| Climate warming is the main feature of the climate change. There is obvious regional difference in regional climate warming level. At the same time, the variations of climate factors can affect regional waters, for example, lakes and wetlands, furthermore, their water qualities and growth of aquatic organisms in water.The climate change at the Taihu Lake area has regional feature. The events of harmful algal bloom and water quality deterioration, due to climate warming and urbanization, have caused the ecosystem service function of Taihu Lake decline. It has been widely accepted that climate warming can help to bring about a development of algal bloom. The research topic of the effects of climate change on ecological enviroment is related to climatology and ecology,the writer of the thesis will further study the climate change in recent 50 years and its effect on ecological environment in Taihu Lake.This thesis is focused on the analysis and simulation of the effects of climate change on eco-environment of Taihu Lake. Based on the climate statistics methods, GAM, EMD,DYRESM-CAEDYM, the spring and summer climate change characteristics in Taihu Lake were studied. Besides, seeking out the key controlling factors of chlorophyll a concentration and dissolved oxygen concentration in different parts of the Taihu lake, where are with different eutrophic waters. The thesis also proved that air temperature and total nitrogen all play the important roles in spring phytoplankton succession. Furthermore, the variation features of water temperature, concentration of chlorophyll a, dissolved oxygen and blue-green algae biomass under the influence of climate warming were also explored by analysis and modeling. The main results are listed below:1. From 1957 to 2010, the spring average temperature had a significant rising trend at a rate of 0.4?/10a. The increasing trend of the summer average temperature was not obvious.They all had a period of 5a and abrupt temperature change in the early in 21th century. The annual, spring, and summer sunshine hours showed a very similarly downward trend, but they all had an abrupt in 2000 and subsequently the sunshine hours began to increase. The annual,spring, and summer average wind speed showed a downward trend, and there was a relative high value in 1960-1970.2. There was significant difference of chlorophyll a and dissolved oxygen controlling factors between Meiliang Bay and Center Lake in Taihu Lake. But air temperature was the main factor controlling the change of chlorophyll a and dissolved oxygen. In addition, in Center Lake, only the air temperature above 9.0?, the chlorophyll a change was related to temperature significantly. For dissolved oxygen change in Center Lake, the concentration of chlorophyll a and COD plays a very important role relative to the Meiliang Bay. Also, only the concentration of chlorophyll a above 8.17?g/L, the dissolved oxygen concentration can be affected by chlorophyll a significantly. When the COD concentration is below 6.05mg/L, the air temperature will mainly control the variation of dissolved oxygen in the Center Lakeand the Meiliang Bay.3. According to the EMD and correlation analysis, over a one-year period,air temperature and total phosphorus were the main factors that affected the change of the concentration of chlorophyll a; The inter annual variability of chlorophyll a was mainly controlled by total nitrogen and total phosphorus.4. Air temperature and total nitrogen were the key factors that controll the spring phytoplankton succession from Cyanobacteria to Chlorophyta, and 18.2? is the critical temperature. When above this temperature, Cyanobacteria dominance began to set up. The temperature increase of spring in Taihu Lake will benefit to dominance of Cyanobacteria.5. Climate change such as rainfall can obviously change the depth of water in Taihu Lake.The water temperature would change faster and stronger in relative shallow water than in deeper water. The spring is a season when Cyanobacteria grow is more suitable, as temperature gradually increasing, and with relatively strong temperature variations,Cyanobacteria would have strong dominace.6. Compare with base scenarios by modelling, when air temperature increase 1 ? and 2?,the water temperature will increase 0.22??0.52? and 0.44??1.02? repectively.Furthermore, the increase value of water temperature is different in four seasons of a year.The dissolved oxygen will decrease when air temperature increase in the two types scenarios,the decreasing values are from 0.04mg/L to 0.16mg/L, and form 0.07 mg/L to 0.30 mg/L repectively, therefore, the seasonal variation of dissolved oxygen is mainly controlled by climate factors. Climate warming can lead to annual average biomass rising. Compare with the base base scenarios, when air temperature increase 1? and 2?, chlorophyll a concentration will increase by 3.9% and 5.3 % repectively. The spring air temperature raise 2?,Cyanobacteria biomass will increase by 2.9%.7. According to RCP4.5, temperature rising will be the main feature in the future. With the increase of air temperature, the water temperature will rise, dissolved oxygen will decline,and the concentration of chlorophyll a and Cyanobacteria biomass will increase. In the future,the biomass of Microcystis aeruginosa will increase,especially in summer and autumn, and Cyanobacteria bloom will be more serious in Taihu Lake. |
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