## 2017 Vol. 36, No. 12

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2017, 36(12): 1-10. doi: 10.1007/s13131-017-1098-8
[Abstract](1079) [PDF 828KB](746)
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Marginal seas play important roles in regulating the global carbon budget, but there are great uncertainties in estimating carbon sources and sinks in the continental margins. A Pacific basin-wide physical-biogeochemical model is used to estimate primary productivity and air-sea CO2 flux in the South China Sea (SCS), the East China Sea (ECS), and the Yellow Sea (YS). The model is forced with daily air-sea fluxes which are derived from the NCEP2 reanalysis from 1982 to 2005. During the period of time, the modeled monthly-mean air-sea CO2 fluxes in these three marginal seas altered from an atmospheric carbon sink in winter to a source in summer. On annual-mean basis, the SCS acts as a source of carbon to the atmosphere (16 Tg/a, calculated by carbon, released to the atmosphere), and the ECS and the YS are sinks for atmospheric carbon (-6.73 Tg/a and -5.23 Tg/a, respectively, absorbed by the ocean). The model results suggest that the sea surface temperature (SST) controls the spatial and temporal variations of the oceanic pCO2 in the SCS and ECS, and biological removal of carbon plays a compensating role in modulating the variability of the oceanic pCO2 and determining its strength in each sea, especially in the ECS and the SCS. However, the biological activity is the dominating factor for controlling the oceanic pCO2 in the YS. The modeled depth-integrated primary production (IPP) over the euphotic zone shows seasonal variation features with annual-mean values of 293, 297, and 315 mg/(m2·d) in the SCS, the ECS, and the YS, respectively. The model-integrated annual-mean new production (uptake of nitrate) values, as in carbon units, are 103, 109, and 139 mg/(m2·d), which yield the f-ratios of 0.35, 0.37, and 0.45 for the SCS, the ECS, and the YS, respectively. Compared to the productivity in the ECS and the YS, the seasonal variation of biological productivity in the SCS is rather weak. The atmospheric pCO2 increases from 1982 to 2005, which is consistent with the anthropogenic CO2 input to the atmosphere. The oceanic pCO2 increases in responses to the atmospheric pCO2 that drives air-sea CO2 flux in the model. The modeled increase rate of oceanic pCO2 is 0.91 μatm/a in the YS, 1.04 μatm/a in the ECS, and 1.66 μatm/a in the SCS, respectively.
2017, 36(12): 11-17. doi: 10.1007/s13131-017-1097-9
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In the Nanliu River Estuary of Guangxi, China, the naturally expanding process of a mangrove swamp (primarily consist of Aegiceras corniculatum) over past decades is studied by satellite images. From 1988 to 2013, the area of studied mangrove swamp increased significantly from 60 hm2 to 134 hm2. The expanding process is not gradual and the significant expansion only took place in some special periods. To reveal the dynamic of mangrove swamp expansion, the evolution of tidal flat elevation and the climate change in past decades are studied respectively. The hydrodynamic condition and nutrient supply are also analysed. The study results show that the climate factors of typhoon intensity and annual minimum temperature are crucial for controlling mangrove expansion. A large number of mangrove seedlings on bare tidal flats can survive only in special climate optimum periods, which are continuous years of low typhoon intensity and high annual minimum temperature. In past decades, the scarcity of climate optimum periods resulted in a non-gradual process of mangrove expanding and a time lag of 30 years between the elevation reaching the low threshold for mangrove seedling survival and the eventual emergance of the mangrove. Compared with the climate factors, the hydrodynamic condition and nutrient supply are not important factors affecting mangrove expansion. In the future, combined with global warming, the enhanced frequency and energy of landing typhoons will most likely restrain the further expansion of this mangrove swamp.
2017, 36(12): 18-23. doi: 10.1007/s13131-017-1124-x
[Abstract](1021) [PDF 821KB](1106)
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The morphological similarities of Pampus fishes have led to considerable confusion in species-level identification, and no accurate information on neotype or DNA barcoding of Pampus echinogaster is available. Two hundred and seven specimens of P. echinogaster were collected from the coastal waters of Dandong, Dongying, Qingdao, Nantong, Zhoushan, Wenzhou, Changle, Taiwan, and Wakayama (Japan), from June 2010 to April 2013. The diagnostic characteristics of P. echinogaster are as follows: dorsal fin VIII-XI-43-51, anal fin V-VIII-43-49, pectoral fin 22-27, caudal fin 19-22, pelvic fin absent; first gill rakers sparse, slender (pointed), 3-4+12-16=15-20; vertebrae 39-41; transverse occipital canal on top of head moderately small, wavy ridges not reaching upper origin of pectoral fin; ventral branch of lateral line canal spare, shorter than dorsal branch of lateral line canal. By combining congener sequences of the cytochrome oxidase I (COI) gene from GenBank, two absolute groups were detected among all specimens, which further indicated that two valid species were present based on genetic differences in amino acid sequences and the distance between the groups. The sequences of Group 1 can be regarded as DNA barcoding of P. echinogaster. The correct morphological redescription and DNA barcoding of P. echinogaster are presented here to provide a guarantee for efficient and accurate studies, a theoretical basis for classification, and enable appropriate fishery management and conservation strategies for the genus Pampus in the future.
2017, 36(12): 24-30. doi: 10.1007/s13131-017-1095-y
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The Guanine nucleotide exchange factor Vav2 (Vav2) is a member of the Vav family that serves as an important regulators for the Rho family of Ras-related GTPases. In the current study, an ortholog (Lj-Vav2) of Vav2 was identified in the lamprey (Lampetra japonica). To elucidate the phylogenetic relationship of Vav2, the metazoan genome databases were analyzed to mine the ortholog of Vav. It was found that Vav2 genes were only existed in vertebrates and Lj-Vav2 was the original one found in agnathans. The evolutionary dynamics of conserved motifs of Vav2 were explored using combined amino acid sequence as markers, and it is revealed that the Calponin homology (CH) domain, Dbl-homologous (DH) domain, Pleckstrin homology (PH) domain, Cysteine-rich (C1) domains, Src homology 3 (SH3) domains and Src homology 2 (SH2) domain were conserved throughout the Vav2 gene family in vertebrates during gene evolution. Relative quantitative real-time PCR analysis showed that the Lj-Vav2 was distributed in the heart, kidney, supraneural myeloid body, liver, gill and lymphocyte-like cells. The Lj-Vav2 was found to be expressed in these tissues, and the level of which was upregulated in lymphocyte-like cells after the animal was stimulated with LPS. These results indicated that the Lj-Vav2 might be involved in the immune response of lymphocyte-like cells in lamprey. Meanwhile, our findings provided a foundation for further investigation of the function of Lj-Vav2 in the primary vertebrate.
2017, 36(12): 31-36. doi: 10.1007/s13131-017-1100-5
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The analysis of cetacean strandings can provide fundamental information about species diversity and composition in a particular region. The present study collected and analyzed cetacean strandings, bycatches and rescues along the western coast of the Taiwan Strait, China, from 2010 to 2015. In total, 48 records, including 37 strandings, 8 bycatches and 3 rescues, involving 13 known species were collected. Among them, Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) were the most common species, consisting of 31.3% and 25%, respectively. Notably, 10 out of the 48 (20.8%) records were collected from the Pingtan Island and included 3 species of Mysticeti and 4 species of Odontoceti. Finally, we compared the cetacean species composition between the western and eastern coasts of the Taiwan Strait; 31 cetacean species occurred in the Taiwan Strait, indicating a relatively high cetacean diversity in this region. Systematic field surveys are urgently needed to explore the cetacean species composition, population stock and the related habitat status in the Taiwan Strait, which may improve conservation management in the future.
2017, 36(12): 37-44. doi: 10.1007/s13131-017-1096-x
[Abstract](1450) [PDF 163KB](872)
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Many fish stocks in the world are depleted as a result of overexploitation, which reduces stock productivity and results in loss of potential yields. In this study we analyzed the catch trends and approximate thresholds of sustainable fishing for fished stocks to estimate the potential loss of catch and revenue of global fisheries as a result of overexploitation during the period of 1950-2010 in 14 FAO fishing areas. About 35% of stocks in the global marine ocean have or had suffered from overexploitation at present. The global catch losses amounted to 332.8 million tonnes over 1950-2010, resulting in a direct economic loss of US$298.9 billion (constant 2005 US$). Unsustainable fishing caused substantial potential losses worldwide, especially in the northern hemisphere. Estimated potential losses due to overfishing for different groups of resources showed that the low-value but abundant small-medium pelagics made the largest contribution to the global catch loss, with a weight of 265.0 million tonnes. The geographic expansion of overfishing not only showed serial depletion of world's fishery resources, but also reflected how recent trends towards sustainability can stabilize or reverse catch losses. Reduction of global fishing capacity and changes in fishery management systems are necessary if the long-term sustainability of marine fisheries in the world is to be achieved.
2017, 36(12): 45-51. doi: 10.1007/s13131-017-1056-5
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Sea cucumber, Apostichopus japonicus (Selenka), is a commercially important marine species in China. Among the differently colored varieties sold in China, white and purple sea cucumbers have the greatest appeal to consumers. Identification of the pigments that may contribute to the formation of different color morphs of sea cucumbers will provide a scientific basis for improving the cultivability of desirable color morphs. In this study, sea cucumbers were divided into four categories according to their body color: white, light green, dark green, and purple. The pigment composition and contents in the four groups were analyzed by high performance liquid chromatography (HPLC). The results show that the pigment contents differed significantly among the white, light-green, dark-green, and purple sea cucumbers, and there were fewer types of pigments in white sea cucumber than in the other color morphs. The only pigments detected in white sea cucumbers were guanine and pteroic acid. Guanine and pteroic acid are structural colors, and they were also detected in light-green, dark-green, and purple sea cucumbers. Every pigment detected, except for pteroic acid, was present at a higher concentration in purple morphs than in the other color morphs. The biological color pigments melanin, astaxanthin, β-carotene, and lutein were detected in light-green, dark-green, and purple sea cucumbers. While progesterone and lycopene, which are also biological color pigments, were not detected in any of the color morphs. Melanin was the major pigment contributing to body color, and its concentration increased with deepening color of the sea cucumber body. Transmission electron microscopy analyses revealed that white sea cucumbers had the fewest epidermal melanocytes in the body wall, and their melanocytes contained fewer melanosomes as well as non-pigmented pre-melanosomes. Sea cucumbers with deeper body colors contained more melanin granules. In the body wall of dark-green and purple sea cucumbers, melanin granules were secreted out of the cell. The results of this study provide evidence for the main factors responsible for differences in coloration among white, light-green, dark-green, and purple sea cucumbers, and also provide the foundation for further research on the formation of body color in sea cucumber, A. japonicus.
2017, 36(12): 52-66. doi: 10.1007/s13131-017-1090-3
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The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tunisian Strait on gene flow disruption in this highly dispersive echinoid species. For this purpose, patterns of morphological and genetic variation were assessed among its populations from the western and eastern Mediterranean coasts. A total of 302 specimens from seven Tunisian sites were collected and examined for morphometric variability at twelve morphometric traits. Concordant results, inferred from CDA (canonical discriminant analyses), pairwise NPMANOVA (non parametric multivariate analysis of variance) comparisons and MDS (multidimensional scaling) plot, unveiled significant inter-population differences in the measured traits among the studied populations. Furthermore, the combined use of the one way ANOSIM (analysis of similarities) and the Discriminant/Hotelling analysis allowed unravelling two morphologically differentiated groups assigned to both western and eastern Mediterranean basins. The SIMPER (similarity percentages) routine analysis showed that total dry weight, test diameter and spine length were major contributors to the morphometric separation between locations and between groups. Pattern of phenotypic divergence discerned in P. lividus across the Siculo-Tunisian Strait is interestingly in congruence with that inferred from the genetic investigation of the purple sea urchin populations from the same region based on the analysis of the mtDNA COI (cytochrome oxidase I) gene in 314 specimens from nineteen locations covering a wider geographic transect, streching westward to the Algerian coast and eastward to the Libyan littoral. The specific haplotypic composition characterizing each Mediterranean basin, as inferred from the minimum spanning network, confirmed the geographic partioning of genetic variation, as revealed by F-statistics and AMOVA (analysis of molecular variance) analyses, yielding significant genetic differentiation between eastern and western Mediterranean populations. The newly detected phylogeographic patterns, observed for the first time in P. lividus throughout the explored distribution range, suggest the involvement of different biotic and abiotic processes in shaping such variation, and provide evidence that a large and geographically exhaustive dataset is necessary to unveil phylogeographic structure within widespread marine species, previously cathegorized as panmictic in part of their distribution range.
2017, 36(12): 67-78. doi: 10.1007/s13131-017-1049-4
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As one of the most common and dominant species in the Southern Ocean, Antarctic krill (Euphausia superba) play a significant role in food web structure and the process of energy flow. The diet of Antarctic krill in the Prydz Bay during austral summer of 2012/2013 was investigated and the ontogenetic shift in krill diet was evaluated using the stable isotope method. The nitrogen stable isotope values (δ15N) of adults ((2.78±0.58)‰) were much higher than those of juveniles ((1.69±0.70)‰), whereas the carbon stable isotope values (δ13C) of adults (-(28.26±1.08)‰) were slightly lower than those of juveniles (-(27.48±1.35)‰). Particulate organic matter (POM) from 0, 25, and 50 m depth combined (0/25/50 m) represented phytoplankton food items. The results showed that phytoplankton food items in surface water and mesozooplankton were two essential food items for Antarctic krill in the Prydz Bay during summer. POM (0/25/50 m) contributes 56%-69% and 26%-34% to the diet of juvenile and adult krill, respectively, whereas mesozooplankton composes 13%-34% and 58%-71% of the diet of juvenile and adult krill, respectively. Thus, an ontogenetic diet shift from POM (0/25/50 m), which consists mainly of phytoplankton, to a higher trophic level diet containing mesozooplankton, was detected. The capacity for adults to consume more zooplankton food items may minimize their food competition with juveniles, which rely mostly on phytoplankton food items. This suggests “diet shift with ontogeny” which may somehow help krill keep their dietary energy budget balanced and well adapted to the Antarctic marine ecosystem as a dominant species.
2017, 36(12): 79-86. doi: 10.1007/s13131-017-1093-0
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Sediment samples were collected in the intertidal zone of the Dagu River Estuary, Jiaozhou Bay, China in April, July and October 2010 and February 2011 for examining seasonal dynamics of meiofaunal distribution and their relationship with environmental variables. A total of ten meiofaunal taxa were identified, including free-living marine nematodes, benthic copepods, polychaetes, oligochaetes, bivalves, ostracods, cnidarians, turbellarians, tardigrades and other animals. Free-living marine nematodes were the most dominant group in both abundance and biomass. The abundances of marine nematodes were higher in winter and spring than those in summer and autumn. Most of the meiofauna distributed in the 0-2 cm sediment layer. The abundance of meiofauna in high-tidal zone was lower than those in low-tidal and mid-tidal zones. Results of correlation analysis showed that Chlorophyll a was the most important factor to influence the seasonal dynamics of the abundance, biomass of meiofauna and abundances of nematodes and copepods. CLUSTER analysis divided the meiofaunal assemblages into three groups and BIOENV results indicated that salinity, concentration of organic matter, sediment sorting coefficient and sediment median diameter were the main environmental factors influencing the meiofaunal assemblages.
2017, 36(12): 87-94. doi: 10.1007/s13131-017-1092-1
[Abstract](1307) [PDF 892KB](1572)
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Maintaining stable water quality is one of the key processes for recirculating coral aquaculture. Traditional aquarium systems which mainly utilized a nitrification of nitrifying bacteria attached to the surface of massive artificial filter material are difficult to maintain the oligotrophic conditions necessary for coral aquaculture. This study investigated the removal effects of dissolved inorganic nitrogen (ammonia and nitrate) by live rock (LR), a key component in the "Berlin system" coral aquarium. The expression levels of bacterial functional genes, AOA3, amoA and nosZ, were measured on the exterior and interior of LR. The nitrifying and denitrifying bacterial abundance on LR was quantified and the nitrogen nutrient regulatory effects of LR were evaluated. The results demonstrated that LR mainly removed ammonium (NH4+) from the water with a mean efficiency of 0.141 mg/(kg·h), while the removal of nitrate (NO3-) was not significant. Bacterial diversity analysis showed that ammonia-oxidizing bacteria (AOB) were the most common bacteria on LR, which accounted for 0.5%-1.4% of the total bacterial population, followed by denitrifying bacteria, which accounted for 0.2% of the total population, and the ammonia-oxidizing archaea (AOA) were the least common type (<0.01%). The low abundance of denitrifying bacteria may be responsible for the poor nitrate (NO3-) removal of LR. Thus, other biological filtration methods are needed in coral aquaria to control nitrates generated from nitrification or biological metabolism.
2017, 36(12): 95-100. doi: 10.1007/s13131-017-1099-7
[Abstract](1068) [PDF 4121KB](1342)
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With the development of aquaculture, there is an urgent demand for an alternative antibacterial agent to reduce the drug resistance and environmental pollution caused by the abuse of antibiotics. Recently, silver nanoparticles (AgNPs) have been viewed as a novel type of antimicrobial agents due to their unique advantages. In this study, AgNPs were biosynthesized with the ginger rhizomes extract. The biosynthesized AgNPs were characterised by UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction and fourier transform infrared spectroscopy. Furthermore, the antimicrobial activities of the AgNPs were fully analyzed against six typical aquatic pathogens. The results indicated that the components in ginger extract could function as the chemical reductant to synthesize AgNPs. Moreover, compared with the AgNPs synthesized by chemical methods, the biosynthesized AgNPs were smaller, and had higher stability and antibacterial activity. Therefore, the biosynthesized AgNPs using ginger extract may have prospective applications in aquaculture.
2017, 36(12): 101-110. doi: 10.1007/s13131-017-1094-z
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A comprehensive study on the phytoplankton standing stocks, species composition and dominant species in the eutrophic Changjiang (Yangtze River) Estuary (CE) was conducted to reveal the response of phytoplankton assemblage to Changjiang Diluted Water (CDW) and upwelling in the spring. Phytoplankton presented peak standing stocks (13.03 μg/L of chlorophyll a, 984.5×103 cells/L of phytoplankton abundance) along the surface isohaline of 25. Sixty-six species in 41 genera of Bacillariophyta and 33 species in 19 genera of Pyrrophyta were identified, as well as 5 species in Chlorophyta and Chrysophyta. Karenia mikimotoi was the most dominant species, followed by Prorocentrum dentatum, Paralia sulcata, Pseudo-nitzschia delicatissima and Skeletonema costatum. A bloom of K. mikimotoi was observed in the stratified stations, where the water was characterized by low nitrate, low phosphate, low turbidity, and specific ranges of temperature (18-22 °C) and salinity (27-32). K. mikimotoi and P. dentatum accumulated densely in the upper layers along the isohaline of 25. S. costatum was distributed in the west of the isohaline of 20. Benthonic P. sulcata presented high abundance near the bottom, while spread upward at upwelling stations. CDW resulted in overt gradients of salinity, turbidity and nutritional condition, determining the spatial distribution of phytoplankton species. The restricted upwelling resulted in the upward transport of P. sulcata and exclusion of S. costatum, K. mikimotoi and P. dentatum. The results suggested that CDW and upwelling were of importance in regulating the structure and distribution of phytoplankton assemblage in the CE and the East China Sea.
2017, 36(12): 111-118. doi: 10.1007/s13131-017-1074-3
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Based on a 3-D Finite Volume Coastal Ocean Model (FVCOM), tidal dynamics has been studied in the sea area around the Phase III Project of Maji Mountain Port (MMP). Furthermore, taking typhoon “Canhong” as an example, a storm surge and sediment model has also been established to study the impact of the Phase III Project on current flows and siltation during extreme weather. Tidal currents before and after the project have been compared. Model results show that the changes of tidal current mainly occur in the engineering areas with a magnitude change of 0.3-0.4 m/s during maximum flood and ebb tides. The flow condition for the port has been improved as the flow direction is changed to parallel to the wharf after the completion of the project. There is little siltation in the adjacent area, which will not affect the safety of ship navigation. Besides, the sudden siltation during typhoon period is relatively weak. The back silting in two days is less than 5 cm indicating no sudden siltation occurs.