| Phosphorus（P）is an important inducer of water eutrophication and harmful algal blooms.Internal sediment loading may be an important source of P for water at a long time when exogenous input is controlled effectively.As the primary drivers of P geochemical cycling in water,phosphate-solubilizing bacteria（PSB）play a critical role in sediment P release.This paper analyzed the physico-chemical properties and organic P fractions of of the sediments from Swan Lake through the field investigation.The community decomposition and diversity of organic phosphate-solubilizing bacteria（OPB）were identified by high-throughput sequencing.In addition,the phosphate-solubilizing ability of PSB on the sediments from different lake areas,and the effect of PSB on P release from the sediments in algal bloom areas and the growth of Chaetomorpha spp.were explored through the indoor simulation.The main results were as follows:（1）The content of organic P in the surface sediments was high in the southwest and the center of Swan Lake.And it was higher in spring and winter than that in other seasons.The average content of bioavailable organic P in sediments was 58.07 mg·kg-1,accounting for 52%of the total organic P.The content of bioavailable organic P was high in the sediments of northern and southern lake,indicating a great bio-availability at these regions.On the whole,the content of medium-active organic P was highest in Swan Lake,and HCl-Po was the main form of organic P.（2）In the surface sediments of Swan Lake,the bacteria containing pho D gene primarily came from the phylum of Proteobacteria and Actinobacteria.At the genus level,it mainly came from Roseovarius,Nitratireductor,and Phaeobacter.The community composition of the bacteria containing pho D gene was different between the sediments of the central and southern lake.In addition,the relative abundance and diversity of pho D gene were relatively high in the southern lake,showing a high potential for phosphate-solubilizing ability at this region.（3）Through the shaking flask culture,the content of soluble reactive P in the water and microbial biomass P increased markedly after the inoculation of PSB.Geobacillus stearothermophilus and Bacillus pumilus had strong phosphate-solubilizing ability for the sediments of different lake regions.The growth status of OPB was one of important factor affecting sediment P release.Compared with other lake areas,the sediments in the southern and central lake had great release potential under the action of OPB,which should be paid more attention in the summer when the microbial activity is high.（4）After the inoculation with Geobacillus stearothermophilus,Bacillus flexus and Bacillus pumilus,the content of total P in overlying water increased significantly.The inoculation of OPB led to a significant increase in the alkaline phosphatase activity（APA）of sediments,Bacillus stearothermophilus and Bacillus flexus had higher ability of enzyme secretion and phosphate solubilizition.At the end of the test,NH4Cl-P content in sediments increased significantly under the inoculation treatments.The OPB promoted the release and transformation of P in the sediments of algal bloom area,while the anaerobic environment in the later stage was conducive to the release of sediment BD-P.（5）The PSB could affect the Chaetomorpha growth by increasing the APA and water P content,and the effect of various strains was different.In this test,Bacillus stearothermophilus showed the significant effect on the growth of Chaetomorpha.In general,there were large quantities of OPB in the sediments of Swan Lake,which can mineralize organic P and release it into the water by excreting alkaline phosphatase,thus providing the nutrients for Chaetomorpha growth.In Swan Lake,the contribution of mineralization of organic P in sediments to the persistence of algal blooms cannot be ignored. |
