Inhibition Of Tribonema Bloom By Acidification Treatments Using Two Kinds Of Organic Acid

In this paper, the inhibition of Tribonema when the water pH valuesadjusted by citric acid and acetic acid was studied in order to find the basictheoretical foundation and the application technology for the filamentousalgal blooms control in the aquaculture ponds.The pH values of the four treatments was adjusted to5.0,5.5,6.0,6.5.Tribonema weight10g was droped in the trail water and cultivatedinflatablely in the room under the condition of22℃,2000lx, and light/dark12h/12h cycles.The pH values and Chlorophyll a were determined every24h in orderto study the influence of Tribonema after the initial pH values adjusted bycitric acid. The entire trail continued for96h. The results showed that thepH values kept rising significantly when the initial pH values adjusted bycitric acid. Chlorophyll a levels of pH5.0and pH5.5showed a grow trendafter the first downward which demonstrated that Tribonema was inhibiteddue to strong acid stimulation. Chlorophyll a levels of pH6.0and6.5hadmaintained an upward trend, which indicated a low acidic concentrationproduced an effective stimulus to promote their growth and reproduction.1. At the experiment of the inhibition of Tribonema when the water pHvalues adjusted by citric acid and acetic acid, Tribonema was sampledevery48h and their changes of external morphology and microstructurewere surveyed. Chlorophyll a levels were measured byspectrophotometer,superoxidedismutase(SOD),catalase(CAT)activitives,malondialdehyde(MDA)contentswere measured by the corresponding kits. The results were as follows:water trabsoarency of pH6.5was higher than other treatments after96h,but the colour of Tribonema was not as good as the control group andTribonema was sinking with no bubbles. The water transparency of pH6.0turned down and the number of yellow-green algae increased. The water turbidity of pH5.5increased and the Tribonema began to fractureobviously which led to the decrease of the filament number. Comparingwith pH5.5, the colour of pH5.0became yellow seriously and the turbidityincreased. The Tribonema turned to decay, death and decrease significantly.The differences between control group and experimental group becamemore significant at144h,. At pH6.5, the water turned more turbid andTribonema became tan with the filament fracturing and drowning in thebottom of the bottle. At pH6.0,the number of Tribonema decreasedremarkablely. At pH5.5and5.0, the Tribonema was invisible almostly thatresulted from the synthetic obstruction of the chloroplast and thedisintegration of cells.After192h, each group appeared remarkable differences in themicrostructure. Compared with the control group, the filament’s chloroplastgathered in the central of the cell and showed different degree ofdissolution with the banded structure decreasing. These pronounced that thesynthesis of the chloroplast obstructed. The cellular structure grew dim andthe gap between the cytoplasmic membrane and the cell wall becamelarger.The influence of different pH values to Tribonema filament’sChlorophyll a contents, SOD activies, CAT activities, MDA contents wereas follows. At48h, Chlorophyll a contents, SOD and CAT activitiesappeared obvious differences that the data is lower in the treated group thanthe control group. At192h the group of pH5.0and5.5claimed to bedowntrend while pH6.0and6.5maintained the trendency of decline afterfirst growth. According to MDA,treated group showed no obviousdifferences with the control group at48h. MDA contents of experimentalgroup trended to increase with the time expanding and reached themaximum at144h. Then it began to decline. These suggested that theinhibition of Tribonema enhanced with acidity augmenting and the timeextensing.Through the adjustment of water pH values by acetic acid, it could be conclued as follows. Compared with the control group, the filament ofTribonema began turbid at48h since different acidity showed differentturbidity. At96h, the water became more turbid in the trail group withoutbubbles. The filament of Tribonema grew yellow, sinking and autolysiswith the filament fractureed. After144h, all four trail group’s water turnedwhite. The algae grew tawny with the obvious autolyzed phenomenon.After192h, the cellular structure of Tribonema at pH5.0,5.5,6.0became blurred. Chlorophyll a contents of Tribonema and banded structuredecreased. Chlorophyll a concertrated in the contral of cell and appearedyellowish-brown color. Plasmolysis phenomenon could be seen in thefilament. At pH6.5, the structure of the algae was clear and Chlorophyll acontents in the cell had tiny decline. But Tribonema chromatophore wasgreen and no obvious plasmolysis phenomenon.The influence of pH values adjusted by acetic acid to Chlorophyll alevels, SOD, CAT, MDA contents were shown as above. At48h,Chlorophyll a levels, SOD, CAT and MDA contents of pH6.0and6.5washigher than the control group. It appeared that the water of pH6.0and6.5made effective stimulus. With the extension of time, the number of thefilament showed decline after the first growth. On the other hand,Chlorophyll a levels of pH5.0and5.5group at48h was lower than thecontrol group. Further, the higher the acidity was, the lower theChlorophyll a levels were. SOD, CAT and MDA contents of pH5.0andpH5.5were higher than the control group and as the time extended, adownward trend appeared. That claimed that the enzyme began inactivatedue to the intense stimulation of acidic environment at pH5.0and pH5.5.In concluding, Tribonema bloom will have a significant inhibitory ifthe pH values are controlled in the range of pH5.0to pH6.5by citric acidand acetic acid.