Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. rad...Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. radioactivity, total β radioactivity, artificial radioactive 90Srand 157Cs, and factors inflencing the distribution and the content of U in seawater are studied.The mainly radioactive pollution substances and their sources in the sea area are studied by γ spectra obtained from sediment in the sea area. The results show that the main radioactivity substances are natural radioactivity U,Th series and 40K. which were produced by the modern industry and transported into the sea through the main current of the Zhujiang River.展开更多
Length-frequency data of eight commercial fish species in the Beibu Gulf (Golf of Tonkin), northern South China Sea, were collected during 2006-2007. Length-weight relationships and growth and mortality parameters w...Length-frequency data of eight commercial fish species in the Beibu Gulf (Golf of Tonkin), northern South China Sea, were collected during 2006-2007. Length-weight relationships and growth and mortality parameters were analyzed using FiSAT II software. Five species had isometric growth, two species had negative allometric growth, and one species had positive allometric growth. Overall, the exploitation rates of the eight species were lower in 2006 2007 than in 1997-1999: for four species (Saurida tumbil, Saurida undosquamis, Argyrosomus macrocephalus, and Nemipterus virgatus) it was lower in 2006-2007 than in 1997 1999, for two species (Parargyrops edita and Trichiurus haumela) it remained the same, and for the other two species (Trachurus japonicus and Decapterus maruadsi) it was higher in 2006~007 than in 1997-1999. The exploitation rates might have declined because of the decline in fishing intensity caused by high crude oil prices. The optimum exploitation rate, estimated using Beverton-Holt dynamic pool models, indicated that although fishes in the Beibu Gulf could sustain high exploitation rates, the under-size fishes at first capture resulted in low yields. To increase the yield per recruitment, it is more effective to increase the size at first capture than to control fishing effort.展开更多
A military escalation between China and the United States in the South China Sea(SCS)is staged which resembles the Cold War crisis in Europe in the 1950’s and 1960’s.The PRC has reclaimed and fortified its holdings ...A military escalation between China and the United States in the South China Sea(SCS)is staged which resembles the Cold War crisis in Europe in the 1950’s and 1960’s.The PRC has reclaimed and fortified its holdings in the SCS since 2013;in 2017,the US has declared an“Indo-Pacific Strategy”to contain China.Due to differences of interest of the relevant countries,it will be difficult to create an effective united front against China in the near future.It remains to be seen whether armed conflict between China and the US be avoided.展开更多
Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains u...Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.展开更多
文摘Through the investigation on radioactive activities of water, sediment and some marine organismsin the Zhujiang Estuary, adjacent sea area and the distributary mouths of the Zhujiang River, activities of total α. radioactivity, total β radioactivity, artificial radioactive 90Srand 157Cs, and factors inflencing the distribution and the content of U in seawater are studied.The mainly radioactive pollution substances and their sources in the sea area are studied by γ spectra obtained from sediment in the sea area. The results show that the main radioactivity substances are natural radioactivity U,Th series and 40K. which were produced by the modern industry and transported into the sea through the main current of the Zhujiang River.
基金Supported by the Chinese Ministry of Agriculture under the Investigation of Fishery Stocks in China Seas Program (No. 070404)the Special Project of the Social Commonwealth Research National Institute (Nos.2009TS08, 2010YD10)
文摘Length-frequency data of eight commercial fish species in the Beibu Gulf (Golf of Tonkin), northern South China Sea, were collected during 2006-2007. Length-weight relationships and growth and mortality parameters were analyzed using FiSAT II software. Five species had isometric growth, two species had negative allometric growth, and one species had positive allometric growth. Overall, the exploitation rates of the eight species were lower in 2006 2007 than in 1997-1999: for four species (Saurida tumbil, Saurida undosquamis, Argyrosomus macrocephalus, and Nemipterus virgatus) it was lower in 2006-2007 than in 1997 1999, for two species (Parargyrops edita and Trichiurus haumela) it remained the same, and for the other two species (Trachurus japonicus and Decapterus maruadsi) it was higher in 2006~007 than in 1997-1999. The exploitation rates might have declined because of the decline in fishing intensity caused by high crude oil prices. The optimum exploitation rate, estimated using Beverton-Holt dynamic pool models, indicated that although fishes in the Beibu Gulf could sustain high exploitation rates, the under-size fishes at first capture resulted in low yields. To increase the yield per recruitment, it is more effective to increase the size at first capture than to control fishing effort.
文摘A military escalation between China and the United States in the South China Sea(SCS)is staged which resembles the Cold War crisis in Europe in the 1950’s and 1960’s.The PRC has reclaimed and fortified its holdings in the SCS since 2013;in 2017,the US has declared an“Indo-Pacific Strategy”to contain China.Due to differences of interest of the relevant countries,it will be difficult to create an effective united front against China in the near future.It remains to be seen whether armed conflict between China and the US be avoided.
基金supported by the National Natural Science Foundation of China(Grant Nos.42090041,42030502&41663001)the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(Grant No.MGQNLMTD201801)the Guangxi Scientific Projects(Grant Nos.AD17129063,AA17204074&2020GXNSFAA297026)。
文摘Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation.However,whether corals can adjust their trophic status under contrasting environmental conditions remains unclear.In our study,70 scleractinian corals(Favia palauensis)were collected from Sanya and the Xisha and Nansha Islands in the South China Sea.We measured the zooxanthellae density(ZD)andδ^(13)C of zooxanthellae(δ^(13)C_(z))and host tissue(δ^(13)C_(h))and analyzed the difference betweenδ^(13)C_(h) andδ^(13)C_(z)(i.e.,△^(h-z)^(13)C).The relatively high ZD andδ^(13)C_(z) values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha.In contrast,the relatively lowδ^(13)C_(h) and△^(h-z)^(13)C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya.In addition,we tested the coral tissue biomass and skeletalδ^(13)C(δ^(13)C_(s))in the samples from Sanya and examined their correlations with△^(h-z)^(13)C.The results showed a negative correlation,indicating that the more the organic material produced by the coral,the stronger its heterotrophic ability.Our results show that corals can adjust their trophic status under different environmental and physiological conditions,which is essential for increasing their adaptability to different environmental conditions.