Agents On The Growth And Competition Of Microcysits Aeruginosa And Scendesmus Quadricauda

Lake eutrophication is a serious problem in our country's water environment. Thescope of lake eutrophication is broad and blue-green algae bloom happens frequently,which trend isprobably to increase in the near future. Lake eutrophication has causedhuge harm to people's life and economical development around the lake areas. Thereforeresearches on lake eutrophication and the mechanism of blue-green algae bloom aremeaningful. Tai Hu Lake is a typical large-scale shallow water eutrophication lake inChina. Our research choose the main Tai Hu Lake algae bloom species Microcysitsaeruginosa and Scendesmus quadricauda to do experiments. This paper discussed theeffects of Fe and La and chelating ligands on the growth and competition of M.aeruginosa and S. quadricauda.The result showed that chlorophyll a content per cell, the maximum photosyntheticrate, Respiration rate, and the slope of P-I curve under light limitation of M. aeruginosadeclined faster than S. quadricauda as the concentration of iron decreased. The ironrequirement for S. quadricauda was lower than M. aeruginosa. So it was favorable for S.quadricauda becoming dominant. When the concentration of nitrogen was low, thegrowth of two algae was limited, the iron concentration change did not affect theInter-species superiority; low concentration of phosphorus was favorable for S.quadricauda becoming dominant, this trend increased as the iron concentration decreased.High concentration of organic ligand EDTA can inhibit the growth of M.aeruginosagreatly through affecting the bioavailability of iron. The different adsorption strategy foriron of the two algae made high concentrations of organic ligand EDTA favorable S.quadricauda becoming dominant. Low concentrations of lanthanum had little effects onthe chlorophyll a contents, photosynthetic rate, and growth rate of the two algae. Highconcentrations of organic ligand or high concentrations of lanthanum favored S.quadricauda becoming dominant. However both functions were not independent, andcertain concentrations of organic ligand and the high concentration of lanthanum couldlead to an antagonistic effect. This will reduce growth inhibition of M. aeruginosa andfavorable M. aeruginosa becoming dominant.