2020 Vol. 42, No. 2
Display Method:
2020, 42(2): .
Abstract:
2020, 42(2): 1-9.
doi: 10.3969/j.issn.0253-4193.2020.02.001
Abstract:
CH3I, CHCl3, C2HCl3 and CH2Br2 are the four important components of volatile halocarbons, which have important influence on atmospheric chemistry. To study the effect of Fe, ocean acidification, coupling effect of ocean acidification and Fe, coupling effect of Fe and N/P (16∶1) and dust on the concentrations of CH3I, CHCl3, C2HCl3 and CH2Br2 released by phytoplankton, an onboard incubation experiments was performed at the western Pacific Ocean in October 2018. Compared with the blank control experiment, the results show that the releases of CH3I, C2HCl3 and CH2Br2 in the experimental groups are suppressed in some extent. While the release of CHCl3 is promoted except when the dust is added. The concentration of Chl a is relatively high but the changes in nutrients concentrations are not obviously unconspicuous. In conclusion, the ocean acidification and iron fertilization might be the two virtual factors for phytoplankton to release volatile halocarbons. Besides, the growth of phytoplankton is affected significantly by the dust.
CH3I, CHCl3, C2HCl3 and CH2Br2 are the four important components of volatile halocarbons, which have important influence on atmospheric chemistry. To study the effect of Fe, ocean acidification, coupling effect of ocean acidification and Fe, coupling effect of Fe and N/P (16∶1) and dust on the concentrations of CH3I, CHCl3, C2HCl3 and CH2Br2 released by phytoplankton, an onboard incubation experiments was performed at the western Pacific Ocean in October 2018. Compared with the blank control experiment, the results show that the releases of CH3I, C2HCl3 and CH2Br2 in the experimental groups are suppressed in some extent. While the release of CHCl3 is promoted except when the dust is added. The concentration of Chl a is relatively high but the changes in nutrients concentrations are not obviously unconspicuous. In conclusion, the ocean acidification and iron fertilization might be the two virtual factors for phytoplankton to release volatile halocarbons. Besides, the growth of phytoplankton is affected significantly by the dust.
2020, 42(2): 10-21.
doi: 10.3969/j.issn.0253-4193.2020.02.002
Abstract:
Distributions of dissolved aluminum in the Zhujiang River Estuary and slope of the northern South China Sea (NSCS) were observed in October 2014 and June 2015, respectively. We discuss the main factors affecting its distribution and seasonal variation, and use dissolved aluminum as a tracer to explore the potential cross-shelf transport of terrestrial materials. The concentrations of dissolved aluminum in the Zhujiang River were 690 nmol/L and 360 nmol/L in summer and autumn, respectively. Dissolved aluminum were significantly removed from the water column in the initial mixing of fresh and saline water in the Zhujiang River Estuary, with scavenging rate of 55.8% and 29.7% in summer and autumn, respectively. In the slope of the NSCS, the concentration of dissolved aluminum in the surface decreased from east to west along the latitude in summer and was completely opposite in autumn. The concentrations of dissolved aluminum in the bottom were gradually decreased across the NSCS shelf with the increasing distance from the coast both in summer and autumn. The negative correlation between dissolved aluminum and salinity in autumn indicated that the behavior of dissolved aluminum was nearly conservative and the mixing of different water masses including shelf mixed water and kuroshio subsurface water was the main influencing factor. Dissolved aluminum showed decreasing trend from the continental shelf to the middle of NSCS along the isopycnal surfaces of 21.6 to 22.2 kg/m3, indicating the potential cross-shelf transport path in the NSCS. In summer, there was a water tough with lower salinity appeared in the middle of the study area, indicating the influence of the Zhujiang diluted water. However, the concentration of dissolved aluminum was relatively low corresponding to the water mass with low salinity. Scavenging by phytoplankton bloom in the top mixed layer was the major influencing factor of semi-conservative behavior of dissolved aluminum in summer.
Distributions of dissolved aluminum in the Zhujiang River Estuary and slope of the northern South China Sea (NSCS) were observed in October 2014 and June 2015, respectively. We discuss the main factors affecting its distribution and seasonal variation, and use dissolved aluminum as a tracer to explore the potential cross-shelf transport of terrestrial materials. The concentrations of dissolved aluminum in the Zhujiang River were 690 nmol/L and 360 nmol/L in summer and autumn, respectively. Dissolved aluminum were significantly removed from the water column in the initial mixing of fresh and saline water in the Zhujiang River Estuary, with scavenging rate of 55.8% and 29.7% in summer and autumn, respectively. In the slope of the NSCS, the concentration of dissolved aluminum in the surface decreased from east to west along the latitude in summer and was completely opposite in autumn. The concentrations of dissolved aluminum in the bottom were gradually decreased across the NSCS shelf with the increasing distance from the coast both in summer and autumn. The negative correlation between dissolved aluminum and salinity in autumn indicated that the behavior of dissolved aluminum was nearly conservative and the mixing of different water masses including shelf mixed water and kuroshio subsurface water was the main influencing factor. Dissolved aluminum showed decreasing trend from the continental shelf to the middle of NSCS along the isopycnal surfaces of 21.6 to 22.2 kg/m3, indicating the potential cross-shelf transport path in the NSCS. In summer, there was a water tough with lower salinity appeared in the middle of the study area, indicating the influence of the Zhujiang diluted water. However, the concentration of dissolved aluminum was relatively low corresponding to the water mass with low salinity. Scavenging by phytoplankton bloom in the top mixed layer was the major influencing factor of semi-conservative behavior of dissolved aluminum in summer.
2020, 42(2): 22-29.
doi: 10.3969/j.issn.0253-4193.2020.02.003
Abstract:
Dissimilatory nitrate reduction processes in sediments play a crucial role in marine nitrogen cycle. The most popular method to determine the rates of different dissimilatory nitrate reduction processes is the 15N labeled technique. Therefore, accurate and rapid determination the concentration of 15N-labeled products, such as 29N2 and 30N2, is the key to quantify the rate of each dissimilatory nitrate reduction process. In this study, we set up a membrane injection mass spectrometry (MIMS) and optimize the operating condition of the MIMS for the determination of 29N2 and 30N2. The optimization experiment results indicated that, when the peristaltic pump for sampling flow rate is 0.80 mL/min, the sampling time is 3～3.5 min, the thermostat water bath temperature is 20～25℃, and the copper reduction furnace temperature is 300～600℃, the precision (expressed in coefficient of variation) of the measured 29N2/28N2 and 30N2/28N2 can be controlled less than 0.1% and 1%, respectively. We used the self-assembled MIMS and combined the 15N labeling technique to study the dissimilatory nitrate reduction processes in the sandy sediment of the Shilaoren beach in Qingdao. There is no significant aerobic denitrification in the Shilaoren sand that can completely reduce nitrate to N2. The potential rates of anammox, anaerobic denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are (0.05±0.01) nmol/(cm3·h), (2.32±0.21) nmol/(cm3·h) and (1.02±0.15) nmol/(cm3·h) (N, wet sed.), respectively. Anaerobic denitrification is the major contributor to nitrate dissimilatory reduction, with a ratio of nearly 70%, followed by DNRA, with a ratio of up to 30%, while anammox has the lowest contribution of only 1%. In the N2 production, the main contributor is anaerobic denitrification, and the contribution of anammox is only 2%.
Dissimilatory nitrate reduction processes in sediments play a crucial role in marine nitrogen cycle. The most popular method to determine the rates of different dissimilatory nitrate reduction processes is the 15N labeled technique. Therefore, accurate and rapid determination the concentration of 15N-labeled products, such as 29N2 and 30N2, is the key to quantify the rate of each dissimilatory nitrate reduction process. In this study, we set up a membrane injection mass spectrometry (MIMS) and optimize the operating condition of the MIMS for the determination of 29N2 and 30N2. The optimization experiment results indicated that, when the peristaltic pump for sampling flow rate is 0.80 mL/min, the sampling time is 3～3.5 min, the thermostat water bath temperature is 20～25℃, and the copper reduction furnace temperature is 300～600℃, the precision (expressed in coefficient of variation) of the measured 29N2/28N2 and 30N2/28N2 can be controlled less than 0.1% and 1%, respectively. We used the self-assembled MIMS and combined the 15N labeling technique to study the dissimilatory nitrate reduction processes in the sandy sediment of the Shilaoren beach in Qingdao. There is no significant aerobic denitrification in the Shilaoren sand that can completely reduce nitrate to N2. The potential rates of anammox, anaerobic denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are (0.05±0.01) nmol/(cm3·h), (2.32±0.21) nmol/(cm3·h) and (1.02±0.15) nmol/(cm3·h) (N, wet sed.), respectively. Anaerobic denitrification is the major contributor to nitrate dissimilatory reduction, with a ratio of nearly 70%, followed by DNRA, with a ratio of up to 30%, while anammox has the lowest contribution of only 1%. In the N2 production, the main contributor is anaerobic denitrification, and the contribution of anammox is only 2%.
2020, 42(2): 30-43.
doi: 10.3969/j.issn.0253-4193.2020.02.004
Abstract:
Redox sensitive elements (Redox Sensitive Elements, RSE) such as V, Cr, Mo and U, et al. are dissolved under oxidation conditions. They are reduced to low-valent state under reducing sedimentary environment and transferred to sediments for enrichment and accumulation. Therefore, the enrichment of redox sensitive elements in sediments can be used to invert the redox status of sedimentary environment. In this paper, the vertical distribution, enrichment characteristics and ratios of redox sensitive elements V, Cr, Ni, Cu, Zn, Mo and U in the Zb7 core sediment in the seasonal low-oxygen sea area of East China Sea were studied. It was found that RSE/Al and enrichment coefficient had increased since 1978, but had decreased since 2009. The overall RSE enrichment coefficient was less than 3, and no obvious enrichment had been observed. RSE ratios V/Cr<2, Ni/Co<5, U/Th<0.75, 0.25<(Cu+Mo)/Zn<0.55 and MoEF/UEF ratios were mainly distributed between 0.08 and 0.3 times of seawater Mo/U ratios, indicating the oxidized sedimentary environment. RSE/Al was significantly correlated with Fe/Al and Mn/Al, which indicated that RSE entered sediments mainly by combining with Fe and Mn oxides after removing terrigenous debris inputs, and also indicated the oxidized sedimentary environment. The results were inconsistent with the results of seasonal hypoxia reflected by the historical data of dissolved oxygen in this region. It may be related to the absence of RSE enrichment signals in the sediments during seasonal hypoxia in summer after the recovery of dissolved oxygen levels in autumn and winter. Although RSE can not effectively indicate the seasonal hypoxic environment in the East China Sea, the increase of RSE enrichment in Zb7 after 1978 and the decrease after 2009 reflected to some extent the trend of seasonal hypoxia aggravating in the region since 1978 and easing after 2009.
Redox sensitive elements (Redox Sensitive Elements, RSE) such as V, Cr, Mo and U, et al. are dissolved under oxidation conditions. They are reduced to low-valent state under reducing sedimentary environment and transferred to sediments for enrichment and accumulation. Therefore, the enrichment of redox sensitive elements in sediments can be used to invert the redox status of sedimentary environment. In this paper, the vertical distribution, enrichment characteristics and ratios of redox sensitive elements V, Cr, Ni, Cu, Zn, Mo and U in the Zb7 core sediment in the seasonal low-oxygen sea area of East China Sea were studied. It was found that RSE/Al and enrichment coefficient had increased since 1978, but had decreased since 2009. The overall RSE enrichment coefficient was less than 3, and no obvious enrichment had been observed. RSE ratios V/Cr<2, Ni/Co<5, U/Th<0.75, 0.25<(Cu+Mo)/Zn<0.55 and MoEF/UEF ratios were mainly distributed between 0.08 and 0.3 times of seawater Mo/U ratios, indicating the oxidized sedimentary environment. RSE/Al was significantly correlated with Fe/Al and Mn/Al, which indicated that RSE entered sediments mainly by combining with Fe and Mn oxides after removing terrigenous debris inputs, and also indicated the oxidized sedimentary environment. The results were inconsistent with the results of seasonal hypoxia reflected by the historical data of dissolved oxygen in this region. It may be related to the absence of RSE enrichment signals in the sediments during seasonal hypoxia in summer after the recovery of dissolved oxygen levels in autumn and winter. Although RSE can not effectively indicate the seasonal hypoxic environment in the East China Sea, the increase of RSE enrichment in Zb7 after 1978 and the decrease after 2009 reflected to some extent the trend of seasonal hypoxia aggravating in the region since 1978 and easing after 2009.
2020, 42(2): 44-51.
doi: 10.3969/j.issn.0253-4193.2020.02.005
Abstract:
In this study, the eddy kinetic energy (EKE) derived from satellite altimeter data and the fishery data during 2010−2016 obtained from the Chinese Squid-jigging Science and Technology Group, are used to analyze the spatial and temporal relationship between the Kuroshio Extension EKE and fishing ground distribution. The results show that the catch per unit effort (CPUE) is negatively related to the EKE of fishing ground in the range of 0–1 500 cm2/s2, the most suitable EKE is between 25–150 cm2/s2. Furthermore, the Kuroshio Extension EKE decreasing from west to east, is correlated with CPUE with the high correlation coefficient of 0.81. According to the longitudinal range, the Kuroshio Extension is divided into four sub-areas, and the monthly average latitudes of fishing ground centroids respond to the sub-areas with the highest EKE in the same month. When the distance (DIST) from fishing grounds to the Kuroshio Extension in the range of 800–1 000 km, CPUE increases with the DIST, and the most suitable DIST from August to October is between 850−950 km. When the Kuroshio Extension path has complicated meanders, EKE is high, while the CPUE is reduced and the fishing grounds move northward.
In this study, the eddy kinetic energy (EKE) derived from satellite altimeter data and the fishery data during 2010−2016 obtained from the Chinese Squid-jigging Science and Technology Group, are used to analyze the spatial and temporal relationship between the Kuroshio Extension EKE and fishing ground distribution. The results show that the catch per unit effort (CPUE) is negatively related to the EKE of fishing ground in the range of 0–1 500 cm2/s2, the most suitable EKE is between 25–150 cm2/s2. Furthermore, the Kuroshio Extension EKE decreasing from west to east, is correlated with CPUE with the high correlation coefficient of 0.81. According to the longitudinal range, the Kuroshio Extension is divided into four sub-areas, and the monthly average latitudes of fishing ground centroids respond to the sub-areas with the highest EKE in the same month. When the distance (DIST) from fishing grounds to the Kuroshio Extension in the range of 800–1 000 km, CPUE increases with the DIST, and the most suitable DIST from August to October is between 850−950 km. When the Kuroshio Extension path has complicated meanders, EKE is high, while the CPUE is reduced and the fishing grounds move northward.
2020, 42(2): 52-64.
doi: 10.3969/j.issn.0253-4193.2020.02.006
Abstract:
Meiofaunal communities and the relationships with environmental variables in the northern East China Sea and its adjacent area were studied in the present paper based on the material collected from 20 sites in September and December, 2016. About 16 meiofaunal groups were identified with nematodes being the most dominant group, followed by copepods, kinorhynchs and polychaetas. The average abundances of meiofauna were (1 758±759) ind./(10 cm2), and (2 011±1 471) ind./(10 cm2) in September and December, respectively. The average biomasses of meiofauna were (1 216.4±464.7) μg/(10 cm2) and (1 143.0±755.0) μg/(10 cm2) in September and December, respectively. Results of CLUSTER analysis show that meiofaunal communities can be divided into two main groups, one was the offshore group, composed of stations in the offshore area, another group was the coastal group, composed of stations in the coastal area. However, the highest value of abundance always occurred in the depth about 60 m isobath where the salinity and temperature showed the characters of Kuroshio Current implying the intrusion of Kuroshio. We suggest that the intrusion of Kuroshio Current is the main cause of the increase of meiofaunal abundance, which can be treated as a response of meiofauna to the intrusion of Kuroshio, around the 60 m isobath. The high abundance of meiofauna may be explained by dissolved oxygen brought by the Kuroshio waters, and high primary production of water column benefitted from the supplying of phosphorus of the Kuroshio waters.
Meiofaunal communities and the relationships with environmental variables in the northern East China Sea and its adjacent area were studied in the present paper based on the material collected from 20 sites in September and December, 2016. About 16 meiofaunal groups were identified with nematodes being the most dominant group, followed by copepods, kinorhynchs and polychaetas. The average abundances of meiofauna were (1 758±759) ind./(10 cm2), and (2 011±1 471) ind./(10 cm2) in September and December, respectively. The average biomasses of meiofauna were (1 216.4±464.7) μg/(10 cm2) and (1 143.0±755.0) μg/(10 cm2) in September and December, respectively. Results of CLUSTER analysis show that meiofaunal communities can be divided into two main groups, one was the offshore group, composed of stations in the offshore area, another group was the coastal group, composed of stations in the coastal area. However, the highest value of abundance always occurred in the depth about 60 m isobath where the salinity and temperature showed the characters of Kuroshio Current implying the intrusion of Kuroshio. We suggest that the intrusion of Kuroshio Current is the main cause of the increase of meiofaunal abundance, which can be treated as a response of meiofauna to the intrusion of Kuroshio, around the 60 m isobath. The high abundance of meiofauna may be explained by dissolved oxygen brought by the Kuroshio waters, and high primary production of water column benefitted from the supplying of phosphorus of the Kuroshio waters.
2020, 42(2): 65-74.
doi: 10.3969/j.issn.0253-4193.2020.02.007
Abstract:
The benthic macroinvertebrate is one of the most important biological groups in salt marsh ecosystem. The Jiuduansha shoals of the Changjiang Estuary were selected as the study areas, and fixed sampling sites were set along the elevation gradient in the different areas, and the benthic macroinvertebrates, sediments and plants were sampled for the analysis on the distribution characteristics of the benthic macroinvertebrates and corresponding influencing factors. The results showed that: (1) The distribution of the benthic macroinvertebrates along elevation gradient has certain regularity: The abundance and biomass of annelids in the low tidal zone appeared to be the highest, the species number of mollusks in the middle tidal zone was the highest, and the abundance and biomass of crustaceans in the high tidal zone were the highest. (2) Due to the differences of environmental conditions, the distribution characteristics of the benthic macroinvertebrates along the elevation gradient were also significantly different among the different areas. (3) Habitat factors that have significant effects on the distribution characteristics of the benthic macroinvertebrates included the median grain size, the redox potential of sediments, the density of plants, etc, and there were some differences among the different areas and habitats. (4) The invasion of Spartina alterniflora changed the habitat conditions and thus affected the distribution characteristics of the benthic macroinvertebrates. In future studies, we should fully consider the differences of environmental conditions between the different areas and elevations to explore the distribution characteristics of the benthic macroinvertebrates and the comprehensive effects of the influencing factors.
The benthic macroinvertebrate is one of the most important biological groups in salt marsh ecosystem. The Jiuduansha shoals of the Changjiang Estuary were selected as the study areas, and fixed sampling sites were set along the elevation gradient in the different areas, and the benthic macroinvertebrates, sediments and plants were sampled for the analysis on the distribution characteristics of the benthic macroinvertebrates and corresponding influencing factors. The results showed that: (1) The distribution of the benthic macroinvertebrates along elevation gradient has certain regularity: The abundance and biomass of annelids in the low tidal zone appeared to be the highest, the species number of mollusks in the middle tidal zone was the highest, and the abundance and biomass of crustaceans in the high tidal zone were the highest. (2) Due to the differences of environmental conditions, the distribution characteristics of the benthic macroinvertebrates along the elevation gradient were also significantly different among the different areas. (3) Habitat factors that have significant effects on the distribution characteristics of the benthic macroinvertebrates included the median grain size, the redox potential of sediments, the density of plants, etc, and there were some differences among the different areas and habitats. (4) The invasion of Spartina alterniflora changed the habitat conditions and thus affected the distribution characteristics of the benthic macroinvertebrates. In future studies, we should fully consider the differences of environmental conditions between the different areas and elevations to explore the distribution characteristics of the benthic macroinvertebrates and the comprehensive effects of the influencing factors.
2020, 42(2): 75-86.
doi: 10.3969/j.issn.0253-4193.2020.02.008
Abstract:
To evaluate the relationship between macrobenthic communities and environmental factors in the Yueqing Bay, five surveys were conducted in this study in January, March, May, August and October 2015. We found that both community structure and spatial distribution were similar in January, March and May, with Yoldia similis and Sternaspis sculata as the characteristic species. The dominant communities were not obvious in neither August nor October, the characteristic species of the main community were S. sculata, Nephtys oligobranchia, Capitella capitata, and Mediomastus sp. With the aid of abundance/biomass curve (ABC curve) analysis, we found that the communities were the most stable in May, and the most vulnerable in August. Results of BVSTEP analysis showed that nitrite was the dominant environmental factor for monthly difference of macrobenthic communities in the Yueqing Bay. In addition, salinity and ammonia nitrogen were the key environmental factors affecting the macrobenthic community structure in March and May, respectively. Canonical correspondence analysis (CCA) further showed that water temperature had the greatest influence on the spatial and temporal distribution of characteristic species of macrobenthic communities in the Yueqing Bay, followed by salinity, dissolved oxygen, nitrogen nutrients and pH, etc. The CCA biplot also showed that the majority of the community species were distributed in the waters with low nitrogen nutrients, indicating that high concentrations of nitrogen nutrients had a negative impact on the distribution of macrobenthos in the Yueqing Bay.
To evaluate the relationship between macrobenthic communities and environmental factors in the Yueqing Bay, five surveys were conducted in this study in January, March, May, August and October 2015. We found that both community structure and spatial distribution were similar in January, March and May, with Yoldia similis and Sternaspis sculata as the characteristic species. The dominant communities were not obvious in neither August nor October, the characteristic species of the main community were S. sculata, Nephtys oligobranchia, Capitella capitata, and Mediomastus sp. With the aid of abundance/biomass curve (ABC curve) analysis, we found that the communities were the most stable in May, and the most vulnerable in August. Results of BVSTEP analysis showed that nitrite was the dominant environmental factor for monthly difference of macrobenthic communities in the Yueqing Bay. In addition, salinity and ammonia nitrogen were the key environmental factors affecting the macrobenthic community structure in March and May, respectively. Canonical correspondence analysis (CCA) further showed that water temperature had the greatest influence on the spatial and temporal distribution of characteristic species of macrobenthic communities in the Yueqing Bay, followed by salinity, dissolved oxygen, nitrogen nutrients and pH, etc. The CCA biplot also showed that the majority of the community species were distributed in the waters with low nitrogen nutrients, indicating that high concentrations of nitrogen nutrients had a negative impact on the distribution of macrobenthos in the Yueqing Bay.
2020, 42(2): 87-95.
doi: 10.3969/j.issn.0253-4193.2020.02.009
Abstract:
The growth of fish is an important factor affecting the stock biomass. Studying the pattern of fish growth underpins fish stock assessment. This study was conducted based on otolith microstructure analysis of young-of-the-year (YOY) Scomberomorus niphonius collected from September to October in 2016 and August to October in 2017 from the Yellow Sea and Bohai Sea. The hatching dates were determined for each individual. The growth models were established and the growth rates were calculated. The results showed that the age range of YOY S. niphonius was 64–151 d. The hatching dates fell between 3 May and 15 June, with a peak between 20 May and 3 June. The Logistic model gave the best fit to growth of fork length and body weight. The average absolute growth rate and specific growth rate of the fork length were 2.45 mm/d and 0.85 %/d, respectively. The growth rate decreased slightly with the increase of age. The average absolute growth rate and specific growth rate of body weight were 5.33 g/d and 2.68%/d, respectively. The maximum absolute growth rate and maximum specific growth rate occurred at 111–120 d and 91–100 d, respectively. The results of this study showed that the growth of YOY S. niphonius varied with age, and the early growth of the S. niphonius accelerated further than before.
The growth of fish is an important factor affecting the stock biomass. Studying the pattern of fish growth underpins fish stock assessment. This study was conducted based on otolith microstructure analysis of young-of-the-year (YOY) Scomberomorus niphonius collected from September to October in 2016 and August to October in 2017 from the Yellow Sea and Bohai Sea. The hatching dates were determined for each individual. The growth models were established and the growth rates were calculated. The results showed that the age range of YOY S. niphonius was 64–151 d. The hatching dates fell between 3 May and 15 June, with a peak between 20 May and 3 June. The Logistic model gave the best fit to growth of fork length and body weight. The average absolute growth rate and specific growth rate of the fork length were 2.45 mm/d and 0.85 %/d, respectively. The growth rate decreased slightly with the increase of age. The average absolute growth rate and specific growth rate of body weight were 5.33 g/d and 2.68%/d, respectively. The maximum absolute growth rate and maximum specific growth rate occurred at 111–120 d and 91–100 d, respectively. The results of this study showed that the growth of YOY S. niphonius varied with age, and the early growth of the S. niphonius accelerated further than before.
2020, 42(2): 96-105.
doi: 10.3969/j.issn.0253-4193.2020.02.010
Abstract:
Many species of holoplanktonic gastropods have a near-cosmopolitan or circumglobal distribution, some of which are used for phylogeography and ocean acidification research. Using mitochondrial COI (mtCOI, 55 animals) and nuclear 18S rRNA (9 animals) sequence data from specimens sampled from Northwest Pacific and North Indian Oceans, and together with the sequences from GenBank, we investigated the taxonomy and phylogeography of Clio species. Four lineages were defined by mtCOI tree for C. pyramidata (Lineages A–D) and C. cuspidata (LineagesE–H), respectively. Lineage A of C. pyramidata showed a circumglobal distribution, while Lineages B, C and D had their restrained dispersal. Only Lineage A was found in Chinese seas and adjacent waters. The divergent mtCOI lineages of C. cuspidata were also phylogeographical structured. Two distinct lineages (E and F) of C. cuspidata were observed in the Northwestern Pacific, which are distributed in the south and north areas of the North Equatorial Current respectively. The K2P distances of intra-lineage were between 0 and 0.026, while the distances of inter-lineage ranged from 0.031 to 0.089. Geographic structures were not observed in C. convexa and C. recurva. The morphospecies C. pyramidata and C. cuspidata may harbour cryptic diversity. Our results also suggested that ocean currents may limit the species dispersal and gene flow.
Many species of holoplanktonic gastropods have a near-cosmopolitan or circumglobal distribution, some of which are used for phylogeography and ocean acidification research. Using mitochondrial COI (mtCOI, 55 animals) and nuclear 18S rRNA (9 animals) sequence data from specimens sampled from Northwest Pacific and North Indian Oceans, and together with the sequences from GenBank, we investigated the taxonomy and phylogeography of Clio species. Four lineages were defined by mtCOI tree for C. pyramidata (Lineages A–D) and C. cuspidata (LineagesE–H), respectively. Lineage A of C. pyramidata showed a circumglobal distribution, while Lineages B, C and D had their restrained dispersal. Only Lineage A was found in Chinese seas and adjacent waters. The divergent mtCOI lineages of C. cuspidata were also phylogeographical structured. Two distinct lineages (E and F) of C. cuspidata were observed in the Northwestern Pacific, which are distributed in the south and north areas of the North Equatorial Current respectively. The K2P distances of intra-lineage were between 0 and 0.026, while the distances of inter-lineage ranged from 0.031 to 0.089. Geographic structures were not observed in C. convexa and C. recurva. The morphospecies C. pyramidata and C. cuspidata may harbour cryptic diversity. Our results also suggested that ocean currents may limit the species dispersal and gene flow.
2020, 42(2): 106-114.
doi: 10.3969/j.issn.0253-4193.2020.02.011
Abstract:
During June and August 2017, two picophytoplankton groups including Synechococcus and picoeukaryotes were found in Qinhuangdao coastal waters, and Synechococcus could be divided into two sub-groups of Synechococcus Ⅰ and Synechococcus Ⅱ. During the sampling period, it was during high-incidence period of brown tide. To investigate the effects of the related environmental factors on the spatical distributions of picophytoplankton in Qinhuangdao coastal waters, we compared their cell abundances, carbon biomass and distributional characteristics during the brown tide. The results showed that the average abundances of picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ in June were 1.14×104 cell/mL, 4.02×104 cell/mL and 1.04×104 cell/mL, respectively, and the average carbon biomass were 27.22 μg/L, 8.49 μg/L and 2.27 μg/L respectively. While in August, the average abundances of picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ were 3.27×103 cell/mL, 5.79×104 cell/mL and 2.58×104 cell/mL, and the average carbon biomass were 6.35 μg/L, 13.41 μg/L and 5.83 μg/L respectively. The abundance of picoeukaryotes decreased by an order of magnitude from June to August, indicating that the growth of dominant species of brown tide was limited by high temperature and low nutrients in August. Picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ showed different distributions in June and August. Synechococcus Ⅰ and Synechococcus Ⅱ increased gradually from estuary to nearshore in June, while picoeukaryotes showed a downward trend. Inversely, picoeukaryotes and Synechococcus Ⅰ showed a decreasing trend from estuary to nearshore in August, and the distribution character of Synechococcus Ⅱ abundance was not obvious in Qinhuangdao coastal waters, mainly existing in surface layer. The results of correlation analysis with related environmental factors indicated that nitrate and ammonium salt were the key factor in controlling the growth of Synechococcus Ⅰ in June while picoeukaryotes was limited by the silicate concentration. There was no significant correlation between Synechococcus Ⅱ and environment factors in June. In August, the growth of picoeukaryotes was affected by a variety of environmental factors, such as nitrate, nitrite, silicate, phosphate, temperature and light while Synechococcus Ⅰ was positively correlated with nitrate. The temperature and light were the key factors affecting the Synechococcus Ⅱ distribution in August.
During June and August 2017, two picophytoplankton groups including Synechococcus and picoeukaryotes were found in Qinhuangdao coastal waters, and Synechococcus could be divided into two sub-groups of Synechococcus Ⅰ and Synechococcus Ⅱ. During the sampling period, it was during high-incidence period of brown tide. To investigate the effects of the related environmental factors on the spatical distributions of picophytoplankton in Qinhuangdao coastal waters, we compared their cell abundances, carbon biomass and distributional characteristics during the brown tide. The results showed that the average abundances of picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ in June were 1.14×104 cell/mL, 4.02×104 cell/mL and 1.04×104 cell/mL, respectively, and the average carbon biomass were 27.22 μg/L, 8.49 μg/L and 2.27 μg/L respectively. While in August, the average abundances of picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ were 3.27×103 cell/mL, 5.79×104 cell/mL and 2.58×104 cell/mL, and the average carbon biomass were 6.35 μg/L, 13.41 μg/L and 5.83 μg/L respectively. The abundance of picoeukaryotes decreased by an order of magnitude from June to August, indicating that the growth of dominant species of brown tide was limited by high temperature and low nutrients in August. Picoeukaryotes, Synechococcus Ⅰ and Synechococcus Ⅱ showed different distributions in June and August. Synechococcus Ⅰ and Synechococcus Ⅱ increased gradually from estuary to nearshore in June, while picoeukaryotes showed a downward trend. Inversely, picoeukaryotes and Synechococcus Ⅰ showed a decreasing trend from estuary to nearshore in August, and the distribution character of Synechococcus Ⅱ abundance was not obvious in Qinhuangdao coastal waters, mainly existing in surface layer. The results of correlation analysis with related environmental factors indicated that nitrate and ammonium salt were the key factor in controlling the growth of Synechococcus Ⅰ in June while picoeukaryotes was limited by the silicate concentration. There was no significant correlation between Synechococcus Ⅱ and environment factors in June. In August, the growth of picoeukaryotes was affected by a variety of environmental factors, such as nitrate, nitrite, silicate, phosphate, temperature and light while Synechococcus Ⅰ was positively correlated with nitrate. The temperature and light were the key factors affecting the Synechococcus Ⅱ distribution in August.
2020, 42(2): 115-123.
doi: 10.3969/j.issn.0253-4193.2020.02.012
Abstract:
To study the tempo-spatial distribution and species succession of green macroalgal micro-propagules in the coastal waters affected by the green tides in the Yellow Sea, a year-round survey was conducted at the four stations (ZGS, YWG, LSG and YY) along the coasts of Jiangsu and Shandong provinces. Through the lab-culture and molecular analysis, there were six green macroalgal species detected, including 4 ulvoid species (Ulva linza, U. prolifera, U. compressa and U. pertusa), an unclassified Ulva sp. and one Blidingia sp. Quantitative analyses revealed evident tempo-spatial variations of the abundance and species composition of micro-propagules at the four stations. The abundances of micro-propagules were significantly higher at ZGS and YY than those at YWG and LSG. A seasonal bi-peak pattern of the abundances was consistent throughout the four stations. The numbers of micro-propagules were generally highest during the spring to early summer, and reached a minor peak in fall, but were low in other seasons. The U. prolifera propagules (77 individuals/L in average over the year) were existing at ZGS of the Subei Shoal throughout the year, and majority (75.7% in average) of them was the ‘floating’ type, an ecotype causing the green tides in the Yellow Sea. In comparison, species composition of micro-propagules fluctuated significantly at YY of Qingdao. The dominant species switched from U. linza to U. prolifera in summer when the large-scale floating biomass of U. prolifera approached the coasts of Qingdao. The quantity of ‘floating’ type of U. prolifera increased dramatically in this period and descended rapidly with the cessation of the green tide. This study suggested that the Subei Shoal is an important ‘habitat’ for U. prolifera, which plays a crucial role in maintaining the U. prolifera population and causing the successive green tides. Whereas in Qingdao coastal water, the large-scale floating U. prolifera biomass could temporarily influence the local micro-propagule community, and cause a rapid shift of the micro-propagule species during the blooming season of the green tides.
To study the tempo-spatial distribution and species succession of green macroalgal micro-propagules in the coastal waters affected by the green tides in the Yellow Sea, a year-round survey was conducted at the four stations (ZGS, YWG, LSG and YY) along the coasts of Jiangsu and Shandong provinces. Through the lab-culture and molecular analysis, there were six green macroalgal species detected, including 4 ulvoid species (Ulva linza, U. prolifera, U. compressa and U. pertusa), an unclassified Ulva sp. and one Blidingia sp. Quantitative analyses revealed evident tempo-spatial variations of the abundance and species composition of micro-propagules at the four stations. The abundances of micro-propagules were significantly higher at ZGS and YY than those at YWG and LSG. A seasonal bi-peak pattern of the abundances was consistent throughout the four stations. The numbers of micro-propagules were generally highest during the spring to early summer, and reached a minor peak in fall, but were low in other seasons. The U. prolifera propagules (77 individuals/L in average over the year) were existing at ZGS of the Subei Shoal throughout the year, and majority (75.7% in average) of them was the ‘floating’ type, an ecotype causing the green tides in the Yellow Sea. In comparison, species composition of micro-propagules fluctuated significantly at YY of Qingdao. The dominant species switched from U. linza to U. prolifera in summer when the large-scale floating biomass of U. prolifera approached the coasts of Qingdao. The quantity of ‘floating’ type of U. prolifera increased dramatically in this period and descended rapidly with the cessation of the green tide. This study suggested that the Subei Shoal is an important ‘habitat’ for U. prolifera, which plays a crucial role in maintaining the U. prolifera population and causing the successive green tides. Whereas in Qingdao coastal water, the large-scale floating U. prolifera biomass could temporarily influence the local micro-propagule community, and cause a rapid shift of the micro-propagule species during the blooming season of the green tides.
2020, 42(2): 124-133.
doi: 10.3969/j.issn.0253-4193.2020.02.013
Abstract:
Real-time quantitative PCR (qRT-PCR) is a common method for quantitative analysis of gene expression. Selection of appropriate reference genes is essential for the accurate analysis of target gene expression levels. In this study, the expression of seven reference genes of Cytb, EF-1α, HPRT, UBC, GAPDH, β-actin and β-tubulin was quantitatively analyzed with different concentrations of iron concentration. The GeNorm, NormFinder and BestKeeper software comprehensively evaluated the stability of these reference genes. The results showed that the expression stability of Cytb and EF-1α was better, and the combination of EF-1α + Cytb was the best. It could be used as a reference gene for the study of gene expression in Skeletonema marinoi, while the expression stability of other genes was poor, and they were not suitable for being used as a reference gene. This study provides a methodological basis for the selection of reference genes during the study of gene expression in S. marinoi.
Real-time quantitative PCR (qRT-PCR) is a common method for quantitative analysis of gene expression. Selection of appropriate reference genes is essential for the accurate analysis of target gene expression levels. In this study, the expression of seven reference genes of Cytb, EF-1α, HPRT, UBC, GAPDH, β-actin and β-tubulin was quantitatively analyzed with different concentrations of iron concentration. The GeNorm, NormFinder and BestKeeper software comprehensively evaluated the stability of these reference genes. The results showed that the expression stability of Cytb and EF-1α was better, and the combination of EF-1α + Cytb was the best. It could be used as a reference gene for the study of gene expression in Skeletonema marinoi, while the expression stability of other genes was poor, and they were not suitable for being used as a reference gene. This study provides a methodological basis for the selection of reference genes during the study of gene expression in S. marinoi.
2020, 42(2): 134-142.
doi: 10.3969/j.issn.0253-4193.2020.02.014
Abstract:
Prediction of chlorophyll a concentration in traditional artificial network methods has some disadvantages, such as slower training speed, lower convergence precision, and easy to fall into local optimum situation. In particular, it is not possible to flexibly use historical information of any length to predict chlorophyll a concentration. To solve these problems, this paper defines the relationship between chlorophyll a concentration and various elements, depending on the long-term and short-term dependence between elements and the concentration of chlorophyll a. In this way, the long-term dependence between each element and the chlorophyll a concentration is separated from the short-term dependence. Then, based on the Long Short-Term Memory (LSTM), a merged LSTM prediction model was proposed. In this model, short and long term dependencies were presented respectively by different neurons and finally merged at the top of the model. The experimental data involves the continuous monitoring data of the station of Sandu Ao. The main result includes that the model has the advantage of fast reduction of training error, but also has significantly higher prediction accuracy compared with other three classical neural network models.
Prediction of chlorophyll a concentration in traditional artificial network methods has some disadvantages, such as slower training speed, lower convergence precision, and easy to fall into local optimum situation. In particular, it is not possible to flexibly use historical information of any length to predict chlorophyll a concentration. To solve these problems, this paper defines the relationship between chlorophyll a concentration and various elements, depending on the long-term and short-term dependence between elements and the concentration of chlorophyll a. In this way, the long-term dependence between each element and the chlorophyll a concentration is separated from the short-term dependence. Then, based on the Long Short-Term Memory (LSTM), a merged LSTM prediction model was proposed. In this model, short and long term dependencies were presented respectively by different neurons and finally merged at the top of the model. The experimental data involves the continuous monitoring data of the station of Sandu Ao. The main result includes that the model has the advantage of fast reduction of training error, but also has significantly higher prediction accuracy compared with other three classical neural network models.
2020, 42(2): 143-154.
doi: 10.3969/j.issn.0253-4193.2020.02.015
Abstract:
The Beibu Gulf is not only a key sea passage in the southwestern China but also one of important fishing grounds in the South China Sea (SCS). In this study, naturally occurring radionuclides (238U, 226Ra, 228Ra, and 40K) in surface sediments and sediment cores of the Beibu Gulf were comprehensively analyzed using high purity germanium (HPGe) γ spectrometry. Our results indicated that radioactivity level of sediments in the Beibu Gulf was lower than that in most of China's seas and was higher than the extremely low radioactivity level of sediments in coral reefs. All nuclides in surface sediments of the Beibu Gulf had a spatial distribution of “butterfly pattern”, attributing to the non-linear regulation of sediment grain size and positive role of total organic carbon in sediment. Additionally, redox state and physical/biological disturbance derived from the proxies of Mn and 210Pb could also affect vertical distribution of redox-sensitive nuclide (eg, 238U) in sediment cores. On the basis of the 232Th/238U, 40K/238U, and 226Ra/238U activity ratio, we found that sediments of the Beibu Gulf had terrigenous characteristics, which were significantly different from biogenic sediments in coral reefs. Our study provided radioactivity level in the Beibu Gulf under the background of the rapid development of nuclear power plant, revealed the "butterfly pattern" of radionuclides and their influence factors, and explored the feasibility of novel geochemical proxies based on radionuclides in marine sedimentation.
The Beibu Gulf is not only a key sea passage in the southwestern China but also one of important fishing grounds in the South China Sea (SCS). In this study, naturally occurring radionuclides (238U, 226Ra, 228Ra, and 40K) in surface sediments and sediment cores of the Beibu Gulf were comprehensively analyzed using high purity germanium (HPGe) γ spectrometry. Our results indicated that radioactivity level of sediments in the Beibu Gulf was lower than that in most of China's seas and was higher than the extremely low radioactivity level of sediments in coral reefs. All nuclides in surface sediments of the Beibu Gulf had a spatial distribution of “butterfly pattern”, attributing to the non-linear regulation of sediment grain size and positive role of total organic carbon in sediment. Additionally, redox state and physical/biological disturbance derived from the proxies of Mn and 210Pb could also affect vertical distribution of redox-sensitive nuclide (eg, 238U) in sediment cores. On the basis of the 232Th/238U, 40K/238U, and 226Ra/238U activity ratio, we found that sediments of the Beibu Gulf had terrigenous characteristics, which were significantly different from biogenic sediments in coral reefs. Our study provided radioactivity level in the Beibu Gulf under the background of the rapid development of nuclear power plant, revealed the "butterfly pattern" of radionuclides and their influence factors, and explored the feasibility of novel geochemical proxies based on radionuclides in marine sedimentation.
2020, 42(2): 155-166.
doi: 10.3969/j.issn.0253-4193.2020.02.016
Abstract:
The radiogenic isotope composition of neodymium (Nd) and strontium (Sr) extracted from Fe-Mn oxyhydroxide and detrital in marine sediments indicated potential for investigate present and past oceanic circulation or input of terrigenous material. However, the isotope compositions of elements obtained from the Fe-Mn oxyhydroxide fraction and detrital are easily disturbed by each other originating from the extraction process, will affect the isotope composition of these fractions. Therefore, it is very important to establish a rigorous leaching procedure that can be used to separate both Fe-Mn oxyhydroxide and the detrital fraction from the same marine sediment sample for Nd and Sr isotopic analysis. In this study, the mixture reagent of hydroxylamine hydrochloride (HH) and acetic acid (HAc) at 12 different concentrations were used to extract Fe-Mn oxyhydroxide fraction and detrital from zeolite clay of the Central Indian Ocean Basin, bathyal sediment of Arctic and offshore marine sediment of the Andaman Sea. Detrital was dissolved by HF-HNO3 system with high-pressure closed digestion method. Elements concentration and Sr and Nd isotope ratios in these fractions were measured. To corroborate the reliability of the extracting methods, REE patterns, Al/Ca ratios, as well as Sr and Nd isotope compositions were applied to assess the absence of detrital contributions to the extracted solutions and to support the seawater origin of the Nd isotope ratios in the Fe-Mn oxyhydroxide fraction. The result showed that different genetic types of sediments have different extraction reagents. The ideal reagent concentration for extraction of Fe-Mn oxyhydroxide fraction from zeolite clay is 0.25 mol/L HH in 15% acetic acid, for bathyal sediment of Greenland Sea and offshore marine sediment is 0.5 mol/L HH in 15% acetic acid. This method can accurately obtain the Sr and Nd isotopic composition of Fe-Mn oxyhydroxide and residue state in marine sediments, providing method support for the study of paleoceanography.
The radiogenic isotope composition of neodymium (Nd) and strontium (Sr) extracted from Fe-Mn oxyhydroxide and detrital in marine sediments indicated potential for investigate present and past oceanic circulation or input of terrigenous material. However, the isotope compositions of elements obtained from the Fe-Mn oxyhydroxide fraction and detrital are easily disturbed by each other originating from the extraction process, will affect the isotope composition of these fractions. Therefore, it is very important to establish a rigorous leaching procedure that can be used to separate both Fe-Mn oxyhydroxide and the detrital fraction from the same marine sediment sample for Nd and Sr isotopic analysis. In this study, the mixture reagent of hydroxylamine hydrochloride (HH) and acetic acid (HAc) at 12 different concentrations were used to extract Fe-Mn oxyhydroxide fraction and detrital from zeolite clay of the Central Indian Ocean Basin, bathyal sediment of Arctic and offshore marine sediment of the Andaman Sea. Detrital was dissolved by HF-HNO3 system with high-pressure closed digestion method. Elements concentration and Sr and Nd isotope ratios in these fractions were measured. To corroborate the reliability of the extracting methods, REE patterns, Al/Ca ratios, as well as Sr and Nd isotope compositions were applied to assess the absence of detrital contributions to the extracted solutions and to support the seawater origin of the Nd isotope ratios in the Fe-Mn oxyhydroxide fraction. The result showed that different genetic types of sediments have different extraction reagents. The ideal reagent concentration for extraction of Fe-Mn oxyhydroxide fraction from zeolite clay is 0.25 mol/L HH in 15% acetic acid, for bathyal sediment of Greenland Sea and offshore marine sediment is 0.5 mol/L HH in 15% acetic acid. This method can accurately obtain the Sr and Nd isotopic composition of Fe-Mn oxyhydroxide and residue state in marine sediments, providing method support for the study of paleoceanography.
Email alert
RSS