Study On The Effect Of Phytoplankton Primary Productivity From Light Intensity And Water Temperature In Meiliang Bay Of Lake Taihu At The Condition Of Eutrophication

Lake taihu Basin is playing an important role in the development of society and economy, and water environment has become increasingly prominent with the social improvement, the growth of planktonic algae has been paid more attention, the outbreak of phytoplankton impacted the daily and production life a lot.Based on field measured data, the article studied the effect of light intensity, water temperature and nutrients to phytoplankton primary productivity. We calculated the parameters of light and temperature coupling model and simulated the primary productivity, at the same time we explored the possible mechanism of phytoplankton outbreak. The article was mainly consists of two parts:l.we managed to find the regular trend by exploring the relations between primary productivity and light intensity、water temperature、nutrients. We take a further step to study the effect on the growth of phytoplankton from underwater irradiance and temperature, after analyzing the vertical distribution of phytoplankton primary productivity and respiration, the conclusions are as follows:(1) the value of respiration per algae is commonly small, and has no obvious regular trend with the vertical distribution of water temperature.(2) underwater irradiance has significant impact to the mixed phytoplankton primary productivity, due to the attenuation of water, the photoinhibition mainly occurs at the depth of 0.1-0.3m underwater.(3) all kinds of salts are inevitable nutritional factors. According to our research, when mass ratio of N/P is greater than 19, the Phytoplankton is in relatively P limit, and N/P smaller than 10 in relatively N limit. Combining with actual condition of Lake taihu, our research is consistent with current studies that relatively N limit happens in summer and P limiting in Autumn and Spring.2. Based on measured data,parameters of light and temperature coupling model were calculated and evaluated. The combining effect of light intensity and temperature was analyzed and provide evidence to understand relative ecological mechanism. Two conclusions are reached:(1) light intensity and temperature was considered as the main limiting factors, the most suitable water temperature of mixed Phytoplankton is 27.5℃, the optimal irradiance of the mixed phytoplankton increases first and decreases along with the increasing of the water temperature, the optimal irradiance at 27.5℃ is 3.4 (106J/m2*4h);(2) the nutrition part of the model indicated a potential production rate of 0.32(mg/l*4h)in eutrophication water of Lake taihu at an ideal irradiance and temperature condition...