Study On The Nutrients Uptake And Photosynthesis Based On Bioremediation In Two Species Of Economic Marine Macroalgae

At present, there were two serious ecological problems in ocean: increasing atmosphericCO₂and eutrophication of seawater. Domestic and foreign scholars have paid close attentionto these hot issues. The large-scale farming of the marine macroalga can repair theeutrophication of seawater and inhibit the increasing atmospheric CO₂. This view is acceptedby many scholars. The incubation densities in the large-scale farming of the marinemacroalgae determine the economic benefits and also affect the physiological functions ofthem. On the basis of reviewing the progresses in the effects of elevated CO₂or nutrient onmarine macroalgae, this studies used two important economic macroalga species, Gracilarialemaneiformis and Porphyra haitanensis derived from the South China Sea as experimentalmaterials, we examined that:1, The physiological effects of different CO₂and nutrientstreatments on Gracilaria lemaneiformis;2, Pi uptake rate of Porphyra haitanensis grown atdifferent incubation densities, temperature and nutrients conditions; and3, The physiologicalresponses of Porphyra haitanensis to different incubation densities and nutrients conditions.The results were as follows:â… Either increased atmospheric CO₂or increased nutrients could enhance the relativegrowth rate in Gracilaria lemaneiformis. The high concentrations of nutrients in the culturemedium could inhibit the photochemical efficiency of Gracilaria lemaneiformis. The highconcentrations of NO3-in the culture medium could improve the Pi uptake rate of Gracilaria.lemaneiformis, but the high concentrations of Pi in the culture medium could inhibit theNO3-uptake rate of this alga.â…¡ Eitherincreased temperature or increased incubation densities could inhibit therelative growth rate in Porphyra haitanensis. The photochemical efficiency in P.haitanensis displayed the same reponses. The increased incubation densities and the increasedC/P in the culture medium could improve the Pi uptake rate of P. haitanensis. In a moderaterange, the increased temperature could improve the Pi uptake rate of P. haitanensis, but hightemperature could inhibit it.â…¢Either increased nutrients or increased incubation densities could inhibit thephotochemical efficiency of P. haitanensis. The Pmax, α, Rd, Ikand Icof P. haitanensis grown at high incubation densities and high nutrients conditions were higher than other treatments.These results indicated that the increased nutrients and the increased incubation densitiescould improve the photosynthetic capacity of P. haitanensis. The Pi absorptive capacity andthe uptake rate of P. haitanensis is much lower than the N absorptive capacity and uptake rate.In conclusion, environmental conditions such as CO₂, incubation densities andconcentration of nutrients would significantly affect the physiological characteristicsof Gracilaria lemaneiformis and Porphyra haitanensis, especially the uptake characteristic ofnutrients. Therefore we proposed that the environmental conditions under which themacroalga are grown should be taken into account when they are considered to be used tosolve the ongoing problem of coastal eutrophication.