Microbial Community In Tilapia(Oreochromis Niloticus) Cultrual Ponds

An aquaculture pond is a complex ecosystem with high strength intervention from the fishery producers.And the microorganisms in it can response to the excessive nutrient input to utilize them for assimilation.So it is very important to study the microbial community in aquaculture pond for the knowledge of how the ecological function and carrying capacity of the pond changes.After 2007,tilapia became the sixth largest freshwater aquaculture species behind the silver carp,the bighead carp,the grass carp,the common carp and the crucian carp.And the yield of tilapia from cultural pond account for about 50%of the total.So the pond culture of tilapia contributes a lot for aquaculture in China.In view of the above mentions,I firstly carried out the studies on communities of bacteria,archaea and fungi with the method of high-throughput sequencing.Then I studied the ammonia monooxygenase?amoA?genes' copies of ammonia oxidizing bacteria and archaea in three ponds with different stocking densities using the method of real-time PCR.And I also isolated three heterotrophic strains from one tilapia pond to study their characteristics of inorganic nitrogen using and their control capacities on inorganic nitrogen in aquaculture water.All the work done was to provide some basic data for further researches on the control of the microbial environment in aquaculture ponds.1.Spatial distribution of the bacterial community in a tilapia cultural pond in the period of peak breedingIn this study,spatial distribution of the bacterial community in a tilapia cultural pond in the period of peak breeding was carried out.The results showed that the phyla of Actinobacteria,Proteobacteria,Cyanobacteria and Bacteroidetes were the dominant bacterial phyla in pond water.The phyla of Proteobacteria,Bacteroidetes and Chloroflexi were the dominant bacterial phyla in surface sediment.And the phyla of Fusobacteria,Proteobacteria and Firmicutes were the dominant phyla in the end of intestines.In addition,the studies on the abundance and the diversity of bacterial communities in these three types of environmental media showed that there was much higher abundance and diversity in surface sediment than in other two media.And through the comparisons of common OTUs in the three media,we found that there were more common OTUs between the sediment and the end of intestine,which might indicate that there were more bacterial communications between these two media.2.The effect of water hyacinth planting on the planktonic bacterial community in a tilapia cultural pondThe differences of bacterial communities between the open water area and the water hyacinth planting area were studied.The results showed that there was higher abundance of Cyanobacteria in water hyacinth planting area than that in open water area.At the same time the increase of the Cyanobacteria abundance was accompanied by the abundance reduce of other main phyla.The study on the abundance and diversity of the planktonic bacterial communities showed that they decreased in water hyacinth planting area,and they showed negative correlations with the concentrations of nitrite and chlorophyll A in water.3.The differences of water qualities,sediment conditions,and growth-related traits in three tilapia cultural ponds under different stocking densities.Three ponds in which the GIFT tilapia were cultured with three different stocking densities?18000 fish/ha,22500 fish/ha and 27000 fish/ha?were used to study their water qualities,sediment conditions and the growth-related traits of adult tilapia.The results are as follows:?1?the water qualities and sediment conditions in the three ponds changed with the change of time.?2?There were significant differences between different ponds for sediment conditions,but no significant differences were found for water qualities.?3?Not only the specifications of the adult fish,but also the effect of the other growth-related traits on the body weight were different between different ponds.To sum up,the physical-chemical factors and the biological factors were all affected by the stocking actions with different densities.4.The dynamic changes of bacterial community in three ponds with tilapia stocked in different densitiesOn the whole,with the changes of the time?May,July,September,October?,the compositions of main phyla in water was stable.The differences reflected between different months were only the relative abundance of them.Among them,the abundance of Proteobacteria was some stable,however the abundance of Cyanobacteria and Actinobacteria changed dramatically.The highest value of planktonic bacterial communities' abundance and diversity appeared at September and October respectively.Between the three ponds,most of the planktonic phyla showed no significant differences in abundance,and no significant differences were found for the abundance and diversity of the planktonic bacterial community.And on the base of bacterial community,the similarity analysis was done on the water samples.The results showed that the variable of time was the main factor affecting the samples grouping.The main compositions of the phyla in sediment samples were more stable with the changes of time than that in water samples.The top four phyla in order were always Proteobacteria,Bacteroidetes,Chloroflexi and Acidobacteria.The highest value of bacterial communities' abundance and diversity in sediment appeared at October and July respectively.On the basis of bacterial community,the similarity analysis was also done on the sediment samples.The results showed that the variable of pond was the main factor affecting the samples grouping.5.The dynamic changes of archaeal community in three ponds with tilapia stocked in different densitiesThe compositions of the archaeal community in "phylum" level in both water and surface sediment samples were Euryarchaeota,Crenarchaeota,Thaumarchaeota and some phylum-not-be determined types.Among them,Euryarchaeota was the dominant phylum,and another phylum also occupying a larger abundance was Thaumarchaeota.And in"family" and "genus" level,Deep_Sea_Hydrothermal_Vent_Gp₆?DHVEG-6?_norank,Methanosaeta,Marine_Benthic_Group_Dand_DHVEG-1_norank,Methanoregula and Methanomicrobiales_unclassified appeared high abundance in both water and surface sediment samples,showing that they responsed significantly to the intensive pond culture of tilapia.With the change of time,the abundance and diversity of archaeal community in water appeared the downward trend;however they showed no significant differences between different ponds.In surface sediment,the abundance and diversity of archaeal community were affected by both pond and time variables.With the change of time and stocking densities,they all showed increasing trends.On the basis of archaeal communities,the similarity analysis was done on the water samples and sediment samples.The results firstly showed that the time was the main factor affecting the grouping of water samples.And then the grouping of the sediment samples could not be found clearly,nonetheless,there was a trend that the samples being grouped upon the variable of pond with different stocking densities.6.The dynamic changes of fungal community in three ponds with tilapia stocked in different densitiesIn this study,most of the fungal OTUs could not be classified using the database of"Unite".The analysis on the OTUs having been classified showed that the phylum of Basidiomycota had the highest abundance in both the water and the sediment samples,and the second important phylum was Ascomycota.The abundance and diversity of fungal community in both the water samples and the sediment samples showed the trends of fall-and-rise and rise-and-fall with the change of time and stocking densities respectively.On the basis of fungal community,the similarity analysis was done with the water samples and the sediment samples.The results showed that the time was the main factor affecting the grouping of water samples.While,the grouping of the sediment samples was affected by both the variables of time and the ponds with different stocking densities.7.Ammonia monooxygenase?amoA?genes' copies of ammonia oxidizing bacteria and archaea in three ponds with different stocking densitiesWith the change of time,the copies of amoA gene from ammonia oxidizing bacteria?AOB?in water appeared the trend of rising-and-falling.And there were no significant differences between different ponds.In the sediment samples,the copies were affected by the variables of both the time and pond.With the change of time,they appeared the trend of rising-falling-rising.And between different ponds,they appeared the trend of increasing with the increase of the stocking densities.The copies of amoA gene from ammonia oxidizing archaea?AOA?in water were affected by the variable of time,but not by the variable of pond with different stocking densities.With the change of time,the copies appeared the trend of rising-and-falling.In the sediment samples,the copies were all affected by the variables of time and pond.They also showed the trend of rising-and-falling with the time changing.With the increase of stocking densities,the copies increased.The ratio of the amoA gene copies AOB to AOA was studied,the results showed that the amoA gene copies from AOA were larger than that from AOB in both water and sediment samples.8.Exploration of three heterotrophic nitrifying strains from a tilapia pond for their characteristics of inorganic nitrogen use and application in aquaculture waterThree heterotrophic nitrifying bacterial strains,HLf01,HBfOland HHfOl,were isolated from a pond where genetically improved fanned tilapia?GIFT??Oreochromis niloticus?was intensively cultured during the annual peak breeding period.Analysis of biochemical,morphological characteristics and sequences analysis of 16S rDNA identified strains HLf01 and HBf01 as Pseudomonas sp.,and strain HHf01 as Acinetobacter bazumannii.The studies on the characteristics of inorganic nitrogen using were carried out;the results showed that they were different from the efficiency of inorganic nitrogen removal and organic carbon consuming.Also,the test of the three strains on aquaculture water showed similar results of efficiency of ammonia nitrogen removal with the test of inorganic nitrogen use.