Study On The Uptake Rate Of Urea And Met By One Microalgae In Shrimp Ponds

Oocystis borgei used in this study separated from the high-level shrimp ponds, and it is the dominant species in the course of shrimp culture. Oocystis borgei is a kind of marine phytoplankton which plays the role of stabling the culture environment and improving water quality in the course aquaculture. There are few studies have reported on this kind of algae and it is not reported on the uptake rate of organic nitrogen by Oocystis borgei at home and abroad. This paper studied the uptake rate of urea-N and Met-N under different nitrogen concentrations,algea concentrations,temperatures,salinities and illuminations. Proposed the best ecological conditions of Oocystis borgei uptake the urea and Met.Ecological factors and Physical and chemical indicators of water quality are very important in the breeding process. We chose the two shrimp ponds to monitoring the change of the temperature,salinities,PH,Eh,Chlorophyll a,chemical oxygen demand,dissolved inorganic phosphorus,dissolved total nitrogen and dissolved organic nitrogen. Analysis the correlation between the factors mentioned above. Results are as follows.1 Field monitoring results indicate that the range of dissolved total nitrogen is 0.253～1.489 mg/L, average content is 0.767 mg/L; The range of dissolved organic nitrogen is 0.11～0.992mg/L, average content is 0.397mg/L; dissolved organic nitrogen occupied the 51.76% dissolved total nitrogen. The range of Chlorophyll is 5.9～215.2μg/L, average content is 91.6μg/L; The correlation equation between Chlorophyll and dissolved total nitrogen is y=0.662x+0.3776(R~2=0.684).2 The range of chemical oxygen demand is 4.2～13.3 mg/L, average content is 9.2 mg/L; Dissolved inorganic phosphorus is 0.019～0.187 mg/L, average content is 0.081 mg/L. The correlation equation between chlorophyll and chemical oxygen demand is y=0.037x+6.0075(R~2=0.5591).3 The range of temperature is 18.58～30.19℃, average content is 26.98℃, The correlation equation between chlorophyll and temperature is y=0.662x+0.3776 (R~2=0.684); The range of salinities is 21.08～31.13, average content is 28.15; The range of PH is 7.58～8.72, average content is 8.06; The range of Eh is 33.84～ 88.13mv, average content is 56.40mv.4 The influence of the urea and Met concentration on the uptake rate of urea-N and Met-N is significant (p<0.05). The maximum uptake rate of urea is 42.327μg/g·h when the urea-N concentration is 44 mg/L. The maximum uptake rate of Met is 0.129μg/g·h when the Met-N concentration is 29mg/L. Michaelis-Menten equation analysis shows that the maximum uptake rate of urea is 143.667μg/g·h, Km is 105.300μg/g·h; the maximum uptake rate of Met is 0.136μg/g·h, Km is 1.686μg/g·h.5 The influence of the algae concentration on the uptake rate of urea-N and Met-N is significant (p<0.05). The maximum uptake rate of urea-N is 4.044μg/g·h when the algae concentration is 3.222×10~8cells/L; The maximum uptake rate of Met-N is 0.107μg/g·h when the algae concentration is 4.784×10~8cells/mL.6 The influence of temperature on the uptake rate of urea-N and Met-N by Oocystis borgei is significant (p < 0.05). The maximum uptake rate of urea-N is 6.656μg/g·h when the temperature is 30℃; The maximum uptake rate of Met-N is 0.020μg/g·h when the algae temperature is 25℃.7 The influence of salinities on the uptake rate of urea-N and Met-N by Oocystis borgei is significant (p < 0.05). The maximum uptake rate of urea-N is 6.687μg/g·h when the salinity is 18.89; Maximum uptake rate of Met-N is 0.026μg/g·h when the salinity is 26.2.8 The influence of illuminations on the uptake rate of urea-N and Met-N by Oocystis borgei is significant (p < 0.05). The maximum uptake rate of urea-N is 19.065μg/g·h when the illumination is 126μmol/m~2·s; Maximum uptake rate of Met-N is 0.030μg/g·h when the illumination is 44μmol/m~2·s.