2024 Vol. 46, No. 9
Display Method:
2024, 46(9): 1-13.
doi: 10.12284/hyxb2024082
Abstract:
The coast of Hainan Island is dominated by embayed beaches, which is an important coastal tourist destination in China and also has a high incidence of drowning accidents caused by rip currents. To investigate the distribution characteristics of rip currents on embayed beaches, the occurrence and distribution characteristics of rip currents are interpreted from the satellite images of 54 embayed beaches around Hainan Island over the past 20 years, and compared with the field survey results. The results show that, in terms of regional distribution, the occurrence probability of rip currents on the eastern and southern coasts is significantly higher than that on the western and northern coasts of Hainan Island. In terms of location distribution, the number of rip currents in the middle of the headland bays is higher than that on the two sides. In terms of geometric characteristics, the average rip length was positively correlated with the average rip width, and the average rip spacing. The distribution density of rip currents is negatively correlated with significant wave height, average wave period, incident wave power, and wave energy. The scale of the headland has a significant effect on the number of rips, which is positively correlated with the bay width, the maximum bay indentation, and length of the headland, but the curvature of the shoreline has no significant correlation with the average number of rips. The results of satellite image interpretation for the occurrence of rips are consistent with the results of the field survey and the evaluation of the Ω-RTR model. These conclusions can provide useful references for the beach safety management and rip current warning work on Hainan Island.
The coast of Hainan Island is dominated by embayed beaches, which is an important coastal tourist destination in China and also has a high incidence of drowning accidents caused by rip currents. To investigate the distribution characteristics of rip currents on embayed beaches, the occurrence and distribution characteristics of rip currents are interpreted from the satellite images of 54 embayed beaches around Hainan Island over the past 20 years, and compared with the field survey results. The results show that, in terms of regional distribution, the occurrence probability of rip currents on the eastern and southern coasts is significantly higher than that on the western and northern coasts of Hainan Island. In terms of location distribution, the number of rip currents in the middle of the headland bays is higher than that on the two sides. In terms of geometric characteristics, the average rip length was positively correlated with the average rip width, and the average rip spacing. The distribution density of rip currents is negatively correlated with significant wave height, average wave period, incident wave power, and wave energy. The scale of the headland has a significant effect on the number of rips, which is positively correlated with the bay width, the maximum bay indentation, and length of the headland, but the curvature of the shoreline has no significant correlation with the average number of rips. The results of satellite image interpretation for the occurrence of rips are consistent with the results of the field survey and the evaluation of the Ω-RTR model. These conclusions can provide useful references for the beach safety management and rip current warning work on Hainan Island.
2024, 46(9): 14-28.
doi: 10.12284/hyxb2024076
Abstract:
In order to understand the long−term variations in the nutritional environment and the key influencing factors of Bohai Bay, sediment cores from the mouth of the bay (BH15) and the outer area of the bay (BH47) were collected in April and June 2018 separately. The contents of total organic carbon (TOC), total nitrogen (TN), phosphorus (P), biogenic silica (BSi), and stable isotopes of carbon and nitrogen (δ13C, δ15N) were analyzed, and the causes of the changes of the above parameters were discussed in combination with the changes of climate and surrounding human activities. The results showed that the TN content in both sediment cores exhibited an increasing trend since the 1980s, which is consistent with the long-term variations in dissolved inorganic nitrogen (DIN) in the sea water. Sewage discharge, fertilizer application and mariculture are the main sources of nitrogen in the Bohai Bay, among which the input of agricultural fertilizer has decreased since 2007, while the discharge of mariculture and domestic sewage into the sea has shown a continuous upward trend. Inorganic Phosphorus (IP) was the main form of phosphorus in sediments. The IP in BH15 in the bay has shown a decreasing trend since the mid-1990s, while the IP in BH47 from the mouth of the bay has shown a decreasing trend after 1970s and a slow increasing trend since 1990s. All of them show obvious terrigenous input characteristics. The results of TOC/TN ratio、δ13C value and δ13C two-endmember mixing model indicated that the sediment organic matter in the mouth of Bohai Bay and adjacent sea area was influenced by both terrestrial input and marine autochthonous sources, with marine organic matter being the dominant source, the contribution of marine organic matter has decreased Since the 1990s. Compared with the BH47 core from the mouth of the bay, the BH15 core is closer to the coastal area, more significantly affected by terrestrial input, with higher TN content and contribution of terrestrial organic matter. This study shows that in order to effectively manage the water environment of Bohai Bay, it is necessary to strengthen the control of mariculture and domestic sewage discharge into the sea while controlling the use of agricultural fertilizers in the future.
In order to understand the long−term variations in the nutritional environment and the key influencing factors of Bohai Bay, sediment cores from the mouth of the bay (BH15) and the outer area of the bay (BH47) were collected in April and June 2018 separately. The contents of total organic carbon (TOC), total nitrogen (TN), phosphorus (P), biogenic silica (BSi), and stable isotopes of carbon and nitrogen (δ13C, δ15N) were analyzed, and the causes of the changes of the above parameters were discussed in combination with the changes of climate and surrounding human activities. The results showed that the TN content in both sediment cores exhibited an increasing trend since the 1980s, which is consistent with the long-term variations in dissolved inorganic nitrogen (DIN) in the sea water. Sewage discharge, fertilizer application and mariculture are the main sources of nitrogen in the Bohai Bay, among which the input of agricultural fertilizer has decreased since 2007, while the discharge of mariculture and domestic sewage into the sea has shown a continuous upward trend. Inorganic Phosphorus (IP) was the main form of phosphorus in sediments. The IP in BH15 in the bay has shown a decreasing trend since the mid-1990s, while the IP in BH47 from the mouth of the bay has shown a decreasing trend after 1970s and a slow increasing trend since 1990s. All of them show obvious terrigenous input characteristics. The results of TOC/TN ratio、δ13C value and δ13C two-endmember mixing model indicated that the sediment organic matter in the mouth of Bohai Bay and adjacent sea area was influenced by both terrestrial input and marine autochthonous sources, with marine organic matter being the dominant source, the contribution of marine organic matter has decreased Since the 1990s. Compared with the BH47 core from the mouth of the bay, the BH15 core is closer to the coastal area, more significantly affected by terrestrial input, with higher TN content and contribution of terrestrial organic matter. This study shows that in order to effectively manage the water environment of Bohai Bay, it is necessary to strengthen the control of mariculture and domestic sewage discharge into the sea while controlling the use of agricultural fertilizers in the future.
2024, 46(9): 14-26.
doi: 10.12284/hyxb2024116
Abstract:
Based on analyses of solid-phase and porewater chemistry of sediment cores at four sites collected from Laizhou Bay of the Bohai Sea, we revealed diagenetic cycles of iron, manganese and sulfur and their responses to terrestrial inputs and anthropogenic perturbations. Results suggest that water eutrophication of the bay has not given rise to organic carbon (OC) enrichment in the sediments. Actually, contents and lability of sediment OC are generally low, largely due to the inputs of terrestrial refractory OC and intense sediment resuspension induced by natural processes and anthropogenic perturbations in the river-dominated area. This feature greatly dampens sulfate reduction, resulting in low accumulation of total reduced inorganic sulfide (0.28−88 μmol/g). Porewater Mn2+ is mainly from reductive dissolution of amorphous and poorly crystalline Mn oxides, while precipitation of MnCO3 is mainly responsible for Mn2+ consumption in sediment below 10 cm depth. Intense sediment resuspension and refractory nature of sediment OC encourage dissimilatory iron reduction, with relative contribution of this pathway to total anaerobic OC mineralization of about 51%, on average. At the site (S6) heavily influenced by the Huanghe River input, dynamic depositional regime facilitates reductive dissolution of manganese oxides, but dampens reduction of iron oxides and sulfate to some extent. Upward diffusive fluxes of porewater Mn2+ and Fe2+ in the sediments are at the lower end for sediments of other areas dominated by major river inputs, which is attributable to overall low lability of sediment OC.
Based on analyses of solid-phase and porewater chemistry of sediment cores at four sites collected from Laizhou Bay of the Bohai Sea, we revealed diagenetic cycles of iron, manganese and sulfur and their responses to terrestrial inputs and anthropogenic perturbations. Results suggest that water eutrophication of the bay has not given rise to organic carbon (OC) enrichment in the sediments. Actually, contents and lability of sediment OC are generally low, largely due to the inputs of terrestrial refractory OC and intense sediment resuspension induced by natural processes and anthropogenic perturbations in the river-dominated area. This feature greatly dampens sulfate reduction, resulting in low accumulation of total reduced inorganic sulfide (0.28−88 μmol/g). Porewater Mn2+ is mainly from reductive dissolution of amorphous and poorly crystalline Mn oxides, while precipitation of MnCO3 is mainly responsible for Mn2+ consumption in sediment below 10 cm depth. Intense sediment resuspension and refractory nature of sediment OC encourage dissimilatory iron reduction, with relative contribution of this pathway to total anaerobic OC mineralization of about 51%, on average. At the site (S6) heavily influenced by the Huanghe River input, dynamic depositional regime facilitates reductive dissolution of manganese oxides, but dampens reduction of iron oxides and sulfate to some extent. Upward diffusive fluxes of porewater Mn2+ and Fe2+ in the sediments are at the lower end for sediments of other areas dominated by major river inputs, which is attributable to overall low lability of sediment OC.
2024, 46(9): 29-37.
doi: 10.12284/hyxb2024112
Abstract:
Against the backdrop of global warming, the Arctic has experienced a series of changes, including permafrost degradation, reduced summer sea ice, increased land runoff, and intensified coastal erosion. With global warming, organic carbon (OC) stored in permafrost is accelerating its migration and release to the sea, which will affect the pattern of carbon cycling in the Arctic Ocean. However, there is currently little evidence to directly confirm this inference. This article analyzes the lignin and carbon isotopes of two hundred year scale sedimentary cores in the Chukchi Sea, and discusses the sources and profile changes of the buried organic matter. The results showed that the organic carbon in the columnar sediments of the Chukchi Sea came from a mixed contribution of herbaceous tissue of terrestrial C3 plants and marine source production. The absolute content of lignin Σ8 in sediment shows an overall upward trend, indicating that with global warming, more terrestrial materials are being transported to the Chukchi Sea. This study indicates that global warming caused by human activities has indeed increased the migration of organic carbon from permafrost to the sea, and the increase in lignin content due to enhanced terrestrial inputs is direct evidence of the enhanced melting of permafrost caused by global warming on a century scale.
Against the backdrop of global warming, the Arctic has experienced a series of changes, including permafrost degradation, reduced summer sea ice, increased land runoff, and intensified coastal erosion. With global warming, organic carbon (OC) stored in permafrost is accelerating its migration and release to the sea, which will affect the pattern of carbon cycling in the Arctic Ocean. However, there is currently little evidence to directly confirm this inference. This article analyzes the lignin and carbon isotopes of two hundred year scale sedimentary cores in the Chukchi Sea, and discusses the sources and profile changes of the buried organic matter. The results showed that the organic carbon in the columnar sediments of the Chukchi Sea came from a mixed contribution of herbaceous tissue of terrestrial C3 plants and marine source production. The absolute content of lignin Σ8 in sediment shows an overall upward trend, indicating that with global warming, more terrestrial materials are being transported to the Chukchi Sea. This study indicates that global warming caused by human activities has indeed increased the migration of organic carbon from permafrost to the sea, and the increase in lignin content due to enhanced terrestrial inputs is direct evidence of the enhanced melting of permafrost caused by global warming on a century scale.
2024, 46(9): 38-51.
doi: 10.12284/hyxb2024090
Abstract:
Phosphonates in the ocean are a kind of potential phosphorus (P) source which could be utilized by phytoplankton. Although dinoflagellates cannot directly utilize phosphonates themselves, their symbiotic bacteria have the capability to degrade phosphonates into phosphate, thereby promoting the growth of algal cells. However, no studies focusing on a specific bacteria strain have been conducted thus far. In this study, Prorocentrum donghaiense was cultured under conditions with 2-Aminoethylphosphonic acid (2-AEP) as the sole P source. Isolation and purification of the symbiotic bacteria from the culture was conducted and five kinds of bacteria were obtained. Genome sequencing results revealed the presence of two types of C-P lyase pathways in the bacterial strain designated as Yoonia sp. PD-AEP-1. The function of the bacteira strain was verified through the co-culture of bacteria and algal cells. The results demonstrated that after the algal cells were treated to phosphorus-starved condition, when 2-AEP and the bacteria suspension were added together, as compared to conditions which only 2-AEP or the bacterial suspension of PD-AEP-1 was introduced, both the growth rate of algal cells and the phosphate concentration in the cultures showed a significant increase. Meanwhile, alkaline phosphatase activity and non-photochemical quenching of the algal cells decreased significantly, indicating that PD-AEP-1 has the ability to degrade 2-AEP into phosphate, thereby alleviating phosphorus limitation for P. donghaiense cells and effectively promoting the growth of algal cells. The study suggests that symbiotic bacteria of P. donghaiense might play a part in providing P sources to the algal cells through the degradation of phosphonates. This process could probably contribute to the outbreak of P. donghaiense bloom, highlighting the importance of algae-bacteira interactions in marine ecosystems.
Phosphonates in the ocean are a kind of potential phosphorus (P) source which could be utilized by phytoplankton. Although dinoflagellates cannot directly utilize phosphonates themselves, their symbiotic bacteria have the capability to degrade phosphonates into phosphate, thereby promoting the growth of algal cells. However, no studies focusing on a specific bacteria strain have been conducted thus far. In this study, Prorocentrum donghaiense was cultured under conditions with 2-Aminoethylphosphonic acid (2-AEP) as the sole P source. Isolation and purification of the symbiotic bacteria from the culture was conducted and five kinds of bacteria were obtained. Genome sequencing results revealed the presence of two types of C-P lyase pathways in the bacterial strain designated as Yoonia sp. PD-AEP-1. The function of the bacteira strain was verified through the co-culture of bacteria and algal cells. The results demonstrated that after the algal cells were treated to phosphorus-starved condition, when 2-AEP and the bacteria suspension were added together, as compared to conditions which only 2-AEP or the bacterial suspension of PD-AEP-1 was introduced, both the growth rate of algal cells and the phosphate concentration in the cultures showed a significant increase. Meanwhile, alkaline phosphatase activity and non-photochemical quenching of the algal cells decreased significantly, indicating that PD-AEP-1 has the ability to degrade 2-AEP into phosphate, thereby alleviating phosphorus limitation for P. donghaiense cells and effectively promoting the growth of algal cells. The study suggests that symbiotic bacteria of P. donghaiense might play a part in providing P sources to the algal cells through the degradation of phosphonates. This process could probably contribute to the outbreak of P. donghaiense bloom, highlighting the importance of algae-bacteira interactions in marine ecosystems.
2024, 46(9): 52-63.
doi: 10.12284/hyxb2024110
Abstract:
In order to investigate the characteristics and spatial-temporal variations of the phytoplankton community in artificial reef areas, as well as to elucidate the relationship between phytoplankton abundance and environmental factors associated with artificial reef construction, four surveys were conducted in 2021 (May, August, November) and 2022 (January) at two artificial reef areas and a control area in Xiangyun Bay. A total of 70 phytoplankton taxa belonging to 39 genera and 3 classes were identified in this study. The annual average abundance of phytoplankton in the artificial reef areas was recorded as 313.5 × 104 cells/m3, which were 1.4 times higher than that observed in the control area. Except in spring, the richness index, diversity index and evenness index of phytoplankton in the artificial reef areas were higher than those in the control area. The succession rate of dominant species from spring to summer and from summer to autumu in the reef areas were lower than that in the control area, suggesting greater stability of community structure within artificial reef areas compared to the control area. The biological increment index for each phytoplankton taxon ranged from 0.9 to 3.6; notably, Bacillariophyta displayed an average biological increment index value of 1.8. Pearson correlation analysis revealed that phytoplankton abundance was primarily influenced by TP, TN, NH4-N, NO3-N and DIP; significant seasonal differences were observed among these variables. These findings demonstrate that artificial reef construction has a positive conservation effect on phytoplankton communities closely related to temporal and spatial changes in nutrient availability.
In order to investigate the characteristics and spatial-temporal variations of the phytoplankton community in artificial reef areas, as well as to elucidate the relationship between phytoplankton abundance and environmental factors associated with artificial reef construction, four surveys were conducted in 2021 (May, August, November) and 2022 (January) at two artificial reef areas and a control area in Xiangyun Bay. A total of 70 phytoplankton taxa belonging to 39 genera and 3 classes were identified in this study. The annual average abundance of phytoplankton in the artificial reef areas was recorded as 313.5 × 104 cells/m3, which were 1.4 times higher than that observed in the control area. Except in spring, the richness index, diversity index and evenness index of phytoplankton in the artificial reef areas were higher than those in the control area. The succession rate of dominant species from spring to summer and from summer to autumu in the reef areas were lower than that in the control area, suggesting greater stability of community structure within artificial reef areas compared to the control area. The biological increment index for each phytoplankton taxon ranged from 0.9 to 3.6; notably, Bacillariophyta displayed an average biological increment index value of 1.8. Pearson correlation analysis revealed that phytoplankton abundance was primarily influenced by TP, TN, NH4-N, NO3-N and DIP; significant seasonal differences were observed among these variables. These findings demonstrate that artificial reef construction has a positive conservation effect on phytoplankton communities closely related to temporal and spatial changes in nutrient availability.
2024, 46(9): 64-72.
doi: 10.12284/hyxb2024092
Abstract:
Benthic harpacticoid copepods are widely distributed in marine ecosystem, which is particularly abundant in the epilithic algal matrix(EAM) of coral reefs. Due to its unique habitat, there is currently limited research on its developmental process and cultivation methods. In this study, we collected epilithic algal matrix from the coral reef of Luhuitou, Sanya, Hainan in the summer of 2023, from which we isolated one species of Harpacticoida, which was belonging to the genus Robertgurneya based on morphological characteristics. The effects of mono-and mixed-algal cultures on the developmental dynamics of Robertgurneya sp. were observed and recorded. The results showed that the adult body length of the Robertgurneya sp. was 0.5−0.7 mm, with an average life cycle of about 61−68 days. There were no significant differences in egg number per female each time, brood number, reproductive cycle, and life cycle between different feed cultivation techniques. However, under mixed algae culture, the average egg diameter, larval survival rate, and maximum body length of nauplii stage VI in the embryonic development stage of the Robertgurneya sp. were significantly higher than those in the mono-algae culture group (p < 0.05). Moreover, the embryonic development time and cumulative copepodid development time were significantly shorter under mixed-algal culture (p < 0.05). The results indicate that Robertgurneya sp. in EAM have a short life cycle and strong reproductive ability. Considering the abundant benthic microalgae and organic debris in the mats, harpacticoida may be able to provide huge potential food resources for predators such as small fish in coral reefs. Therefore, it may play an important role in the material cycle and energy flow of coral reef ecosystems.
Benthic harpacticoid copepods are widely distributed in marine ecosystem, which is particularly abundant in the epilithic algal matrix(EAM) of coral reefs. Due to its unique habitat, there is currently limited research on its developmental process and cultivation methods. In this study, we collected epilithic algal matrix from the coral reef of Luhuitou, Sanya, Hainan in the summer of 2023, from which we isolated one species of Harpacticoida, which was belonging to the genus Robertgurneya based on morphological characteristics. The effects of mono-and mixed-algal cultures on the developmental dynamics of Robertgurneya sp. were observed and recorded. The results showed that the adult body length of the Robertgurneya sp. was 0.5−0.7 mm, with an average life cycle of about 61−68 days. There were no significant differences in egg number per female each time, brood number, reproductive cycle, and life cycle between different feed cultivation techniques. However, under mixed algae culture, the average egg diameter, larval survival rate, and maximum body length of nauplii stage VI in the embryonic development stage of the Robertgurneya sp. were significantly higher than those in the mono-algae culture group (p < 0.05). Moreover, the embryonic development time and cumulative copepodid development time were significantly shorter under mixed-algal culture (p < 0.05). The results indicate that Robertgurneya sp. in EAM have a short life cycle and strong reproductive ability. Considering the abundant benthic microalgae and organic debris in the mats, harpacticoida may be able to provide huge potential food resources for predators such as small fish in coral reefs. Therefore, it may play an important role in the material cycle and energy flow of coral reef ecosystems.
2024, 46(9): 73-87.
doi: 10.12284/hyxb2024094
Abstract:
The seasonal variations of zooplankton communities in the nearby seas of the Island was investigated to know the relationship between the structure of zooplankton communities and environmental factors in the sea areas around Weizhou Island in Guangxi. Collecting samples of zooplankton communities were conducted in January (winter), April (spring), August (summer), and November (autumn) of 2022. The study examines the variations in zooplankton species composition, abundance, biomass, and dominant species across the four seasons, while also investigating their primary environmental influencing factors. A total of 224 species (classes) of zooplankton were identified throughout the four seasons of the year, including 25 species (classes) planktonic larvae, belonging to 18 groups. Copepods were the most abundant (78 species), followed by hydrozoan jellyfish (35 species). The number of zooplankton species shows a seasonal variation pattern of spring > autumn > winter > summer, and the composition of species shows a seasonal variation pattern of spring > winter > autumn > summer. The dominant species group exhibits a seasonal replacement phenomenon of copepods, red tide organisms, and glial organisms, as well as hairy jawbones and copepods. The seasonal variation characteristics of the zooplankton community structure are obvious. The annual average abundance and biomass of zooplankton are (246.50 ± 158.75) ind./m3 and (126.08 ± 192.27) mg/m3, respectively. The abundance and biomass in spring are the highest (712.80 ± 630.28) ind./m3 and (367.79 ± 264.33) mg/m3, while the abundance in winter is the lowest (62.09 ± 29.61) ind./m3 and the biomass in summer is the lowest (35.48 ± 19.88) mg/m3. The results of redundancy analysis indicate that water temperature, salinity, nutrients and chlorophyll a are the main environmental factors affecting the seasonal changes of zooplankton community structure in the sea area of Weizhou Island, Guangxi. The seasonal changes in water masses cause by the ocean monsoon drive the succession of dominant species of zooplankton. The seasonal variation characteristics of the abundance of copepods, an important group of zooplankton in the sea area, are consistent with the migration patterns of the Balaenoptera edeni in the waters of Weizhou Island, indicating that the basic feed organisms of the fishing industry affect the migration activities of the B. edeni. In addition, the ecological impact of the decreased dominant group of copepods caused by the proliferation and growth of protozoa and glial organisms in spring on the waters of Weizhou Island deserves attention and exploration.
The seasonal variations of zooplankton communities in the nearby seas of the Island was investigated to know the relationship between the structure of zooplankton communities and environmental factors in the sea areas around Weizhou Island in Guangxi. Collecting samples of zooplankton communities were conducted in January (winter), April (spring), August (summer), and November (autumn) of 2022. The study examines the variations in zooplankton species composition, abundance, biomass, and dominant species across the four seasons, while also investigating their primary environmental influencing factors. A total of 224 species (classes) of zooplankton were identified throughout the four seasons of the year, including 25 species (classes) planktonic larvae, belonging to 18 groups. Copepods were the most abundant (78 species), followed by hydrozoan jellyfish (35 species). The number of zooplankton species shows a seasonal variation pattern of spring > autumn > winter > summer, and the composition of species shows a seasonal variation pattern of spring > winter > autumn > summer. The dominant species group exhibits a seasonal replacement phenomenon of copepods, red tide organisms, and glial organisms, as well as hairy jawbones and copepods. The seasonal variation characteristics of the zooplankton community structure are obvious. The annual average abundance and biomass of zooplankton are (246.50 ± 158.75) ind./m3 and (126.08 ± 192.27) mg/m3, respectively. The abundance and biomass in spring are the highest (712.80 ± 630.28) ind./m3 and (367.79 ± 264.33) mg/m3, while the abundance in winter is the lowest (62.09 ± 29.61) ind./m3 and the biomass in summer is the lowest (35.48 ± 19.88) mg/m3. The results of redundancy analysis indicate that water temperature, salinity, nutrients and chlorophyll a are the main environmental factors affecting the seasonal changes of zooplankton community structure in the sea area of Weizhou Island, Guangxi. The seasonal changes in water masses cause by the ocean monsoon drive the succession of dominant species of zooplankton. The seasonal variation characteristics of the abundance of copepods, an important group of zooplankton in the sea area, are consistent with the migration patterns of the Balaenoptera edeni in the waters of Weizhou Island, indicating that the basic feed organisms of the fishing industry affect the migration activities of the B. edeni. In addition, the ecological impact of the decreased dominant group of copepods caused by the proliferation and growth of protozoa and glial organisms in spring on the waters of Weizhou Island deserves attention and exploration.
2024, 46(9): 101-108.
doi: 10.12284/hyxb2024100
Abstract:
In order to investigate the impact of climate change on the catch of bigeye tuna, we utilized the annual Pacific bigeye tuna catch data from 1960 to 2021, which was statistically compiled by the Western and Central Pacific Fisheries Commission. We also employed corresponding monthly climate indices, including Niño1+2, Niño3, Niño4, Niño3.4, Southern Oscillation Index (SOI), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), North Pacific Index (NPI), and global sea-air temperature anomaly (dT). By using a BP neural network and variable sensitivity analysis, we examined the relationship between these low-frequency climate factors and bigeye tuna catch. Our findings revealed that Niño1+2, SOI, NAO, PDO, NPI, and dT are relatively independent climate factors that have an impact on bigeye tuna catch. The optimal lag orders for these climate factors were determined to be 8 years for Niño1+2, 2 years for SOI, 9 years for NAO, 0 years for PDO, 9 years for NPI, and 3 years for dT. Among these factors, Niño1+2, SOI, and NAO were identified as the key climate factors influencing bigeye tuna catch. We constructed an optimal BP neural network model with a structure of 6-8-1, and the ratio of the difference between the predicted and actual bigeye tuna catch to the actual catch has been maintained within 15% since 1971. Additionally, the trend of the predicted and actual catch was found to be basically consistent, indicating a satisfactory level of model fit.
In order to investigate the impact of climate change on the catch of bigeye tuna, we utilized the annual Pacific bigeye tuna catch data from 1960 to 2021, which was statistically compiled by the Western and Central Pacific Fisheries Commission. We also employed corresponding monthly climate indices, including Niño1+2, Niño3, Niño4, Niño3.4, Southern Oscillation Index (SOI), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), North Pacific Index (NPI), and global sea-air temperature anomaly (dT). By using a BP neural network and variable sensitivity analysis, we examined the relationship between these low-frequency climate factors and bigeye tuna catch. Our findings revealed that Niño1+2, SOI, NAO, PDO, NPI, and dT are relatively independent climate factors that have an impact on bigeye tuna catch. The optimal lag orders for these climate factors were determined to be 8 years for Niño1+2, 2 years for SOI, 9 years for NAO, 0 years for PDO, 9 years for NPI, and 3 years for dT. Among these factors, Niño1+2, SOI, and NAO were identified as the key climate factors influencing bigeye tuna catch. We constructed an optimal BP neural network model with a structure of 6-8-1, and the ratio of the difference between the predicted and actual bigeye tuna catch to the actual catch has been maintained within 15% since 1971. Additionally, the trend of the predicted and actual catch was found to be basically consistent, indicating a satisfactory level of model fit.
2024, 46(9): 109-119.
doi: 10.12284/hyxb2024106
Abstract:
Oil spill is one of the critical target of marine environmental monitoring. Synthetic Aperture Radar (SAR), thermal infrared remote sensing, and optical remote sensing for monitoring of marine oil spills have been elucidated, and it is crucial for marine environmental protection to utilize the features and advantages of multi-source remote sensing to achieve accurate monitoring and quantitative assessment of marine oil spills. On April 27, 2021, the collision between the Panamanian vessel Sea Justice and the Liberian oil tanker A Symphony resulted in an estimated 9400 t of cargo oil seeping into the sea. Here, we monitor and analyze the oil spill pollution coverage and emulsified oil spill characteristics in this accident using multi-source satellite remote sensing data. Based on the response mechanism and characteristics of oil spill multi-source remote sensing, the processing of multi-source data is optimized to realize the identification of oil spill and the classification of multiple oil spill types. The findings indicate that from May 1 to May 22, 2021, the cumulative pixel coverage area of oil spills from A Symphony tanker was2368.7 km2, of which the emulsified oil pixel coverage area was 1019.3 km2, accounting for 43.0%. The maximum daily oil spill pixel area reached 734 km2. The results of multi-remote sensing monitoring mutually validated each other, and optical remote sensing is more capable of identifying different oil spill pollution, in which the emulsified oil represents the key of pollution hazards. It improves the accuracy of monitoring and assessment of marine oil spill pollution, and provides reliable technical and methodological references for the hazard assessment and refined monitoring of oil pollution events.
Oil spill is one of the critical target of marine environmental monitoring. Synthetic Aperture Radar (SAR), thermal infrared remote sensing, and optical remote sensing for monitoring of marine oil spills have been elucidated, and it is crucial for marine environmental protection to utilize the features and advantages of multi-source remote sensing to achieve accurate monitoring and quantitative assessment of marine oil spills. On April 27, 2021, the collision between the Panamanian vessel Sea Justice and the Liberian oil tanker A Symphony resulted in an estimated 9400 t of cargo oil seeping into the sea. Here, we monitor and analyze the oil spill pollution coverage and emulsified oil spill characteristics in this accident using multi-source satellite remote sensing data. Based on the response mechanism and characteristics of oil spill multi-source remote sensing, the processing of multi-source data is optimized to realize the identification of oil spill and the classification of multiple oil spill types. The findings indicate that from May 1 to May 22, 2021, the cumulative pixel coverage area of oil spills from A Symphony tanker was
2024, 46(9): 120-130.
doi: 10.12284/hyxb2024096
Abstract:
Recognition of reef-building corals is important for protecting and monitoring coral reef ecosystems. Deep learning, as an advanced technology in image recognition, has been increasingly applied in coral recognition. However, its performance is still challenged by several issues, such as the imbalance of samples among different coral categories within a dataset and the limitation of data diversity. The former makes the deep learning model more likely to extract features from classes with a large number of samples and, therefore, decreases its ability to recognize small-sample-size corals, which often refer to endangered ones needing to be protected. The latter further reduces the performance of deep learning in recognizing corals with different appearances and are captured in variant environments. To solve these two problems, this study develops a reef-building coral recognition method by integrating a category-quantity adaptive deep data augmentation algorithm and transfer learning. To address the first problem, a category-quantity adaptive deep data augmentation algorithm named DeepSMOTE-F1 is proposed. This algorithm improves the existing DeepSMOTE by introducing a sample-size determination stagey using an F1-score based evaluation metric. It can adaptively augment the number of samples of each category of corals according to its recognition performance so that the deep learning model can fully learn features from each class of corals. For the second problem, transfer learning is used to further enhance the model's ability to extract features. The experimental results on three widely used public coral recognition datasets, RSMAS, EILAT, and EILAT2 show that the recognition accuracy of the proposed DeepSMOTE-F1 is improved by 2.88%, 0.39%, and 1.54%, respectively, compared with the traditional DeepSMOTE; and the accuracy of the integrated method is improved by 0.76%, 1.40% and 1.30% compared with the existing deep learning methods for coral recognition.
Recognition of reef-building corals is important for protecting and monitoring coral reef ecosystems. Deep learning, as an advanced technology in image recognition, has been increasingly applied in coral recognition. However, its performance is still challenged by several issues, such as the imbalance of samples among different coral categories within a dataset and the limitation of data diversity. The former makes the deep learning model more likely to extract features from classes with a large number of samples and, therefore, decreases its ability to recognize small-sample-size corals, which often refer to endangered ones needing to be protected. The latter further reduces the performance of deep learning in recognizing corals with different appearances and are captured in variant environments. To solve these two problems, this study develops a reef-building coral recognition method by integrating a category-quantity adaptive deep data augmentation algorithm and transfer learning. To address the first problem, a category-quantity adaptive deep data augmentation algorithm named DeepSMOTE-F1 is proposed. This algorithm improves the existing DeepSMOTE by introducing a sample-size determination stagey using an F1-score based evaluation metric. It can adaptively augment the number of samples of each category of corals according to its recognition performance so that the deep learning model can fully learn features from each class of corals. For the second problem, transfer learning is used to further enhance the model's ability to extract features. The experimental results on three widely used public coral recognition datasets, RSMAS, EILAT, and EILAT2 show that the recognition accuracy of the proposed DeepSMOTE-F1 is improved by 2.88%, 0.39%, and 1.54%, respectively, compared with the traditional DeepSMOTE; and the accuracy of the integrated method is improved by 0.76%, 1.40% and 1.30% compared with the existing deep learning methods for coral recognition.
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