Variations Of Sea Ice And Sea Water Characteristics And Their Effects On Immune Enzyme Activity Of Shellfish In Liaodong Bay

Sea ice forms in the Bohai Sea and the Northern Huanghai Sea with different levels every year, and it would cause the variations of ice physical property, water temperature, salinity, dissolved oxygen and pH. It is not clear whether the change of environment factors, including the ice environmental factors and water environmental factors under ice, falls beyond the physiological tolerance of shellfish in Bohai. In this study, field investigations of air-ice-water environmental factors were performed in an ice-covered pond of Liaodong Gulf for three winters. Combining with the Antarctic investigation results in late winter and early spring, relationship among porosity, crystal structure and Chl-a concentration of sea ice was developed. The variation rang of water temperature, salinity, dissolved oxygen and pH was analyzed the simulation test of water temperature in sharp and slow decrease processes was done in a low-temperature laboratory based on field investigation results. Respond of shellfish immune enzyme activity on change of water temperature was obtained, and a mathematical method describing the process was built. The results can provide scientific supports for the overwintering of aquaculture animals.Through comparing the physical property and crystal structure of sea ice in Liaodong Gulf culture pond with small area with that in Antarctic with large area, it was found that the ice porosity distributions controlled by temperature, salinity, density of ice are almost the same; their major ice crystal structure grew by thermodynamics is columnar ice. Based on the physical property and Chl-a concentration in Antarctic sea ice. the relationship between brine volume and concentration and distribution of Chl-a in different type crystal structure, a surface fitting relationship between snow/ice thickness and content of Chl-a, and a logistic growth models for brine volume and Chl-a concentration were developed. The results for the columnar ice in Antarctic can be also applied to that for the sea ice in Liaodong Gulf culture pond.The temperature of water under ice was controlled by both ice temperature and soil temperature, and it can affect the dissolved oxygen concentration and pH value in water. The water temperature was in the range of freezing point to 0 ? during the whole ice-covered period. Salinity gradual rises during ice growth period. But salinity in the surface of waters existed large variation during the melt period, it still kept stable at the water bottom. During the whole ice period, the concentration of dissolved oxygen always is higher than the critical concentration of oxygen, and even showed over-saturation at low temperature condition. The variation of pH was also in the normal range. The change of salinity, dissolved oxygen and pH in the ice period did not lead to the maladjustment of aquaculture organisms. While water temperature decreased from above freezing to below freezing and kept below zero for a long time, which will significantly affect the immunity and death rate of aquaculture organisms.The variation range and way of water temperature in sharp and slow decrease processes within a certain range of salinity, dissolved oxygen and pH affect the immune response (the immunity indexes include levels of superoxide dismutase (SOD), catalase (CAT), lysozyme (LZM), acid phosphatase (ACP) and alkaline phosphatase (AKP)) and death rate of shellfish. Manila clam (Ruditapes philippinarum) and Potamocorbula laevis were selected to the water temperature sharp test, while for the slow decrease process of water temperature, only Manila clam was selected as test material. While Potamocorbula laevis showed adaptive response to the slowdown of water temperature, the two shellfishes showed stress response to the sharp down of water temperature. In the stress response of two shellfishes to the sharp temperature decrease, the of processes immune enzyme activity variation can be divided to three types, including different fiducial value of immune enzyme activity to different water temperature, the fluctuation of stress response enzyme activity caused by the water temperature difference, the fluctuation of cold stress response enzyme activity caused by low-temperature environment, and these response can be describe by mathematical statistical method. A process of immune enzyme activity levels along with time was developed by mathematical statistical method, too. In the sharp and slow decrease experiments of water temperature, the death rates of two shellfishes were affected by the fall of water temperature, rate of temperature fall and initial temperature of the test.