Biological Effections Of Several Physical And Chemical Factors On The Dominant Microalages In The Eel Pond

In this study, using N, P, N/P, Cu2+, Fe3+, pH and six kinds of aquatic fish medicines to observe the influences on the growth and competition of advantage alages in the eel pond. The results were as follows:1,The optimum growth concentrations of N, P for Microcystis aeruginosa and Microcystis flos-aquae was:150mg/L-350mg/L for N and 0.005mg/L-5mg/L for P, respectively. The most appropriate concentration range for Chlorella vulgaris was 25mg/L-250mg/L for N and 75mg/L-100mg/L for P. The optimal concentration range for Scenedesmus quadricauda was 25mg/L-150mg/L for N and 50mg/L-100mg/L for P.2,Microcystis aeruginosa and Microcystis flos-aquae were fairly sensitive to Cu+, when the concentration of Cu2+ is in the range of 40μg/L-640μg/L, the inhabitation was more prominent. Cu2+ in this range of concentration for Chlorella vulgaris and Scenedesmus quadricauda had different degrees of enhancement. Four kinds of alage in the competition experiment, Microcystis aeruginosa and Microcystis flos-aquae in the control group had advantages. When the concentration of Cu2+is 40μg/L and 640μg/L, Chlorella vulgaris and Scenedesmus quadricauda were increasingly dominant. When the concentration of Cu2+ reached 1280μg/L, the four algae were subject to inhibition. The results of SOD and MDA showed along with the concentration of Cu2+ increasing, enzyme activity of SOD is decreasing3,Fe3+ had effect on Microcystis aeruginosa and Chlorella vulgaris, especially, iron deficiency had more obvious limitation on the growth of Microcystis aeruginosa, when the initial concentration of Fe3+ was 0.1μmol/L, the growth curve showed negative growth trend.μmax of Microcystis aeruginosa appeared in 25μmol/L, butμmax of Chlorella vulgaris is 20μmol/L. When the concentration of Fe3+ reached 100μmol/L, the two algae were subject to inhibition, but the growth rate was still higher than low concentration group.4,pH had a significant impact on the alage growth and competition, Microcystis aeruginosa in the range of pH8-11 grew well, and the optium pH value is 9, however, Chlorella vulgaris in the range of pH8-11 grew well, with the optium pH value is 8. Co-culture of two algae indicated that Microcystis aeruginosa had competitive advantage, if pH8-10,βvalue is more than a value, but when pH value is 7, Chlorella vulgarishad advantages and a valueis more thanβvalue.5,The concentration of chlorine dioxide, dichloro-hydantoin, trichlorfon and potassium permanganate on Chlorella 96EC50 were:176.63mg/L,61.68mg/L, 212.97mg/L,3.72mg/L, respectively. The inhibitory intensity for Chlorella vulgaris was as follows:potassium permanganate> dichloro hydantoin> chlorine dioxide> trichlorfon.In this concentration range of the mebendazole and oxytetracycline could promote growth, and in pace with the increasing of concentration, the density and the content of chlorophyll a increased.6,The concentration of chlorine dioxide, dichloro-hydantoin, trichlorfon and potassium permanganate on Microcystis aeruginosa 96EC50 were:2.09g/L,66.26mg/L,93.85mg/L,153.54mg/L,1.62mg/L, respectively. The inhibitory intensity for Microcystis aeruginosa was as follows:potassium permanganate> dichloro hydantoin> oxytetracycline> Trichlorfon> chlorine dioxide. However, In this concentration range of the mebendazole acted on the growth showed positive effects, with the increasing of concentration, the growth of Microcystis aeruginosa increased gradually.