Study On The Effect Of Alkaline Phosphatase On P Uptake By Synedra Sp. And Its Influence Factors

Eutrophication and algal blooms have been important environment problems in the three gorges reservoir sincethe impoundment in 2003,particularly in tributary bay.In recent years,diatom algal blooms frequently broke out in Jialing River which is the largest tributary of the three gorges reservoir and the important source of drinking water. This problem causes cloggingof thefilter nozzles in water plant and threatens water quality safety. Therefore, there is an urgent need of deep research on the mechanism of the algal blooms in backwater area of Jialing River.Previous research found that the total phosphorus, can better predict the change of the density of algae than the total nitrogen. But the correlation is not significant between the nutrients and the density of algae. Alkaline phosphatase(AP) which plays an important role in the process of algae using organic phosphorus can hydrolyze some forms of organic phosphorus into inorganic phosphate.Therefore, research on the alkaline phosphatase activity(APA) of the dominant algaes in backwater area of Jialing River and its relationship with growth has great significance in understanding the mechanism of algae outbreak.This paper mainly studiesSynedra acus which is the dominant algae in backwater area of Jialing River and Microcystisaeruginosawhich is the common bloom specie.The paper studies the effects of phosphorus absence and three forms of organic phosphorus on the growth, APA and organic phosphorus(DOP) absorption. And it also studies the effect of pH, temperature, initial concentration of phosphorus, nitrogen and phosphorus ratio and flow velocity on algae growth, APA and organic phosphorus absorption.This paper analyzes the fuction ofAP in the process of organic phosphorus using by Synedra acus and the reason why Synedra acus is the dominant algae in Jialing River, mainly draws the following conclusion:(1) Synedra acus can survive better than microcystis aeruginosa under the condition of phosphorus absence and phosphorus limitation. This is because Synedra acus can absorb a large number of phosphorus source to store in the cell, which creats a growth advantage for Synedra acus under the condition of phosphorus limited. The sensitivity and abilityof the expression of AP by Synedra acus is stronger than microcystis aeruginosa, and the condition of phosphorus absence can improve the APA. The characteristics of the AP creats advantages for the use of organic phosphorus for Synedraacus.(2) APplay an important role in the process of the algae growth by using organic phosphorus source. The more bioavailable organic phosphorus source,the positive correlation betweencell density and the APAis more significant when the total phosphorus in water is consistent and algae is in the condition of phosphorus limitation.So the change of the APA can indirectly reflect the change of density of algae.(3) The survival state of algae cells might also influence the expression of AP. The expression of AP could be inhibited when algae cells suffer damage, which affect the absorption of organic phosphate.Synedra acus has a better absorption of organic phosphorus when the cells are in a good state. But APA is not necessarily higher in this state.This is Because APA is induced or inhibited by phosphate concentration.(4) The correlation between TP and algal density is associated with the biological availability of total phosphorus in water. This is because Synedraacus and Microcystisaeruginosa can grow by using the four source of phosphorus. But when three are other forms ofunbioavailable DOPin extracellular total phosphorus, this correlation might not exist.(5) Based on long-term monitoring of Jialing River in the past, it can be seen that the temperature remains 20 degrees around betweenMarch to May,pH is weak alkaline and nitrogen meets the demand of algae around the year. In a word, temperature, pH and TN inspring of Jialing River is fit for algae growth.Diatom algal blooms broke out in Jialing River in spring. At the same time some sampling points of Jialing River showed phosphorus limitationand flow velocity was increased. AP of Synedra acus is sensitive to the changes of phosphorus in water and can be induced in time. The improve of APA enhanced the ability of using organic phosphorus under the condition of phosphoruslimitation, which created growth advantageSynedra acus.And Synedra acuscan grow well under high flow velocity. It can adapt to the change of flow velocity better than any other algae, which could be one of the reasons why Synedra acus can be a dominant algae.