Research On The Effect Of Ipomoea Aquatica Floating-Bed Used In Intensive Fish Pond

In recent years, biological floating-bed technology has been introduced into the aquaculture industry to purify water quality and improve breeding efficiency. This study aimed to determine the purification characteristics and effects of intensive fish pond water by Ipomoea aquatica floating-bed, analyze the combined effect of Ipomoea aquatica floating-bed used in intensive fish pond, based on the water tank test and the pond test. Finally, this study aimed to provide more scientific basis for aquaculture and water pollution control. The results are as follows:(1) Two kinds of treatments (different density and harvest) were used to study the characteristic and effect of eutrophic water purification by Ipomoea aquatica in water tank. After12days outdoor culture, the removal rate of NO2--N, NO3--N, PO43--P, TN, TP and Chl-a in high density group (10g/L) were90.88%,93.98%,98.96%,82.36%,88.89%and89.33%, respectively. The high density group is significantly higher than those of the control group (0g/L). It was shown that harvest would accelerate the tiller of Ipomoea aquatica, promote the absorption of nitrogen and phosphorus, and improve the DO in water. The phosphorus and nitrogen concentration of the plant tissue changed, indicating that positive correlation with the growth of the water body of the phosphorus and nitrogen. It was also shown a positive correlation between the nitrogen removal rate and the plant density. The high density group (10g/L) of Ipomoea aquatica removed52.05%of TN and40.41%of nitrogen.(2) From June to October in2011,4traditional "four major Chinese carps" intensive fish ponds (7000m2per pond) with7.5%coverage of Ipomoea aquatica floating-bed, and2fish ponds with no floating-bed ponds (as control) were treated to study the effects of water quality, phytoplankton, economic efficiency and ecological benefits by Ipomoea aquatica floating-bed. The results showed that:①There is no significant reduction of DO was found in treatment pond. However, NO2--N, NO3--N, TN, PO43--P, TP, and Ch1-a had significant removal efficiencies by Ipomoea aquatica floating-bed, removal efficiencies were47.68%,25.17%,24.75%,75.27%,49.70%and24.15%. At the end of experiment, it was shown that biological floating-bed can absorb400.94±199.85g suspended solids (dry weight) per square meter, and the transparency of the treatment ponds was significantly higher than that of the control ponds, which has a positive significance to reduce sediment.②During the period of the investigation,236species (including subspecies),99 genus of phytoplankton belonging to8phyla were observed, most species (215species,89genus,8phyla) were identified in coverage area of the treatment ponds. The dominant species trended as follows:coverage area (28species)> open water (23kinds)> control pond (14species). The phytoplankton mean desity and biomass of control pond was (8.21±0.36)×108ind/L and195.89±9.81mg/L, which was significantly higher than those of the treatment pond. The biodiversity index (H’, D, D’, J) trended as follows:coverage area> open water> control pond, which meant that the diversity and evenness of phytoplankton in the treatment pond has been improved by laying biological floating-bed.③The statistical result showed that, survival rate of fish in the treatment pond was92.2%, significantly higher than that of the control pond,87.7%. The fish feeding artificial in the treatment pond grew significantly higher than that of the control pond. The profit of the treatment pond was3757.51yuan/667m (1.74times of the control pond). The nitrogen and phosphorous utilized by the fish in the treatment pond were39.07%and34.75%, significantly higher than those of the control pond (31.64%and29.27%). The nitrogen and phosphorous utilized by Ipomoea aquatica floating-bed were5.77%and1.92%, which showed relatively low proportion, were determined by the laying density.In summary, the use of Ipomoea aquatica floating-bed in intensive fishpond, can purify the breeding water quality, balance algae phase, reduce farming risk, improve fish survival and growth rates, enhance fish energy conversion efficiency, and increase the profits of culture. Therefore, Ipomoea aquatica floating-bed has a good application prospects in the aquaculture industry.