Study Of Complexing Iron On The Population Density And The Absorption Of Routine Nutritive Elements Of Freshwater Algae

The phenomenon of algal blooms caused by water eutrophication is the most common water environment problem in recent years. Algal blooms directly destroyed the ecological balance of water, resulting in the deaths of a large number of aquatic animals and plants, seriously deteriorated water quality and caused great harm to the human production and life, severely restricted the harmonious development of the society and economy. So how to monitor and pre-alarm algal blooms and how to control and solve this phenomenon of algal blooms effectively is an important research topic in the environment field with practical significance in recent years.Currently a large number of studies mainly focus on the impact of major elements to algal blooms. Studies have shown that major elements nitrogen and phosphorus are the main control However, with the putting forward of factors of eutrophication, affecting the eutrophication process and the algae breeding rate. However, with the putting forward of iron-limited theory which indicating that trace elements iron can limit algal blooms proliferation, the study of the relationship between trace elements and algae proliferation became a hot spot of the algae research. Iron is one of the most widely distributed metallic elements on the earth as well as one of the important metallic element for algae growth. It plays an important role in algae’s metabolic activities such as photosynthesis, respiration, and enzymatic reaction. The forms of iron existing in the natural environment are many and varied and the absorption and utilization process of iron are also not the same for different algae species. So studying the relation between different algae species and the morphology of iron can better explore the formation process of dominant algae of algal blooms, which can provide theoretical help for algal blooms control and prediction.This paper is devoted to the study of the differences in proliferation trend of three common freshwater algae species under different complexing iron conditions, comparing the influence of different iron source to different algae proliferation, exploring and complaring the rules of algae’s absorption and utilization of constant nutrition elements nitrogen and phosphorus in terms of the change in the form of iron. Three kinds of typical freshwater algae including Anabaena flos-aquae, Scenedesmus and Melosira were chosen, belonging to cyanobacteria, green algae and diatoms respectively.Using algae Growth Potential (Algal Growth Potential, AGP), the experiment studied the biomass and absorbing state of nitrogen and phosphorus of the three pure freshwater algae under the condition of different complexing state of iron, and used ferric ion as control group to compare the similarities and differences of the respond of different algae species to different forms of iron. The experimental results are as follows:In this experiment the iron concentration within the scope of 0.2 to 1.0 mg/L, iron morphology and iron concentration have significant effects on Anabaena flos-aquae. Organic complexed Fe is a kind of iron morphology which can be absorbed and utilized by Anabaena flos-aquae. Complexing agent and the stability of iron complexes have no obvious regularity with Anabaena flos-aquae proliferation. The degree of iron morphology’s acceleration to Anabaena flos-aquae are, in order, ammonium ferric citrate> EDTA-Fe> ferric humate> ferric ion and ferric oxalate. Anabaena flos-aquae’s adsorption capacity of ferric ion was the strongest. Under the iron concentration condition of 0.2 mg/L, the peak of Anabaena flos-aquae all reached higher values, which mean low iron environment were more conducive to the growth of Anabaena flos-aquae. Compare with ferric iron, Anabaena flos-aquae’s absorption rate of phosphorus under the condition of ammonium ferric citrate, EDTA-Fe, ferric humate and ferric oxalate were faster. Under the condition of ferric ion, Anabaena flos-aquae’s average absorptive amount of nitrogen was the least (5.85 mg/L), and under the conditions of EDTA-Fe, ammonium ferric citrate, ferric humate and ferric oxalate the average absorptive amount of nitrogen were:8.20 mg/L,9.11 mg/L,7.96 mg/L and 6.30 mg/L, respectively. Under the concentration condition of this experiment, the change of iron concentration showed little influence on Anabaena flos-aquae’s absorption of nitrogen source.The degree of iron morphology’s acceleration to Scenedesmus are, in order, ammonium ferric citrate> Fe3+, ferric humate> EDTA-Fe and ferric oxalate. In this experiment the iron concentration within the scope of 0.2 to 1.0 mg/L, Compare with ferric ion, EDTA-Fe and ferric oxalate had adverse effects on the growth of Scenedesmus. In this experiment, iron concentration had no significant influence on Scenedesmus biomass while iron morphology had obvious effects on Scenedesmus biomass. Scenedesmus’s adsorption capacity of ferric ion was the strongest among the five different forms of iron. Scenedesmus’s use of iron sources were affected by the form of iron. Complexed Fe with stronger stability were able to restrict Scenedesmus’s absorption of iron, which affected the proliferation of Scenedesmus. The change of iron morphology influenced Scenedesmus’s adsorption of phosphorus and algae adsorption amount of iron source and its adsorption of phosphorus were in negative correlation. The change of iron concentration showed little influence on Scenedesmus’s absorption of nitrogen source.Ferric humate showed the largest promoting effects to the growth of Melosira. Ferric ion’s acceleration to the proliferation of Melosira better effects than ammonium ferric citrate, ferric oxalate and EDTA-Fe group. The average algal biomass of ferric ion group was 7.7 ×105cap/L, double that of ammonium ferric citrate, ferric oxalate and EDTA-Fe group. The degree of iron morphology’s acceleration to growth rate of Melosira are, in order, ferric humate> Fe3+> ammonium ferric citrate> ferric oxalate> EDTA-Fe. Melosira’s adsorption capacity of ferric ion was the strongest Compared to other forms of iron. In this experiment the iron concentration within the scope of 0.2 to 1.0 mg/L, iron concentration had no significant influence on Melosira biomass while iron morphology had obvious effects on Melosira biomass. Under the concentration condition of this experiment, the change of iron morphology and concentration showed little influence on Melosira’s absorption of nitrogen and phosphorus source.Under the condition of five kinds of iron source, proliferation rate and growth rate of Anabaena flos-aquae were larger than that of Scenedesmus and Melosira. The average proliferation rate was 3.1 times and 5.3 times that of Scenedesmus and Melosira. It’s believed that Anabaena flos-aquae are more likely to form the dominant algae. The utility pattern of the same source of iron varied among different algae species. Under the condition of EDTA-Fe and ferric oxalate, Scenedesmus and Melosira’s absorption of iron source showed similar utilization partten, which were different from that of Anabaena flos-aqu. It is believed that Scenedesmus and Melosira’s absorption and utilization approaches of iron source were the same.