| Carbon is the basic element of biological molecular skeleton on the earth, which is the basic components of living organisms and the carrier of the biosphere of matter and energy circulation. Carbon cycle in the environment has a variety of forms and important effects on for human development and global climate changes. Ocean carbon pool is the second largest active carbon pool following the lithosphere carbon and it is an important link in the carbon cycle. The three main process "Dissolution pump"、"Biological pump", "Carbonate pump" of the ocean carbon cycle are all processing under the action of marine organisms. In the area of coastal sea and mariculture waters, a large number of mariculture organisms will bring significant influences to the coastalocean carbon cycle.Therefore, this study takes Jiaozhou Bay as a representative of the coastal mariculture waters.The biological resources of Ruditapes philippinarum in Jiaozhou Bay in February, May, August and November,2014 were investigated. Through the analysis of the shell length, biomass, density and the age of the Ruditapes philippinarum in 15 stations of Jiaozhou Bay, the distribution and biological resource status of Ruditapes philippinarum of Jiaozhou Bay were assessed. Meanwhile, the diminant mariculture shellfish species Ruditapes philippinarum of Jiaozhou Bay was selected as the study organism and the method of controlled ecological laboratory experiment and "Alkalinity anomaly technique" were used to measure the calcification and respiration rates, in order to reveal the physiological ecology of Ruditapes philippinarum, and analyze the effect of Ruditapes philippinarum mariculture on the coastal carbon cycle. The main results are as follows:1. The age compositon of Ruditapes philippinarum in the whole year’s investigated included first age, second age and third age while the first age and second age organism were dominant. The average biomass of Ruditapes philippinarum during each cruises from Feb 2014 to NOV 2014 were 398.5 ind./m2, with the highest biomass 3444.75 g/m2 at Site 2. The annual average density was 263.31 ind./m2 with the highest density value 2377.5 ind./m2 at Site 2.2. According to the investigation, the age structure of Ruditapes philippinarum had younger trend. Given the commercial specification of the length of Ruditapes philippinarum is 30 mm, the commodity percentage of Ruditapes philippinarum in Jiaozhou bay in 2014 is 6.8%, if given the specification of the length of the Ruditapes philippinarum is 25 mm, the commodity of Ruditapes philippinarum in Jiaozhou bay in 2014 is 33.17%。From the point of biomass and the commodity of Ruditapes philippinarum, the appropriatest period for capture is May, and the second age organisms is the best age for harvest.3.There were significant differences under different salinity gradients in the calcification and respiratory rates of Ruditapes philippinarum. The calcification and respiration rates increased with increasing salinity between 20-28 while with the salinity continued rising to 35, both of them decreased. When salinity is 20. the calcification rate of Ruditapes philippinarum is the lowest value of-0.992 μmol.FW g-l.h-1; When salinity is 30. the calcification rate get the maximum value of -0.407 μmol.FW g-1’.h-1,when the salinity is 25. the respiration rate reached the maximum value of 1.682 μmol.FW g-1.h-1.4. There were also significant differences under different temperature gradients for the oxygen consumption rate of Ruditapes philippinarum. The calcification rate increased with increasing temperature and when temperature continued rising to 15, there was a slow increasing trend for the rate of calcification. The respiration rate of the Ruditapes philippinarum increased with increasing temperature in the temperature range of 5-15℃. The maximum respiration rate of Ruditapes philippinarum was 1.51 μmol.FWg-1.h-1 at the temperature of 15℃. When the temperature exceeded 15℃ and continued increasing, the respiration rate decreased.5. There were highly significant differences under different pH gradient for the calcification and respiratory rates of Ruditapes philippinarum. The effect of pH on respiration rate of Ruditapes philippinarum was not significant. However, both of the calcification and respiratory rates decreased when the pH increased. The calcification rate of Ruditapes philippinarum and pH had a linear relationship:G= 0.1746-0.3424pH (R2=0.9963,p<0.01). Calcification had a seriously reduce trend from -0.148 μmol.FWg-1Vh-1 to-1.193 μmol.FWg-1.h-1, with pH decreasing from 8.1-7.7. Respiration rates, however had exhibited another trend of decreasing after a huge rise. The max value of respiration rate was 2.533 μmol.FWg-1.h-1 when pH value had reached 7.7.6. The carbon release by respiration of Ruditapes philippinarum are about 0.43×104t (113.51mgC.m-2.d-1)-0.65×104t (173.32mgC.m-2.d-1)while there are about 0.49×104t-8.98×104t (129.69mgC.m-2.d-1-2372.25 mgC.m-2.d-1)carbon sinking to the sea bottom by biodepositon. Some carbon dioxide could be rather converted to organic carbon sinking into the bottom by biodepositon of shellfish than releasing into environment by respiration of Ruditapes philippinarum which breeds in Jiaozhou Bay.7. Most of the carbon was buried by biodepositon, they are hard to be suspended and utilized through the decomposition. Though carbon dioxide was released in the respiration and calcification processes by Ruditapes philippinarum, more carbon were buried by the biodepositon of bivalves and left the bio-geochemical cycle. So depositon by bivalves plays a vital role in the carbon sink. |
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