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Spatial distribution characteristics of bacterial community structure and gene abundance in sediments of the Bohai Sea
Quanrui Chen, Jingfeng Fan, Jie Su, Hongxia Ming, Zhihao Sun, Mengfei Li, Xiaohui Zhao, Yantao Wang, Yingxue Zhang, Huizhen Zhang, Yuan Jin, Xiaowan Ma, Bin Wang
In Press, Accepted Manuscript,   Available online  ,  
Abstract(40) FullText HTML(3) FullText PDF(0)
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This study investigated differences in the community structure and environmental responses of the bacterial community in sediments of the Bohai Sea. Illumina high-throughput sequencing technology and real-time PCR were used to assay the bacterial 16S rRNA genes in the surface sediments of 13 sampling stations in the Bohai Sea. The results showed that sediments at the majority of the 13 sampling stations were contaminated by heavy metal mercury. The main phyla of bacteria recorded included Proteobacteria (52.92%), Bacteroidetes (11.76%), Planctomycetes (7.39%), Acidobacteria (6.53%) and Chloroflexi (4.97%). The genus with the highest relative abundance was Desulfobulbus (4.99%), which was the dominant genus at most sampling stations, followed by Lutimonas and Halioglobus. The main factors influencing bacterial community structure were total organic carbon, followed by depth and total phosphorus. The content of lead, cadmium, chromium, copper and zinc had a consistent effect on community structure. Arsenic showed a negative correlation with bacterial community structure in most samples, while the impact of mercury on community structure was not significant. The bacterial community in sediment samples from the Bohai Sea was rich in diversity and displayed an increase in diversity from high to low latitudes. The data indicated that the Bohai Sea had abundant microbial resources and was rich in bacteria with the potential to metabolize many types of pollutants.
N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean (WTNP)
Run Zhang, Dongsheng Zhang, Min Chen, Zhibing Jiang, Chunsheng Wang, Minfang Zheng, Yusheng Qiu, Jie Huang
In Press, Accepted Manuscript,   Available online  ,  
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In the present study, we report N2 fixation rate (15N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13–20°N, 120–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation. In surface waters, volumetric N2 fixation rate (calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged (1.2±0.5) nmol/(L·d), with <0 μm size fraction contributed predominantly (88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m2·d) and 480 μmol/(m2·d) (average (225±105) μmol/(m2·d). N2 fixation can account for 6.2%±3.7% of the depth-integrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.
Assessing benthic habitat quality in the Laizhou Bay, China, using biotic indices
Li Wang, Xianxiang Luo, Jianqiang Yang, Juan Zhang, Yuqing Fan, Jiayu Shen
In Press, Accepted Manuscript,   Available online  ,  
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As an important part of the Bohai economic rim, the Laizhou Bay has been stressed by serious eco-environmental problems in recent years. In this study, the Shannon-Wiener Index (H′), AZTI’s Marine Biotic Index (AMBI) and the Multivariate AMBI (M-AMBI) were used to assess the ecological quality status (EQS) of the Laizhou Bay according to macrobenthos data collected annually in August 2011-2014. The results showed that the overall benthic habitat quality in the Laizhou Bay was assessed as " Good”. However, 25% of the samples were classified as " Moderate”, " Bad” or " Poor” status under degraded conditions. Ecological group III (EGIII) species which had a certain tolerance to environmental disturbances had a higher proportion in each station, and most of them had appeared the pollution indicator species Capitella capitata. This indicated that the benthic habitat in the Laizhou Bay had been disturbed and polluted to some extent. The comparison of the three indices evaluation result and the RDA analysis showed that the H' and M-AMBI index were more suitable when the relative abundance of the single species was high and the macrobenthic community was significantly imbalanced; when the relative abundance of opportunistic species (EGIV and EGV) was high, the AMBI and M-AMBI could reflected the EQS objectively; in an undisturbed and polluted environment, all the three indices could indicate the benthic habitats quality. In summary, the better correlation between the three indices and environmental factors showed that they were well responsive to the tendency of the benthic habitats quality in the Laizhou Bay.
Zooneuston and zooplankton abundance and diversity in relation to spatial and nycthemeral variations in the Gulf of Aqaba and northern Red Sea
Gopikrishna Mantha, Abdulmohsin A. Al-Sofyani, Al-Aidaroos Ali M, Michael P Crosby
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1427-1
Abstract(75) FullText HTML(33) FullText PDF(3)
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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.
Protoraphis Simonsen, a newly recorded marine epizoic diatom genus for China
Lang Li, Changping Chen, Lin Sun, Jiawei Zhang, Junrong Liang, Yahui Gao
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1467-z
Abstract(22) FullText HTML(7) FullText PDF(0)
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Epizoic diatoms on marine copepods are common in nature and may have a special ecological relationship with their hosts. However, this special ecological group is not well known, and it has only rarely been studied in the China seas. To address this knowledge gap, the species diversity and classification of epizoic diatoms on planktonic copepods were studied with samples collected from the East China Sea. In the present study, a marine araphid diatom genus Protoraphis and its type species, Pr. hustedtiana, were observed and identified by light and electron microscopy, thus representing the first record of this genus and its type species in China. This genus is characterized by a median sternum strongly bent to opposite sides and terminate in two transapical grooves at the valve ends. Protoraphis hustedtiana was found to be epizoic on the posterior body appendages and segments of the marine calanoid copepod Candacia bradyi. An internal view shows a complex, ear-shaped process that is close to the apical slit field. The ecological habitats and geographical distributions of Protoraphis were also discussed, and, together with complementary morphological studies, our results have increased the number of records for marine epizoic diatoms to three genera with three species in China, including Pseudohimantidium and Pseudofalcula.
Model assessment of nutrient removal via planting Sesuvium portulacastrum in floating beds in eutrophic marine waters: the case of aquaculture areas of Dongshan Bay
Xuehai Liu, Xinming Pu, Donglian Luo, Jing Lu, Zili Liu
In Press, Accepted Manuscript,   Available online  ,  
Abstract(7) FullText HTML(4) FullText PDF(0)
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Many coastal seas are severely eutrophic and required to reduce nutrient concentrations to meet a certain water quality standard. We proposed a method for nutrient removal by planting Sesuvium portulacastrum at the water surface using the floating beds in the aquaculture area of the Dongshan Bay as an example, which is an important net-cage culture base in China and where dissolved inorganic nitrogen (DIN) and phosphate (DIP) reach 0.75 mg/L and 0.097 mg/L, respectively far exceeding China’s Grade IV water quality standards. Numerical simulations were taken using the ecological model, field observations and field plantation experimental results to assess the environmental restoration effects of planting S. portulacastrum at some certain spatial scales. Our field experiments suggested that the herbs can absorb 377 g/m2 nitrogen and 22.9 g/m2 phosphorus in eight months with an inserting density of ~60 shoot/m2. The numerical experiments show that the greater the plantation area is, the more nutrient removal. Plantation in ~12% of the study area could lower nutrient to the required Grade II standards, i.e., 0.2 mg/L<DIN≤0.3 mg/L and 0.015 mg/L<DIP≤0.03 mg/L. Here the phytoremediation method and results provide helpful references for environmental restoration in other eutrophic seas.
The effect of substrate grain size on burrowing ability and distribution characteristics of Perinereis aibuhitensis
Tao Sun, Chun’e Liu, Xingzuo Li, Dongzhengyang An, Hairui Yu, Zheng Ma, Feng Liu
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1348-z
Abstract(467) FullText HTML(5) FullText PDF(0)
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Perinereis aibuhitensis (Grube, 1878) lives in marine sediments of estuary or shoal areas, where substrate has some crucial environmental factors affecting its burrowing and distribution. In order to provide basic data for the habitat selection and suitability evaluations of the artificial aquaculture of P. aibuhitensis, this paper conducted a quantified analysis of its burrowing ability and explored its behavioral preferences in different substrates, including mud (<75 μm), fine sand (125–250 μm), medium sand (250–500 μm), coarse sand (500–2 000 μm), gravel (2 000–4 000 μm) and ceramsite (4 000–8 000 μm). The research results revealed that substrate grain size significantly affected the burrowing time, burrowing rate, burrowing depth and distribution rate (P<0.01). Moreover, P. aibuhitensis demonstrated preferential selections relating to substrate grain sizes, had higher burrowing ability in ceramsite, mud and fine sand compared with other substrates. The strongest burrowing ability and the highest distribution rate were observed in ceramsite. The study indicated that P. aibuhitensis was sensitive to substrate grain size, which also had an impact on its burrowing process and population distribution. In the natural sea, substrates mainly composed of mud and fine sand are fit for aquaculture and stock enhancement. Based on behavioral preferences and ecological rehabilitation function of P. aibuhitensis, this paper proposes a symbiotic system of marine animals and halophytes, and constructs an ecosystem model of " Marine fish-Halophytes-Perinereis aibuhitensis” with P. aibuhitensis as the link.
Residues and sources of HCHs and DDTs in the sediments of land-based sewage outlet to the Zhanjiang Bay, China
Lirong Zhao, Yuzhen Shi, Hui Zhao, Jibiao Zhang, Xingli Sun
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1432-4
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Due to the large usage of DDT-containing antifouling paints and lindane in China, heavy residuals of DDTs and HCHs have been found in many fishing harbors, but there is lack of studies on this issue for the Zhanjiang Bay which is an important fishing harbor and mariculture zone in South China. To evaluate the pollution status and sources of HCHs and DDTs in the Zhanjiang Bay, the concentrations, spatial distributions and sources in the sediments of 11 land-based sewage outlets to the Zhanjiang Bay were investigated. Since the 1980s, HCHs residuals had obviously decreased in studied areas, but DDTs had little change, even abnormally high levels were found in some sites. The content percentages and diagnostic ratios of HCHs isomers and DDTs showed that the source of HCHs was derived from soils around the bay and recent input of lindane, and DDTs were from historical residues of technical DDTs and fresh input of DDT-containing antifouling paints on fishing ships. Based on sediment quality guidelines, DDTs would be of more concern for the ecotoxicological risk on marine environment and adverse effects on benthonic organisms. This study indicated that lindane and DDT-containing products may be still used in some places of Zhanjiang City. It should be urgent to control their usage and clean the DDTs-contaminated sites by the local government.
Dynamic genetic analysis for body weight and main length ratio in turbot Scophthalmus maximus
Xin’an Wang, Aijun Ma
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-0000-0
Abstract(14) FullText HTML(7) FullText PDF(0)
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The objective of this study was to estimate genetic parameters of body width (BW) to body length (BL) ratio (BW/BL) and of body weight traits (BWT) in turbot, and to elucidate the genetic mechanism of the two traits during ontogeny by dynamic genetic analysis. From 3 to 27 months, BW, BL, and BWT of each communally stocked fish were measured every 3 months. The BW/BL ratio was measured at different sampling ages. A two-trait animal model was used for genetic evaluation of traits. The results showed that the heritability values of BW/BL ratio ranged from 0.2168 to 0.3148, corresponding to moderate heritability. The BWT heritability values ranged from 0.2702 to 0.3479 corresponding to moderate heritability. The heritability of BW/BL ratio was lower than that of BWT, except at 3 months of age. Genetic correlation between BW/BL ratio and BWT decreased throughout the measurement period. Genetic correlations were higher than the phenotypic correlations. The current results for estimating genetic parameters demonstrate that the BW/BL ratio could be used as a phenotypic marker of fast-growing turbot; the BW/BL ratio and BWT could be improved simultaneously through selective breeding.
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
Abstract(64) FullText HTML(36) FullText PDF(1)
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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.
Physiological performance of three calcifying green macroalgae Halimeda species in response to altered seawater temperatures
Zhangliang Wei, Jiahao Mo, Ruiping Huang, Qunju Hu, Chao Long, Dewen Ding, Fangfang Yang, Lijuan Long
In Press, Accepted Manuscript,   Available online  ,   doi: 10.1007/s13131-019-1471-3
Abstract(23) FullText HTML(12) FullText PDF(0)
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The effects of seawater temperature on the physiological performance of three Halimeda species were studied for a period of 28 d. Five treatments were established for Halimeda cylindracea, Halimeda opuntia and Halimeda lacunalis, in triplicate aquaria representing a factorial temperature with 24°C, 28°C, 32°C, 34°C and 36°C, respectively. The average Fv/Fm of these species ranged from 0.732 to 0.756 between 24°C and 32°C but declined sharply between 34°C (0.457±0.035) and 36°C (0.122±0.014). Calcification was highest at 28°C, with net calcification rates (Gnet) of 20.082±2.482 mg/(g·d), (12.825±1.623) mg/(g·d) and (6.411±1.029) mg/(g·d) for H. cylindracea, H. opuntia and H. lacunalis, respectively. Between 24°C and 32°C, the specific growth rate (SGR) of H. lacunalis (0.079–0.110%/d) was lower than that of H. cylindracea (0.652–1.644%/d) and H. opuntia (0.360–1.527%/d). Three Halimeda species gradually bleached at 36°C during the study period. Malondialdehyde (MDA) and proline levels in tissues of the three Halimeda were higher in 34–36°C than those in 24–32°C. The results indicate that seawater temperature with range of 24–32°C could benefit the growth and calcification of these Halimeda species, however, extreme temperatures above 34°C have negative impacts. The measured physiological parameters also revealed that H. cylindracea and H. opuntia displayed broader temperature tolerance than H. lacunalis.
Bimodality and growth of the spectra of typhoon-generated waves in northern South China Sea
Dongxue MO, Yahao LIU, Yijun HOU, Ze LIU
In Press, Accepted Manuscript,   Available online  ,  
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Buoy-based observations of wave spectra during the passage of three typhoons in the northern South China Sea are examined. Though most spectra of mature typhoon-generated waves are unimodal, double-peaked spectra account for a significant proportion during the growing and decaying stages. This is due either to the superposition of swells on local wind waves or to the mechanism of nonlinear interaction between different wave components. The growth rate of energy density is an effective way to predict spectrum variation. The dominant wave direction depends on the location of the typhoon center to the site, but the direction spread shows no regularity in distant regions. In this study, a new six-parameter spectral formula is proposed to represent double-peaked spectra and is shown to provide a better fit than previous models. The theoretical relationship between shape parameter and spectral width is still applicable to each peak. The characteristics of the variations of spectral parameters are analyzed. It is demonstrated that the spectral parameters are not only related to the typhoon intensity and typhoon track, but also have strong intercorrelations. Moreover, the growth relation between significant wave height and significant wave period is obtained to fit the typhoon-generated waves.
Upwelling off the west coast of Hainan Island: sensitivity to wave-mixing
Peng BAI, Jingling YANG, Shuwen ZHANG, Lingling XIE, Junshan WU
In Press, Accepted Manuscript,   Available online  ,  
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The coupled ocean–atmosphere–wave–sediment transport (COAWST) modeling system is employed to investigate the role of wave-mixing playing in the upwelling off the west coast of Hainan Island (WHU). Waves, tides and sea surface temperature (SST) are reproduced reasonably well by the model when validated by observations. Model results suggest the WHU is tidally driven. Further investigations indicate that inclusion of wave-mixing promotes the intensity of the WHU, making the simulated SST become more consistent with remote-sensed ones. Dynamically, wave-mixing facilitates the " outcrop” of more upwelled cold water, triggering stronger WHU and leading to a three-dimensional dynamical adjustment. From the perspective of time, wave-mixing contributes to establishing an earlier tidal mixing front strong enough to generate WHU and that is, WHU may occur earlier when taking wave-mixing into consideration.
Intra-trench variations in flexural bending of the subducting Pacific Plate along the Tonga-Kermadec Trench
Fan Zhang, Jian Lin, Zhiyuan Zhou
In Press, Accepted Manuscript,   Available online  ,  
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We conducted a detailed analysis of along-trench variations in the flexural bending of the subducting Pacific Plate at the Tonga-Kermadec Trench. Inversions were conducted to obtain best-fitting solutions of trench-axis loadings and variations in the effective elastic plate thickness for the analyzed flexural bending profiles. Results of the analyses revealed significant along-trench variations in plate flexural bending: the trench relief (W0) of 1.9 to 5.1 km; trench-axis vertical loading (V0) of –0.5×1012 to 2.2×1012 N/m; axial bending moment (M0) of 0.1×1017 to 2.2×1017 N; effective elastic plate thickness seaward of the outer-rise region (TeM) of 20 to 65 km, trench-ward of the outer-rise (Tem) of 11 to 33 km, and the transition distance (Xr) of 20 to 95 km. The Horizon Deep, the second greatest trench depth in the world, has the greatest trench relief (W0 of 5.1 km) and trench-axis loading (V0 of 2.2×1012 N/m); these values are only slightly smaller than that of the Challenger Deep (W0 of 5.7 km and V0 of 2.9×1012 N/m) and similar to that of the Sirena Deep (W0 of 5.2 km and V0 of 2.0×1012 N/m) of the Mariana Trench, suggesting that these deeps are linked to great flexural bending of the subducting plates. Analyses using three independent methods, i.e., the TeM/Tem inversion, the flexural curvature/yield strength envelope analysis, and the elasto-plastic bending model with normal faults, all yielded similar average Te reduction of 28%–36% and average Te reduction area SΔTe of 1 195–1 402 km2 near the trench axis. The calculated brittle yield zone depth from the flexural curvature/yield strength envelope analysis is also consistent with the distribution of the observed normal faulting earthquakes. Comparisons of the Manila, Philippine, Tonga-Kermadec, Japan, and Mariana Trenches revealed that the average values of TeM and Tem both in general increase with the subducting plate age.
Sea surface temperature data from coastal observation stations: quality control and semidiurnal characteristics
Hua YANG, Qingqing GAO, Huifeng JI, Peidong HE, Tianmao ZHU
In Press, Accepted Manuscript,   Available online  ,  
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Sea surface temperature (SST) data obtained from coastal stations in Jiangsu, China during 2010–2014 are quality controlled before analysis of their characteristic semidiurnal and seasonal cycles, including the correlation with the variation of the tide. Quality control of data includes the validation of extreme values and checking of hourly values based on temporally adjacent data points, with 0.15°C/h considered a suitable threshold for detecting abnormal values. The diurnal variation amplitude of the SST data is greater in spring and summer than in autumn and winter. The diurnal variation of SST has bimodal structure on most days, i.e., SST has a significant semidiurnal cycle. Moreover, the semidiurnal cycle of SST is negatively correlated with the tidal data from March to August, but positively correlated with the tidal data from October to January. Little correlation is detected in the remaining months because of the weak coastal–offshore SST gradients. The quality control and understanding of coastal SST data are particularly relevant with regard to the validation of indirect measurements such as satellite-derived data.

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Roles of fishing and climate change in long-term fish species succession and population dynamics in the outer Beibu Gulf, South China Sea
Xuehui Wang, Yongsong Qiu, Feiyan Du, Weida Liu, Dianrong Sun, Xiao Chen, Weiwen Yuan, Yong Chen
2019, 38(10): 1-8  doi: 10.1007/s13131-019-1484-5
Abstract(10) FullText HTML(4) FullText PDF(0)
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A prevailing, controversial hypothesis is that fishing pressure has played a greater role than climatic and environmental drivers, in changing fish species succession and biomass fluctuation in the South China Sea (SCS). Based on otter trawl survey data from 1959 to 2010 in the outer Beibu Gulf (OBG), northern SCS, large seasonal and interannual variation is reported for fish species composition, the proportional abundances of dominant taxa, and fish biomass. Generalized additive models are developed to quantify relationships between fish biomass and the external factors of fishing pressure and climate change. Fishing pressure proved to be the main driver of sharp declines in demersal fish stocks, with high-value species being replaced by low-value ones over time. Abrupt decreases in fish biomass during the years of 1993 and 1998 correspond to El Niño events, with climate change possibly the main driver of proportional representation of pelagic species in fisheries trawl catch. The need to differentiate impacts of fishing and environmental drivers on fish species with different life history strategies is stressed to better understand fish community dynamics.
Evaluation of the performance of alternative assessment configurations to account for the spatial heterogeneity in age-structure: a simulation study based on Indian Ocean albacore tuna
Wenjiang Guan, Jiawen Wu, Siquan Tian
2019, 38(10): 9-19  doi: 10.1007/s13131-019-1485-4
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Various population structures or spatial heterogeneities in population distribution have been an important source of model misspecification and have had an impact on estimation performance in fisheries stock assessment. In this study, we simulated the Indian Ocean albacore spatial heterogeneity in age-structure using Stock Synthesis according to the stage-dependent migration rate and region-dependent fishing mortality rate and generated the stock assessment data. Based on these data, we investigated the performances of different spatial configurations, selectivity curves and selections of CPUE (catch per unit effort) indices of the assessment models which were used to account for spatial heterogeneity. The results showed: (1) although the spatially explicit configurations, which exactly matched the operating model, provided unbiased and accurate estimates of relative spawning biomass, relative fishing mortality rate and maximum sustainable yield in all simulation scenarios, their performance may be very poor if there were mismatches between them and the operating model due to gaps in knowledge and data; (2) for spatially explicit assessment configuration, the correct boundary was required, but for non-spatially explicit assessment configuration, it seemed more important for analysts to partition the area to properly reflect the transition in field data and to effectively account for the impacts of ignoring the spatial structure by using the additional spatially referenced parameters; (3) although the areas-as-fleets methods and flexible time-varying selectivity curves could be used as better alternative approaches to account for spatial structure, these configurations could not completely eliminate the impacts of model misspecification and the quality of estimates of different quantities from the same assessment model may be inconsistent or the performance of the same assessment configuration may fluctuate significantly between simulation scenarios; (4) although the worst estimates could generally be avoided by using multiple CPUE indices, there were no best solutions to select or regenerate the CPUE indices to account for the impacts of the ignored spatial structure to obviously improve the quality of stock assessment. Compared with the results of assessment model configurations which are used to account for the spatial structure by different modelers, the performances of the configurations are always case-specific except for spatially explicit configurations which exactly match the operating model. In this sense, our study will not only provide some insights into the current Indian Ocean albacore stock assessment but also enrich existing knowledge regarding the performance of assessment configurations to account for spatial structure.
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
2019, 38(10): 20-26  doi: 10.1007/s13131-019-1343-4
Abstract(60) FullText HTML(23) 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.
Trophic structure and energy flow of the resettled maritime area of the Bay of Bengal, Bangladesh through ECOPATH
Ehsanul Karim, Qun Liu, Ying Xue, Shanur Jahedul Hasan, M Enamul Hoq, Yahia Mahmud
2019, 38(10): 27-42  doi: 10.1007/s13131-019-1423-5
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The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal (BoB), Bangladesh from July 2016 to June 2017 through ECOPATH approach covering over 90 000 km2. A total of 19 functional groups were considered representing all trophic levels in the foodweb where estimated trophic interactions between the groups were varied from 1 (primary producers and detritus) to 3.45 (sharks). The ecotrophic efficiency (EE) of most of the consumers was greater than 0.80; symbolizing a largely exploited ecosystem and high energy transfer from lower to higher trophic levels. Moreover, the gross efficiency (0.001 8) and transfer efficiency (11.12%) of the whole system symbolizes the " Developing Systems” with somewhat maturity currently. Ecosystem’s overhead (64.6) and ascendancy (35.4) also designate the ecosystem’s stability. Thus, this study determines that the resettled maritime area of BoB reserves significant backup strength to face stress situations having capacity to rapid restoration to the original states.
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
2019, 38(10): 43-52  doi: 10.1007/s13131-019-1431-5
Abstract(53) FullText HTML(32) 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.
δ13C and δ15N in Humboldt squid beaks: understanding potential geographic population connectivity and movement
Bilin Liu, Xinjun Chen, Weiguo Qian, Yue Jin, Jianhua Li
2019, 38(10): 53-59  doi: 10.1007/s13131-019-1487-2
Abstract(9) FullText HTML(4) FullText PDF(0)
Abstract:
We quantified the δ13C and δ15N values in the lower beaks of Humboldt squid, Dosidicus gigas, collected from international waters off Costa Rica, Ecuador, Peru and Chile by Chinese squid jigging vessels during 2009, 2010 and 2013. There was a significant difference in the isotopic values among regions with the lowest value off Ecuador and the highest off Chile, which were interpreted as a function of trophic effects as well as baseline values. However, constant trophic level of D. gigas across its geographic range showed that spatial variation in the baseline of primary production is the main driver responsible for the observed geographic isotope variability. Inter-regional difference and intra-regional convergence of isotope values indicated squid off Costa Rica, Ecuador and Chile belong to different geographically segregated populations, which were previously proved by integrated population identifying method. In contrast, the higher variations in δ13C and δ15N values in a given size group suggest the squid off Peru move and forage in different places. Moreover, potential population exchange could be responsible for the overlap of the isotope values between the squid off Peru and off Chile. On the whole, the spatial difference in isotopic values of Humboldt squid beaks improves our understanding of potential geographic population connectivity and movement.
Decadal variations in the community status of economically important invertebrates in the Bohai Sea
Qiang Wu, Lisha Guan, Zhongyi Li, Xiujuan Shan, Xianshi Jin
2019, 38(10): 60-66  doi: 10.1007/s13131-019-1488-1
Abstract(11) FullText HTML(4) FullText PDF(0)
Abstract:
With the decline of fish stocks, the proportions of economically important invertebrates like crustaceans and cephalopods have increased in the Bohai Sea. The community structure and trophic level of economically important invertebrates were analyzed using the bottom trawl survey data collected by the Yellow Sea Fisheries Research Institute in the Bohai Sea in May and August of 1958–1959, 1982, 1992–1993, 2004, 2009 and 2015. A total of 37 species of economically important invertebrates, belonging to 5 orders, 24 families, were captured. The biomass densities of economically important invertebrates in the Bohai Sea displayed an overall downward trend from 1982 to 2015. Oratosquilla oratoria and Loligo spp. were the most dominant species in the past 30 years, the biomass proportion of O. oratoria increased gradually in both May and August from 1982 to 2015. Moreover, biodiversity indices of economically important invertebrates in the Bohai Sea appeared to decline from 1982 to 2004 and then increased in 2015. Similarly, the mean trophic level of economically important invertebrates declined from 1982 to 2004 and increased slightly in 2015. Overall, although the proportions of invertebrates have increased, the biomass densities in the Bohai Sea have displayed an overall downward trend from 1982 to 2015. The increases in the biodiversity and trophic level of economically important invertebrates after the 2000s, possibly benefit from stock enhancement projects implemented by governments at different levels and national fishery management measures such as the " double-control” of the total number and engine power of fishing vessels and summer moratorium of fishing.
A morphological evaluation of Chrysaora chinensis of Peninsular Malaysia and distinguishing its populations using geometric morphometrics
Liang Boon Low, Wan Mohd Syazwan, Mohammed Rizman-Idid
2019, 38(10): 67-74  doi: 10.1007/s13131-019-1483-6
Abstract(9) FullText HTML(4) FullText PDF(0)
Abstract:
The morphology of seven specimens of Chrysaora chinensis (Scyphomedusae, Semaestomae) obtained from four sites off the coast of Peninsular Malaysia was examined. Morphological characteristics of C. chinensis that encompasses structures such as the bell, tentacles, oral arms, stomach, manubrium, radial canals and gonads were described in detail. A total of 107 specimens that represented C. chinensis populations of four coastal areas of Peninsular Malaysia (East-Central, East-North, West-Central, and West-North) were also analysed for shape variation using geometric morphometric analysis. Procrustes superimposition, Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) were applied to the images of gastrovascular pouches of C. chinensis to extract the shape information. Independent contrasts were used for comparisons between shapes. There were no significant differences in shape variation between all the specimens based on the PCA results. However, CVA results showed shape variations between specimens taken from the four areas of Peninsular Malaysia, especially with higher magnitudes of Mahalanobis distances between the east and west coast areas, including between East-Central and East-North, but lower magnitudes were detected between the West-Central and West-North.
Feeding strategies of Euphausia superba in the eastern South Shetland Islands in austral summer
Mengtan Liu, Zhencheng Tao, Ye Zhang, Guang Yang, Song Sun, Chaolun Li, Fengfeng Le
2019, 38(10): 75-83  doi: 10.1007/s13131-019-1392-8
Abstract(24) FullText HTML(9) FullText PDF(0)
Abstract:
Euphausia superba is a key species in the Southern Ocean that serves as a link between primary production and higher trophic levels. To investigate the feeding strategies of E. superba from the eastern South Shetland Islands, fatty acid biomarkers, stable isotope signatures, and an incubation experiment were conducted. The results of the incubation experiment proved that adult E. superba mainly fed on 2–20 μm particles, demonstrating the importance of nanoplankton in their diet. Moreover, significant positive relationships between δ15N and body size demonstrated that size-related dietary shifts were present in E. superba. Evidence from principal component analysis and the C16:1ω7/C18:4ω3 ratio showed that juveniles preferentially fed on dinoflagellates and adults were more likely to feed on diatoms. Fatty acid profiles in adult E. superba roughly mirrored the different trophic conditions and feeding strategies between stations. Adult E. superba at Stas D2-07, D5-07, DA-01 and DA-02 exhibited elevated levels of C16:1ω7, C18:4ω3, C18:1ω9 and C18:1ω9/C18:1ω7, indicating higher levels of feeding on both phytoplankton and higher trophic diets. In contrast, adult E. superba at Stas D1-03 and D1-04 were characterized by high levels of polyunsaturated fatty acids/saturated fatty acids ratios and low levels of C16:1ω7, C18:1ω7, C18:4ω3, C18:1ω9 and total fatty acids. We inferred that adult krill at Stas D1-03 and D1-04 still suffered from difficult dietary conditions after overwintering. The different dietary conditions between stations suggest a highly plastic feeding strategy of E. superba in the eastern South Shetland Islands.
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
2019, 38(10): 84-92  doi: 10.1007/s13131-019-1345-2
Abstract(52) FullText HTML(20) FullText PDF(0)
Abstract:
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.
An improved ARTSIST sea ice algorithm based on 19 GHz modified 91 GHz
Zhankai Wu, Xingdong Wang, Xuemei Wang
2019, 38(10): 93-99  doi: 10.1007/s13131-019-1482-7
Abstract(9) FullText HTML(4) FullText PDF(0)
Abstract:
An enhanced ARTSIST Sea Ice (ASI) algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data. Algorithms that use low-frequency data to calculate total sea ice concentration are less affected by atmosphere, but their spatial resolutions tend to be lower. In contrast, algorithms using high-frequency data have higher spatial resolution but are significantly influenced by atmosphere. Although errors can be eliminated using weather filters, the concentration of mixed pixels cannot be modified. Here, an enhanced ASI algorithm uses the 19 GHz polarization difference to modify the 91 GHz polarization difference, which is substituted into the ASI algorithm to calculate total sea ice concentration. Arctic total sea ice concentration results are obtained based on Special Sensor Microwave Imager Sounder (SSMIS) data on January 3, from 2008 to 2017. Total sea ice area and average concentration using the enhanced ASI algorithm are compared to traditional ASI and NASA Team results. In the Marginal Ice Zone, there is a considerable difference between the enhanced and traditional ASI algorithm results, with the former much closer to the NASA Team results. The proposed algorithm effectively modifies the concentration of the mixed pixels in the marginal zone.
Comparative analysis of CPUE standardization of Chinese Pacific saury (Cololabis saira) fishery based on GLM and GAM
Chuanxiang Hua, Qingcheng Zhu, Yongchuang Shi, Yu Liu
2019, 38(10): 100-110  doi: 10.1007/s13131-019-1486-3
Abstract(11) FullText HTML(4) FullText PDF(0)
Abstract:
Pacific saury is an important high-seas fishery resource in the Northwest Pacific Ocean for the Chinese Mainland. Reliable and accurate catch per unit effort (CPUE) plays a significant rule in Pacific saury stock assessment. Many statistical models have been used in the previous CPUE standardization research. Here, we compare the performance of Generalized Linear Models (GLMs) and Generalized Additive Models (GAMs) using CPUE data collected from Chinese saury fishery in the Northwest Pacific Ocean from 2003 to 2017 (excluding data from Chinese Taipei), and evaluate the influence of spatial, temporal, environmental variables and vessel length on CPUE. Optimal GLM/GAM models were selected using the Bayesian information criterion (BIC). Explained deviance and 5-fold bootstrap cross-validation results were used to compare the performance of the two model types. Fitted GLMs accounted for 21.57% of the total model-explained deviance, while GAMs accounted for 38.95%. Predictive performance metrics and 5-fold cross-validation results showed that the best GAM performed better than the best GLM. Therefore, we recommend GAM as the preferred model for standardizing CPUE of Pacific saury in the Northwest Pacific Ocean.
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
2019, 38(10): 111-115  doi: 10.1007/s13131-019-1429-z
Abstract(65) FullText HTML(27) FullText PDF(1)
Abstract:
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.

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