| As the rapid development of aquaculture industry, the pollution of the culture waters become more and more serious,because of the corruption of culture animals'excreta and accumulation of the bait in recent years. Macroalgae can absorb nitrogen, phosphorus and other nutrients during its growth progress, so it can be used as an important tool for restoring the coastal environment.It's functions increasingly get many attentions of people.In the species of economic macroalgae that have been artificial bred in large-scale, Gracilaria has many features,such as it has good adaptabilities,it can grow fast and has a large nutrition store,et al,so it is the ideal repair tool and management tool to the eutrophic sea area. In this thesis, G. lichenoides and G. tenuistipitata var. liui were made as the experiment material, compares effects of temperature, salinity and light intensity on nitrogen and phosphorus uptake rates of two species of Gracilaria and the effects of different concentrations of nutrient and nutrient concentration changes on the physiology, growth and biochemical compositions of the two species of Gracilaria. Besides, a preliminary study on effects of different environmental conditions on chlorophyll fluorescence parameters of the two species of Gracilaria by using chlorophyll fluorescence was conducted. This study can be a theoretical basis that which species of Gracilaria can be chosen as the restoring in the culture waters. So it has important theoretical and practical meanings to the improvement and restoring of the cultuture waters, and it also is important to the sustainable development of aquaculture.The main results were summarized as followings:1. Effects of N and P on the growth and biochemical composition of Gracilaria lichenoides and G. tenuistipitata var. liui were compared under the conditions of laboratory. The results showed that concentration of N and P had different effects on two species. For G. lichenoides, in the conditions of moderate N and P (N:10μmol·L-1, P:3μmol·L-1), it achieves the maximum growth rate and the highest content of chlorophyll a, carbohydrate and protein. For G. Grateloupia, in the conditions of moderate N and P (N:10μmol·L-1, P:3μmol·L-1), it achieves the highest content of chlorophyll, the highest content of protein. In the conditions of low concentration and moderate P (N:10μmol·L-1, P:3μmol·L-1), it gets the highest content of carbohydrate. Generally, the requirements of the nutrient concentrations of G lichenoides are higher than the requirements of G tenuistipitata var. liui relatively from the results of the present study.2. Effects of temperature, salinity and light intensity on uptake rates of different state compounds of nitrogen and phosphorus of G. lichenoides and G. tenuistipitata var. liui were compared under the conditions of laboratory. The results showed that temperature and light intensity have a significant effect on uptake rates of different state compounds of nitrogen and phosphorus of the two species of Gracilaria(P< 0.05). G lichenoides had a higher uptake rate of different state compounds of nitrogen and phosphorus when the temperature was 25-35℃and the light intensity was 120-200μmol·m-2·s-1.And when the temperature was 25-35℃and the light intensity was 120μmol·m-2·s-1, G. tenuistipitata var. liui had a higher uptake rate of different state compounds of nitrogen and phosphorus. Temperature and salinity also had a significant effect on uptake rates of different state compounds of nitrogen of the two species of Gracilaria(P<0.05). Salinity had a significant effect on uptake rates of phosphorus of G. lichenoides(P<0.05),however,it had no effect on uptake rates of phosphorus of G. tenuistipitata var. liui(P>0.05). When the temperature was 25-35℃and the salinity was 35-40, G lichenoides had higher uptake rates of different state compounds of nitrogen and phosphorus.And G. tenuistipitata var. liui had higher uptake rates of different state compounds of nitrogen and phosphorus,when the temperature was 25-35℃and the salinity was 20-25.3. Effects of nutrient concentration changes on growth, biochemical compositions and physiology of G lichenoides and G. tenuistipitata var. liui were compared under the conditions of laboratory. The results showed that different forms of nutrient concentration changes have different impacts on growth, content of PE, chlorophyll-a, total carbon, total nitrogen,NR activities and CAT activities of the two species of Gracilariae. G lichenoides has the best growth in the middle concentration of nutrient. G. tenuistipitata var. liui has different growth which depends on the concentration of nutrient in the preliminary environment. Generally, the content of PE, chlorophyll-a, total carbon, total nitrogen and NR activities of the two species of Gracilariae will be increased when the nutrient concentration changes from 3μmol·L-1 to 45μmol·L-1 and 150μmol·L-1. However, when the nutrient concentration changes from 45μmol·L-1 and to 3μmol·L-1 those data above-mentioned will decline. It has no effects to the NR activities of the two species of Gracilariae when the nutrient concentration mutually changes from 45μmol·L-1 to 150μmol·L-1.The activities of CAT will decline dramatically as the concentration of inorganic nitrogen increases. When the nutrient concentration changes from 3μmol·L-1 to 150μmol·L-1, the CAT activities of the two species of Gracilariae decline dramatically. Oppositely, when the nutrient concentration changes from 150μmol·L-1 to 3μmol·L-1, the data are increased somewhat. Comprehensive comparison shows that G. tenuistipitata var. liui is much susceptible to be influenced by the nutrient concentration changes in the environment, and it's adaptability of nutrient concentration changes may be lower than G lichenoides.4. FL3500 submersible fluorometer was used to research effects of nutrient concentration changes,different temperatures, salinities and light intensities on chlorophyll fluorescence of G. lichenoides and G. tenuistipitata var. liui under the conditions of laboratory. The results showed that within 24h of the nutrient concentration changes, chlorophyll fluorescence parameters of the two species of Gracilaria had fluctuations.Two days later, chlorophyll fluorescence parameters of G. tenuistipitata var. liui would be steady.However,chlorophyll fluorescence parameters of Gracilaria lichenoides would have a fluctuation,more or less.Ten days later, chlorophyll fluorescence parameters of the two species of Gracilaria would be unanimous. Fv/Fm and Fm/Fo of the treatment that the nutrient concentration changed to 45μmol·L-1 were higher than the other two treatments. G. lichenoides's Fv/Fm and Fm/Fo were higher than G. tenuistipitata var. liui.However, the changes of AF4 was contrary to Fv/Fm and Fm/Fo. Fv/Fm and Fm/Fo of G. tenuistipitata var. liui were higher when the temperature was 25-35℃, light intensity was 160μmol·m-2·s-1 and salinity was 20-25.And when the temperature was 25-35℃, light intensity was 160μmol·m-2·s-1 and salinity was 25-30, G. lichenoides would have high Fv/Fm and Fm/Fo.When the temperature was 15℃,ΔF4 of the two species of Gracilaria would be lower.
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