Home  >  Query result

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
Morphological studies of six free-living spirotrichean ciliates (Protozoa: Ciliophora) with three new records from the coastal South China Sea
Xumiao CHEN, Kuidong XU
doi: 10.1007/s13131-018-1304-3
The living morphology and infraciliature of six spirotrichous ciliates collected from the coastal South China Sea were investigated using live observation and protargol impregnation. These are Euplotes woodruffi Gaw, 1939, Hemigastrostyla enigmatica (Dragesco and Dragesco-Kernéis, 1986) Song and Wilbert, 1997, Neourostylopsis flavicana (Wang et al., 2011) Chen et al., 2013, Protogastrostyla pulchra (Perejaslawzewa, 1886) Gong et al., 2007, Pseudoamphisiella alveolata (Kahl, 1932) Song and Warren, 2000, and Pseudokahliella marina (Foissner et al., 1982) Berger et al., 1985. Among these, Protogastrostyla pulchra, Pseudoamphisiella alveolata and Pseudokahliella marina are reported from the South China Sea for the first time, which manifest obvious differences apart from other Chinese populations. As new contribution, the detailed description of isolates from mangrove habitat of E. woodruffi andH. enigmatica, and aquaculture pond isolate of N. flavicana, are present.
key words: South China Sea, new record, ciliates, Spirotrichea, taxonomy

Year of publication

Related authors

Related hot words