Studies Of Three Water Quality Controlling Technologies On Microbial Enzyme Activity And Microbial Community Structure In The Sediment Of Apostichopus Japonicus Culture Ponds

With the popularity and development of sea cucumber aquaculture,the death of sea cucumbers caused by poor regulation of pond water quality is frequent.At present,effective water control technology has become the key to healthy cultivation of sea cucumber.Three different water quality controlling technologies(Natural water exchange,Submerged aeration system,Nourishing water machine system)were selected in this study from January 2017 to December 2017.In order to compare the effects with the three water quality controlling technologies,the physical and chemical indicators of the ponds were monitored including water temperature,salinity,dissolved oxygen,ammonia,nitrite,nitrate,phosphate,total nitrogen and total phosphorus of sediment pore water,enzyme activity and community structure of sediment,the results are as follows:(1)During the experiment,the variation range of physicochemical indexes of sediment pore water of three ponds: water temperature-3.0-27.9 ?,salinity 30.08-38.50 ‰,dissolved oxygen 0.35-22.48 mg/L,ammonia nitriten 0.023-0.150 mg/L,nitrite nitrogen 0.004-0.045 mg/L,nitrate nitrogen 0.688-6.117 mg/L,phosphorus 0.0040-0.0871 mg/L,total nitrogen 0.447-5.438 mg/L,total phosphorus 0.060-0.319 mg/L.Of which three ponds water temperature changes are basically the same;Natural water exchange salinity was always higher than that of the other two ponds,Nourishing water machine system salinity between Natural water exchange and Nourishing water machine system;dissolved oxygen of Natural water exchange in summer was lower than Submerged aeration system and Nourishing water machine system,only 0.25 mg/L.There was little difference between the three ponds in other seasons;The ammonia nitriten of Nourishing water machine system was lower than Submerged aeration system and Nourishing water machine system except December.The annual average of ammonia nitriten of Submerged aeration system was higher than the other two ponds,Natural water exchange second.The annual average of nitrite nitrogen,nitrate nitrogen,phosphorus and total nitroge of Nourishing water machine system was lower than the other two ponds.The annual average of total phosphorus of Nourishing water machine system was between Submerged aeration system and Nourishing water machine system.(2)During the experiment,the variation range of sediment enzyme activity of three ponds: organic matter content 0.07-2.60 %,urease activity 95.00-279.42 U/g,acid phosphatase activity 87.27-1040.51 nmol/(g·h),dehydrogenase activity 1.50-36.83 U/g,microbial activity 1.660-14.810 ?g/(g·min).The organic matter content in ponds of Nourishing water machine system was lower than that of Submerged aeration system and Natural water exchange except for February and March.The urease activity of ponds of Nourishing water machine system was lower than that of Submerged aeration system and Natural water except for December;Acid phosphatase activity in Nourishing water machine system was lower than the other two ponds except for April and September;The dehydrogenase activity in ponds of Nourishing water machine system was lower than that of Submerged aeration system and Natural water exchange except for February,April and September;Overall,the microbial activity of Nourishing water machine system > Submerged aeration system > Natural water exchange.(3)During the experiment,the variation range of enzyme activity of sediment of three ponds: total microorganism 13.5-123.4 ng/g,total bacteria 9.5-94.6 ng/g,total gram positive bacteria 3.1-14.5 ng/g,total gram negative bacteria 0.5-7.9 ng/g,total aerobic bacteria 0.9-15.9 ng/g,total fugus 0.5-7.9 ng/g,the ratio of fugus and bacteria 0.15-0.33,the ratio of single unsaturated and branched chain 0.09-2.65,the ratio of 18:1?9c and 18:1?9t chain 0.09-2.65.The total microorganism of Natural water exchange > Submerged aeration system> Nourishing water machine system,large differences between summer and autumn.The total bacteria of Natural water exchange > Submerged aeration system > Nourishing water machine system,large differences in summer and autumn.The total gram positive bacteria of Natural water exchange > Submerged aeration system > Nourishing water machine system,large differences between Natural water exchange and other two ponds in summer and autumn.The total gram negative bacteria of Natural water exchange > Submerged aeration system > Nourishing water machine system,large differences between Natural water exchange and other two ponds in summer and autumn.There was little difference in total aerobic bacteria between Submerged aeration system and Nourishing water machine system,Natural water exchange was far blow other two ponds in summer.The annual average of the ratio of fugus and bacteria of Submerged aeration system was lower than other two ponds.The annual average of the ratio of single unsaturated and branched chain and the ratio of 18:1?9c and 18:1?9t was higher than other two ponds.