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Effects of Microcystis Aeruginosa on Population Dynamics and Sexual Reproduction of Large-bodied Cladocerans

Author: ZhangSai
Tutor: DengDaoGui
School: Huaibei Normal
Course: Botany
Keywords: Microcystis aeruginosa Large cladocerans Population dynamics Sexual reproduction Chaohu Mesocosm
CLC: X174
Type: Master's thesis
Year: 2011
Downloads: 50
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Abstract

The cyanobacteria bloom water eutrophication triggered one of the important environmental issues of today's world within. Since the 1970s - the biological manipulation ‖ theories have been proposed, the researchers began to focus on the use of biological methods to control algal blooms. Large zooplankton (eg Daphnia genus Daphnia) effective measures to control the density of phytoplankton biomass, so as to maintain a certain number of large cladocerans (eg Daphnia genus Daphnia) can to some extent control the the eutrophic water's algae water China. Zooplankton control of phytoplankton the Daphnia genus Daphnia species different experimental results show large differences. In eutrophic water, blue-green algae blooms often occur in the warm summer and autumn. Cyanobacterial bloom period, accompanied by large cladocerans (Daphnia genus Daphnia) the dominant position of small cladocerans are often replaced, even large cladocerans (eg Daphnia genus Daphnia) populations the Midsummer weakened or disappeared phenomenon. The one hand, the field survey and mesocosm experiment Chaohu spring and summer season (March-August) of planktonic crustaceans community succession and population fluctuation genus Daphnia magna. On the other hand, the use of the experimental population ecology Microcystis aeruginosa genus Daphnia species population dynamics and reproductive conversion of several Daphnia. Order to reveal the the eutrophic water cyanobacteria bloom outbreaks with large Cladocera class (such as Daphnia genus Daphnia) populations Midsummer diminished or disappeared mechanism. The main conclusions are as follows: 1, groups of higher biomass of Microcystis important factors affect Chaohu spring and summer of planktonic crustaceans community succession. 6,7 month mesocosm and Chaohu water body cyanobacteria average biomass of 0.1 mg L ^{-1 and 0.03 mg L ^{-1 3.0 mg L ^{-1 and 6.2 mg L ^{-1 , respectively, 24% and 5% of the total algae average biomass, 50% and 64%. Enclosures during the experiment, the biomass of Microcystis always at a lower level, large Cladocera density than small cladocerans, with a significant competitive advantage, Chaohu water bodies groups Microcystis biomass at a higher level crustacean zooplankton dominant small cladocerans (like trunk Daphnia Bosmina and angularis textured magna Ceriodaphnia cornuta). The large cladocerans Daphnia only a certain population density in the Chaohu spring (April), an average of 10.4 ind L ^{-1 . Mesocosm experiment, transparent magna D. hyalina and Daphnia pulex, D. pulex population density were 84 ind · L ^{-1 and 98 ind · L ^{-1 . Mesocosm Daphnia populations spawning mother magna small proportion, and fecundity of only 1-5, 64% of the average total Daphnia population density of larvae animal. The decline in the amount of adult spawning and larval mortality mesocosm within large Cladocera Daphnia population dynamics. D. pulex, Daphnia pulex males density of 52 ind L ^{-1 53% of its population density. Density and population density of D. pulex, Daphnia pulex males showed a significant positive correlation (r = 0.997, n = 5, p lt; 0.01). Enclosures during the experiment, the the Daphnia pulex D. pulex and transparent magna empty eggs saddle proportion up to 84% and 67%, respectively. The experimental results suggest, Chaohu Daphnia population dynamics of addition by mechanical interference effects of fish predation of Microcystis and groups, food quality and population density is also important influencing factors. 3, D. pulex, Daphnia pulex and Daphnia carinata D. carinata population density and the density of males increased with the increase of the biomass of Microcystis. Individual the Daphnia carinata the D. carinata population density of more than smaller individuals of Daphnia pulex D. pulex by groups microcystin mechanical interference. The the the two Daphnia male body density increased rapidly at the beginning of the experiment, and then remained at a stable level or decline. The male body density and population density presents a significant correlation (Daphnia pulex D. pulex: r = 0.863, n = 60, p = 0.000; Daphnia carinata D. carinata: r = 0.793, n = 156, p = 0.000 ). Groups microcystin promote Daphnia pulex the D. pulex eggs saddle generation (r = 0.811, n = 12, p = 0.001), but significantly inhibited Daphnia carinata the D. carinata egg the Saddle (r = -0.798, n = 12, p = 0.002) formation. The proportion of the number of eggs saddle lower microcystin biomass, containing one or two resting eggs is relatively high, and a relatively high proportion of the number of eggs saddle excluding high microcystin biomass under resting eggs 's. The experimental results suggest that: different Daphnia species produce eggs saddle and the formation of resting eggs are two complex process. Fertilization between gender female and male body is difficult in the case of a lower proportion of males, and the results will lead to more empty egg saddle. Groups microcystin mechanical interference may accelerate the the Microcystis dominated lake Daphnia populations Midsummer weakened.}}}}}}}}

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