Nutrients Absorption Of Aquaculture Wastewater And Bioremediation Of Sea Area By Macroalgae

Eutrophication and red tide have become a global environmental problem. A very real issue in front of researchers all over the world was how to control eutrophication effectively and without side effects. Numerous studies have confirmed that the large-scale cultivation of seaweed was an effective means of in-situ remediation to treat the eutrophication of coastal waters and serious pollution of the mariculture sea. This approach has many advantages such as simple, economy, environmental protection, safety and so on. This paper has studied the biological purification of aquaculrure wastewater by Ulva pertusa and Porphyra haitanensis, and the bioremediation effect of waste water by Ulva pertusa that cultured in pool, and the ecological restoration of eutrophication of open sea and semi-enclosed bays by some macroalgae, as well as the growth inhibition by extracts of Porphyra haitanensis to Skeletonema costatumum, Phaeocystis globosa and Alexandrium tamarense. The results were as following:1. The biological purification of aquaculrure wastewater by Ulva pertusa and Porphyra haitanensisUlva pertusa and Porphyra haitanensis proved to be effective in removing nutrient N and P. The removal of NO3-N by Ulva pertusa was around99.8%, NO2-N99.6%, NH4-N95.9%, PO4-P98.7%and DIN98.6%. The removal was around NO3-N99.8%, NO2-N99.6%, NH4-N95.9%, PO4-P98.7%and DIN98.6%by Porphyra haitanensis. Ulva pertusa was able to absorb NH4-N as well as NO3-N and NO2-N. The major difference between two nutrients was that the absorption of ammonia nitrogen could be rapidly completed in the first day while nitrate nitrogen was absorbed mostly in two or three days. But Porphyra haitanensis gave priority to absorb NH4-N. Ulva pertusa has achieved health growth in the shrimp effluents with a satisfactory daily growth rate and maintained the steady increase in the fresh weight. TP removal was efficient, but the change of TN was minimal by Porphyra haitanensis.2. The bioremediation effect of waste water by Ulva pertusa that cultured in poolUlva pertusa that cultured in pool was used to treat waste water which include aquaculture wastewater and sewage during March to November in2011. The result showed that the quality indicators of eutrophication of waste water had significant changes after it discharged into the pond, especially in removing nutrient N and P. Study confirmed that the waste water can be effectively purified by the cultivation of Ulva pertusa.3. The ecological restoration of eutrophication of open sea and semi-enclosed bays by plant macroalgaeA large-scale cultivation of Laminaria japonica could improve water quality and reduce concentrations of DIN and DIP in Sanqi bay, Pintan Island, in which from March to May in2012, reduce percentages of DIN in the area of algal cultivation were25.48%,19.62%,44.65%and percentages of DIP were20.17%,32.00%,38.72%, respectively. However the cultivation of Gracilaria sjoestedtii and Laminaria japonica did not produce differences to Yantian coast of Sansha Bay.4. The growth inhibition by extracts of Porphyra haitanensis to Skeletonema costatumum, Phaeocystis globosa and Alexandrium tamarenseSkeletonema costatumum, Phaeocystis globosa and Alexandrium tamarense were choosed to study the inhibition by Porphyra haitanensis. The result showed that its powder exhibited promoting effect at the low powder concentration and performed inhibitory effect when concentration at high-level. Its organic solvents extracts extracted with methanol, acetone, ethyl acetate, chloroform and petroleum ether all had inhibitory effect to three red tide microalgae in which extracts extracted with chloroform was better than others. Those extracts decreased cell size, caused cavities, pieces in cells and gofers on cells mostly.