Effects Of Perinereis Aibuhitensis On The Occurrence Form Of Nitrogen And Phosphorus And Microbial Community Composition In Pond Sediments

There is a serious problem of nitrogen and phosphorus pollution in aquaculture,and most nitrogen and phosphorus are not used by aquaculture organisms and deposited in ponds.As the accumulation pool of nitrogen and phosphorus in aquaculture system,organic sediments play an important role in the regulation of nitrogen and phosphorus levels in aquaculture water.The form of nitrogen and phosphorus in sediments determines the adsorption and release of nitrogen and phosphorus in sediments.At present,the research on the form of nitrogen and phosphorus in sediments is mostly concentrated in natural waters such as rivers and lakes,and the distribution and transformation of benthic animals in sediments is less studied.Benthic animals are an organic part of sediments.Studying the role of benthic animals in the transformation and distribution of nitrogen and phosphorus in sediments is helpful to reveal the impact of benthic animals on ecosystems and provide data support for the application of benthic animals in pollution control.Perinereis aibuhitensis Grube is a typical benthic animal.In order to study the effect of disturbance of P.aibuhitensis on sediment in mariculture ponds,different sizes of P.aibuhitensis culture experiments were designed with 400 g/m~2 biomasses.The small size(0.7±0.3 g),medium size(2.5±0.3 g)and large size(4.3±0.3 g)treatment groups were used as the control group,and the culture period was 45 days.The temperature,salinity,p H value and dissolved oxygen of overly water were monitored regularly,and the changes of nitrogen and phosphorus nutrients in overly water were detected.Sediments were collected at the beginning and end of the experiment by five-point sampling method,and the content changes of nitrogen and phosphorus occurrence forms were determined.16S r RNA high-throughput sequence was used to detect the changes of microbial communities in sediments.The results show that:1.At the end of the experiment,compared with the control group,the effects of each treatment group of temperature,salinity and p H value were relatively small,which significantly reduced the dissolved oxygen value of coated water(P<0.05).The respiration of P.aibuhitensis and the increase in redox potential for sediments was the reasons for the decrease of dissolved oxygen in coated water.During the experiment,although the dissolved oxygen in the treatment group decreased,it was in a safe range.The concentrations of ammonia nitrogen,nitrate,total nitrogen,phosphate and total phosphorus in the water were significantly increased in each treatment group(P<0.05).Compared with the small size group,the medium and large size double-toothed sericulture has a greater impact on the nutrients in the upper water,which may be due to the strong drilling ability of the medium and large size groups,which releases more sediment particles of the water and changes the concentration of nitrogen and phosphorus nutrients in the upper water.2.At the end of the experiment,P.aibuhitensis with different specifications significantly increased the contents of ion exchangeable nitrogen(IEF-N),weak acid extractable nitrogen(WAEF-N)and strong alkali extractable nitrogen(SAEF-N)in the upper and middle layers of sediments(P<0.05),and the medium and small specifications significantly decreased the content of strong oxidant extractable nitrogen(SOEF-N)in sediments(P<0.05).Different specifications of P.aibuhitensis significantly increased the content of non-apatite inorganic phosphorus(NAIP)in the upper and middle layers of sediments(P<0.05),and medium and small specifications significantly decreased the content of organic phosphorus(OP)in sediments(P<0.05).This study showed that P.aibuhitensis with medium and small sizes could accelerate the mineralization of organic nitrogen and phosphorus in sediments,promote the upward migration of other forms of nitrogen and phosphorus in sediments,and make it easier to decompose and release,thus being used by aquatic phytoplankton.3.At the end of the experiment,the PLS-DA(partial least squares discriminant analysis)samples grouping analysis showed that the microorganisms in each treatment group changed significantly in the control group.The dominant phyla were Proteobacteria,Bacteroidota,Actinobacteriota,Firmicutes and Chloroflexi.Alpha diversity analysis showed that there were no significant differences in Shannon index,ACE index,Chao index and Heip index between the treatment groups and the control group(P>0.05).Community diversity showed an upward trend with the increase in specification.Through heatmap analysis,Bacteroidota is related to the decomposition of organic nitrogen;firmicutes and Fusobacteriota are both related to the decomposition of organic nitrogen and organic phosphorus,and participate in the synthesis of WAEF-N and SAEF-N;acidobacteriota and SAEF-N are negatively correlated with NAIP.Some bacteria in Acidobacteriota can utilize inorganic nutrients,and some bacteria are also involved in iron reduction,which makes it negatively correlated with SAEF-N and NAIP.Proteobacteria was involved in phosphorus transformation.In conclusion,P.aibuhitensis plays an important role in the transformation and release of nitrogen and phosphorus in sediments,and has potential applications in environmental governance.P.aibuhitensis can be introduced into marine pond aquaculture to improve the utilization rate of nitrogen and phosphorus in the aquaculture system and the accumulation of nutrients in the sediment of the pond.It can also be applied to the treatment of seawater pond tail water and the purification of aquaculture tail water combined with aquatic plants.