| Eutrophication has become a serious problem in most of the sea area in china, which makes red tide breaks out frequently. At present, lots of researches about removing nutrition in the seawater and prevention of red tide through seaweed have been carried on. Seaweed can absorb large quantities of N and P, and produce large amounts of O2. This paper has studied the growth and nutrient uptake kinetics of G. lichenoides, as well as the inhibitory effects on Phaeocystis globosa, and cultivation in pond to reduce marine eutrophication. The results were as following:1. The bioremediation of sewage by cultivation of Gracilaria lichenoides in pond A productive cultivation of Gracilaria lichenoides was carried out in NO.5 pond. After bioremediation of tow days in Summer, the relative degradation rate of NH4-N, NO3-N, NO2-N, TP and Chl-a was 9.50%,22.80%,23.69%,8.08% and 66.01%, respectively. In Autumn, the concentration of NH4-N, NO3-N, NO2-N, TP, BOD and Chl-a decreased by 84.72%,82.63%,74.17%,8.99%,57.94% and 72.73%. The concentration of dissolved oxygen increased by 32.12% and seawater transparency increased by 18.52%. G. Lichenoides had a maximum specific growth rate of 5.608%-d"1 in Autumn.2. The biopurification of sewage by Gracilaria lichenoidesG. lichenoides(12g) was cultivated in the bucket with 6L sewage. All NH4-N and NO3-N of the sewage were absorbed by G. lichenoides within 11 days. In addition, the concentration of NO2-N decreased by 24.04%-98.11%, the concentration of TP decreased by 67.90%-95.63%. The sewage was effectivell purified by cultivation of G. lichenoides.3. The nutrient uptake of Gracilaria lichenoidesG. lichenoides was previously cultured for 20 days by the depletion of nitrogen or phosphorous. The study showed that the uptake rates of G. lichenoides in different initial concentrations of NH4-N, NO2-N, NO3-N and PO4-P were nonlinear and the maximum uptake rate decreased along with time. When the concentration of NH4-N, NO2-N, NO3-N and PO4-P were increased to 20.72μmol·L-1,21.63μmol·L-1,31.16μmol·L-1 and 24.11μmol·L-1, the maximum uptake rates of G. lichenoides were 90.91μmol·g-1h-1, 57.47μmol·g-1h-1,83.33μmol·g-1h-1 and 4.684μmol·g-1h-1, respectively.4. The algicidal effects of Gracilaria lichenoides on the harmful alga Phaeocystis globosaThe growth of Phaeocystis globosa was strongly inhibited by crude GLL, dry powder and aqueous extract of G. lichenoides. When Phaeocystis globosa at a initial cell density of 9×105cells·mL-1 was co-cultured with dry powder at 1-3g·L-1 or aqueous extract at 10-40g FW·L-1, the growth of Phaeocystis globosa was significantly lowered and all Phaeocystis globosa cells died within 8 days. The inhibition effect of crude GLL was better than dry powder and aqueous extract of G. lichenoides. The addition of 0.2g·L-1 crude GLL could kill all Phaeocystis globosa cells within 6 days.5. The character of G. Lichenoides lectin (GLL)GLL agglutination activity was stable below 60℃and pH6.0-10.0. It displayed some agglutination activities with erythrocytes from chicken and duck. Furthermore, GLL had antifungal and antibacterial activities. The width zone of inhibition of GLL to Canidia albicans and Bacillus subtilis (24h) was 5mm, Aspergillus niger and Colletotrichum gloeosporioides Penz was 4mm and 2.19mm(48h). The movement capacity of Pavlova virdis, Isochrysis galbana and Pyramimonas sp. could be influenced by GLL. |
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