2020 Vol. 42, No. 10
Display Method:
2020, 42(10): 1-13.
doi: 10.3969/j.issn.0253-4193.2020.10.001
Abstract:
Surface sediments were collected by high-resolution sampling from the Changjiang River Estuary and its adjacent shelf in March, 2014. Grain size composition, Specific Surface Area (SSA), Total Organic Carbon (TOC) and stable carbon isotope composition (δ13C), n-alkanes and its related indices in sediments were analyzed to discuss the high-resolution distribution patterns of sedimentary organic carbon (OC) and n-alkanes in this region. A three end-members mixing model based on Principal Component Analysis (PCA) and Monte-Carlo Simulation was constructed to characterize the sources of sedimentary OC quantitatively. The results showed that TOC contents were 0.45%±0.16%, which were relatively higher in coastal mud area than offshore sandy area. Absolute contents (Σn−Alk) and relative contents (Σn−Alk/TOC) of total n-alkanes (C14 to C35) were (1.42±0.73) μg/g and (0.34±0.21) mg/g , respectively. There was a strong odd to even carbon preference of long-chain n-alkanes in muddy sediments, while there was an even to odd carbon preference of short-chain n-alkanes in sandy area. Inputs from the Changjiang River, the Old Yellow River Estuary and small rivers in the Zhe-Min coasts and hydrodynamic sorting restricted the transport and dispersal patterns of n-alkanes. The results of the three end-members mixing model indicated a mixture input of marine, soil and higher plant derived OC in this region. Among them, sedimentary OC was dominated by marine source (42.70%±18.18%), increasing from coast to outer sea gradually. Contributions of soil OC and higher plant OC were 28.99%±15.37% and 28.31%±17.12%, respectively. Influenced by hydrodynamic forces, obvious differentiation of these two terrestrial OC pools occurred during transport after entering into ocean. Soil OC was mainly associated with fine grains, and was transported southward along the Zhe-Min coast, while higher plant derived OC was mainly transported along northeast direction in the Changjiang River Estuary.
Surface sediments were collected by high-resolution sampling from the Changjiang River Estuary and its adjacent shelf in March, 2014. Grain size composition, Specific Surface Area (SSA), Total Organic Carbon (TOC) and stable carbon isotope composition (δ13C), n-alkanes and its related indices in sediments were analyzed to discuss the high-resolution distribution patterns of sedimentary organic carbon (OC) and n-alkanes in this region. A three end-members mixing model based on Principal Component Analysis (PCA) and Monte-Carlo Simulation was constructed to characterize the sources of sedimentary OC quantitatively. The results showed that TOC contents were 0.45%±0.16%, which were relatively higher in coastal mud area than offshore sandy area. Absolute contents (Σn−Alk) and relative contents (Σn−Alk/TOC) of total n-alkanes (C14 to C35) were (1.42±0.73) μg/g and (0.34±0.21) mg/g , respectively. There was a strong odd to even carbon preference of long-chain n-alkanes in muddy sediments, while there was an even to odd carbon preference of short-chain n-alkanes in sandy area. Inputs from the Changjiang River, the Old Yellow River Estuary and small rivers in the Zhe-Min coasts and hydrodynamic sorting restricted the transport and dispersal patterns of n-alkanes. The results of the three end-members mixing model indicated a mixture input of marine, soil and higher plant derived OC in this region. Among them, sedimentary OC was dominated by marine source (42.70%±18.18%), increasing from coast to outer sea gradually. Contributions of soil OC and higher plant OC were 28.99%±15.37% and 28.31%±17.12%, respectively. Influenced by hydrodynamic forces, obvious differentiation of these two terrestrial OC pools occurred during transport after entering into ocean. Soil OC was mainly associated with fine grains, and was transported southward along the Zhe-Min coast, while higher plant derived OC was mainly transported along northeast direction in the Changjiang River Estuary.
2020, 42(10): 14-27.
doi: 10.3969/j.issn.0253-4193.2020.10.002
Abstract:
The Bering Sea and western Arctic Ocean, as high production areas, play a key role in the Arctic Ocean biological pump, and are vulnerable to abrupt climate change, especially sea water warming and sea ice melt. Alterations in biological pump can influence the sources and degradation of sedimentary organic matter, and thus can be indicated by fatty acid (FA) content and composition of sediment. FA analysis of surface sediments, collected during the 5th and 6th Chinese Arctic Research Expeditions, showed that the total FA of the Chukchi Shelf was exceptionally high ((97.15 ± 55.31) μg/g), while the Bering Basin was the lowest ((15.00 ± 1.3) μg/g), and the Canada Basin, the Chukchi Shelf and the Bering Shelf were intermediate ((88.65 ± 3.52) μg/g, (70.35 ± 11.32) μg/g and (38.28 ± 14.89) μg/g, respectively). Marine FAs (short chain saturated FA + unsaturated FA) accounted for the most abundant (86.82% ± 7.08%), terrestrial FAs (long chain saturated FA) as the second abundant (8.45% ± 6.62%), while bacterial FAs (odd FA) as the least (4.63% ± 2.24%); diatom index (16:1ω9/16:0) was high at the southern and northern Chukchi Shelf (> 0.82) and the Bering Shelf edge (> 0.65), while it was low at the rest areas. These results indicated that: (1) marine source was the major contributor of sedimentary organic matter of the Bering Sea and the western Arctic Ocean, while terrestrial one contributes minor; diatom predominates was the primary producers of the southern and northern Chukchi Shelf and the Bering Shelf edge; percentage of bacterial FAs was remarkably low, comparing with tropical and temperate seas, suggesting a suppressed bacterial activity under low temperature; (2) labile organic matter accumulation rate was extremely high at the Chukchi Shelf, and was extremely sensitive to sea water warming and sea ice melt; (3) chlorophyceae and prymnesiophyceae dominate phytoplankton community at the Canada Basin and the Chukchi Slope. In conclusion, FA of surface sediment can be used to indicate sources and degradation of organic matter in the Bering Sea and the western Arctic Ocean; further, combining with other samples and biomarkers, FA was viable to shed light on the response of biological pump under the abrupt Arctic climate change.
The Bering Sea and western Arctic Ocean, as high production areas, play a key role in the Arctic Ocean biological pump, and are vulnerable to abrupt climate change, especially sea water warming and sea ice melt. Alterations in biological pump can influence the sources and degradation of sedimentary organic matter, and thus can be indicated by fatty acid (FA) content and composition of sediment. FA analysis of surface sediments, collected during the 5th and 6th Chinese Arctic Research Expeditions, showed that the total FA of the Chukchi Shelf was exceptionally high ((97.15 ± 55.31) μg/g), while the Bering Basin was the lowest ((15.00 ± 1.3) μg/g), and the Canada Basin, the Chukchi Shelf and the Bering Shelf were intermediate ((88.65 ± 3.52) μg/g, (70.35 ± 11.32) μg/g and (38.28 ± 14.89) μg/g, respectively). Marine FAs (short chain saturated FA + unsaturated FA) accounted for the most abundant (86.82% ± 7.08%), terrestrial FAs (long chain saturated FA) as the second abundant (8.45% ± 6.62%), while bacterial FAs (odd FA) as the least (4.63% ± 2.24%); diatom index (16:1ω9/16:0) was high at the southern and northern Chukchi Shelf (> 0.82) and the Bering Shelf edge (> 0.65), while it was low at the rest areas. These results indicated that: (1) marine source was the major contributor of sedimentary organic matter of the Bering Sea and the western Arctic Ocean, while terrestrial one contributes minor; diatom predominates was the primary producers of the southern and northern Chukchi Shelf and the Bering Shelf edge; percentage of bacterial FAs was remarkably low, comparing with tropical and temperate seas, suggesting a suppressed bacterial activity under low temperature; (2) labile organic matter accumulation rate was extremely high at the Chukchi Shelf, and was extremely sensitive to sea water warming and sea ice melt; (3) chlorophyceae and prymnesiophyceae dominate phytoplankton community at the Canada Basin and the Chukchi Slope. In conclusion, FA of surface sediment can be used to indicate sources and degradation of organic matter in the Bering Sea and the western Arctic Ocean; further, combining with other samples and biomarkers, FA was viable to shed light on the response of biological pump under the abrupt Arctic climate change.
2020, 42(10): 28-36.
doi: 10.3969/j.issn.0253-4193.2020.10.003
Abstract:
The n-alkanes
The n-alkanes
2020, 42(10): 37-46.
doi: 10.3969/j.issn.0253-4193.2020.10.004
Abstract:
As one of the forms of land-ocean interactions, submarine groundwater discharge (SGD) can release solutes into the coastal sea and has a significant impact on the nutrients budget in coastal seawater. Here, using 222Rn tracer, the SGD and the associated dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) inputted to the Zhenzhu Bay, a typical mangrove-dominated bay, were quantified. The results show that the average concentrations of 222Rn, DIC and DOC in groundwater are relatively higher than those in river water and surface sea water. A 222Rn mass balance implies that SGD rate is (0.36±0.36) m/d during January 2019. And SGD-derived DIC and DOC fluxes are estimated to be (2.41±2.63)×107 mol/d and (1.96±2.20)×106 mol/d. It confirmed that SGD-derived carbon is the most important carbon source in this bay, with 91% DIC and 89% DOC of the total input fluxes by SGD, respectively. Our results highlight the importance of groundwater-derived carbon fluxes in the Zhenzhu Bay, especially in the blue carbon assessments and biogeochemical process in tidal zones such as mangrove ecosystems.
As one of the forms of land-ocean interactions, submarine groundwater discharge (SGD) can release solutes into the coastal sea and has a significant impact on the nutrients budget in coastal seawater. Here, using 222Rn tracer, the SGD and the associated dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) inputted to the Zhenzhu Bay, a typical mangrove-dominated bay, were quantified. The results show that the average concentrations of 222Rn, DIC and DOC in groundwater are relatively higher than those in river water and surface sea water. A 222Rn mass balance implies that SGD rate is (0.36±0.36) m/d during January 2019. And SGD-derived DIC and DOC fluxes are estimated to be (2.41±2.63)×107 mol/d and (1.96±2.20)×106 mol/d. It confirmed that SGD-derived carbon is the most important carbon source in this bay, with 91% DIC and 89% DOC of the total input fluxes by SGD, respectively. Our results highlight the importance of groundwater-derived carbon fluxes in the Zhenzhu Bay, especially in the blue carbon assessments and biogeochemical process in tidal zones such as mangrove ecosystems.
2020, 42(10): 47-58.
doi: 10.3969/j.issn.0253-4193.2020.10.005
Abstract:
90Sr is recognized to be one of most important artificial radionuclides. A huge amount of radioactive substance (e.g., 90Sr) was released into marine environment after the Fukushima Nuclear Accident (FNA). High 90Sr activity was still observed in the treated wastewater which was stored on site in many tanks. However, 90Sr was rarely investigated in marine environment due to its complicated and time-consuming analytical procedure after the FNA, constraining a comprehensive understanding of the fate of 90Sr in marine environment. We discussed the 90Sr activity and environmental half-life (EHL) in seas surrounding Japan (SSJ) and the South China Sea (SCS) on the basis of previous data and our 90Sr data in seawater and marine biotas (e.g., sargassum, shrimp, oyster, mangrove, reef coral) collected from the SCS during 2015−2018. We found that the EHL of 90Sr in the SSJ was 15.4 years during 1975−2010. 90Sr in the SSJ was significantly elevated after the FNA. Radiation dose rate of 90Sr on marine fish was increased by five orders of magnitude after the FNA relative to the baseline before the FNA. As the downstream basin of the North Pacific Subtropical Gyre, the SCS was not identified with noticeable 90Sr-derived from the FNA. The EHL of 90Sr in the SCS was calculated to be 26.7 years during 1984−2018 based on the compilation of historical 90Sr data. The contrasting patterns of the EHL of 90Sr and 137Cs in the marginal seas and open oceans were attributed to the distinct sources (river input) and sinks (marine biological pump) of 90Sr and 137Cs. In the context of challenge of 90Sr analytical method in marine environment, extremely high 90Sr concentration factor (around 1000 L/kg) was observed in the reef coral skeleton after comparing with concentration factors of 90Sr in more than 10 kinds of marine biotas. Additionally, reef coral is potential to be a reliable 90Sr marine bioindicator with other advantages of easy availability in large quantity, growth at a fixed location, continue record with high resolution, and simple pretreatment. The study of 90Sr in reef coral will not only help to reveal distinct sources and sinks of artificial radionuclides in marine environment, but also provide valuable insights to optimization and improvement of standards/guidelines of marine radioactivity monitoring program.
90Sr is recognized to be one of most important artificial radionuclides. A huge amount of radioactive substance (e.g., 90Sr) was released into marine environment after the Fukushima Nuclear Accident (FNA). High 90Sr activity was still observed in the treated wastewater which was stored on site in many tanks. However, 90Sr was rarely investigated in marine environment due to its complicated and time-consuming analytical procedure after the FNA, constraining a comprehensive understanding of the fate of 90Sr in marine environment. We discussed the 90Sr activity and environmental half-life (EHL) in seas surrounding Japan (SSJ) and the South China Sea (SCS) on the basis of previous data and our 90Sr data in seawater and marine biotas (e.g., sargassum, shrimp, oyster, mangrove, reef coral) collected from the SCS during 2015−2018. We found that the EHL of 90Sr in the SSJ was 15.4 years during 1975−2010. 90Sr in the SSJ was significantly elevated after the FNA. Radiation dose rate of 90Sr on marine fish was increased by five orders of magnitude after the FNA relative to the baseline before the FNA. As the downstream basin of the North Pacific Subtropical Gyre, the SCS was not identified with noticeable 90Sr-derived from the FNA. The EHL of 90Sr in the SCS was calculated to be 26.7 years during 1984−2018 based on the compilation of historical 90Sr data. The contrasting patterns of the EHL of 90Sr and 137Cs in the marginal seas and open oceans were attributed to the distinct sources (river input) and sinks (marine biological pump) of 90Sr and 137Cs. In the context of challenge of 90Sr analytical method in marine environment, extremely high 90Sr concentration factor (around 1000 L/kg) was observed in the reef coral skeleton after comparing with concentration factors of 90Sr in more than 10 kinds of marine biotas. Additionally, reef coral is potential to be a reliable 90Sr marine bioindicator with other advantages of easy availability in large quantity, growth at a fixed location, continue record with high resolution, and simple pretreatment. The study of 90Sr in reef coral will not only help to reveal distinct sources and sinks of artificial radionuclides in marine environment, but also provide valuable insights to optimization and improvement of standards/guidelines of marine radioactivity monitoring program.
2020, 42(10): 59-69.
doi: 10.3969/j.issn.0253-4193.2020.10.006
Abstract:
The metal contents in the core sediments collected from the Daya Bay, a typical marine environment in the Guangdong-Hong Kong-Macao Greater Bay Area were measured in this study. National standard for marine sediment quality and fuzzy comprehensive assessment were applied to evaluate the historical evolution of the sediment quality in the past one hundred years. Our results indicate that the metal contamination in the bay experienced three major stages: (1) Before 1980s, the concentrations of most metals were low and the sediment quality fell into the category of class I. Accordingly, the metal risk was low in this period. Cr contributed most and Cd contributed least to the risk, respectively. (2) Between 1980 and 2000, the metal contents were significantly higher than the background values, suggesting that there was a sharp increase of metal input. The category of sediment quality fell down to class II and class III. However, the sediments in the margin areas of the Daya Bay were only slightly affected and still belonged to class I quality. Cu acted as a major metal pollutant instead of Cr in this period. (3) After the year of 2000, the metal levels and the metal risk decreased sharply. The sediment quality recovered back to class I and Cr contributed most to the risk at the time.
The metal contents in the core sediments collected from the Daya Bay, a typical marine environment in the Guangdong-Hong Kong-Macao Greater Bay Area were measured in this study. National standard for marine sediment quality and fuzzy comprehensive assessment were applied to evaluate the historical evolution of the sediment quality in the past one hundred years. Our results indicate that the metal contamination in the bay experienced three major stages: (1) Before 1980s, the concentrations of most metals were low and the sediment quality fell into the category of class I. Accordingly, the metal risk was low in this period. Cr contributed most and Cd contributed least to the risk, respectively. (2) Between 1980 and 2000, the metal contents were significantly higher than the background values, suggesting that there was a sharp increase of metal input. The category of sediment quality fell down to class II and class III. However, the sediments in the margin areas of the Daya Bay were only slightly affected and still belonged to class I quality. Cu acted as a major metal pollutant instead of Cr in this period. (3) After the year of 2000, the metal levels and the metal risk decreased sharply. The sediment quality recovered back to class I and Cr contributed most to the risk at the time.
A general regression neural network approach to reconstruct global 1°×1° resolution sea surface pCO2
2020, 42(10): 70-79.
doi: 10.3969/j.issn.0253-4193.2020.10.007
Abstract:
Sea surface partial pressure of carbon dioxide (pCO2) is a crucial parameter for estimating ocean carbon source and sink term, but its sparse and uneven in situ measurements in space and time lead to large uncertainty in the estimate of sea-air CO2 flux and characteristics of ocean carbon source and sink. To eliminate this uncertainty, a general regression neural network approach using the Surface Ocean CO2 Atlas (SOCAT) dataset, based on the non-liner regression of pCO2 and longitude, latitude, time, temperature, salinity and concentration of chlorophyll, was successfully used in the reconstruction of global 1°×1° resolution monthly sea surface pCO2 from 1998 to 2018, with a root mean square error (RMSE) of 16.93 μatm and a mean relative error (MRE) of 2.97%, lower than existing feed-forward neural network (FFNN), self-organizing neural network (SOM) and machine learning approaches. The global distribution of pCO2 obtained by this approach agrees well with existing researches.
Sea surface partial pressure of carbon dioxide (pCO2) is a crucial parameter for estimating ocean carbon source and sink term, but its sparse and uneven in situ measurements in space and time lead to large uncertainty in the estimate of sea-air CO2 flux and characteristics of ocean carbon source and sink. To eliminate this uncertainty, a general regression neural network approach using the Surface Ocean CO2 Atlas (SOCAT) dataset, based on the non-liner regression of pCO2 and longitude, latitude, time, temperature, salinity and concentration of chlorophyll, was successfully used in the reconstruction of global 1°×1° resolution monthly sea surface pCO2 from 1998 to 2018, with a root mean square error (RMSE) of 16.93 μatm and a mean relative error (MRE) of 2.97%, lower than existing feed-forward neural network (FFNN), self-organizing neural network (SOM) and machine learning approaches. The global distribution of pCO2 obtained by this approach agrees well with existing researches.
2020, 42(10): 121-131.
doi: 10.3969/j.issn.0253-4193.2020.10.012
Abstract:
Photochemical properties and photochemical degradation of chromophoric dissolved organic matter (CDOM) were investigated in the upper water of the western Pacific Ocean during the autumn in 2018. The results showed that the absorption coefficient a(320) of CDOM ranged from 0.025 m−1 to 0.64 m−1, with an average of (0.20 ± 0.08) m−1. The a(320) showed relatively lower values in the surface water, which was mainly related to the photobleaching removal of the surface CDOM. The higher values of a(320) were observed in the 100−200 m water layers, which was mainly related to the biological production in the subsurface layer. The tyrosine-like component C1 and the marine humic-like component C2 were identified by FDOM excitation/emission matrix spectroscopy and a parallel factor analysis. The production of C1 was mainly originated from the production of phytoplankton and the degradation of microorganisms, while C2 was mainly originated from the input of the marine humic brought by Kuroshio. Moreover, the absorption loss spectra of CDOM indicated that the UV radiation was responsible for the photodegradation of CDOM. The tyrosine-like component was more susceptible to photodegradation than the marine humic-like component. The results also indicated that photodegradation was the important removal route of CDOM in the western Pacific Ocean.
Photochemical properties and photochemical degradation of chromophoric dissolved organic matter (CDOM) were investigated in the upper water of the western Pacific Ocean during the autumn in 2018. The results showed that the absorption coefficient a(320) of CDOM ranged from 0.025 m−1 to 0.64 m−1, with an average of (0.20 ± 0.08) m−1. The a(320) showed relatively lower values in the surface water, which was mainly related to the photobleaching removal of the surface CDOM. The higher values of a(320) were observed in the 100−200 m water layers, which was mainly related to the biological production in the subsurface layer. The tyrosine-like component C1 and the marine humic-like component C2 were identified by FDOM excitation/emission matrix spectroscopy and a parallel factor analysis. The production of C1 was mainly originated from the production of phytoplankton and the degradation of microorganisms, while C2 was mainly originated from the input of the marine humic brought by Kuroshio. Moreover, the absorption loss spectra of CDOM indicated that the UV radiation was responsible for the photodegradation of CDOM. The tyrosine-like component was more susceptible to photodegradation than the marine humic-like component. The results also indicated that photodegradation was the important removal route of CDOM in the western Pacific Ocean.
2020, 42(10): 132-143.
doi: 10.3969/j.issn.0253-4193.2020.10.013
Abstract:
Biogenic elements are the basis of primary production in marine systems. Their cycles in marine environments are affected by various physical, chemical, and biological processes. Understanding the concentration distribution, structural characteristics, and influencing factors of biogenic elements are essential to understand the dynamics of marine ecosystems. In February 2019, a field investigation was conducted in the Shenhu Area of the northern South China Sea and seawater samples were collected to analyze dissolved inorganic nutrients. Combined with the hydrological environment parameters, such as temperature, salinity, chlrophyll a (Chl a), pH and dissolved oxygen (DO), the distribution and controlling factor of nutrient concentration and structure in the Shenhu Area were discussed. Concentrations of each nutrient in the seawaters from 0 m to 30 m were very low, and the nutrient concentrations gradually increased with the increase of depth. At the depth of about 3 000 m, the concentrations of dissolved inorganic nitrogen (DIN), phosphate and silicate reached 38.02 μmol/L, 2.71 μmol/L and 149.07 μmol/L, respectively. Temperature, pH and DO were significantly correlated with nutrients, indicating that environmental factors greatly affected the biogeochemical processes of nutrients. In addition, the concentration of nutrients in the northeast direction of the study area at a depth of 75 m was relatively low and showed a gradual increasing trend in the southwest direction, which may be related to the intrusion of Kuroshio water with high temperature, high salinity and low nutrients. Meanwhile, the difference between the conservative mixing concentrations calculated based on an end-member mixing model and the measured values of nutrients showed that, at 75 m depth, silicate and phosphate were consumed by biological activities, while nitrates were controlled by biological addition. With the increase of phosphate, the DIN at each site increased linearly, but the silicate increased with a power function, indicating that the regeneration rate and recycling efficiency were different for different nutrients. The ratios of N/P in the Shenhu Area showed opposite trends compared with the ratios of Si/N and Si/P. At 0−30 m, the N/P ratios were low and the Si/N and Si/P ratios were high. At 75 m, the N/P ratios increased along with the decrease of Si/N and Si/P ratios possibly because of different biological effects. Below 75 m, the N/P ratios gradually decreased to 14.44, while the Si/N and Si/P ratios gradually increased. All nutrient ratios remained stable below 1 000 m. The calculation results of the N−anomaly showed that nitrogen fixation in seawater above 300 m was stronger than denitrification, and denitrification below 300 m was enhanced. The distribution characteristics of the concentration and structure of nutrients in the Shenhu Area indicated that the Kuroshio intrusion and biological activities significantly affected the biogeochemical process of nutrients in this area.
Biogenic elements are the basis of primary production in marine systems. Their cycles in marine environments are affected by various physical, chemical, and biological processes. Understanding the concentration distribution, structural characteristics, and influencing factors of biogenic elements are essential to understand the dynamics of marine ecosystems. In February 2019, a field investigation was conducted in the Shenhu Area of the northern South China Sea and seawater samples were collected to analyze dissolved inorganic nutrients. Combined with the hydrological environment parameters, such as temperature, salinity, chlrophyll a (Chl a), pH and dissolved oxygen (DO), the distribution and controlling factor of nutrient concentration and structure in the Shenhu Area were discussed. Concentrations of each nutrient in the seawaters from 0 m to 30 m were very low, and the nutrient concentrations gradually increased with the increase of depth. At the depth of about 3 000 m, the concentrations of dissolved inorganic nitrogen (DIN), phosphate and silicate reached 38.02 μmol/L, 2.71 μmol/L and 149.07 μmol/L, respectively. Temperature, pH and DO were significantly correlated with nutrients, indicating that environmental factors greatly affected the biogeochemical processes of nutrients. In addition, the concentration of nutrients in the northeast direction of the study area at a depth of 75 m was relatively low and showed a gradual increasing trend in the southwest direction, which may be related to the intrusion of Kuroshio water with high temperature, high salinity and low nutrients. Meanwhile, the difference between the conservative mixing concentrations calculated based on an end-member mixing model and the measured values of nutrients showed that, at 75 m depth, silicate and phosphate were consumed by biological activities, while nitrates were controlled by biological addition. With the increase of phosphate, the DIN at each site increased linearly, but the silicate increased with a power function, indicating that the regeneration rate and recycling efficiency were different for different nutrients. The ratios of N/P in the Shenhu Area showed opposite trends compared with the ratios of Si/N and Si/P. At 0−30 m, the N/P ratios were low and the Si/N and Si/P ratios were high. At 75 m, the N/P ratios increased along with the decrease of Si/N and Si/P ratios possibly because of different biological effects. Below 75 m, the N/P ratios gradually decreased to 14.44, while the Si/N and Si/P ratios gradually increased. All nutrient ratios remained stable below 1 000 m. The calculation results of the N−anomaly showed that nitrogen fixation in seawater above 300 m was stronger than denitrification, and denitrification below 300 m was enhanced. The distribution characteristics of the concentration and structure of nutrients in the Shenhu Area indicated that the Kuroshio intrusion and biological activities significantly affected the biogeochemical process of nutrients in this area.
2020, 42(10): 144-154.
doi: 10.3969/j.issn.0253-4193.2020.10.014
Abstract:
Dissolved oxygen is an indispensable element for the survival of marine organisms. With the increase of human activities, the situation of hypoxia in the global coastal waters has become exacerbated, which is considered as an important factor threatening the health of the marine ecosystem. The vertical distributions of water temperature, salinity and density were investigated in the offshore area of Qinhuangdao from May to September in 2017. Additionally, the average monthly oxygen consumption rate was evaluated, and hence the mechanism of hypoxia and acidification was discussed. The results showed that the water column in the studied area was vertically homogenous in May, and no obvious difference for dissolved oxygen (DO) between the surface and bottom layers, with the value larger than 8 mg/L. From June to August, the pycnocline presented in the mid of the water column. In this period, DO and pH in bottom water gradually decreased, and reached 2−3 mg/L for DO and less than 7.8 for pH in the end of August, suggesting significant hypoxia and acidification in this area. However, DO and pH in bottom water sharply increased in September, after the pycnocline disappeared. The result indicated that hypoxia and acidification of Qinhuangdao offshore waters are seasonal. DO was significantly correlated with chlorophyll a and pH, indicating that the hypoxic and acidified processes in the offshore area of Qinhuangdao were local. The evaluated oxygen consumption rate, based on the box model, in bottom water and sediment ranged from 951 mg/(m2·d) to 1193 mg/(m2·d) (mean: 975 mg/(m2·d)) from June to August in 2017. Comprehensive analysis showed that water stratification was the prerequisite for the occurrence of hypoxia and acidification in Qinhuangdao offshore waters, and DO consumption caused by organic matter decomposition was an important reason of hypoxia and acidification in bottom water.
Dissolved oxygen is an indispensable element for the survival of marine organisms. With the increase of human activities, the situation of hypoxia in the global coastal waters has become exacerbated, which is considered as an important factor threatening the health of the marine ecosystem. The vertical distributions of water temperature, salinity and density were investigated in the offshore area of Qinhuangdao from May to September in 2017. Additionally, the average monthly oxygen consumption rate was evaluated, and hence the mechanism of hypoxia and acidification was discussed. The results showed that the water column in the studied area was vertically homogenous in May, and no obvious difference for dissolved oxygen (DO) between the surface and bottom layers, with the value larger than 8 mg/L. From June to August, the pycnocline presented in the mid of the water column. In this period, DO and pH in bottom water gradually decreased, and reached 2−3 mg/L for DO and less than 7.8 for pH in the end of August, suggesting significant hypoxia and acidification in this area. However, DO and pH in bottom water sharply increased in September, after the pycnocline disappeared. The result indicated that hypoxia and acidification of Qinhuangdao offshore waters are seasonal. DO was significantly correlated with chlorophyll a and pH, indicating that the hypoxic and acidified processes in the offshore area of Qinhuangdao were local. The evaluated oxygen consumption rate, based on the box model, in bottom water and sediment ranged from 951 mg/(m2·d) to 1193 mg/(m2·d) (mean: 975 mg/(m2·d)) from June to August in 2017. Comprehensive analysis showed that water stratification was the prerequisite for the occurrence of hypoxia and acidification in Qinhuangdao offshore waters, and DO consumption caused by organic matter decomposition was an important reason of hypoxia and acidification in bottom water.
2020, 42(10): 80-91.
doi: 10.3969/j.issn.0253-4193.2020.10.008
Abstract:
Based on the fishery resources survey data in the outer waters of the Zhoushan Islands in April (spring) and October (autumn) 2018, the composition, quantity distribution and dominant species of fishes were analyzed, and the relationship between them and hydrological environment was analyzed by the CCA method. The results showed that there were 106 species of fish in the waters outside Zhoushan Islands, belonging to 12 orders, 47 families and 80 genera. The fish mass densities in spring and autumn are 210.50 kg/km2 and 829.06 kg/km2 respectively, and the abundance densities are 8.08×103 ind/km2 and 165.94×103 ind/km2 respectively. The density of fish resources in spring is higher in the northwest sea area and lower in the east sea area of the investigated sea area, while the density of fish resources in autumn is higher in the east sea area and lower in the northwest sea area. The dominant species of fish change substantially between the two seasons. The dominant species in spring and autumn were Lophius litulon、Lepidotrig lajaponica、Apogon lineatus and Apogon lineatus、Acropom japonicum. The number of fish species showed significant seasonal and spatial changes, and the number of fish species is higher in the west and northwest near the coastal islands, with most fishes inhabiting in waters with water depth of 50−80 m. The results showed that the spatial and temporal separations of fish communities were obtained from CCA analysis. Surface temperature, bottom temperature and surface salinity were the key environmental factors that affected the composition and quantity distribution of fish species in the sea area under investigation. The strong correlation between fish community and environmental factors reflected the climate change effect on the separation of fish species.
Based on the fishery resources survey data in the outer waters of the Zhoushan Islands in April (spring) and October (autumn) 2018, the composition, quantity distribution and dominant species of fishes were analyzed, and the relationship between them and hydrological environment was analyzed by the CCA method. The results showed that there were 106 species of fish in the waters outside Zhoushan Islands, belonging to 12 orders, 47 families and 80 genera. The fish mass densities in spring and autumn are 210.50 kg/km2 and 829.06 kg/km2 respectively, and the abundance densities are 8.08×103 ind/km2 and 165.94×103 ind/km2 respectively. The density of fish resources in spring is higher in the northwest sea area and lower in the east sea area of the investigated sea area, while the density of fish resources in autumn is higher in the east sea area and lower in the northwest sea area. The dominant species of fish change substantially between the two seasons. The dominant species in spring and autumn were Lophius litulon、Lepidotrig lajaponica、Apogon lineatus and Apogon lineatus、Acropom japonicum. The number of fish species showed significant seasonal and spatial changes, and the number of fish species is higher in the west and northwest near the coastal islands, with most fishes inhabiting in waters with water depth of 50−80 m. The results showed that the spatial and temporal separations of fish communities were obtained from CCA analysis. Surface temperature, bottom temperature and surface salinity were the key environmental factors that affected the composition and quantity distribution of fish species in the sea area under investigation. The strong correlation between fish community and environmental factors reflected the climate change effect on the separation of fish species.
2020, 42(10): 92-99.
doi: 10.3969/j.issn.0253-4193.2020.10.009
Abstract:
Jumbo squid Dosidicus gigas is the main fishing target by Chinese squid-jigging fisheries, which mainly distributes in the eastern Pacific Ocean. Its habitat can be greatly affected by climatic changes. In this study, we calculated the habitat suitability index (HSI) on the squid fishing ground in the Southeast Pacific Ocean off Peru based on data of sea surface temperature (SST), the anomalies of sea surface height (SSHA) and Niño3.4 index during 1950 to 2015. Spatio-temporal variations in the squid habitat were further examined under the El Niño, the normal and the La Niña conditions. The results showed that variations in SST anomalies (SSTA) and SSHA in the fishing ground were consistent with those of the Niño3.4 index. Cross correlation analysis indicated that both SSTA and SSHA were significantly positively correlated with the Niño3.4 index. However, the HSI values were significantly negatively correlated with the Niño3.4 index. We divided the years between 1950 and 2015 into three types, the El Niño years, the normal years and the La Niña years. During the El Niño years, water temperature became warm, and the SSH increased; these changes led to contracted areas of suitable SST and SSHA, therefore, the range of suitable habitats largely decreased. However, during the normal and the La Niña years, water temperature was cold, the SSH decreased, and ranges of suitable SST and SSHA enlarged; these changes resulted in the increases in suitable habitat for the squid. Furthermore, the latitudinal gravity centers of suitable HSI on the squid fishing ground were significantly positively correlated with the Niño3.4 index. The latitudinal gravity centers of suitable HSI shifted southward in the El Niño years. Our findings suggested that ENSO events significantly affected environmental conditions on the squid fishing ground, and thus affected ranges and latitudinal distribution of suitable habitat for the squid in the Southeast Pacific Ocean off Peru.
Jumbo squid Dosidicus gigas is the main fishing target by Chinese squid-jigging fisheries, which mainly distributes in the eastern Pacific Ocean. Its habitat can be greatly affected by climatic changes. In this study, we calculated the habitat suitability index (HSI) on the squid fishing ground in the Southeast Pacific Ocean off Peru based on data of sea surface temperature (SST), the anomalies of sea surface height (SSHA) and Niño3.4 index during 1950 to 2015. Spatio-temporal variations in the squid habitat were further examined under the El Niño, the normal and the La Niña conditions. The results showed that variations in SST anomalies (SSTA) and SSHA in the fishing ground were consistent with those of the Niño3.4 index. Cross correlation analysis indicated that both SSTA and SSHA were significantly positively correlated with the Niño3.4 index. However, the HSI values were significantly negatively correlated with the Niño3.4 index. We divided the years between 1950 and 2015 into three types, the El Niño years, the normal years and the La Niña years. During the El Niño years, water temperature became warm, and the SSH increased; these changes led to contracted areas of suitable SST and SSHA, therefore, the range of suitable habitats largely decreased. However, during the normal and the La Niña years, water temperature was cold, the SSH decreased, and ranges of suitable SST and SSHA enlarged; these changes resulted in the increases in suitable habitat for the squid. Furthermore, the latitudinal gravity centers of suitable HSI on the squid fishing ground were significantly positively correlated with the Niño3.4 index. The latitudinal gravity centers of suitable HSI shifted southward in the El Niño years. Our findings suggested that ENSO events significantly affected environmental conditions on the squid fishing ground, and thus affected ranges and latitudinal distribution of suitable habitat for the squid in the Southeast Pacific Ocean off Peru.
2020, 42(10): 100-109.
doi: 10.3969/j.issn.0253-4193.2020.10.010
Abstract:
Global climate change has a profound impact on the world fisheries. Recently, the composition of catch in Northeast Atlantic Ocean has changed significantly. Based on the catch data in the Northeast Atlantic Ocean from 1982 to 2016 provided by the United Nations Food and Agricuture Organization, the diversity of catch, mean trophic level and the variation of principal component were analyzed in time series. Finally, combined with climate and environmental factors (sea surface temperature, SST; sea surface salinity, SSS; sea surface height, SSH; Sea Ice Concentration, SIC; North Atlantic Oscillation, NAO; Arctic Oscillation, AO; Atlantic Multidecadal Oscillation, AMO) in the Northeast Atlantic Ocean, the relationship between catches composition and climate change was explored by generalized additive model (GAM). The results showed that the diversity generally presented a declining trend, it was at a relatively low level during 2002 to 2010. The mean trophic level decreased slowly before 2002, then began to rise sharply. The correlation analysis showed that the changes of these two indicators were related to the environmental factors. The principal component analysis of catch composition showed that the variance of the first principal component was 35.3%, and it also has a close relationship with climatic and environmental factors, which could characterize the change of catch structure under the influence of climate. The results of GAM analysis showed that the orders of the contribution to structure change of catches were in sequence of SST, SSH, SSS, SIC and NAO.
Global climate change has a profound impact on the world fisheries. Recently, the composition of catch in Northeast Atlantic Ocean has changed significantly. Based on the catch data in the Northeast Atlantic Ocean from 1982 to 2016 provided by the United Nations Food and Agricuture Organization, the diversity of catch, mean trophic level and the variation of principal component were analyzed in time series. Finally, combined with climate and environmental factors (sea surface temperature, SST; sea surface salinity, SSS; sea surface height, SSH; Sea Ice Concentration, SIC; North Atlantic Oscillation, NAO; Arctic Oscillation, AO; Atlantic Multidecadal Oscillation, AMO) in the Northeast Atlantic Ocean, the relationship between catches composition and climate change was explored by generalized additive model (GAM). The results showed that the diversity generally presented a declining trend, it was at a relatively low level during 2002 to 2010. The mean trophic level decreased slowly before 2002, then began to rise sharply. The correlation analysis showed that the changes of these two indicators were related to the environmental factors. The principal component analysis of catch composition showed that the variance of the first principal component was 35.3%, and it also has a close relationship with climatic and environmental factors, which could characterize the change of catch structure under the influence of climate. The results of GAM analysis showed that the orders of the contribution to structure change of catches were in sequence of SST, SSH, SSS, SIC and NAO.
2020, 42(10): 110-120.
doi: 10.3969/j.issn.0253-4193.2020.10.011
Abstract:
Antarctic red algae play important roles in the coastal ecosystems and industrial applications. Meanwhile, their unique physiological acclimation mechanisms to the extreme environments endow them to be ideal organisms for discovering new genes and new metabolic pathways. In this study, we sequenced the transcriptomes of Antarctic red algae Iridaea cordata (Turner) Bory and Curdiea racovitzae Hariot, and compared with their moderate temperature close relatives. The transcriptome sequences of I. cordata and C. racovitzae were assembled into 14055 and 12006 Unigenes, with an average length of 1473 bp and 1448 bp, respectively. The Lhca2, Lhca6 and Lhcb genes homologous to the green algae genes were found in I. cordata transcriptome while not in other red algae. Lhcf gene encoding fucoxanthine and Chl a/c binding protein presenting in brown algae and diatoms were identified in both I. cordata and C. racovitzae. Photolyase repairs UV-induced DNA damages. 6-4 photolyase, CPD I and CPD II genes were identified in the transcriptome of I. cordata, while only CPD II gene was found in the transcriptome of C. racovitzae. Although the functions of those specific genes in Antarctic red algae are expected further investigation, our study provides a foundation for the following researches on the acclimation mechanisms of seaweeds to the extreme light environments in Antarctica.
Antarctic red algae play important roles in the coastal ecosystems and industrial applications. Meanwhile, their unique physiological acclimation mechanisms to the extreme environments endow them to be ideal organisms for discovering new genes and new metabolic pathways. In this study, we sequenced the transcriptomes of Antarctic red algae Iridaea cordata (Turner) Bory and Curdiea racovitzae Hariot, and compared with their moderate temperature close relatives. The transcriptome sequences of I. cordata and C. racovitzae were assembled into 14055 and 12006 Unigenes, with an average length of 1473 bp and 1448 bp, respectively. The Lhca2, Lhca6 and Lhcb genes homologous to the green algae genes were found in I. cordata transcriptome while not in other red algae. Lhcf gene encoding fucoxanthine and Chl a/c binding protein presenting in brown algae and diatoms were identified in both I. cordata and C. racovitzae. Photolyase repairs UV-induced DNA damages. 6-4 photolyase, CPD I and CPD II genes were identified in the transcriptome of I. cordata, while only CPD II gene was found in the transcriptome of C. racovitzae. Although the functions of those specific genes in Antarctic red algae are expected further investigation, our study provides a foundation for the following researches on the acclimation mechanisms of seaweeds to the extreme light environments in Antarctica.
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