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N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean (WTNP)
Run Zhang, Dongsheng Zhang, Min Chen, Zhibing Jiang, Chunsheng Wang, Minfang Zheng, Yusheng Qiu, Jie Huang
In the present study, we report N2 fixation rate (15N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13–20°N, 120–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation. In surface waters, volumetric N2 fixation rate (calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged (1.2±0.5) nmol/(L·d), with <0 μm size fraction contributed predominantly (88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m2·d) and 480 μmol/(m2·d) (average (225±105) μmol/(m2·d). N2 fixation can account for 6.2%±3.7% of the depth-integrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.
key words: western tropical North Pacific Ocean (WTNP), N2 fixation, 15N isotope tracer assay, unicellular diazotroph
Taxonomic notes on Anthomedusae (Cnidaria: Hydrozoa: Hydroidomedusa) from the south-central South China Sea, with a new genus and four new species
Feiyan DU, Lianggen WANG, Zhenzu XU, Jiaqi HUANG, Donghui GUO
doi: 10.1007/s13131-018-1310-5
This study describes and illustrates four new species Laticanna nanhaiensis Xu, Huang and Wang, gen. nov. and sp. nov., Protiaropsis gemmifera Xu, Huang and Du, sp. nov., Merga nanhaiensis Xu, Huang and Guo, sp. nov. and Rhabdoon apiciloculus Xu, Huang and Du, sp. nov. based on specimens from the south-central South China Sea. Additionally, keys to known genera of family Bythotiaridae and species of genera Protiaropsis, Merga, and Rhabdoon are described. All type specimens are deposited in the South China Sea Fisheries Research Institute, Chinese Academy of Fishery Science.
key words: Hydroidomedusae, Bythotiaridae, Pandeidae, Tubulariidae, new genus and species, South China Sea
Taxonomic notes on Hydroidomedusae (Cnidaria) from the South China Sea IV: Family Bougainvilliidae (Anthomedusae)
Donghui GUO, Zhenzu XU, Jiaqi HUANG, Mao LIN, Chunguang WANG
doi: 10.1007/s13131-018-1308-z
This study reviews all genera and species belonging to the family Bougainvilliidae from the South China Sea. The Nubiella atentaculata Xu and Huang, 2004 formerly included in the genus Nubiella, now is transferred to a new genus Paranubiella and included in the Bougainvilliidae as Paranubiella atentaculata (Xu and Huang, 2004) n. comb.. Two new species, Paranubiella nanhaiensis Xu, Huang and Guo, sp. nov. and Nubiella apapillaris Xu, Huang and Guo, sp. nov. from the South China Sea are described and illustrated in the present paper. In addition, the key to known genera of family Bougainvilliidae and species of genus Nubiella are described. Other data are briefly summarized to the list of species presented on the family Bougainvilliidae in the South China Sea. The type species were deposited at the Third Institute of Oceanography, State Oceanic Administration.
key words: Anthomedusae, Bougainvilliidae, new genus, new species, new combination, South China Sea

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