Institutional Repository of South China Sea Institute of Oceanology, CAS
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Effects of nutrient load on microbial activities within a seagrass-dominated ecosystem: Implications of changes in seagrass blue carbon
No full textNutrient loading is a leading cause of global seagrass decline, triggering shifts from seagrass-to macroalgal-dominance. Within seagrass meadows of Xincun Bay (South China Sea), we found that nutrient loading (due to fish farming) increased sediment microbial biomass and extracellular enzyme activity associated with carbon cyding (polyphenol oxidase, invertase and cellulase), with a corresponding decrease in percent sediment organic carbon (SOC), suggesting that nutrients primed microorganism and stimulated SOC remineralization. Surpisingly, however, the relative contribution of seagrass-derived carbon to bacteria (delta C-13(bacteria)) increased with nutrient loading, despite popular theory being that microbes switch to consuming macroalgae which are assumed to provide a more labile carbon source. Organic carbon sources of fungi were unaffected by nutrient loading. Overall, this study suggests that nutrient loading changes the relative contribution of seagrass and algal sources to SOC pools, boosting sediment microbial biomass and extracellular enzyme activity, thereby possibly changing seagrass blue carbon. (C) 2017 Elsevier Ltd. All rights reserved
Molecular characterization of Pacific white shrimp (Litopenaeus vannamei) sodium bicarbonate cotransporter (NBC) and its role in response to pH stress
No full textThe sodium bicarbonate cotransporter (NBC) is an integral membrane ion transporter that can transport HCO3- (or a related species, such as CO32- across the plasma membrane. Previous researches revealed that NBC might play an important role in the regulation of intracellular pH in vertebrates. In the present study, an NBC cDNA was identified from Pacific white shrimp (Litopenaeus vannamei) and designated as Lv-NBC The full-length Lv-NBC cDNA is 4479 bp in size, containing a 5 '-untranslated region (UTR) of 59 bp, a 3 '-UTR of 835 bp and an open reading frame (ORF) of 3585 bp that encodes a protein of 1194 amino acids with a deduced molecular weight of 134.34 kDa. The Lv-NBC protein contains two functional domains (Band_3_cyto and HCO3_cotransp) and twelve transmembrane (TM) domains. Expression of the Lv-NBC mRNA was ubiquitously detected in all selected tissues, with the highest level in the gill. By in situ hybridization (ISH) with Digoxigenin-labeled probe, the Lv-NBC positive cells were shown mainly located in the secondary gill filaments. After low or high pH challenge, the transcript levels of Lv-NBC in the gill were found to be up-regulated. After knockdown of the Lv-NBC level by siRNA, the mortality of shrimp significantly increased under pH stress. Our study, as a whole, may provide evidences for the role of NBC in shrimp responding to pH stress, and give a new insight of the acid/base homeostasis mechanism in crustaceans. (C) 2017 Elsevier Ltd. All rights reserved
Differential mantle transcriptomics and characterization of growth-related genes in the diploid and triploid pearl oyster Pinctada fucata
No full textTo explore the molecular mechanism of triploidy effect in the pearl oyster Pinctada fucata, two RNA-seq libraries were constructed from the mantle tissue of diploids and triploids by Roche-454 massive parallel pyrosequencing. The identification of differential expressed genes (DEGs) between diploid and triploid may reveal the molecular mechanism of triploidy effect. In this study, 230 down-regulated and 259 up-regulated DEGs were obtained by comparison between diploid and triploid libraries. The gene ontology and KEGG pathway analysis revealed more functional activation in triploids and it may due to the duplicated gene expression in transcriptional level during whole genome duplication (WGD). To confirm the sequencing data, a set of 11 up-regulated genes related to growth and development control and regulation were analyzed by RT-qPCR in independent experiment. According to the validation and annotation of these genes, it is hypothesized that the set of up-regulated expressed genes had the correlated expression pattern involved in shell building or other interactive probable functions during triploidization. The up- regulation of growth-related genes may support the classic hypotheses of 'energy redistribution' from early research. The results provide valuable resources to understand the molecular mechanism of triploidy effect in both shell building and producing high-quality seawater pearls. (C) 2017 Elsevier B.V. All rights reserved
Ochracenes A-I, Humulane-Derived Sesquiterpenoids from the Antarctic Fungus Aspergillus ochraceopetaliformis
No full textNine new humulane-derived sesquiterpenoids, ochracenes A-I (1-9), were isolated from the Antarctic fungus Aspergillus ochraceopetaliformis SCSIO 05702. Their structures including absolute configurations were elucidated on the basis of spectroscopic analysis, Mosher's method, and electronic circular dichroism analysis. Compared with previous humulane-type sesquiterpenoids, ochracenes A-I (1-9) featured novel carbon skeletons with corresponding methyl migration, ring cleavage, and carbon loss. Two unprecedented 8,9-secocyclic sesquiterpenoids (2 and 3) exhibited inhibitory effects on lipopolysaccharide-induced NO release in RAW 264.7 mouse macrophage cell lines with IC50 values of 14.6 +/- 0.5 and 18.3 +/- 1.7 mu M, respectively
Diversity and abundance of epipelagic larvaceans and calanoid copeods in the eastern equatorial Indian Ocean during the spring inter-monsoon
No full textThis study investigated the species composition, distribution and abundance of larvaceans and calanoid copepods in the eastern equatorial Indian Ocean. In total, 25 species of larvaceans and 69 species of calanoid copepods were identified in the study area. Although the average diversity and evenness indexes of larvaceans were lower than those of calanoid copepods, the abundance of larvaceans was higher than that of calanoids with means of 40.1 +/- 14.9 ind m(-3) Oikopland 28.4 +/- 9.1 ind m(-3), respectively. Larvacean community was numerically dominated by Oikopleura fusiformis, Oikopleura longicauda, Oikopleura cophocerca, Fritillaria formica and Fritillaria pellucida, accounting for 83% of total larvacean abundance. The calanoid community was dominated by the following five species, represented 61% of calanoid copepods: Clausocalanus furcatus, Clausocalanus farrani, Acartia negligens, Acrocalanus longicornis as well as the copepodite stage of Euchaeta spp. This study highlights that the importance of larvaceans in the eastern equatorial Indian Ocean
An Expendable Microstructure Profiler for Deep Ocean Measurements
No full textMeasurements of turbulence in the deep ocean, particularly close to the bottom, are extremely sparse because of the difficulty and operational risk of obtaining deep profiles near the seafloor. A newly developed expendable instrument-the VMP-X (Vertical Microstructure Profiler-Expendable)-carries two microstructure shear probes to measure the fluctuations of vertical shear into the dissipation range and can profile down to a depth of 6000 m. Data from nine VMP-X profiles in the western Pacific Ocean near 11.6 degrees N over rough topography display bottom-intensified turbulence with dissipation rates increasing by two factors of 10 to 4 x 10(-9) W kg(-1) within 200 m above the bottom. In contrast, over smooth topography in the southern South China Sea near 11 degrees N, three profiles show that turbulence in the bottom boundary layer increases only slightly, with dissipation rates reaching 1 x 10(-10) W kg(-1). The eddy diffusivity over rough topography reached to 5 x 10(-3) m(2) s(-1). The average diffusivity over all depths was 0.3 x 10(-4) and 0.9 x 10(-4) m(2) s(-1) for the tests in the southern South China Sea and in the western Pacific Ocean, respectively, and these values are much larger than previous estimates of less than approximate to 0.1 x 10(-4) m(2) s(-1) for the main thermocline
Reconstruction of ocean's interior from observed sea surface information
No full textObservational surface data are used to reconstruct the ocean's interior through the "interior + surface quasigeostrophic'' (isQG) method. The input data include the satellite-derived sea surface height, satellite-derived sea surface temperature, satellite-derived or Argo-based sea surface salinity, and an estimated stratification of the region. The results show that the isQG retrieval of subsurface density anomalies is quite promising compared to Argo profile data. At similar to 1000 m depth, the directions of retrieved velocity anomalies are comparable to those derived from Argo float trajectories. The reconstruction using surface density input field approximated only by SST (with constant SSS) performs less satisfactorily than that taking into account the contribution of SSS perturbations, suggesting that the observed SSS information is important for the application of the isQG method. Better reconstruction is obtained in the warm season than in the cold season, which is probably due to the stronger stratification in the warm season that confines the influence of the biases in the surface input data (especially SSS) in a shallow layer. The comparison between the performance of isQG with Argo-based SSS input and that with satellite-derived SSS input suggests that the biases in the SSS products could be a major factor that influences the isQG performance. With reduced biases in satellite-derived SSS in the future, the measurement-based isQG method is expected to achieve better reconstruction of ocean interior and thus is promising in practical application
Circulations associated with cold pools in the Bohai Sea on the Chinese continental shelf
No full textCirculations associated with cold pools in the Bohai Sea were investigated in the summers of 1959 and 2006 using observations and numerical simulations. The climatological forcing was incorporated to drive a model based on the Regional Ocean Modeling Systems (ROMS) to reconstruct the monthly evolution of flow structure. Cold pools were found to be separated into two parts by an undersea ridge in the central Bohai Sea. A set of numerical experiments were conducted to evaluate the relative contributions from the exchange across the strait, heat flux, wind, and tides. Baroclinic circulation was the dominant component of the circulation. A basin scale cyclonic gyre was the main feature during the stratified seasons from May through August. Cyclonic and anticyclonic sub-basin scale gyres emerged in late spring and peaked during July and early August, accompanied by intensifying frontal jets along the west and south coasts of the Bohai Sea. The cyclonic frontal jet in the model was responsible for rapid reduction of particles released from the surface layer of the Bohai Sea in summer; and 2) Experiments using Lagrangian particle tracking also showed that particles released in Liaodong and Bohai bays were retained longer than those released in the other regions as the surface convergence in the western Bohai Sea resulted in an intense concentration of particles
Detailed spatiotemporal impacts of El Nino on phytoplankton biomass in the South China Sea
No full textThe lagging and leading correlations among satellite observations, reanalyzed biogeophysical data, and the Nino3.4 El Nino index were investigated to reveal the impacts of El Nino on the phytoplankton biomass (chlorophyll a [Chl a]) in the South China Sea (SCS), in an attempt to identify the probable responsible factors in greater spatiotemporal detail. A basin-scale high Chl a concentration during the developing phase of El Nino changed to basin-scale low Chl a during the weakening phase. Cyclonic wind circulation in the northern basin, increased wind speed in the southern basin, and strengthened upwelling off the Vietnamese coast likely caused a basin-scale nutrient increase during the developing phase of an El Nino event; the opposite conditions led to low nutrient levels during the weakening phase. Decreases in Chl a east of the Vietnamese coast and northwest of Borneo Island were due to decreases in nutrients supplied by rivers. These spatiotemporal changes are considered biogeophysical responses to a variety of types of El Nino. Regardless of the El Nino type, reanalyzing biogeophysical data sets during central Pacific warming separately from those during eastern Pacific warming is recommended for a more robust understanding of the detailed spatiotemporal impacts of different El Nino types on the biogeophysical environment of the SCS
The summer-fall anticyclonic eddy west of Luzon: Structure and evolution in 2012 and interannual variability
No full textThe Conductivity-Temperature-Depth (CTD) and acoustic Doppler current profiler (ADCP) measurements along 18 degrees N off the western Luzon in the South China Sea (SCS), collected during a cruise from August 12-14,2012, were used to explore the vertical structure of an anticyclonic eddy (AE) during the observational period. Further, the French Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) sea level anomaly (SLA) and corresponding anomalous surface geostrophic velocity were used to study the temporal evolution of the AE. The vertical structure of the AE along 18 degrees N in August 2012 showed a trough located near 117.5 degrees E. The AE extended vertically downward and its distinct feature was identifiable to 200 m depth. Seasonal variations of SIA indicate that the AE lasted for 5 months (June to early November), going through the growth and nearly stationary period from mid-June to late August and then propagating westward along 18 degrees N with varying phase speeds and shapes to the continental slope off the southeastern Hainan Island during late September to November. Furthermore, T-S characteristics suggest that the AE was generated off the western Luzon. Interannual variations of the summer (July-September) SLA presented by Empirical Orthogonal Function analysis, indicates that the local circulation was enhanced by the anomalous anticyclonic eddy along 18 degrees N in the years of 2008, 2010, 2012 and 2013 during the period from1993 to 2014. (c) 2017 Elsevier B.V. All rights reserved