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Zooneuston and zooplankton abundance and diversity in relation to spatial and nycthemeral variations in the Gulf of Aqaba and northern Red Sea
Mantha Gopikrishna, Abdulmohsin A. Al-Sofyani, Al-Aidaroos Ali M, Michael P Crosby
doi: 10.1007/s13131-019-1427-1
Zooplankton and zooneuston observations were made at seven stations (four from the Gulf of Aqaba and three from the northern Red Sea), during September and October 2016. The main objective of this study was to assess the variability of nycthemeral fauna in relation to the sampling methods using two different types of nets namely, WP2 net and Neuston net along the two study sites, i.e., the Gulf of Aqaba and the northern Red Sea. Zooplankton was sampled vertically using a standard WP2 net from a depth of 200 m to the surface, whereas zooneuston was made using a standard Neuston net from a depth of 0–10 cm of the water surface. Total zooplankton density was maximum during night time ((617.83 ± 201.84) ind./m3) at the Gulf of Aqaba and total zooneuston was maximum during night at the northern Red Sea ((60.94±29.48) ind./m3), respectively. The most abundant taxa were Copepoda, Gastropoda, Bivalva, Chaetognatha, Tunicata and Ostracoda. The abundance was almost 50% higher at night time at both the Gulf of Aqaba and the northern Red Sea. Overall, 30 taxa covering 10 phyla and 27 taxa covering 8 phyla were recorded in the Gulf of Aqaba and the northern Red Sea. Present work is a preliminary attempt to study the variability of nycthemeral and spatial zooplankton and zooneuston diversity and abundance in the Gulf of Aqaba and northern Red Sea regions, which necessity the need for more extended investigations to understand the local and large-scale processes of this complex, but unique ecosystem.
key words: zooplankton, zooneuston, nycthemeral variation, Cyclopoida, Gulf of Aqaba, northern Red Sea
Assessment of the Tessier and BCR sequential extraction procedures for elemental partitioning of Ca, Fe, Mn, Al, and Ti and their application to surface sediments from Chinese continental shelf
Yanli LIU, Jing ZHANG, Huijun HE
doi: 10.1007/s13131-018-1189-1
Surface sediments can integrate a wide variety of information of seawater in marginal seas, e.g., the Quaternary sedimentary shelf such as the East China Sea (ECS) and Yellow Sea (YS). The Tessier and BCR sequential extraction procedures (SEPs) have been widely applied for extraction of various geochemical phases from sediments. To choose a suitable SEP for phase extraction of sediments from the above Quaternary sedimentary shelf, efficiency and selectivity experiments were conducted on typical individual minerals and the applicability of each SEP was assessed for natural sediments (the natural sediment standard GSD-9 and three surface sediment samples). The geochemical represented elements (Ca, Fe, Mn, Al, and Ti) were measured using both SEPs. Both SEPs have good dissolution efficiency and selectivity for the targeted geochemical phases; the optimized extractant volume for each fraction was determined. The Tessier SEP is particularly recommended for the study of adsorption-desorption process. The application of the Tessier SEP to surface sediments can furnish valuable information, including the productivity conditions (via the reducible fraction Mn) and sedimentary environments (via the carbonate fraction Ca). These results confirm that the Tessier SEP is suitable for elemental fractionation in sediments from the Chinese continental shelf.
key words: elemental fractionation, surface sediments, Tessier SEP, BCR SEP, efficiency, selectivity
Distribution of reactive aluminum under the influence of mesoscale eddies in the western South China Sea
Jiaxing LIU, Linbin ZHOU, Yehui TAN, Qiong WANG, Zifeng HU, Jiajun LI, Xin JIANG, Zhixin KE
doi: 10.1007/s13131-017-1046-7
To understand the distribution of aluminum (Al) under the influence of mesocale eddies in the western South China Sea (SCS), sea level anomaly, geostrophic current, environmental parameters and reactive Al were investigated in the western SCS in August 2013. The highest reactive Al concentration ((180±64) nmol/L) was observed in the surface waters, indicating a substantial atmospheric input. Vertically, the reactive Al decreased from the surface high concentration to the subsurface minima at the depth of chlorophyll a (Chl a) maxima and then increased again with depth at most of the stations. The average concentration of reactive Al in the upper 100 m water column was significantly lower in the cyclonic eddy ((137±6) nmol/L) as compared with that in the non-eddy waters ((180±21) nmol/L). By contrast, the average concentrations of Chl a and silicate in the upper 100 m water column were higher in the cyclonic eddy and lower in the anticyclonic eddy. There was a significant negative correlation between the average concentrations of reactive Al and Chl a in the upper 100 m water column. The vertical distribution of reactive Al and the negative correlation between reactive Al and Chl a both suggest that the reactive Al in the upper water column was significantly influenced by biological removal processes. Our results indicate that mesoscale eddies could regulate the distribution of reactive Al by influencing the primary production and phytoplankton community structure in the western SCS.
key words: reactive aluminum, mesoscale eddy, chlorophyll a, biological removal, phytoplankton, primary production, western 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
A dual-period response of the Kuroshio Extension SST to Aleutian Low activity in the winter season
Peilong YU, Lifeng ZHANG, Hu LIU, Xing LIU, Juan ZHU
doi: 10.1007/s13131-017-1104-1
Based on our previous work, the winter sea surface temperature (SST) in the Kuroshio Extension (KE) region showed significant variability over the past century with periods of ~6 a between 1930 and 1950 and ~10 a between 1980 and 2009. How the activity of the Aleutian Low (AL) induces this dual-period variability over the two different timespans is further investigated here. For the ~6 a periodicity during 1930–1950, negative wind stress curl (WSC) anomalies in the central subtropical Pacific associated with an intensified AL generate positive sea surface height (SSH) anomalies. When these wind-induced SSH anomalies propagate westwards to the east of Taiwan, China two years later, positive velocity anomalies appear around the Kuroshio to the east of Taiwan and then the mean advection via this current of velocity anomalies leads to a strengthened KE jet and thus an increase in the KE SST one year later. For the ~10 a periodicity during 1980–2009, a negative North Pacific Oscillation-like dipole takes 2–3 a to develop into a significant positive North Pacific Oscillation-like dipole, and this process corresponds to the northward shift of the AL. Negative WSC anomalies associated with this AL activity in the central North Pacific are able to induce the positive SSH anomalies. These oceanic signals then propagate westward into the KE region after 2–3 a, favoring a northward shift of the KE jet, thus leading to the warming of the KE SST. The feedbacks of the KE SST anomaly on the AL forcing are both negative for these two periodicities. These results suggest that the dual-period KE SST variability can be generated by the two-way KE-SST-AL coupling.
key words: sea surface temperature, Kuroshio Extension, Aleutian Low activity, dual-period variability
Grazing and performance of the copepod Pseudodiaptomus poplesia on a Chinese strain of Aureococcus anophagefferens
Xuejia HE, Didi HAN, Liuyu HAN, Songhui LU
doi: 10.1007/s13131-018-1168-6
Brown tides have recurred in estuary areas globally, but trophic interactions between the causative species Aureococcus anophagefferens and planktonic copepods remain poorly understood. In this study, we investigated performance (ingestion, growth, development and reproduction) of the planktonic copepod, Pseudodiaptomus poplesia, offered either mono-algal or mixed-algal diets containing a Chinese strain of A. anophagefferens. A typical Michaelis-Menten pattern existed between ingestion rate and food level when copepod fed on the mono-algal diet of this species. Nauplii exhibited the highest maximum ingestion rate (Imax) than copepodids and adult females. In addition, Imax value was higher in nauplii feeding on A. anophagefferens than on Skeletonema costatum. When fed mixtures of A. anophagefferens and S. costatum, P. poplesia selected against A. anophagefferens cells, but less strongly at the naupliar stage. Nauplii did not undergo metamorphosis and died at late naupliar stages feeding on A. anophagefferens alone, similar to those under starvation. Furthermore, the presence of A. anophagefferens greatly reduced the reproduction rate of females in mixtures but did not influence the growth rate of copepodids. These results suggest that P. poplesia nauplii may exert grazing pressure on A. anophagefferens population during a brown tide, which, however, may not be persistent because of copepod population decline.
key words: A. anophagefferens, copepod, grazing, growth, development, reproduction
Sedimentary geochemical proxies for methane seepage at Site C14 in the Qiongdongnan Basin in the northern South China Sea
Tiantian SUN, Daidai WU, Fei YANG, Lihua LIU, Xuegang CHEN, Ying YE
doi: 10.1007/s13131-019-1460-6
Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events. In this work, the correlation between the Sr/Ca and Mg/Ca ratios of sediment samples is analyzed and the sulfate concentration profile in Site C14 from cold-seep sediments in the Qiongdongnan Basin in northern South China Sea is obtained. The results confirmed that, sulfate at 0–247 cm below sea floor (Unit I) is mainly consumed by organic matter sulfate reduction (OSR), while sulfate at 247–655 cm (Unit II) is consumed by both the OSR and the anaerobic oxidation of methane (AOM). In addition, the bottom sediment layer is affected by weak methane seepage. The Mo and U enrichment factors also exhibit similar trends in their respective depth profiles. The responses of trace elements, including Co/Al, Ni/Al, Cr/Al and Zn/Al ratios to methane seepage allowed the study of depositional conditions and methane seepage events. Based on the results, it is speculated that the depositional conditions of Unit II changed with depth from moderate conditions of sulfidic and oxic conditions to locally anoxic conditions, and finally to suboxic conditions due to methane fluid leakage. The stable isotope values of chromium-reducible sulfide produced by AOM and those of sulfide formed by OSR in the early diagenetic environment suffered serious depletion of 34S. This was probably due to weak methane leakage, which caused the slower upward diffusion and the effect of early diagenesis on the samples. It is necessary to consider the effects of depositional environments and diagenesis on these geochemical parameters.
key words: Qiongdongnan Basin, trace elements, stable isotope values, anaerobic oxidation of methane, methane activity
A new free-living nematode, Actinonema falciforme sp. nov. (Nematoda: Chromadoridae), from the continental shelf of the East China Sea
Benze SHI, Tingting YU, Kuidong XU
doi: 10.1007/s13131-018-1318-x
Actinonema falciforme sp. nov. was discovered from the continental-shelf sediments of the East China Sea. It is characterized by six outer labial setae and four cephalic setae in one circle, complex and heterogeneous cuticular ornamentation with lateral differentiation, large and conspicuous amphideal fovea which is transversely oval-shaped, a single anterior testis, two opposed reflexed ovaries, falciform telamon (lateral pieces of gubernaculum), and the lack of spicule and gubernaculum. Within the genus Actinonema, only A. longicaudatum and the new species possess telamon and lack spicule and gubernaculum. Actinonema falciforme sp. nov. can be easily differentiated from A. longicaudatum by its much shorter body length, the peculiar shape of the telamon and a shorter tail.
key words: East China Sea, free-living marine nematodes, new species
A new record of Auchenoplax Ehlers, 1887 (Polychaeta: Ampharetidae) from the East China Sea
Jixing SUI, Xinzheng LI
doi: 10.1007/s13131-018-1312-3
A new record of the ampharetid genus Auchenoplax, A. worsfoldi Jirkov and Leontovich, 2013, is reported and described from the East China Sea. The specimens agree well with the original description of Auchenoplax worsfoldi with two pairs of branchiae, two thoracic uncinigers with enlarged neuropodia and 12 abdominal uncinigerous segments. The present specimens have long and filiform branchiae extending to thoracic chaetiger 9, which was not included in the original description. This is the first record of this species in Chinese waters.
key words: polychaete, Auchenoplax, taxonomy, East China Sea
Differential gene expression in the body wall of the sea cucumber (Apostichopus japonicus) under strong lighting and dark conditions
Libin ZHANG, Qiming FENG, Lina SUN, Yan FANG, Dongxue XU, Tao ZHANG, Hongsheng YANG
doi: 10.1007/s13131-017-1101-4
Sea cucumber, Apostichopus japonicus is very sensitive to light changes. It is important to study the influence of light on the molecular response of A. japonicus. In this study, RNA-seq provided a general overview of the gene expression profiles of the body walls of A. japonicus exposed to strong light (" light”), normal light (" control”) and fully dark (" dark”) environment. In the comparisons of " control” vs. " dark”, ”control” vs. " light” and " dark” vs. " light”, 1 161, 113 and 1 705 differentially expressed genes (DEGs) were identified following the criteria of |log2ratio|≥1 and FDR≤0.001, respectively. Gene ontology analysis showed that " cellular process” and " binding” enriched the most DEGs in the category of " biological process” and " molecular function”, while " cell” and " cell part” enriched the most DEGs in the category of " cellular component”. And the DEGs were mapped to 214, 41 and 229 pathways in the Kyoto Encyclopedia of Genes and Genomes database, and 51, 2 and 57 pathways were significantly enriched, respectively. Light-specific DEGs identified in this study will be important targets for further investigation to establish the biochemical mechanisms involved in the adaption of this sea cucumber to changes in the level of environmental light.
key words: sea cucumber, Apostichopus japonicus, gene expression, dark, light, body wall

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