Micro-Nutrients Effects on Algae Colony: Growth Rate and Biomass Response to Various Micro-Nutrients and Competitive Inhibitions among Multi-Microelements

Drinking waters worldwide have experienced an increase in the occurrence of harmful algal blooms. Nutrients variance is hypothesised to be the main factor that causes algae populations outbreaks. The effects of trace nutrients and their interaction on the proliferation of planktonic algae colony, is one of the most complex factor in the formation process of algae blooms, and in addition the factor that is most liable to be neglected in the research activities of cause analysis of algal blooms. Experiments on the impacts of three typical trace metals (Fe, Mn, Zn) on growth rates and biomass of the widespread algal blooms organisms (cyanobacteria, Chlorophyta) were carried out by single-factorial experimental design under laboratory culture conditions with fully simulated the natural ecological environment. The data obtained appeared to show that a positive motivation to the growth rate and biomass of algae was emerged with the increase of the concentrations of Fe, Mn and Zn (range from 0.01~0.20, 0.01~0.13, 0.001~0.033mg/L, respectively), while there is a negative motivation with the increase of the concentrations of Fe, Mn and Zn above 0.20, 0.13, 0.033mg/L, respectively. By fitting the numerical relationship between concentrations of Fe, Mn, Zn and algal cell-specific growth rate, regression equations with correlation coefficient of 0.93, 0.87, 0.90 were obtained respectively. The effects of P, Fe, Mn, Zn and their interaction on growth rate and biomass of the algae colony were performed by a L16(4⁴) orthogonal experimental design under equivalent conditions with single-factorial experiments. Four way ANAVA (analysis of variance) reported that these nutrients stimulated cell-specific growth rates with Zinc>Phosphorus>Iron>Manganese. Experiment consequence suggested that the significant levels of Manganese to algae had been severely weakened by the inhibitory effect among multi-microelements during orthogonal experiments. These results reveal - - that the mechanism of Manganese is rather complicated that further researches are needed to be performed. The results make it be able to predict the time and severity of outbreak of algae blooming to a certain precision extent according to the correlation between trace elements and algae growth rate or biomass.