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Spatio-temporal variability of phytoplankton assemblages and its controlling factors in spring and summer in the Subei Shoal of Yellow Sea, China
Yuanzi HUO, Honghua SHI, Jianheng ZHANG, Qiao LIU, Yuanliang DUAN, Qing HE, Kefeng YU, Hongsheng BI, Chunlei Fan, Peimin HE
doi: 10.1007/s13131-019-1345-2
The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea. In the present study, the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea. Phytoplankton species composition and abundance data were accomplished by Utermöhl method. Diatoms represented the greatest cellular abundance during the study period. In spring, the phytoplankton cell abundance ranged from 1.59×103 to 269.78×103 cell/L with an average of 41.80×103 cell/L, and Skeletonema sp. and Paralia sulcata was the most dominant species. In summer, the average phytoplankton cell abundance was 72.59×103 cell/L with the range of 1.78×103 to 574.96×103 cell/L, and the main dominant species was Pseudo-nitzschia pungens, Skeletonema sp., Dactyliosolen fragilissima and Chaetoceros curvisetus. The results of a redundancy analysis (RDA) showed that turbidity, temperature, salinity, pH, dissolved oxygen (DO), the ratio of dissolved inorganic nitrogen to silicate and SiO4-Si (DIN/SiO4-Si) were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.
key words: phytoplankton, Subei Shoal, eutrophication, turbidity, harmful algae blooms, Yellow Sea
Distribution and controlling factors of phytoplankton assemblages associated with mariculture in an eutrophic enclosed bay in the East China Sea
Yuanzi HUO, Zhangliang WEI, Qiao LIU, Fangfang YANG, Lijuan LONG, Qi ZHANG, Hongsheng BI, Qing HE, Peimin HE
doi: 10.1007/s13131-018-1238-9
The distribution of phytoplankton and its correlation with environmental factors were studied monthly during August 2012 to July 2013 in the Yantian Bay. A total of 147 taxa of phytoplankton were identified, and the average abundance was in the range of 0.57×104 to 7.73×104 cell/L. A total of 19 species dominated the phytoplankton assemblages, and several species that are widely reported to be responsible for microalgae blooms were the absolutely dominant species, such as Skeletonema costatum, Navicula sp., Thalassionema nitzschioides, Pleurosigmasp., and Licmophora abbreviata. The monthly variabilities in phytoplankton abundance could be explained by water temperature, dissolved oxygen, salinity, dissolved inorganic nitrogen (DIN), and suspended solids. The results of a redundancy analysis showed that pH and nutrients, including DIN and silicate (SiO4), were the most important environmental factors controlling phytoplankton assemblages in specific months. It was found that nutrients and pH levels that were mainly influenced by mariculture played a vital role in influencing the variation of phytoplankton assemblages in the Yantian Bay. Thus, a reduction of mariculture activities would be an effective way to control microalgae blooms in an enclosed and intensively eutrophic bay.
key words: Sansha Bay, phytoplankton, eutrophication, microalgae blooms, bioremediation, East China Sea
Source and nature of ore-forming fluids of the Edmond hydrothermal field, Central Indian Ridge: evidence from He-Arisotope composition and fluid inclusion study
Yejian WANG, Xiqiu HAN, Zhongyan QIU
doi: 10.1007/s13131-016-0963-1
To understand the source and nature of the ore-forming fluids of the Edmond hydrothermal field on the Central Indian Ridge, we studied the He-Ar isotope composition and fluid inclusions of the hydrothermal precipitates. Our results show that the sulfide samples contain noble gases He, Ne, Kr, and Xe with their abundances in between those of air-saturated water (ASW) and mid-ocean ridge basalt (MORB). The3He/4He ratio varies from 1.3 to 8.7 Ra (n=10, average: 5.1 Ra), whereas the40Ar/36Ar ratio is from 285.3 to 314.7 (n=10, average: 294.8). These results suggest that the He was derived from a mixture of MORB with variable amounts of seawater, but the Ar in the ore-forming fluids trapped in the sulfides is predominantly derived from seawater. The fluid inclusions of barite have a wide range of homogenization temperatures and salinities varying from 163°C to 260°C and 2.6 wt% to 8.5 wt% NaCl equiv., respectively. It is suggested that the ore-forming fluids were produced by phase separation, which agreed with the present-day vent fluid study.
key words: fluid inclusion, helium and argon isotopes, phase separation, massive sulfides, Central Indian Ridge

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