2014 Vol. 33, No. 9

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Ventilation of the Sulu Sea retrieved from historical data
LI Li, GAN Zijun
2014, 33(9): 1-11. doi: 10.1007/s13131-014-0517-3
Based on historical observations, ventilation of the Sulu Sea (SS) is investigated and, its interbasin exchange is also partly discussed. The results suggest that near the surface the water renewal process not only occurs through the Mindoro Strait (MS) and the Sibutu Passage, but also depends on the inflows through the Surigao Strait and the Bohol Sea from the Pacific and through the Balabac Strait from the South China Sea (SCS). Both inflows are likely persistent year round and their transports might not be negligible. Below the surface, the core layer of the Subtropical Lower Water (SLW) lies at about 200 m, which enters the SS through the Mindoro Strait not hampered by topography. Moreover, there is no indication of SLW inflow through the Sibutu Passage even though the channel is deep enough to allow its passage. The most significant ventilation process of the SS takes place in depths from 200 m to about 1 200 m where intermediate convection driven by quasi-steady inflows through the Mindoro and Panay straits (MS-PS) dominates. Since the invaded water is drawn from the upper part of the North Pacific Intermediate Water (NPIW) of the SCS, it is normally not dense enough to sink to the bottom. Hence, the convective process generally can only reach some intermediate depths resulting in a layer of weak salinity minimum (about 34.45). Below that layer, there is the Sulu Sea Deep Water (SSDW) homogeneously distributed from 1 200 m down to the sea floor, of which the salinity is only a bit higher (about 34.46) above the minimum. Observational evidence shows that hydrographic conditions near the entrance of the MS in the SCS vary significantly from season to season, which make it possible to provide the MS-PS overflow with denser water of higher salinity sporadically. It is hence proposed that the SSDW is derived from intermittent deep convection resulted from property changes of the MS-PS inflow.
The annual mean sketches and climatological variability of the volume and heat transports through the inter-basin passages: A study based on 1 400-year spin up of MOM4p1
ZHU Yaohua, WEI Zexun, WANG Yonggang, GUAN Yuping, WANG Xinyi
2014, 33(9): 12-24. doi: 10.1007/s13131-014-0513-7
The annual mean volume and heat transport sketches through the inter-basin passages and transoceanic sections have been constructed based on 1 400-year spin up results of the MOM4p1. The spin up starts from a state of rest, driven by the monthly climatological mean force from the NOAA World Ocean Atlas (1994). The volume transport sketch reveals the northward transport throughout the Pacific and southward transport at all latitudes in the Atlantic. The annual mean strength of the Pacific-Arctic-Atlantic through flow is 0.63×106 m3/s in the Bering Strait. The majority of the northward volume transport in the southern Pacific turns into the Indonesian through flow (ITF) and joins the Indian Ocean equatorial current, which subsequently flows out southward from the Mozambique Channel, with its majority superimposed on the Antarctic Circumpolar Current (ACC). This anti-cyclonic circulation around Australia has a strength of 11×106 m3/s according to the model-produced result. The atmospheric fresh water transport, known as P-E+R (precipitation minus evaporation plus runoff), constructs a complement to the horizontal volume transport of the ocean. The annual mean heat transport sketch exhibits a northward heat transport in the Atlantic and poleward heat transport in the global ocean. The surface heat flux acts as a complement to the horizontal heat transport of the ocean. The climatological volume transports describe the most important features through the inter-basin passages and in the associated basins, including: the positive P-E+R in the Arctic substantially strengthening the East Greenland Current in summer; semiannual variability of the volume transport in the Drake Passage and the southern Atlantic-Indian Ocean passage; and annual transport variability of the ITF intensifying in the boreal summer. The climatological heat transports show heat storage in July and heat deficit in January in the Arctic; heat storage in January and heat deficit in July in the Antarctic circumpolar current regime (ACCR); and intensified heat transport of the ITF in July. The volume transport of the ITF is synchronous with the volume transport through the southern Indo-Pacific sections, but the year-long southward heat transport of the ITF is out of phase with the heat transport through the equatorial Pacific, which is northward before May and southward after May. This clarifies the majority of the ITF originating from the southern Pacific Ocean.
Laboratory simulation of the influence of geothermal heating on the interior ocean
ZHOU Shengqi, QU Ling, ZHAO Xiaozheng, WAN Wei
2014, 33(9): 25-31. doi: 10.1007/s13131-014-0512-8
This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux perturbation δF/F is employed. The increments of flow and thermal properties, including eddy diffusivity KT, flow velocity V and bottom temperature Tb, are found to be independent of the applied heat flux F. Together with the scaling analysis of convective flow at different configurations, where the flow is thermally driven in the relatively low or extremely high turbulent thermal convections or the horizontal convection, the variances of flow properties, δKT/KT and δV/V, are found to be close to 0.5% and 0.75% at δF/F=2%. This means that the small heat flux perturbation plays a negligible role in the global convective flow. However, δTbT is found to be 1.5% at δF/F=2%, which would have a significant effect in the local region. The results might provide a clue to understanding the influence of geothermal heating on global oceanic circulation. It is expected that geothermal heating will contribute less than 1% in turbulent mixing and volume flux to global oceanic circulation, so its influence can be negligible in this situation. However, when it comes to the local environment, the influence of geothermal heating cannot be ignored. For example, temperature increases of about 0.5℃ with geothermal heating would have a significant effect on the physical environments within the benthic boundary layer.
The impact of surface waves on the mixing of the upper ocean
WANG Zhifeng, WU Kejian, XIA Changshui, ZHANG Xiaoshuang
2014, 33(9): 32-39. doi: 10.1007/s13131-014-0514-6
A new three-dimensional numerical model is derived through a wave average on the primitive N-S equations, in which both the "Coriolis-Stokes forcing" and the "Stokes-Vortex force" are considered. Three ideal experiments are run using the new model applied to the Princeton ocean model (POM). Numerical results show that surface waves play an important role on the mixing of the upper ocean. The mixed layer is enhanced when wave effect is considered in conjunction with small Langmuir numbers. Both surface wave breaking and Stokes production can strengthen the turbulent mixing near the surface. However, the influence of wave breaking is limited to a thin layer, but Stokes drift can affect the whole mixed layer. Furthermore, the vertical mixing coefficients clearly rise in the mixed layer, and the upper ocean mixed layer is deepened especially in the Antarctic Circumpolar Current when the model is applied to global simulations. It indicates that the surface gravity waves are indispensable in enhancing the mixing in the upper ocean, and should be accounted for in ocean general circulation models.
Numerical study on water waves and wave-induced longshore currents in Obaköy coastal water
TANG Jun, LYU Yigang, SHEN Yongming
2014, 33(9): 40-46. doi: 10.1007/s13131-014-0515-5
In this paper, the water waves and wave-induced longshore currents in Obaköy coastal water which is located at the Mediterranean coast of Turkey were numerically studied. The numerical model is based on the parabolic mild-slope equation for coastal water waves and the nonlinear shallow water equation for the wave-induced currents. The wave transformation under the effects of shoaling, refraction, diffraction and breaking is considered, and the wave provides radiation stresses for driving currents in the model. The numerical results for the water wave-induced longshore currents were validated by the measured data to demonstrate the efficiency of the numerical model. Then the water waves and longshore currents induced by the waves from main directions were numerically simulated and analyzed based on the numerical results. The numerical results show that the movement of the longshore currents was different while the wave propagated to a coastal zone from different directions.
Nontidal sea level changes in Hiroshima Bay, Japan
ZHANG Chuanzheng, KANEKO Arata, ZHU Xiaohua, LIN Ju
2014, 33(9): 47-55. doi: 10.1007/s13131-014-0516-4
Nontidal sea level changes generated in Hiroshima Bay of the Seto-Inland Sea in Japan are studied over various time scales, from the sub-tidal (2 d to 1 month) to inter-annual scales (>2 years). The total sea level variation produces a standard deviation (STD) of 12.5 cm. The inter-annual component of the sea level variation in Hiroshima Bay oscillates with a STD of 3.4 cm, forming a long-term trend of 4.9 mm/a. The STD of the sea level variation is 9.8 cm for the seasonal component (8 months to 2 years) and 4.7 cm for the intra-seasonal one (1 month to 8 months). Significant sea level variations with a STD of 4.2 cm also occur in the sub-tidal range. Special attention is paid to the sub-tidal sea level changes. It is found that the upwelling and associated transient sea level changes generated along the north coast of Hiroshima Bay (opened southward) by the strong northerly wind, play a significant role in sub-tidal sea level changes. The transient sea level changes are over 10 cm in most cases when caused by typhoons that pass through the Pacific Ocean off the Kii Peninsula, located at about 400 km east of Hiroshima Bay. Reasonable sea level changes are evaluated by the balance of pressure forces at the onshore and offshore boundary of the study domain.
Biases of the Arctic climate in a regional ocean-sea ice-atmosphere coupled model: an annual validation
LIU Xiying
2014, 33(9): 56-67. doi: 10.1007/s13131-014-0518-2
The Coupling of three model components, WRF/PCE (polar climate extension version of weather research and forecasting model (WRF)), ROMS (regional ocean modeling system), and CICE (community ice code), has been implemented, and the regional atmosphere-ocean-sea ice coupled model named WRF/PCEROMS-CICE has been validated against ERA-interim reanalysis data sets for 1989. To better understand the reasons that generate model biases, the WRF/PCE-ROMS-CICE results were compared with those of its components, the WRF/PCE and the ROMS-CICE. There are cold biases in surface air temperature (SAT) over the Arctic Ocean, which contribute to the sea ice concentration (SIC) and sea surface temperature (SST) biases in the results of the WRF/PCE-ROMS-CICE. The cold SAT biases also appear in results of the atmospheric component with a mild temperature in winter and similar temperature in summer. Compared to results from the WRF/PCE, due to influences of different distributions of the SIC and the SST and inclusion of interactions of air-sea-sea ice in the WRF/PCE-ROMS-CICE, the simulated SAT has new features. These influences also lead to apparent differences at higher levels of the atmosphere, which can be thought as responses to biases in the SST and sea ice extent. There are similar atmospheric responses in feature of distribution to sea ice biases at 700 and 500 hPa, and the strength of responses weakens when the pressure decreases in January. The atmospheric responses in July reach up to 200 hPa. There are surplus sea ice extents in the Greenland Sea, the Barents Sea, the Davis Strait and the Chukchi Sea in winter and in the Beaufort Sea, the Chukchi Sea, the East Siberian Sea and the Laptev Sea in summer in the ROMS-CICE. These differences in the SIC distribution can all be explained by those in the SST distributions. These features in the simulated SST and SIC from ROMS-CICE also appear in the WRF/PCE-ROMS-CICE. It is shown that the performance of the WRF/PCE-ROMS-CICE is determined to a large extent by its components, the WRF/PCE and the ROMS-CICE.
Fractal-based weak target detection within sea clutter
LI Yang, LV Xiaowen, LIU Kuisheng, ZHAO Shangzhuo
2014, 33(9): 68-72. doi: 10.1007/s13131-014-0519-1
The target on the sea surface is complex and difficult to detect due to the interference of backscattered returns from the sea surface illuminated by the radar pulse. Detrended fluctuation analysis (DFA) has been used successfully to extract the time-domain Hurst exponent of sea-clutter series. Since the frequency of the sea clutter mainly concentrates around Doppler center so that we consider to extract frequency-domain fractal characterization and then detect a weak target within sea clutter by using the difference of frequency-domain fractal characterization. The generalized detrended fluctuation analysis (GDFA) is more flexible than traditional DFA owing to its smoothing action for the clutters. In this paper, we apply the GDFA to evaluate the generalized Hurst exponent of sea-clutter series in the frequency domain. The difference of generalized Hurst exponents between different sea-clutter range bins would be used to determine whether the target exists. Moreover, some simulations with the real IPIX radar data have also been demonstrated in order to support this conclusion.
Point association analysis of vessel target detection with SAR, HFSWR and AIS
JI Yonggang, ZHANG Jie, MENG Junmin, WANG Yiming
2014, 33(9): 73-81. doi: 10.1007/s13131-014-0498-2
A space-borne synthetic aperture radar (SAR), a high frequency surface wave radar (HFSWR), and a ship automatic identification system (AIS) are the main remote sensors for vessel monitoring in a wide range. These three sensors have their own advantages and weaknesses, and they can complement each other in some situations. So it would improve the capability of vessel target detection to use multiple sensors including SAR, HFSWR, and AIS to identify non-cooperative vessel targets from the fusion results. During the fusion process of multiple sensors' detection results, point association is one of the key steps, and it can affect the accuracy of the data fusion and the efficiency of a non-cooperative target's recognition. This study investigated the point association analyses of vessel target detection under different conditions: spaceborne SAR paired with AIS, as well as HFSWR, paired with AIS, and the characteristics of the SAR and the HFSWR and their capability of vessel target detection. Then a point association method of multiple sensors was proposed. Finally, the thresholds selection of key parameters in the points association (including range threshold, radial velocity threshold, and azimuth threshold) were investigated, and their influences on final association results were analyzed.
Research on data pre-deployment in information service flow of digital ocean cloud computing
SHI Suixiang, XU Lingyu, DONG Han, WANG Lei, WU Shaochun, QIAO Baiyou, WANG Guoren
2014, 33(9): 82-92. doi: 10.1007/s13131-014-0520-8
Data pre-deployment in the HDFS (Hadoop distributed file systems) is more complicated than that in traditional file systems. There are many key issues need to be addressed, such as determining the target location of the data prefetching, the amount of data to be prefetched, the balance between data prefetching services and normal data accesses. Aiming to solve these problems, we employ the characteristics of digital ocean information service flows and propose a deployment scheme which combines input data prefetching with output data oriented storage strategies. The method achieves the parallelism of data preparation and data processing, thereby massively reducing I/O time cost of digital ocean cloud computing platforms when processing multi-source information synergistic tasks. The experimental results show that the scheme has a higher degree of parallelism than traditional Hadoop mechanisms, shortens the waiting time of a running service node, and significantly reduces data access conflicts.
Remote sensing of phytoplankton distribution in the Red Sea and Gulf of Aden
ALKAWRI Abdulsalam, GAMOYO Majambo
2014, 33(9): 93-99. doi: 10.1007/s13131-014-0527-1
Analysis of high-resolution 4 km sea surface temperature, Chlorophyll a (Chl a), and wind datasets provides a detailed description of the spatio-temporal seasonal succession of phytoplankton biomass in the Red Sea and Gulf of Aden. Based on Moderate Resolution Imaging Spectroradiometer on-board aqua platform (MODIS Aqua) data andsynoptic observations in the Red Sea, Chl a varies from north to south, with the northern part appearing to be oligotrophic. This is likely due to the absence of strong mixing and low nutrient intrusion in comparison to the southern part during winter. In the Gulf of Aden, the emergence of upwelling cell is clearly evident along the coast of Yemen, and is only distinct from the summer-autumn seasons. Most notable is the pulsating nature of the upwelling, with warm and cold events clearly distinguished with phytoplankton response to this physical forcing also evident. The phytoplankton biomass distribution varies considerably between the two regions of study. In both study areas, water temperature and prevailing winds control nutrient concentrations.
Reduced inorganic sulfur in the sediments of the Yellow Sea and East China Sea
KANG Xuming, LIU Sumei, ZHANG Guoling
2014, 33(9): 100-108. doi: 10.1007/s13131-014-0499-1
Cold diffusion methods are used to separate and quantify the three reduced inorganic sulfur species into acid volatile sulfide (AVS), pyrite-S and element sulfur (ES) in the sediments of the Yellow and East China Seas. The results show that up to 25.02 μmol/g of AVS, 113.1 μmol/g of pyrite-S and 44.4 μmol/g of ES are observed in the sediments of the Yellow Sea and East China Sea. Pyrite-S is the predominant sulfide mineral in the sediments, while the concentration of AVS is quite low at most stations in the study area. The amounts and reactivity of organic matter are the primary limited factor for the sulfide formation, while an iron limitation and a sulfate limitation are not observed in the sediments of the Yellow Sea and East China Sea. The irregular profiles of the three reduced inorganic sulfur species also reflected the comprehensive influence of sediment composition and sedimentation rates.
On the integrity of a commercial cassette ultrafiltration membrane: implications for marine colloidal biogeochemistry
LIN Liangshi, CAI Yihua, SUN Xiuwu, CHEN Min
2014, 33(9): 109-116. doi: 10.1007/s13131-014-0521-7
The performance and integrity of a cassette cross-flow ultrafilter (Pellicon 2, Millipore) are examined with a suite of macromolecules of different molecular masses. The retention coefficient during the cross-flow ultrafiltration experiments increases with increasing molecular mass and reaches 90% with 10 kDa dextran in both milli-Q water and ultrafiltered seawater media. Based on a 90% retention coefficient, the molecular mass cut-off for the ultrafiltration membrane is defined at 10 kDa, which is ten times (1 kDa) that rated by the manufacturer. To further validate the accuracy of the laboratory calibration, the samples from the lower Zhujiang River and the Jiulong River Estuary are ultrafiltered with the cassette ultrafiltration membrane and the colloidal organic carbon abundances in these samples are quantified with the ultrafiltration permeation model based on time series permeation subsamples. The colloidal organic carbon abundances are 5.8%-21.1% in the Jiulong River Estuary and 5.6%-11.0% in the lower Zhujiang River. These are consistent with the reported values for both estuaries as well as with the colloidal organic carbon abundances in marine environments over the coastal and open oceans with 10 kDa cut-off membranes. Therefore, these field data support the laboratory calibration result and indicate the validity of the experimental and quantification procedure adopted. The discrepancy between the nominal molecular mass cut-off and the actual pore size of the ultrafiltration membrane should be of great concern for research in colloidal and nanoparticle biogeochemistry. Careful examination of the membrane integrity should be taken during ultrafiltration experiments in order to avoid misleading molecular mass cut-off information.
Assessing the benthic habitat quality in the Huanghe (Yellow River) Estuary and its adjacent areas using AMBI and M-AMBI
LUO Xianxiang, ZHANG Juan, YANG Jianqiang, SONG Wenpeng, CUI Wenlin
2014, 33(9): 117-124. doi: 10.1007/s13131-014-0522-6
The protection of the biological diversity and the maintenance of the regional ecological integrity for the Huanghe (Yellow River) Estuary and its adjacent areas are practically significant and valuable. However, frequent human activities and natural climate changes have caused vigorous disturbances on the ecosystem in these sea areas. An objective assessment on the benthic habitat quality (BHQ) of the Huanghe Estuary and its adjacent areas is conducted, using AZTI's Marine Biotic Index (AMBI) and multivariate AMBI (M-AMBI) based on the data of macrobenthos in May and August 2011. The results show that both the indices do not correlate significantly, and their assessment results are greatly different. All of the samples assessed using the AMBI were "high" or "good", because the ecological group I (EGI) and the ecological group II (EGII) were dominant macrobenthic ecological groups in the research area. Owing to a low species' richness and a high individual abundance in some samples, the BHQ levels using the M-AMBI were worse than those of the AMBI. Significant correlations are observed between the M-AMBI, water depth, bottom water salinity and dissolved inorganic nitrogen, thus the M-AMBI could sensitively respond to environmental changes and distinguish influences from uninfluenced stations, but the AMBI could not. The consistent results between the AMBI and the M-AMBI mainly appeared in the uninfluenced (undisturbed or slightly disturbed) stations. Therefore, the M-AMBI is more effective than the AMBI in assessing the benthic habitat quality in the Huanghe Estuary and its adjacent areas. Using the M-AMBI to assess the BHQ of the Huanghe Estuary and its adjacent areas, the results show that 3% of the stations are undisturbed and the BHQs are "high", and 61% of the stations are slightly disturbed and those of the BHQ are "good", and the rest are meanly disturbed and those of the BHQ are "moderate".
Weak coupling between heterotrophic nanoflagellates and bacteria in the Yellow Sea Cold Water Mass area
LIN Shiquan, HUANG Lingfeng, LU Jiachang
2014, 33(9): 125-132. doi: 10.1007/s13131-014-0523-5
A study was carried out to investigate the grazing pressure of heterotrophic nanoflagellates (HNF) on bacteria assemblages in the Yellow Sea Cold Water Mass (YSCWM) area in October, 2006. The results show that the HNF abundance ranges from 303 to 1 388 mL-1, with a mean of 884 mL-1. The HNF biomass is equivalent to 10.6%-115.6% of that of the bacteria. The maximum abundance of the HNF generally occurred in the upper 30 m water layer, with a vertical distribution pattern of surface layer abundance greater than middle layer abundance, then bottom layer abundance. The hydrological data show that the YSCWM is located in the northeastern part of the study area, typically 40 m beneath the surface. A weak correlation is found between the abundances of HNF and bacteria in both the YSCWM and its above water layer. One-way ANOVA analysis reveals that the abundance of HNF and bacteria differs between inside the YSCWM and in the above water mass. The ingestion rates of the HNF on bacteria was 8.02±3.43 h-1 in average. The grazing rate only represented 22.75%±6.91% of bacterial biomass or 6.55%+4.24% of bacterial production, implying that the HNF grazing was not the major factor contributing to the bacterial loss in the YSCWM areas.
The effects of DDT on the feeding, respiration, survival, and reproduction of Sinocalanus tenellus (Copepoda: Calanoida)
XU Donghui, LIU Guangxing
2014, 33(9): 133-138. doi: 10.1007/s13131-014-0524-4
DDT (dichloro-diphenyl-trichloroethane) as a type of organochlorine pesticides, is an important component of pesticides pollution whose impact on the marine ecosystem is urgently to be evaluated. To investigate the biological effects of DDT on the marine ecosystem, copepods being the main contributor of secondary productivity in the marine ecosystem, were selected as target animals. The influence of DDT on the feeding, respiration, survival, and reproduction of Sinocalanus tenellus (S. tenellus) was analyzed and the antioxidant enzymes activities in the individuals were measured under different exposure concentrations of DDT. The 48 h median lethal concentration (LC50) and 96 h LC50 of DDT to S. tenellus were 5.44 and 2.50 μg/dm3, respectively. The filtration rates, grazing rates, and respiration of S. tenellus decreased apparently with increased DDT concentrations. Under lower concentration (<625 ng/dm3) of DDT, the activities of the antioxidant enzymes, including superoxide dismutase and catalase in the animals increased significantly compared with those in the animals without any exposure to DDT, which suggested that the antioxidant enzymes can protect the animals from oxidative damage. However, the activity of the antioxidant enzyme decreased when the animals were exposed to higher concentration (1 250-2 500 ng/dm3) of DDT. The survival rate of both females and males was reduced when they were exposed to DDT less than 250 ng/dm3, but females showed higher survival rate than males when they are under the same concentration. The hatching ratio and the egg diameters of S. tenellus decreased significantly when they were exposed to DDT with a concentration of 25 and 250 ng/dm3, however, the cumulative egg production did not show any significant variation when the animals were exposed to the above DDT concentration. These data in the preset study suggested that exposure to DDT can cause the variation of the species composition of copepods, and further affect the marine ecosystem.
Phylogeny of genera Laminaria and Saccharina (Laminariales, Phaeophyceae) based on three molecular markers
CHI Shan, QIAN Hao, LI Tianyong, WANG Xumin, LIU Cui, REN Lei, TANG Xuexi, LIU Tao
2014, 33(9): 139-151. doi: 10.1007/s13131-014-0525-3
In the past two decades, many studies have focused on the classification within genus Laminaria, ultimately trying to divide it into two subgroups or genera: Laminaria and Saccharina. A significant debate still surrounds the question of its division, as the conflicting phylogenetic hypotheses that have resulted from the classification studies are based on different taxon sampling, molecular markers, or analysis methods. It is aimed at elucidate the molecular phylogeny within Laminaria and Saccharina. The nine species of Laminariales are sampled from northern Asia and Europe, and 23 new sequences in the nuclear, plastid, and mitochondrial genomes are determined to identify their taxonomic status. The phylogenetic analyses of 71 species are performed, including representatives from six of the seven families of the order Laminariales, based on three separate data sets. An evidence is provided to strongly support a clear split that maintains the two recognized genera, Laminaria and Saccharina, with Laminaria appearing to be the ancestor group. Further, analyses indicate that all taxa in Saccharina and Laminaria did not form a monophyletic lineage, instead Laminariaceae and Lessoniaceae grouped together interlacedly, and Costariaceae appeared as the sister taxon of the Lessoniaceae-Laminariaceae clade. In the phylogenetic analysis, mitochondrial c oxidase I (COI) sequences appeared to be the most credible molecular marker which was more befitting than nuclear encoded internal transcribed spacer (ITS) and plastid encoded rbcL for establishment of Laminariales systematics. It is the most comprehensive phylogeny of the order Laminariales, and contributes to an enhanced understanding and estimation of the phylogenetic relationships for the economically important seaweeds, Laminaria and Saccharina.
Validation of housekeeping genes as internal controls for studying the gene expression in Pyropia haitanensis (Bangiales, Rhodophyta) by quantitative real-time PCR
LI Bing, CHEN Changsheng, XU Yan, JI Dehua, XIE Chaotian
2014, 33(9): 152-159. doi: 10.1007/s13131-014-0526-2
Pyropia haitanensis is an economically important mariculture crop in China and has a high research value for several life phenomena, for example environmental tolerance. To explore the mechanisms underlying these characteristics, gene expression has been investigated at the whole transcriptome level. Gene expression studies using quantitative real-time PCR should start by selecting an appropriate internal control gene; therefore, the absolute expression abundance of six housekeeping genes (18S rRNA (18S), ubiquitin-conjugating enzyme (UBC), actin (ACT), β-tubulin (TUB), elongation factors 2 (EF2), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) examined by the quantitative real-time PCR in samples corresponding to different strains, life-cycle stages and abiotic stress treatments. Their expression stabilities were assessed by the comparative cycle threshold (Ct) method and by two different software packages: geNorm and Norm-Finder. The most stable housekeeping gene is UBC and the least stable housekeeping is GADPH. Thus, it is proposed that the most appropriate internal control gene for expression analyses in P. haitanensis is UBC. The results pave the way for further gene expression analyses of different aspects of P. haitanensis biology including different strains, life-history stages and abiotic stress responses.
Colonization dynamics of periphytic diatoms in coastal waters of the Yellow Sea, northern China
Liu Yuanyuan, Zhang Wei, Xu Henglong
2014, 33(9): 160-165. doi: 10.1007/s13131-014-0466-x
The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50% maximum abundance (10 d) showed no significant differences (P>0.05) between two depths 1 and 3 m. Although the diatom communities represented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness represented a higher variability with significantly different values (P<0.05) at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at 1 m is more effective to detect the ecological features for bioassessment in marine ecosystems.
Research Notes
The bacterial abundance and production in the East China Sea: seasonal variations and relationships with the phytoplankton biomass and production
CHEN Bingzhang, HUANG Bangqin, XIE Yuyuan, GUO Cui, SONG Shuqun, LI Hongbo, LIU Hongbin
2014, 33(9): 166-177. doi: 10.1007/s13131-014-0528-0
The East China Sea is a productive marginal sea with a wide continental shelf and plays an important role in absorbing atmospheric carbon dioxide and transferring terrigenous organic matter to the open ocean. To investigate the roles of heterotrophic bacteria in the biogeochemical dynamics in the East China Sea, bacterial biomasses (BB) and productions (BP) were measured in four cruises. The spatial distributions of the BB and the BP were highly season-dependent. Affected by the Changjiang River discharge, the BB and the BP were high in shelf waters (bottom depth not deeper than 50 m) and generally decreased offshore in August 2009. In December 2009 to January 2010, and November to December 2010, the BB and the BP were high in waters with medium bottom depth. The onshore-offshore decreasing trends of the BB and the BP also existed in May-June 2011, when the BB was significantly higher than in other cruises in shelf break waters (bottom depth deeper than 50 m but not deeper than 200 m). The results of generalized additive models (GAM) suggest that the BB increased with the temperature at a range of 8-20℃, increased with the chlorophyll concentration at a range of 0.02-3.00 mg/m3 and then declining, and decreased with the salinity from 28 to 35. The relationship between the temperature and the log-transformed bacterial specific growth rate (SGR) was linear. The estimated temperature coefficient (Q10) of the SGR was similar with that of the phytoplankton growth. The SGR also increased with the chlorophyll concentration. The ratio of the bacterial to phytoplankton production ranged from less than 0.01 to 0.40, being significantly higher in November-December 2010 than in May-June 2011. Calculated from the bacterial production and growth efficiency, the bacterial respiration consumed, on average, 59%, 72% and 23% of the primary production in August 2009, November-December 2010, and May-June 2011, respectively.
The research on direct-drive wave energy conversion system and performance optimization
CHEN Zhongxian, YU Haitao, HU Minqiang
2014, 33(9): 178-183. doi: 10.1007/s13131-014-0529-z
A direct-drive wave energy conversion system based on a three-phase permanent magnet tubular linear generator (PMTLG) and a heaving buoy is proposed to convert wave energy into electrical energy. Sufficient experimental methods are adopted to compare the computer simulations, the validity of which is verified by the experiment results from a wave tank laboratory. In the experiment, the motion curves of heaving buoy are with small fluctuations, mainly caused by the PMTLG's detent force. For the reduction of these small fluctuations and a maximum operational efficiency of the direct-drive wave energy conversion system, the PMTLG's detent force minimization technique and the heaving buoy optimization will be discussed. It is discovered that the operational efficiency of the direct-drive wave energy conversion system increases dramatically after optimization. The experiment and optimization results will provide useful reference for the future research on ocean wave energy conversion system.