Study On The Character Of Chlorophyll-a Vertical Distribution Of The Lakes In Changchun

Eutrophication which is one of the global environmental problems, has become themost serious one on water pollution. Excessive nutrients in eutrophic water may makephytoplanktons propagate and water quality worsen, sometimes even arise algae bloom. Sothe structure and function of plankton population can reflect the deterioration and changes ofwater quality. Chloroplast as a key functional organ in phytoplankton is one of the targetorgans for water quality monitoring, whose function and temporal and temporal dynamics arerealized by photosynthesis of chlorophyll. Thus, it will be a good way to find out the waterquality, extent of eutrophication and the distribution and dynamic characteristics of nutrientsin water, especially for N and P. The paper aiming at four shallow lakes with different water quality and nutrition types,choosing chlorophyll-a as the monitoring index, compares the vertical distributioncharacteristics of chlorophyll-a, and the effects of ecological factors such as temperature, DO,pH, turbidity, and transparency. The results are as follows.(1) There are obvious differences in the vertical distribution of chlorophyll-a for the fourlakes. The sequence of the four lakes in which chlorophyll-a concentration is from low to highis Shitoukoumen Reservoir, Jingyue Pond, Xinlicheng Reservoir and South Lake. Theconcentration of chlorophyll-a is almost the same at each layer of Shitoukoumen Reservoirand Xinlicheng Reservoir. And the concentration in the Jingyue Pond has a great differencewith the change of depth, and exhibits an inversion S-shaped distribution. South Lake has thehighest chlorophyll-a concentration in the four lakes, but without regular distribution in thewhole water。(2) Through correlation analysis and significant test for vertical distribution ofchlorophyll-a and ecological factors of the four lakes, the results show that: there is asignificantly positive relation between the distribution of chlorophyll-a and temperature, DO,pH and turbidity in Shitoukoumen Reservoir. And in Xinlicheng Reservoir, there is asignificantly positive relation between the distribution of chlorophyll-a and pH and turbidity,but negative with temperature and DO. The distribution of chlorophyll-a in Jingyue Pond hasa positive relation with the factors except transparency。(3) When determining the trophic types of the four lakes by chlorophyll-a, DO,saturation of DO and total content of P, Shitoukoumen Reservoir, Jingyue Pond andXinlicheng Reservoir all belong to mesotrophic water, and South Lake belongs to eutrophicwater.(4) The data obtained by continuous monitoring for two month indicates that theconcentration of chlorophyll-a in the South Lake has reached the level of eutrophication. Thetrends of vertical change are similar for the five samples,though each sample has its ownenvironmental characteristics.(5) There is close relation between the dynamic changes of chlorophyll-a distribution andecological factors in South Lake. During the investigation, the concentration of chlorophyll-ais negative with temperature and DO, and positive with pH and transparency.Although the research is just the pilot study for vertical distribution of chlorophyll-a, it isan effective way to recognize and grasp the effects of nutrients and ecological factors oneutrophication, and provides basic researches on eutrophication mechanism and hydrology ofnutrient dynamic changes for further study. Therefore, it is necessary to make use of dynamiccharacteristics of lakes and choose adaptive time to cut off the input of nutrients, and establishwise prevention and cure measures.