The Effect Of Several Kinds Of Aquatic Plants And Animal On Controlling Algae In Eutrophic Water

Eutrophication is the process of the deterioration of water quality, and that is algal blooms, lower transparency and dissolved oxygen due to the excessive concentration of nitrogen and phosphorus in urban water body. Because of the prominent problem, remediation technology of water environment becomes more important. Small urban landscape water bodies have the shortcoming of small and poor self-purification ability, so under simulated conditions we used two means to control algae biomass and nutrient concentrations in order to purification water by aquatic plants and animal.Using the annual plankton population changes of natural water as contrast, we studied the relationship of water temperature, dissolved oxygen, pH, Total Nitrogen, Total Phosphorus and the other environmental factors, and analyzed the role of every studied environmental factor in the process of algae growth. In the spring and summer, stocking Aristichthys nobilis can effectively prevent from algal blooms. By feeding different densities of the planktivore, we studied it fed on planktonic algae in the simulated water, and combined with the result of the changes of the environmental factor to investigate a reasonable of Aristichthys nobilis's single-species stocking density.As we known, submerged plants having the ability of absorption, the plant systems can effectively enriched nutrients and then degraded high concentration of nutrients in water. Thus, submerged plants can inhibit the growth of phytoplankton and increase water transparency. In this study, we transplanted submerged plants into the water of high algae density, compared the same biomass of Hydrilla verticillata, Vallisneria natans, Potamogeton malaianus, Potamogeton maackianus, Potamogeton crispus's absorption of nitrogen, phosphorus nutrients, and its functional intensity on algae biomass.1. We evaluated the present situation of the nature water quality, and 8 phyla,55 genera of phytoplankton were detected from November 2008 to October 2009. Mostly what we had surveyed were Chlorophyta, Cyanophyta and Bacillariophyta, accounted for 76.2% at genera level. Then the analysis revealed the annual of population composition and species number of phytoplankton had a massive difference.2. All the biochemical indicators of the nature water had a remarkable periodicity. Total nitrogen monthly average ranged 0.21-6.78 mg/L, and total phosphorus ranged 0.093-0.547 mg/L. In addition, total algae biomass (Ta) and total phosphorus (TP) had remarkable correlation, and the regression equation:Ta=-123.304+925.208×TP (R=0.654). The relativity was not distinct between phytoplankton biomass and total nitrogen. Between other environmental factors also existed closer correlativity.3. The different controlling effect when the stocking density of Aristichthys nobilis was different, although the condition was the same. The algae decreased with time accumulating when the fish density was 0.29g/L, and kept the lower biomass in the later period. However, when the density of fish was 0.57g/L and 0.86g/L, the algae biomass would reincrease in the later period. So the density of Aristichthys nobilis between 0.29-0.57g/L could especially better for managing algae.4. Between the body weight of Aristichthys nobilis and biomass of algae, total nitrogen, total phosphorus showed extremely positive correlation. There was the most significant effection on removing algae and total nitrogen, total phosphorus when stocking density was approximately 0.29g/L by ANOVA analysis.5. Compared the removal efficiency on nutrients between these five submerged plants under the same experiment condition, knew that the total nitrogen sequence was Potamogeton malaianus> Hydrilla verticillata> Vallisneria natans> Potamogeton maackianus> Potamogeton crispus, and the total phosphorus was Potamogeton malaianus> Hydrilla verticillata>Potamogeton maackianus> Vallisneria natans> Potamogeton crispus.6. Compared with control group, it was showed that Potamogeton malaianus had the best effect on purifying the water quality and controlling the biomass of algae, Vallisneria natans and Potamogeton maackianus, Potamogeton crispus had taken the second place. Hydrilla verticillata had the significant removal effect on total phosphorus (p=0.000) and phytoplankton (p=0.010), except total nitrogen (p=0.209).