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Ontogenetic difference of beak elemental concentration and its possible application in migration reconstruction for Ommastrephes bartramii in the North Pacific Ocean
Zhou Fang, Bilin Liu, Xinjun Chen, Yong Chen
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1431-5
Abstract(32) FullText HTML(15) FullText PDF(1)
Abstract:
The migration route of oceanic squid provides critical information for us to understand their spatial and temporal variations. Mark-recapture and electronic tags tend to be problematic during processing. Cephalopod hard structures such as the beak, containing abundant ecological information with stable morphology and statolith-like sequences of growth increments, may provide information for studying spatio-temporal distribution. In this study, we developed a method, which is based on elemental concentration of beaks at different ontogenetic stages and sampling locations, to reconstruct the squid migration route. We applied this method to Ommastrephes bartramii in the North Pacific Ocean. Nine trace elements were detected in the rostrum sagittal sections (RSS) of the beak using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). For those elements, significant differences were found between the different ontogenetic stages for phosphorus (P), copper (Cu) and zinc (Zn). Sodium (Na), P and Zn were chosen as indicators of sea surface temperature (SST) and a regression model was estimated. The high probability of occurrence in a particular area represented the possible optimal squid location based on a Bayesian model. A reconstructed migration route in this study, combining all the locations at different ontogenetic stages, was consistent with that hypothesized in previous studies. This study demonstrates that the beak can provide useful information for identifying the migration routes of oceanic squid.
Cloning, characterization and expression analysis of a microsomal glutathione S-transferase gene from the seagrass Zostera marina
Wenjie Yan, Jiao Liu, Samphal Seng, Bin Zhou, Kuke Ding
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1429-z
Abstract(36) FullText HTML(16) FullText PDF(1)
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In the text, the response of glutathione S-transferase (GST) in Zostera marina to temperature variation was analyzed at molecular level by cloning the microsomal GST gene and texting the microsomal GST expression regularity under different temperature. Specific speaking, express ZmGST in Escherichia coli, then purify the recombinant protein and make the thermal stability analysis. Therefore, the experiments were carried out to provide a theoretical basis for the further elaboration to the population degradation mechanisms of Z. marina. In conclusion, the thermostability and the response of ZmGST gene to temperature changes can determine its temperature tolerance range, and affect its resilience in turn.
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
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1427-1
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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.
Family-level diversity of extracellular proteases of sedimentary bacteria from the South China Sea
Jinyu Yang, Yangyang Feng, Xiulan Chen, Binbin Xie, Yuzhong Zhang, Mei Shi, Xiying Zhang
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1391-9
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Protease-producing bacteria and their extracellular proteases are key players in degrading organic nitrogen to drive marine nitrogen cycling and yet knowledge on both of them is still very limited. This study screened protease-producing bacteria from the South China Sea sediments and analyzed the diversity of their extracellular proteases at the family level through N-terminal amino acid sequencing. Results of the 16S rRNA gene sequence analysis showed that all screened protease-producing bacteria belonged to the class Gammaproteobacteria and most of them were affiliated with different genera within the orders Alteromonadales and Vibrionales. The N-terminal amino acid sequence analysis for fourteen extracellular proteases from fourteen screened bacterial strains revealed that all these proteases belonged to the M4 family of metalloproteases or the S8 family of serine proteases. This study presents new details on taxa of marine sedimentary protease-producing bacteria and types of their extracellular proteases, which will help to comprehensively understand the process and mechanism of the microbial enzymatic degradation of marine sedimentary organic nitrogen.
Spatio-temporal variability of phytoplankton assemblages and its controlling factors in spring and summer in the Subei Shoal of Yellow Sea, China
Yuanzi HUO, Honghua SHI, Jianheng ZHANG, Qiao LIU, Yuanliang DUAN, Qing HE, Kefeng YU, Hongsheng BI, Chunlei Fan, Peimin HE
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1345-2
Abstract(33) FullText HTML(12) FullText PDF(0)
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The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea. In the present study, the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea. Phytoplankton species composition and abundance data were accomplished by Utermöhl method. Diatoms represented the greatest cellular abundance during the study period. In spring, the phytoplankton cell abundance ranged from 1.59×103 to 269.78×103 cell/L with an average of 41.80×103 cell/L, and Skeletonema sp. and Paralia sulcata was the most dominant species. In summer, the average phytoplankton cell abundance was 72.59×103 cell/L with the range of 1.78×103 to 574.96×103 cell/L, and the main dominant species was Pseudo-nitzschia pungens, Skeletonema sp., Dactyliosolen fragilissima and Chaetoceros curvisetus. The results of a redundancy analysis (RDA) showed that turbidity, temperature, salinity, pH, dissolved oxygen (DO), the ratio of dissolved inorganic nitrogen to silicate and SiO4-Si (DIN/SiO4-Si) were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.
Estimating biological reference points for Largehead hairtail (Trichiurus lepturus) fishery in the Yellow Sea and Bohai Sea
Yupeng Ji, Qun Liu, Baochao Liao, Qingqing Zhang, Ya’nan Han
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1343-4
Abstract(34) FullText HTML(11) FullText PDF(1)
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It is important to find a reliable method to estimate maximum sustainable yield (MSY) or total allowable catch (TAC) for fishery management, especially when the data availability is limited which is a case in China. A recently developed method (CMSY) is a data-poor method, which requires only catch data, resilience and exploitation history at the first and final years of the catch data. CMSY was used in this study to estimate the biological reference points for Largehead hairtail (Trichiurus lepturus, Temminck and Schlegel) in the Yellow Sea and Bohai Sea, based on the fishery data from China Fishery Statistical Year Books during 1986 to 2012. Additionally, Bayesian state-space Schaefer surplus production model (BSM) and the classical surplus production models (Schaefer and Fox) performed by software CEDA and ASPIC, were also projected in this study to compare with the performance of CMSY. The estimated MSYs from all models are about 19.7×104–27.0×104 t, while CMSY and BSM yielded more reasonable population parameter estimates (the intrinsic population growth rate and the carrying capacity). The biological reference points of B/BMSY smaller than 1.0, while F/FMSY higher than 1.0 revealed an over-exploitation of the fishery, indicating that more conservative management strategies are required for Largehead hairtail fishery.

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Nitrogen uptake regime regulated by ice melting during austral summer in the Prydz Bay, Antarctica
Run Zhang, Qiang Ma, Min Chen, Minfang Zheng, Jianping Cao, Yusheng Qiu
2019, 38(8): 1-7  doi: 10.1007/s13131-019-1434-2
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Using a combination of stable isotope (15N) and radionuclide (226Ra) analyses, we examine possible controls on the interactions between melting ice and the uptake of nitrogen in the Prydz Bay during the 2006 austral summer. We find that specific rates of uptake for nitrate and ammonium correlate positively to their concentrations, thus suggesting a substrate effect. In the study area, we observe that regions along open, oceanic water have high f-ratios (nitrate uptake/nitrate+ammonium uptake), while areas near the Amery Ice Shelf have significantly low f-ratios. Further analysis reveals a negative correlation between the f-ratio and the melt water fraction, thus implying that the melting of ice plays an essential role in regulating pelagic N dynamics in the Southern Ocean (SO). Stratification, produced by melting ice, should profoundly affect the efficiency of the SO’s biological pump and consequently affect the concentration of CO2 in the atmosphere. Results presented in this study add information to an already significant base of understanding of the controls on pelagic C and N dynamics in the SO. This provides unique insights for either interpreting past changes in geologic records or for predicting future climate change trends.
Adsorption kinetics of platinum group elements onto macromolecular organic matter in seawater
Kai Liu, Xuelu Gao, Qianguo Xing, Fushan Chen
2019, 38(8): 8-16  doi: 10.1007/s13131-019-1433-3
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Adsorption kinetics of the interaction between Pt, Pd and Rh (defined here as platinum group elements, PGEs) ions and macromolecular organic compounds (MOCs, >10 kDa), including humic acid, carrageenan and bovine serum albumin, and different cutoff fractions of natural organic matter (>1 kDa and >3 kDa) obtained from seawater using centrifugal ultrafiltration devices were investigated. For a given element, all the adsorption kinetics did not reach equilibrium except the interaction between Pt and >1 kDa cutoff, and between Pd and humic acid. For all the tested MOCs, the adsorption kinetics could be divided into two stages, a rapid adsorption process in the first 8 h and the desorption stage after the first 8 h until the equilibrium. The change trend of partition coefficient (log10Kd) values with experiment time was consistent with that of the kinetic curves. However, in the interaction between PGE ions and natural dissolved organic matter (NDOM), an obvious difference in the change trends of log10Kd and kinetic curves was observed. It indicated that the partition behavior of PGE ions interacting with NDOM in seawater was a combined effect of different organic constituents. The adsorption and log10Kd of PGEs in the >1 kDa NDOM fraction were higher and more stable than those in the >3 kDa NDOM fraction. The results also indicated that the 1–3 kDa NDOM may dominate the interaction between PGEs ions and NDOM. Moreover, no kinetic model could perfectly simulate the adsorption process. It indicated that the colloidal struction and morphology of MOCs or NDOM in seawater might be inhomogeneous. Hence, the interaction between PGE ions and organic matter in seawater was a complicated process and needs further research.
Distribution, residence time, autotrophic production, and heterotrophic removal of DOP in the Mirs Bay, northern South China Sea
Huaming Shi, Yu Ma, Xulu Li, Xiaoyong Shi, Junxiao Zhang
2019, 38(8): 17-26  doi: 10.1007/s13131-019-1384-8
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The importance of dissolved organic phosphorus (DOP) as a potential nutrient source for primary producers in marine systems has been recognized for up to eight decades, but currently, the understanding of the biogeochemistry of DOP is in its infancy. In the present study, monthly data between 2000 and 2014 were used to analyze the temporal and spatial distributions of DOP in the Mir Bay, the northern South China Sea. The DOP residence time (TDOP) was also investigated using a simple regression analysis in combination with chlorophyll a (Chl a) measurements while excess DOP (ΔDOP), produced by the biogeochemical processes of autotrophic production and heterotrophic removal, was determined using a two-component mixing mass-balance model in combination with salinity measurements. The results showed that the DOP concentration was (0.017±0.010) mg/L higher in the surface-water compared with the bottom-water and higher in the inner Tolo Harbour and waters adjacent to Shatoujiao compared with the main zone of the bay. Although seasonal changes and annual variability in the DOP were small, the surface DOP concentration was higher in the wet season (April–September) than in the dry season (October–March) due to the impacts of seaward discharges and atmospheric deposition into the bay. Measurement and regression results showed that the DOP release rate from phytoplankton production was about 1.83 (g P)/(g Chl a) and the TDOP was about 7 d, which implied that the DOP cycle in the bay was rapid. The ΔDOP was calculated from the model to be about 0.000 mg/L in the main zone of the bay and about 0.002 mg/L in the inner Tolo Harbour and waters adjacent to Shaotoujiao, suggesting that the autotrophic production of DOP was almost balanced by the heterotrophic removal in the main zone of the bay and dominated in the inner Tolo Harbour and waters adjacent to Shaotoujiao. In conclusion, the Mirs Bay is very productive and fairly heterotrophic.
The sub-fossils of leaf fragments in sediments as an indicator of mangrove development in the Yingluo Bay, Guangxi, Southwest China over the last 130 years
Wanzhu Wang, Xianwei Meng, Xiangqin Wang, Zhen Li
2019, 38(8): 27-34  doi: 10.1007/s13131-018-1221-5
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Located in the intertidal zone of the tropical and subtropical coasts, mangrove forests are an important ecosystem in the global carbon cycle and serve as a protector of local seashores. Under the double impacts of climate change, especially sea-level rise, and human activity, mangrove forests around the world have faced degradation, against which the reconstruction of the historical development of mangrove forests using an effective indicator has been regarded as a necessary strategy for designing a predictable model. As the primary product of mangrove forest, it is reasonable that the content of leaf fragments of mangrove (CLFM) buried in sediments in the form of sub-fossils potentially has the same indicative function for the development of mangrove forests as that of widely-used mangrove pollen. In this study, the leaf fragments of mangrove in two sediment cores (YLW02 and YLW03) drilled in the Yingluo Bay in Guangxi, Southwest China were picked out and weighted for calculation of CLFM, which was used as an indicator of mangrove development after examination of parallelism and a statistical correlation of the CLFM with the concentration of mangrove pollen. The results clearly show that the vertical distribution of the CLFM for the core taken from the landward margin of mangrove forests (YLW03) only parallels that of the local mangrove species (Rhizophora. stylosa) with a significantly positive correlation (R=0.56, P=0.05), while the vertical distribution of the CLFM for the core taken from the interface between seaward margin of mangrove forest and the trunk of tidal creeks of the bay (YLW02) parallels the summed concentration of mangrove pollen (SCMP) with a more positive correlation than that of YLW03 (R=0.85, P=0.01), indicating that the trunk outlet of tidal creeks must have been the site where mangrove production gathered from the overall forest rather than from local production. The variations in the CLFM of both cores indicate that overall the mangrove forests in the Yingluo Bay have increasingly flourished over the last 130 years except for the interval of 1940–1950 AD in response to an increase in air temperature and decrease in rainfall, which would have resulted in an increase in seawater salinity; while the coupled extreme increases in air temperature and in rainfall in summer, which would have resulted in extreme decreases in seawater salinity, would be responsible for the relative degradation of mangrove forests in the interval of 1940–1950 AD.
Migration patterns and habitat use of the tapertail anchovy Coilia mystus in the Oujiang River Estuary and the Zhujiang River Estuary, China
Tao Jiang, Hongbo Liu, Honghui Huang, Jian Yang
2019, 38(8): 35-40  doi: 10.1007/s13131-019-1436-0
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Habitat use of the tapertail anchovy (Coilia mystus Linnaeus, 1758) from the Oujiang River Estuary and the Zhujiang (Pearl) River Estuary was studied by examining the environmental signatures of Sr and Ca in otoliths using electron probe microanalysis. Individuals from the Oujiang River had higher and varied Sr:Ca ratios (expressed as (Sr:Ca)×1 000, 3.83–13.0 average) in the otolith core regions, suggesting that they were born in brackish or sea waters, and that a freshwater habitat might not be necessary for egg hatching and larval growth. While, individuals from the Zhujiang River had lower Sr:Ca ratios (0.39–2.51 average) in the core regions, suggesting a freshwater origin. After hatching, anchovies from the Zhujiang River migrate downstream to the river estuary close to brackish water. Our results demonstrated varied habitat use for spawning during stages of early life history between the two populations, and suggested that such variations are promoting diversity of life history strategies of this species.
Identification of SNP markers correlated with the tolerance of low-salinity challenge in swimming crab (Portunus trituberculatus)
Yanyan Feng, Dening Zhang, Jianjian Lv, Baoquan Gao, Jian Li, Ping Liu
2019, 38(8): 41-47  doi: 10.1007/s13131-019-1428-0
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Water salinity condition is an important factor for artificial propagation of the swimming crab (Portunus trituberculatus). Low salinity (LS)-resistant strains are preferred by crab industries. Single nucleotide polymorphism (SNP), the third generation of molecular markers, can be utilized in the breeding of LS-resistant species of P. trituberculatus. Our earlier study identified 615 genes differentially expressed in low-salinity stress compared to the controls. Although thousands of SNP loci have been found, it is hard to identify a SNP marker in correlation with a desired trait. In this study, time-of-flight mass spectrometry (TOF-MS), as an efficient method to select SNPs for the tolerance of LS challenge, was utilized for SNP typing. Fifty gene segments were amplified based on comparative transcriptomics in our earlier study, a total of 18 511 bp DNA fragments were amplified, and eighty-five SNP markers were found. The frequency of the SNPs was estimated to be 0.46 per 100 base pairs of DNA sequences. The rate of the conversion mutation was 81%, while the transversion mutation was 19%. The mutation rate of the G/T (C/A), A/T and G/C was 26%, 12% and 7%, respectively. Eight SNP markers were found to significantly correlate with the adaption of low salinity. Of the eight SNP markers, three linked-SNPs were found in the cuticle proportion gene, and another three SNPs were found in three new genes, and the rest two were found in aquaporin gene and chloride channel gene. The development of these SNP markers found in our study could be primarily used for breeding LS-resistant strains of P. trituberculatus.
Effects of key species mud snail Bullacta exarata (Gastropoda) on oxygen and nutrient fluxes at the sediment-water interface in the Huanghe River Delta, China
Baoquan Li, Tjeerd J. Bouma, Quanchao Wang, Laura M. Soissons, Francesco Cozzoli, Guanghai Feng, Xiaojing Li, Zhengquan Zhou, Linlin Chen
2019, 38(8): 48-55  doi: 10.1007/s13131-019-1430-6
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Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River (Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos (MPBs; i.e., sedimentary microbes and unicellular algae) productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen (DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro- and meiofauna significantly increased the NH4-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH4-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B. exarata on the ecosystem functioning via benthic fluxes.
Changes in the population structure of Calanus sinicus during summer–autumn in the southern Yellow Sea
Yongqiang Shi, Song Sun, Chaolun Li, Guangtao Zhang, Bo Yang, Peng Ji
2019, 38(8): 56-63  doi: 10.1007/s13131-019-1435-1
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Calanus sinicus is a calanoid copepod widely distributed in coastal waters of China and Japan, and over-summering strategies may have major impacts on their population dynamics which in turn affect local marine food web structure. The abundance, stage composition, and sex composition of the planktonic copepod C. sinicus were studied from August to October 2002 in the southern Yellow Sea to understand how its population recovers from the over-summering state. Results showed that C. sinicus had low reproduction in August due to high temperature, except in waters near the Cheju Island with rich food and moderate bottom temperature, but the reproduction rates here decreased in September–October as food availability declined. When temperature dropped in September–October, C. sinicus actively propagated in coastal shallow waters. However, reproduction rates of C. sinicus individuals inhabiting the Yellow Sea Cold Water Mass (YSCWM) remained low during the three months of the study. The percentage of C. sinicus females was high during the reproductive period, which suggests that the sex composition of adult C. sinicus may reflect whether or not the population is in the reproductive mode. Numerous fifth copepodite stage (CV) C. sinicus aggregated in the YSCWM in a suspended developmental stage during the three months of this study, and they potentially served as the parental individuals for population development when conditions became optimal for reproduction later in the year.
Phylogenetic diversity of dimethylsulfoniopropionate-dependent demethylase gene dmdA in distantly related bacteria isolated from Arctic and Antarctic marine environments
Yinxin ZENG
2019, 38(8): 64-71  doi: 10.1007/s13131-019-1393-7
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Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton as an osmolyte, antioxidant, predator deterrent, or cryoprotectant. DMSP is also an important carbon and sulfur source for marine bacteria. Bacteria may metabolize DMSP via the demethylation pathway involving the DMSP demethylase gene (dmdA) or the cleavage pathway involving several different DMSP lyase genes. Most DMSP released into seawater is degraded by bacteria via demethylation. To test a hypothesis that the high gene frequency of dmdA among major marine taxa results in part from horizontal gene transfer (HGT) events, a total of thirty-one bacterial strains were isolated from Arctic Kongsfjorden seawater in this study. Analysis of 16S rRNA gene sequences showed that, except for strains BSw22118, BSw22131 and BSw22132 belonging to the genera Colwellia, Pseudomonas and Glaciecola, respectively, all bacteria fell into the genus Pseudoalteromonas. DmdA genes were detected in five distantly related bacterial strains, including four Arctic strains (Pseudoalteromonas sp. BSw22112, Colwellia sp. BSw22118, Pseudomonas sp. BSw22131 and Glaciecola sp. BSw22132) and one Antarctic strain (Roseicitreum antarcticum ZS2–28). Their dmdA genes showed significant similarities (97.7%–98.3%) to that of Ruegeria pomeroyi DSS–3, which was originally isolated from temperate coastal seawater. In addition, the sequence of the gene transfer agent (GTA) capsid protein gene (g5) detected in Antarctic strain ZS2–28 exhibited a genetically closely related to that of Ruegeria pomeroyi DSS–3. Among the five tested strains, only Pseudomonas sp. BSw22131 could grow using DMSP as the sole carbon source. The results of this study support the hypothesis of HGT for dmdA among taxonomically heterogeneous bacterioplankton, and suggest a wide distribution of functional gene (i.e., dmdA) in global marine environments.
Distribution of green algae micro-propagules and their function in the formation of the green tides in the coast of Qinhuangdao, the Bohai Sea, China
Hongbin Han, Wei Song, Zongling Wang, Dewen Ding, Chao Yuan, Xuelei Zhang, Yan Li
2019, 38(8): 72-77  doi: 10.1007/s13131-018-1278-1
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Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a " seed source” of green macroalgae, and their distributions could reflect and influence the " algae source” of green tides. In this study, monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the " seed” source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.
Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary
Gang Li
2019, 38(8): 78-85  doi: 10.1007/s13131-019-1389-3
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Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor- and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water (salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield (ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching (NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water (salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′ to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon (14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.
A 10-year wave energy resource assessment and trends of Indonesia based on satellite observations
Amiruddin, Agustinus Ribal, Khaeruddin, Sri Astuti Thamrin
2019, 38(8): 86-93  doi: 10.1007/s13131-019-1400-z
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Wave energy resource assessment and trends around Indonesian’s ocean has been carried out by means of analyzing satellite observations. Wave energy flux or wave power can be approximated using parameterized sea states derived from satellite data. Unfortunately, only some surface parameters can be measured from remote sensing satellites, for example for ocean surface waves: significant wave height. Others, like peak wave period and energy period are not available, but can instead be estimated using empirical models. The results have been assessed by meteorological season. The assessment shows clearly where and when the wave power resource is promising around Indonesian’s ocean. The most striking result was found from June to August, in which about 30–40 kW/m (the 90th percentile: 40–60 kW/m, the 99th percentile: 50–70 kW/m) wave power energy on average has been found around south of the Java Island. The significant trends of wave energy at the 95% level have also been studied and it is found that the trends only occurred for the extreme cases, which is the 99th percentile (i.e., highest 1%). Wave power energy could increase up to 150 W/m per year. The significant wave heights and wave power have been compared with the results obtained from global wave model hindcast carried out by wave model WAVEWATCH III. The comparisons indicated excellent agreements.
An improved frequency shift method for ATI-SAR flat earth phase removal
Yubin Zhang, Jie Zhang, Junmin Meng, Chenqing Fan
2019, 38(8): 94-100  doi: 10.1007/s13131-019-1426-2
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An improved frequency shift method is proposed to remove the flat earth phase in ATI-SAR ocean surface motion detection in this study. First, two conventional flat earth effect removal methods (i.e., the frequency shift method and the orbital parameter method) are introduced and compared. Then, two improvements to frequency shift method are suggested. In the first improvement, the phase diagram is divided into several sub-blocks to calculate the phase fringe frequency. In the second improvement, a function between the phase of land regions and position is fitted to correct the residual flat earth phase based on the phase of the land regions that tend toward zero in an along-track interferogram. It is found that the improved frequency shift method is greatly improved; and it agrees well with the orbital parameter method, and achieves similar accuracy.
Changes in sea ice kinematics in the Arctic outflow region and their associations with Arctic Northeast Passage accessibility
Dawei Gui, Xiaoping Pang, Ruibo Lei, Xi Zhao, Jia Wang
2019, 38(8): 101-110  doi: 10.1007/s13131-019-1451-1
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Abstract:
Amplification of climate warming in the Arctic is causing a dramatic retreat of sea ice, which means the Arctic sea routes are becoming increasingly accessible. This study used a satellite-derived sea ice motion product to quantify the kinematic features of sea ice in the Arctic outflow region which specially referred to the Fram Strait and to the north of the Northeast Passage (NEP). An observed trend of increased southward sea ice displacement from the central Arctic to the Fram Strait indicated enhancement of the Transpolar Drift Stream (TDS). In the regions to the north of the NEP, the long-term trend of northward sea ice speed in the Kara sector was +0.04 cm/s per year in spring. A significant statistical relationship was found between the NEP open period and the northward speed of the sea ice to the north of the NEP. The offshore advection of sea ice could account for the opening of sea routes by 33% and 15% in the Kara and Laptev sectors, respectively. The difference in sea level pressure across the TDS, i.e., the Central Arctic Index (CAI), presented more significant correlation than for the Arctic atmospheric Dipole Anomaly index with the open period of the NEP, and the CAI could explain the southward displacement of sea ice toward the Fram Strait by more than 45%. The impact from the summer positive CAI reinforces the thinning and mechanical weakening of the sea ice in the NEP region, which improves the navigability of the NEP.
Spatial-temporal variations in net primary productivity in the Arctic from 2003 to 2016
Haili Li, Changqing Ke, Qinghui Zhu, Su Shu
2019, 38(8): 111-121  doi: 10.1007/s13131-018-1274-5
Abstract(12) FullText HTML(6) FullText PDF(0)
Abstract:
The area of Arctic sea ice has dramatically decreased, and the length of the open water season has increased; these patterns have been observed by satellite remote sensing since the 1970s. In this paper, we calculate the net primary productivity (NPP, calculated by carbon) from 2003 to 2016 based on sea ice concentration products, chlorophyll a (Chl a) concentration, photosynthetically active radiation (PAR), sea surface temperature (SST), and sunshine duration data. We then analyse the spatiotemporal changes in the Chl a concentration and NPP and further investigate the relations among NPP, the open water area, and the length of the open water season. The results indicate that (1) the Chl a concentration increased by 0.025 mg/m3 per year; (2) the NPP increased by 4.29 mg/(m2·d) per year, reaching a maximum of 525.74 mg/(m2·d) in 2016; and (3) the Arctic open water area increased by 57.23×103 km2/a, with a growth rate of 1.53 d/a for the length of the open water season. The annual NPP was significantly positively related to the open water area, the length of the open water season and the SST. The daily NPP was also found to have a lag correlation with the open water area, with a lag time of two months. With global warming, NPP has maintained an increasing trend, with the most significant increase occurring in the Kara Sea. In summary, this study provides a macroscopic understanding of the distribution of phytoplankton in the Arctic, which is valuable information for the evaluation and management of marine ecological environments.

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