Fractions And Release Of Phosphorus In The Surface Sediments From Haizhou Bay Marine Ranching

Marine ranches are a new type of sustainable marine production.Typical marine ranches are usually composed of artificial reefs,floating reefs,large algae,and mollusks.Artificial reefs and floating reefs can provide habitat for fish and other organisms.It is a marine resource conservation and ecological restoration project advocated by the state in recent years.Haizhou Bay Marine Ranch is located in the middle of the Yellow Sea.It is an early-stage public welfare marine pasture in China.Phosphorus is an important source of life in marine ecosystems and plays an important role in the biogeochemical cycle.Sediment is also an important accumulation place for nutrients in water.The migration and transformation process of phosphorus in the sediment-water interface directly affects the nutrient status of water.Research on sediments as nutrient sources or sinks of overlying water bodies has not been carried out in depth,especially for the study of phosphates at the sediment-water interface in marine pasture areas.In this paper,the phosphorus form of the surface sediments of Haizhou Bay marine grazing is extracted by the SMT method?Standard Measurement Test?,which is the most common sediment in the world,and the sediments in the marine pasture area of Haizhou Bay are determined.The phosphorus content of the form,combined with the indoor simulation experiment of phosphorus flux in the sediment-water interface,explores the migration direction and exchange flux of phosphorus at the sediment-water interface.Furthermore,it is determined whether the phosphorus in the sediments of the marine pastures in Haizhou Bay is the“source”or“sink”for the overlying water,in order to provide a scientific basis for the ecological restoration projects such as the artificial reefs of the Haizhou Bay marine pasture.Environmental samples for spring,summer and autumn were collected in May,August and November 2017.There are three reef-area sites in the Haizhou Bay Marine Ranch area,and two control points are set outside the ranch area.According to the marine monitoring regulations,surface sediment samples and water samples such as overlying water and gap water on the corresponding sites were collected.According to the corresponding testing standards or norms,the phosphorus forms of sediments,overlying water and interstitial water were measured,and the influence of various environmental factors was analyzed.Combined with the indoor phosphorus flux release experiment,the phosphorus in the sediments of Haizhou Bay marine pasture was studied for overlying water.Is it a"source"or a"sink"issue.The main findings are as follows:The results showed that the contents of the total phosphorus?TP?,inorganic phosphorus?IP?and Ca-P in the surface sediments of Haizhou Bay marine pastureland in spring were ranged from 392.44 to 463.46 ug·g^-1,219.21 to 282 ug·g^-1 and 117.73 to130.07 ug·g^-1,respectively.The IP was found as the major form of phosphorus.The order of the contents of different forms of phosphorus was Ca-P>Ex-P>Fe/Al-P.The contents of phosphorus in the control area were greater than that in the reef area.The concentrations of various forms of phosphorus in the overlying water were higher than the sediment pore water.Laboratory phosphorus flux simulation experiments showed that the content of various forms of phosphorus in sediments were higher after the incubation process,and IP still the main form of phosphorus.The exchange fluxes of TP,TDP,and PO₄^3-at the sediment-water interface were estimated as-0.53?-0.05mmol/m²·d,-0.15?-0.01 mmol/m²·d and-0.03?-0.29 mmol/m²·d,respectively.The exchange rate was faster at the initial stage of the incubation experiment,and then tended to stabilize.Compared with the control area,the exchange flux of phosphate in the marine pastureland was slightly larger,but both showed the tendency that phosphorus migrate from the overlying water to sediment.It suggests that phosphorus in surface sediments act as a sink of overlying water.The results showed that the contents of the TP,IP and Ca-P in the surface sediments of Haizhou Bay marine pastureland in summer were ranged from 330.78 to417.68 ug·g^-1,223.31 to 256.9 ug·g^-1 and 160.69 to 177.52 ug·g^-1,respectively.The IP was found as the major form of phosphorus.The order of the contents of different forms of phosphorus was Ca-P>Ex-P>Fe/Al-P.The contents of phosphorus in the control area were greater than that in the reef area.The concentrations of various forms of phosphorus in the overlying water were lower than the sediment pore water.The indoor simulation experiment showed that the contents of TP,Ex-P and OP in the sediment decreased,the concentration of IP,Fe/Al-P and Ca-P increased slightly after the culture.The exchange fluxes of TP,TDP,and PO₄^3-at the sediment-water interface were estimated as-0.025?-0.193 mmol/m²·d,0.003?0.056 mmol/m²·d and-0.089?0.030mmol/m²·d,respectively.At the beginning of the experiment,the exchange rate was faster.The average exchange flux of TP and TDP in the reef area was slightly smaller than that of the control area.The average exchange flux of PO₄^3-the average exchange flux was slightly larger than that of the control area,but both showed the tendency that phosphorus migrate from the sediment to overlying water.It suggests that phosphorus in surface sediments act as a source of overlying water.The results showed that the contents of the TP,IP and Ca-P in the surface sediments of Haizhou Bay marine pastureland in spring were ranged from 336.38 to 458.32 ug·g^-1,197.14 to 251.80 ug·g^-1 and 150.89 to 192.93 ug·g^-1,respectively.IP is the main form of phosphorus.The order of the contents of different forms of phosphorus was Ca-P>Ex-P>Fe/Al-P.Except OP,the content of various phosphorus forms in the control area is larger than that in the reef area.The concentrations of various forms of phosphorus in the overlying water were lower than the sediment pore water.The indoor simulation experiment showed that the average concentration of other phosphorus forms was slightly decreased except OP,and the concentration of each phosphorus form in the RA1 site was significantly increased,and the concentration of each phosphorus form in the marine pasture reef area was smaller than that of the control area.The exchange fluxes of TP,TDP,and PO₄^3-at the sediment-water interface were estimated as-0.012?0.070 mmol/m²·d,0.010?0.078 mmol/m²·d and 0.034?-0.094 mmol/m²·d,respectively.At the beginning of the experiment,the exchange rate was faster.Compared with the control area,the exchange flux of phosphorus in the marine pasture area was slightly larger,but both showed the tendency that phosphorus migrate from the sediment to overlying water.It suggests that phosphorus in surface sediments act as a source of overlying water.The seasonal changes of phosphorus forms in RA2 and CA2 at Haizhou Bay Marine Ranch site were consistent,and the control area and the reef area also showed certain consistency.The average content of TP and IP in spring was higher than that in the other two seasons.The average content of each form in summer was lower than that in the other two seasons.The average content of Ex-P,Fe/Al-P and OP in autumn was higher than that in the other two seasons.The seasonal variation of the three phosphorus forms in the interstitial water was consistent with the overlying water.The content of TP,TDP and PO₄^3-in the overlying water in the reef area in spring was higher than that in the other two seasons,but TP and TDP were the most obvious.In the spring,the TP content in the overlying water in the control area was abnormal,and the TDP and PO₄^3-were not much different,but also in autumn.A tendency to have a large content.The phosphorus content of the interstitial water in the control area and the reef area is similar to that of the overlying water.The exchange capacity of TP,TDP and PO₄^3-between sediment-water interface showed seasonal changes.The exchange rate of TP in spring was greater than that in summer and autumn.The exchange rate of TDP in summer was significantly less than that in spring and autumn.The exchange volume of PO₄^3-in spring was greater than that in summer and autumn..The average exchange flux of each phosphorus form in spring is negative,and it is positive in summer and autumn.