The Effect Of Phosphorus, Temperature And Illumination On Interaction Among Cyclotella Sp.-D. Magna-C. Demersum Co-culture

Eutrophication has become one of the more preminent environmental problems in China. According tothe statistics, the eutrophication lakes caused by nitrogen and phosphorus pollution accounts for77%of thestatistical lakes in our country. Serious eutrophication can result in the destruction of water ecologicalstructure, accelerating the aging process of the water. How to control the eutrophication of water body andthe resulting blooms outbreak becomes one of the hot spots environmental science, freshwater ecology andlimnology research. A large number of studies have shown that, ecological restoration is an effective way tocontrol the bloom, which can be realized through two kinds of measures: Biological manipulation andReconstruction of large aquatic plants. And phosphorus concentration is one of the key parameters affectingthe biological manipulation and large aquatic plants reconstruction. Besides, there is closely relationbetween temperature, illumination and blooms outbreak, the growth large aquatic plant. Therefore,according to the characteristics of domestic eutrophication of water bodies, this reseach established themicro model of the universe containing phytoplankton (Cyclotella sp.), zooplankton (Daphnia magna) andlarge aquatic plants (Ceratophyllum demersum), studying their respective growth situation and theconsumption of nitrogen and phosphorus in water under different phosphorus concentration, temperatureand light, viewing to reveal the effecting mechanisms on the interaction between the three conducted byphosphorus concentration, temperature and light.Through the experiment, it get the following conclusion:(1).Set the nitrogen concentration of the medium to11mg/L, phosphorus concentration gradient to0.05mg/L,0.1mg/L,0.5mg/L and2mg/L, temperature for culture conditions25℃, the light intensity2600lx, light:darkness14h:10h. While co-culturing Cyclotella sp. with Daphnia magna, the growth rate ofCyclotella sp. and is in direct proportion to the phosphorus concentration, the growth rate of Daphniamagna far outweigh Cyclotella sp.. While phosphorus concentration not more than2mg/L, Daphniamagna has significant inhibitory effect on Cyclotella sp.(P<0.05). While co-culturing Cyclotella sp. withCeratophyllum demersum, the two growth rate are proportional to the phosphorus concentration. But when adopting phosphorus concentration0.05~0.5mg/L, Ceratophyllum demersum is dominant. Whenphosphorus concentration2mg/L, Cyclotella sp. is dominant. When Cyclotella sp., Daphnia magna andCeratophyllum demersum are co-cultured in the incubator, the growth rates of Cyclotella sp. and Daphniamagna are proportional to the phosphorus concentration. The growth rate of Ceratophyllum demersum isinversely proportional to the phosphorus concentration. The growth rates of Cyclotella sp. is significantlylower than the one in the co-culture of Cyclotella sp. with Daphnia magna or the co-culture of Cyclotellasp. with Ceratophyllum demersum. The best effect of controlling alga is reflected in phosphorusconcentration0.05~0.5mg/L.(2).Set the nitrogen concentration of the medium to11mg/L, phosphorus concentration gradient to0.05mg/L,0.1mg/L,0.5mg/L and2mg/L, the light intensity for culture condition2600lx, light:darkness14h:10h, Temperature gradient15℃,20℃,25℃and30℃. Conducting the temperature15℃, theCyclotella sp. growes negatively under all phosphorus concentrations, and the growth rates ofCeratophyllum demersum and Daphnia magna are higher than the Cyclotella sp., concludeing that there isno great impact on controlling water bloom. Under the condition of temperature20~25℃, phosphorusconcentrations in0.05~0.5mg/L, Ceratophyllum demersum and Daphnia magna grow well, getting agood effect of controlling water bloom. At30℃, when phosphorus concentrations below0.05mg/L,Cyclotella sp. growes negatively. Furthermore, when phosphorus concentrations0.1~2mg/L, it is notbeautiful to control algae.(3).Set the nitrogen concentration of the medium to11mg/L, phosphorus concentration gradient to0.05mg/L,0.1mg/L,0.5mg/L and2mg/L, temperature for culture conditions25℃, light:darkness14h:10h, light intensity gradient1000lx,2600lx,4200lx,5800lx. When light intensity is between1000lx-2600lx, the both growth rates of Ceratophyllum demersum and Daphnia magna are higher thanCyclotella sp. under all phosphorus concentrations. When light intensity is between4200lx-5600lx,phosphorus concentrations play a stronger role on the controlling algae than the influence of illumination.Besides, it reveals good effect to control algae when phosphorus concentrations in0.05~0.5mg/L. Thegrowth rate of Cyclotella sp. at the phosphorus concentration of2mg/L is higher than that ofCeratophyllum demersum, so that the2mg/L phosphorus concentration is bad for reconstruction of large aquatic plants.(4).Set the nitrogen concentration of the medium to11mg/L, phosphorus concentration gradient to0.05mg/L,0.1mg/L,0.5mg/L and2mg/L, temperature for culture conditions25℃, the light intensity2600lx, photoperiodic gradient10h:14h,12h:12h,14h:10h,16h:8h. Taking photoperiodic10h:14h,Cyclotella sp. growes negatively under all phosphorus concentrations, with the growth rates ofCeratophyllum demersum and Daphnia magna conditions being lower than that in other photoperiod.When applying photoperiod12h:12h or14h:10h, phosphorus concentrations between0.05~0.5mg/L,Daphnia magna and Ceratophyllum demersum grows best, while Cyclotella sp. is obviously inhibition. Butwhen phosphorus concentration2mg/L, it is not beautiful to control algae. It is reflected in photoperiodic16h:8h to control algae best.To sum up, the effect of controlling algae by Biological manipulation and Reconstruction of largeaquatic plants is significantly affected by the phosphorus concentration, temperature and illumination. Theeffect controlling algae weakened with the increase of phosphorus concentration between0.05~2mg/L.And the effect weakened with the increase of temperature in15~30℃temperature range. Also it weakenedwith the increase of light intensity during the scope of the illumination of1000~5800lx. Setting light cycle10h:14h,12h:12h,14h:10h,16h:8h, under the condition of light increasesing with time, the effect ofcontrolling alga roughly weakened.