Dynamics of soil carbon storage under different land use years in arid agriculture

Abstract: During fishery transportation, the alive shellfish should be stored in favorable living conditions for longer survival time. Typically, the survival rate declines over time, affected by 3 steps, i.e. water purification, temporary rearing and low temperature waterless-transportation. In this paper, the analytical results were presented by using the Patinopecten yessoensis samples to explore the efficiencies of the above procedures. The recycled water system for purification and temporary rearing consists of the aquaculture rearing pool, water circulating device, oxygenation device, temperature control and disinfection device. The recycled water system for purification and temporary rearing was used to realize both purification and temporary rearing of Patinopecten yessoensis. In the experiment, certain parameters were monitored, including water temperature, salinity, pH value and dissolution oxygen level. The samples were divided into 3 groups based on 3 different procedures involved: Group 1 was purified for 56 h straight; Group 2 was first purified for 32 h and cooled for 24 h gradually afterward; Group 3 was directly kept in a polyethylene insulation box. Then Group 1 and Group 2 were transported in a 3 L polyethylene insulation box with ice packs (250 mL) to study the quality of transport based on the different pretreatment. The results showed that the temperature of water dropped from (15?0.13) ℃ in purification to 4.76 ℃ before low temperature waterless- transportation by gradient cooling during the purification and temporary rearing, the salinity of water fluctuated between 32.47‰ and 33.00‰, the pH value of water fluctuated between 8.29 and 8.44, and the dissolved oxygen in the water remained above 8.34 mg/L. It was demonstrated that the water environment was valid within the living condition requirements of the shellfish throughout the experiment. As a result, in Group 1, the first death was shown after 64 h, and all shellfishes died after 104 h with total bacteria density of 2 300 CFU/mL. In Group 2, the first death was shown after 104 h and the total number of bacteria was increasing steadily within 0-104 h. After 120 h, all shellfishes died with total bacteria density of 960 CFU/mL. In Group 3, all shellfishes died in 64 h. The total number of bacteria in Group 1 and 2 declined significantly in the purification. The bacteria number in Group 3 was significantly different from Group 1 and 2 (P<0.05). The crude protein, crude fat and glycogen of all groups declined over time. However, compared to Group 1 and 3, the consumption of glycogen in Group 2 was delayed by the gradual cooling procedure (P<0.05). The result proved that the purification and temporary rearing procedures improved the sterilization of the bacteria, and the survival rate was less sensitive to the temperature change, and got longer. Therefore the consumption of crude protein, crude fat and glycogen was delayed. With this experiment, the procedures of 32 h purification followed by 24 h gradient cooling are proved to be efficient for the low temperature waterless-transportation. The results provide sound references for the Patinopecten yessoensis' quality studies with purification, temporary rearing and low temperature waterless-transportation technologies.