Grass Crap Breeding,phosphorus Cycle And Its Effect On Plankton In The Process Of Research

Understanding of phosphorus cycling approach in the aquaculture ecosystem provides theory basis with improvement of cultural benefits and decrease in phosphorus emissions.Therefore,we manipulated different phosphorus concentrations in order to study the aspects of phosphorus concentration on phosphorus cycling in intensive aquaculture ponds of Ctenopharyngodon idellus.We carried out for 64 days(sampling once a week,a total of 10 weeks)sampling survey from April 16,2014 to June 18.The main content of this experiment is to study two kinds of phosphorus content of feed on Ctenopharyngodon idellus growth,feed efficiency,the influence of the composition,abundance and biomass of plankton,and phosphorus cycle experiment in the system.Phosphorus is the restricting factor to eutrophication.The cycle of phosphorus can reflect the whole process of eutrophication and water quality change.Understanding cultivating ecological system in the phosphorus cycle approach can effectively improve breeding efficiency and provide theoretical basis to reduce phosphorus discharge.Thus it could help us to increase production and protect the water environment.The main results are as follows:1 Feed efficiency and environmental benefitsWe carried out different phosphorus content in feed on grass carp growth,feed efficiency and the effect of phosphorus cycle in the experiment system.We set two experimental treatment group,feeding with the different phosphorus content of 1.02% and 1.02% respectively in compound feed.The experimental results showed that the group with phosphorus of 1.02% had low feed efficiency of 68.4%,and the biomass of grass carp increased at a rate of 72.3%.The other group with phosphorus content 0.52% had high feed efficiency at 77.3%,and the biomass of grass carp increased at a rate of 74.3%.Low phosphorus in feed has higher feed conversion rate,and higher amount of the fish gain than the high phosphorus group.In addition,total phosphorus and total nitrogen concentrations in water and sediment content were lower in low phosphorus feed group than that in high phosphorus feed group.Our results showed that high phosphorus feed is not conducive to get higher amount of fish biomass,but too much nutrient aquaculture water discharge and serious environmental pollution.Suitable phosphorus content(0.52%)is more advantageous to gain the fish production and environmental benefits.2 The influence of different phosphorus concentrations feed on phytoplanktonThere were 21 species phytoplankton,belonging to 5phyla.The Bacillaphyta of 3 genera,green algae(Chlorophyta)of 10 genera(species),Cyanophyta of 5 genera,Euglenophyta of 1 genus(species),Cryptophyta of 1 genus,Dinophyta of 1 genus were detected in grass carp ponds.High phosphorus feed group was detected of phytoplankton biomass in 4.8~39.5 mg/L,and low phosphorus group was 10.4~50.3 mg/L.Low phosphorus feed phytoplankton biomass was significantly higher than that of high phosphorus group.We speculated that phytoplankton may accelerate the water body of the food chain material circulation efficiency.And it also explains the treatment group has a higher efficiency and higher fish feed production.Shannon-Wiener diversity index can reflect the biodiversity of the phytoplankton community.During the test,phytoplankton diversity index of high phosphorus feed group was 0.93~1.85,and was 0.76~1.61 in low phosphorus feed group.Two treatment groups exists significant differences in phytoplankton diversity.Phytoplankton diversity in low phosphorus feed group was significantly lower than that in high phosphorus feed group.3 The influence of different concentration of phosphorus in feed on zooplanktonThere were 9 genera zooplankton,belonging to 15 species during the experiment.Rotifers of 2 genera and 5 species,protozoa of 6 genera and 8 species,cladocerans of 1 species,and copepods of 1 species were found.Protozoan and rotifers are dominant species in aquaculture ponds.Protozoa and rotifer species number were up to 87% of the total zooplankton species.Through analysis of the degree of dominance,our results showed that Brachionus angularis,Asplanchnopus multiceps,Anuraeopsis fissa,and Trichocerca capuina were the dominant species.During the experiment,zooplankton density in high phosphorus feed group was 216~853 ind./L,and the biomass was 0.12~3.21 mg/L.Zooplankton density in low phosphorus feed group was 289~1129 ind./ L,the biomass was 0.15~4.57 mg/L.Biomass of zooplankton density was significantly higher in low phosphorus feed group than that in high phosphorus feed group.