Behavior Study On The Role Of Irradiance And Temperature On The Algae Bloom Of Typical Algae In Three-Gorges Valley

The Three-Gorges project had been well known to most people in the world for a long time, which is a huge and famous water hinge conservancy and has obvious economical benefit and engineering functions such as shipping, preventing flood and generating electricity. In the meanwhile, the structure and function of its zoology environment will be influenced obviously because of the form of the Three-Gorges reservoir. After the Three-Gorges reservoir's erection, the flow velocity of Yangtze River and branch rivers becoming slower, the self-clean capacity of the water body decreased, the temperature difference lessened and the light intensity strengthened, the water-level-fluctuating zones formed along both sides of the river and the more gentle backwater area formed in estuary abouchement section—all these will have a direct impact on algae succession, proliferation and clustering behavior, because of the hydrodynamic conditions change, the phytoplankton species and quantity would normally change, and even appear "blooming" and lead to outbreaks of algal blooms. The occurrence of eutrophication is a complex and dynamic process, from the appearence, multiplication, congregation of planktonic algae to form a series of campaign development process, these processes roughly divided into three phases:(1) a high degree of concentration of nutrients start lead to the rapid growth of algae proliferation;(2) the rapid development of algae quantity consumed a great deal of nutrients, resulting nutrient concentrations have declined;(3) The nutrient concentrations decrease, which will affect a large number of algae reproduction and death. This largely reflects the eutrophication in the inception and development, maintenance to the whole process of death. Therefore, the change of phytoplankton grasped for the eutrophication of the reservoir and the implementation of ecosystem management is of great significance especially for cause "algal blooms" was the typical outbreak of the biological dynamics of the study are particularly important.Based on studying the algae characteristics and seasonal succession laws of Three-Gorges reservoir area typical of the Yangtze River and Jialing River Basin water, the author found that there were6planktonic algae, 36 genera and 80 species (including varieties) from November 2007to October 2008. In the composition of algae community, the Bacillariophyta has the absolute domination (52.5%), and then are Cyanophyta and Chlorophyta, and the proportion of others, less. Bacillariophyta cell density percentage was quite high. The Bacillariophyta density of Jialing River water accounted for a higher proportion in spring and a lower proportion in autumn compared with Yangtze River and differences in other seasons were not obvious. The cell density proportion of Cyanophyta in Yangtze and the Jialing River, comparatively low, were not more than 12.3% and12.2% respectively and the growth peak occurred in spring. Cell density percentage of Chlorophyta in Yangtze River both in spring and winter was the highest, and its proportion in autumn was the lowest.According to planktonic algae's growth characteristics in Yangtze River and Jialing River Typical of Three Gorges reservoir area, the thesis, integrating laboratory simulation method, studied systematically the impact of the major environmental factors (light intensity and temperature) after the formation of Three Gorges reservoir on the growth of algae. Chlorophyta and Cyanophyta are the main algae types in static water under different light intensity. We proposed a model of description on the relationship of temperature and irradiance with Bf. This model clearly shows that the growth optimal light intensity (Iopt) of typical algae gradually increases to be maximum of 4500 lx-5200 lx with temperature (t) gradually changes from 25℃to 30℃. Iopt of typical algae decreases to 1195lx as temperature up to 30℃. Asymmetric inverse V-shape Iopt curve can be well described by Blanchard's equation. The Bf of Chlorophyta and Cyanophyta have two obvious peak values, one is under 4500 lx-5200 lx light intensities, and the other one is 2600 lx. The results demonstrated that occurrence of the algae bloom was decided by light and temperature in the Three-Gorges Valley area in spring and summer season.