Algal blooms,the spread of algae on the surface of water bodies,have adverse effects not only on aquatic ecosystems but also on human life.The adverse effects of harmful algal blooms(HABs)necessitate a convenient solu...Algal blooms,the spread of algae on the surface of water bodies,have adverse effects not only on aquatic ecosystems but also on human life.The adverse effects of harmful algal blooms(HABs)necessitate a convenient solution for detection and monitoring.Unmanned aerial vehicles(UAVs)have recently emerged as a tool for algal bloom detection,efficiently providing on-demand images at high spatiotemporal resolutions.This study developed an image processing method for algal bloom area estimation from the aerial images(obtained from the internet)captured using UAVs.As a remote sensing method of HAB detection,analysis,and monitoring,a combination of histogram and texture analyses was used to efficiently estimate the area of HABs.Statistical features like entropy(using the Kullback-Leibler method)were emphasized with the aid of a gray-level co-occurrence matrix.The results showed that the orthogonal images demonstrated fewer errors,and the morphological filter best detected algal blooms in real time,with a precision of 80%.This study provided efficient image processing approaches using on-board UAVs for HAB monitoring.展开更多
Based on 10 multidisciplinary investigations conducted from February 2015 to January 2016,the phytoplankton community and its association with ambient seawater physicochemical parameters in the Changjiang(Yangtze)Rive...Based on 10 multidisciplinary investigations conducted from February 2015 to January 2016,the phytoplankton community and its association with ambient seawater physicochemical parameters in the Changjiang(Yangtze)River estuary(CE)and its adjacent waters were comprehensively examined.In total,265 taxa were identified,belonging to 5 phyla and 94 genera.Diatoms(63.78%)and dinoflagellates(33.21%)were the dominant groups.The variation of diatom abundance showed a positive relationship with the nutrient concentrations while the dinoflagellate abundance showed a negative relationship.Two algal bloom events occurred during the investigation period.The Changjiang Diluted Water(CDW)induced environmental gradients in the upper layer,favoring the diatom bloom in July.The invasion of the nearshore Kuroshio branch current could affect the formation of a bloom of Prorocentrum donghaiense.With the blooming and senescence of phytoplankton,low dissolved oxygen(DO)and hypoxia occurred in the bottom waters.The bottom DO concentration displayed a significantly negative correlation with phytoplankton carbon flux.The present study provides straightforward evidence for the source of organic matter for oxygen consumption in the CE and its adjacent waters.展开更多
Harmful algal blooms (HABs) have become a recurring problem, posing severe impacts on marine ecosystems, fisheries, mariculture industry, and even public health. In this study, the geographic information system (GIS) ...Harmful algal blooms (HABs) have become a recurring problem, posing severe impacts on marine ecosystems, fisheries, mariculture industry, and even public health. In this study, the geographic information system (GIS) was utilized to determine spatial and temporal characteristics of HAB events in the coastal waters of Guangdong from 1980–2016. We analyzed distribution patterns and characteristics of HABs by dividing the coast of Guangdong into well-known bays, estuary and coastal waters. Results showed that there were a total of 337 HABs recorded in Guangdong coastal waters. Spatial and temporal distributions varied among diff erent regions. Most HABs occurred in the Mirs Bay, followed by the west coast of Daya Bay, while a few occurred in the west and east coasts of Guangdong but with an increasing trend in the past two decades. HABs occurred mostly in warmer months of March to May in the western coast of Guangdong, March and April in Mirs Bay, April in Zhujiang (Pearl) River estuary, November in eastern coast of Guangdong. For Daya Bay, most HABs were reported between March and September. The most frequently occurring HABs species were Noctiluca scintillans , Phaeocystis globosa , Skeletonema costatum and Scrippsiella trochoidea , occurring mostly in Mirs Bay, western Guangdong coast area, eastern Guangdong coast area and Zhujiang River estuary and Daya Bay, respectively. Ichthyotoxic blooms were more common than toxic blooms, and Heterosigma akashiwo , Chattonella marina , Karenia mikimotoi and P haeocystis globosa were the most common ichthyotoxic species. Our results provide baseline information useful for policy making and management of HABs in the region.展开更多
The variations in nutrients（molar ratios） and chlorophyll a in the Jiaozhou Bay were examined before and after a diatom bloom in a period that lasted from November 2003 to March 2004. Negative relationships between ...The variations in nutrients（molar ratios） and chlorophyll a in the Jiaozhou Bay were examined before and after a diatom bloom in a period that lasted from November 2003 to March 2004. Negative relationships between nutrient concentrations, Si/P, Si/N ratios and chlorophyll a content were found during the bloom, which reflected the relationship between nutrient concentrations, phytoplankton biomass and growth. Large increase in nutrient concentrations, particularly SiO_3-Si after the late autumn, is one of major reasons inducing the diatom bloom in winter, and the bloom was finally controlled due to SiO_3-Si depletion by phytoplankton. The bloom was mainly controlled by SiO_3-Si. Before 1998, relatively low level of SiO_3-Si kept ecological balance of eutrophication waters in the Jiaozhou Bay. In recent years, however, human activities have increased SiO_3-Si concentration, which is likely one of the primary cause for the increased diatom blooms in the Jiaozhou Bay. Therefore, it is necessary to control SiO_3-Si concentration in the Jiaozhou Bay.展开更多
Prorocentrum donghaiense is one of the most common red tide causative dinoflagellates in the Changjiang （Yangtze） River Estuary and the adjacent area of the East China Sea. It causes large-scale blooms in late sprin...Prorocentrum donghaiense is one of the most common red tide causative dinoflagellates in the Changjiang （Yangtze） River Estuary and the adjacent area of the East China Sea. It causes large-scale blooms in late spring and early summer that lead to widespread ecologic and economic damage. A means for distinguish- ing dinoflagellate blooms from diatom （Skeletonema costatum） blooms is desired. On the basis of measure- ments of remote sensing refectance [Rrs（λ）] and inherent optical parameters, the potential of using a mul- tispectral approach is assessed for discriminating the algal blooms due to P. donghaiense from those due to S. costatum. The behavior of two reflectance ratios [R1 = Rrs（560）/Rrs（532） and Re = Rrs（708）/Rrs（665）], suggests that differentiation of P. donghaiense blooms from diatom bloom types is possible from the current band setup of ocean color sensors. It is found that there are two reflectance ratio regimes that indicate a bloom is dominated by P. donghaiense; （1） R1 〉 1.55 and R2 〈 1.0 or （2） R1 〉 1.75 and R2 ≥ 1.0. Various sensitivity analyses are conducted to investigate the effects of the variation in varying levels of chlorophyll concentration and colored dissolved organic matter （CDOM） as well as changes in the backscattering ratio （bbp/bp） on the efficacy of this muitispectral approach. Results indicate that the intensity and inherent op- tical properties of the algal species explain much of the behavior of the two ratios. Although backscattering influences the amplitude of Rrs（λ）, especially in the 530 and 560 nm bands, the discrimination between P. donghaiense and diatoms is not significantly affected by the variation of bbp/bp. Since aCDOM （440） in coastal areas of the ECS is typically lower than 1.0 m-1 in most situations, the presence of CDOM does not interfere with this discrimination, even as SCDOM varies from 0.01 to 0.026 nm-1. Despite all of these effects, the dis- crimination of P. donghaiense blooms from diatom blooms based on multispectral measurements of Rrs（λ） is feasible.展开更多
After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly...After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly appeared in the tributaries of the reservoir region such as the Xiangxi River,Daning River,Shennong River and Xiaojiang River,but they did not occur every year. The reasons for outbreaks of algal blooms in the tributaries are shown as follows: the existence of sources of algae(blue-green algae) in the Three Gorges Reservoir is the root cause,and the sources include sources existing and being produced in the reservoir and sources from upstream main stream and its tributaries and other related lakes and reservoirs,of which the sources are mainly from the Dianchi Lake; slight or moderate eutrophication of water is the basic condition;hydrologic and hydrodynamic conditions and suitable temperature are conducive to proliferation and aggregation of algae(blue-green algae) after the operation of the Three Gorges Reservoir until outbreaks of algal blooms appear. Outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region mainly appear in backwater reaches; they mainly occur in the tributaries in the north of the reservoir region and near to the dam;they mainly appear from March to July; the dominant species of algae( blue-green algae) in the Three Gorges Reservoir are Pyrrophyta,Bacillariophyta and Chlorophyta,but they tend to change into blue-green algae and other algae. To control outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region,it is needed to prevent water containing blue-green algae collected from the Dianchi Lake and other lakes and reservoirs from being input into the lower reaches,reduce pollution load flowing into the Three Gorges Reservoir,use enclosures to change hydrodynamic conditions of backwater reaches of the tributaries appropriately,and adopt biological measures such as culturing fish and planting plants to improve ecosystem of the tributaries and other measures to inhibit and eliminate algae and decrease eutrophication level.展开更多
Blooms of some pico/nanophytoplankton have occurred frequently along the Qinhuangdao coast since 2009, and it is necessary to identify the critical environmental factors inducing them. In this study, variations in the...Blooms of some pico/nanophytoplankton have occurred frequently along the Qinhuangdao coast since 2009, and it is necessary to identify the critical environmental factors inducing them. In this study, variations in the physical and nutrient characteristics of the seawater were analyzed following the development of local blooms in 2013. The local environmental characteristics were also compared with those of the Changjiang River estuary, China, and the Long Island estuaries in the USA, which are also prone to blooms of special algal species. In Qinhuangdao the local water temperature varied seasonally and rose above 15°C in 2013 early summer, coincident with the water discoloration. The salinity was more than 28 with a variation range of <3 throughout the year. Our results suggest that the physical conditions of the Qinhuangdao coastal area were suitable for the explosive proliferation of certain pico/nanophytoplankton, e.g. Aureococcus anophageff erens. The water supporting the bloom was not in a condition of serious eutrophication, but there were relatively high concentrations of reduced nitrogen(especially ammonium), which acted as an important nitrogen source for the pico/nanophytoplankton bloom. There was also a large gap between total nitrogen(TN) and dissolved inorganic nitrogen(DIN). Although the phosphate concentration was relatively low, there was no evidence of phosphorus limitation to the growth of pico/nanophytoplankton during bloom events.展开更多
Harmful algal blooms (HABs) are a serious worldwide issue which has posed great risks on marine ecosystems and public health by directly releasing toxins or indirectly leading to anoxia in marine environment. In recen...Harmful algal blooms (HABs) are a serious worldwide issue which has posed great risks on marine ecosystems and public health by directly releasing toxins or indirectly leading to anoxia in marine environment. In recent years HABs have caused huge economic losses in China, particularly in the Yangtze Estuary and the adjacent East China Sea (ECS). The present study investigated the spatial-temporal and species characteristics of large-scale HABs in this area using geographic information system (GIS) Kernel Density Estimation (KDE) spatial analysis, statistical methods and satellite image interpretation. Results revealed that the Yangtze Estuary, Zhoushan island, Xiangshan bay and Jiushan island are the regions with highest frequency of large-scale HABs. HABs in the ECS reached a peak in terms of total number and area in 2003 to 2005 and occupied a high percentage (around 70% in area and 60% in occurrence) in the four Chinese coastal waters. The number of large-scale HABs (> 1000 km2) in the Yangtze Estuary and the adjacent ECS declined after 2005 while that of HABs (> 100 km2) declined after 2008. Large-scale HABs occurrences concentrated in summer (May to July), and the averaged duration increased continually from the shortest time (1.3 days) in 2001 to the longest (10.9 days) in 2010 for each HAB. 17 causative species were found with Prorocentrum dentutam as the most frequent dominant species, followed by Skeletonema costatum, Karenia mikimotoi, and Chaetoceros curvisetus. Water discoloration observed in MODIS satellite true color images was well consistent with the corresponding HABs reported by State Oceanic Administration of China (SOA). Multiple factors involving eutrophication, physical dynamics, topography and deposition conditions contributed to the formation of frequent HABs in the ECS. Three strategies including establishing a synthesized system, improving the previous database and investigating multiple contributors were proposed for future HABs monitoring and management.展开更多
Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined ...Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined during two cruises conducted in the Yellow Sea (YS) from February to April of 2009. During the pre-bloom period from February to March, low CH4 saturation (< 134%) was observed in the surface water, except at two nearshore stations where the CH4 levels were above 140% in March due to mixing with the coastal water. During the bloom period, CH4 increased obviously at two bloom-tracking stations, especially at the surface with mean saturations of 140% and 170%. The increase in CH4 concentration/saturation is thought to be the result of in situ CH4 production. The particulate organic carbon (POC) and chlorophyll a contents were believed to be important factors that influ- enced the CH4 production. In addition, the presence of different dominant phytoplankton species and the grazing pressure may have stimulated the CH4 production by supplying potential methanogenic substrates (such as dimethylsulphoniopropionate (DMSP)). Both the incubation data and the in situ estimations further evidenced the significant influence of the spring blooms on the CH4 production. The calculated sea-to-air CH4 fluxes during the bloom period were not significantly higher than those during the pre-bloom period despite the bloom-increased CH4 saturation. This is due to the variation in physical forcing (such as wind speed), which is the main driver for determining the CH4 flux. Finally, we estimated the annual CH4 flux in the YS as 9.0 μmol m 2 d 1;the findings suggest that the YS is a natural source of atmospheric CH4.展开更多
文摘Algal blooms,the spread of algae on the surface of water bodies,have adverse effects not only on aquatic ecosystems but also on human life.The adverse effects of harmful algal blooms(HABs)necessitate a convenient solution for detection and monitoring.Unmanned aerial vehicles(UAVs)have recently emerged as a tool for algal bloom detection,efficiently providing on-demand images at high spatiotemporal resolutions.This study developed an image processing method for algal bloom area estimation from the aerial images(obtained from the internet)captured using UAVs.As a remote sensing method of HAB detection,analysis,and monitoring,a combination of histogram and texture analyses was used to efficiently estimate the area of HABs.Statistical features like entropy(using the Kullback-Leibler method)were emphasized with the aid of a gray-level co-occurrence matrix.The results showed that the orthogonal images demonstrated fewer errors,and the morphological filter best detected algal blooms in real time,with a precision of 80%.This study provided efficient image processing approaches using on-board UAVs for HAB monitoring.
基金Supported by the Science&Technology Basic Resources Investigation Program(No.2018FY100200)the National Natural Science Foundation of China(Nos.41976136,41606128)+3 种基金the NSFC-Shandong Joint Research Fund(No.U1706218)the Science Foundation of Shandong Jianzhu University(No.XNBS1937)the Young Visiting Scholar Program of Shandong Provincethe Introduction and Cultivation Plan for Young Innovative Talents of Colleges and Universities by the Education Department of Shandong Province。
文摘Based on 10 multidisciplinary investigations conducted from February 2015 to January 2016,the phytoplankton community and its association with ambient seawater physicochemical parameters in the Changjiang(Yangtze)River estuary(CE)and its adjacent waters were comprehensively examined.In total,265 taxa were identified,belonging to 5 phyla and 94 genera.Diatoms(63.78%)and dinoflagellates(33.21%)were the dominant groups.The variation of diatom abundance showed a positive relationship with the nutrient concentrations while the dinoflagellate abundance showed a negative relationship.Two algal bloom events occurred during the investigation period.The Changjiang Diluted Water(CDW)induced environmental gradients in the upper layer,favoring the diatom bloom in July.The invasion of the nearshore Kuroshio branch current could affect the formation of a bloom of Prorocentrum donghaiense.With the blooming and senescence of phytoplankton,low dissolved oxygen(DO)and hypoxia occurred in the bottom waters.The bottom DO concentration displayed a significantly negative correlation with phytoplankton carbon flux.The present study provides straightforward evidence for the source of organic matter for oxygen consumption in the CE and its adjacent waters.
基金Supported by the National Key Research and Development Program of China(No.2017YFC1404300)the National Nature Science Foundation of China(Nos.41606175,41576162)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA11020304)
文摘Harmful algal blooms (HABs) have become a recurring problem, posing severe impacts on marine ecosystems, fisheries, mariculture industry, and even public health. In this study, the geographic information system (GIS) was utilized to determine spatial and temporal characteristics of HAB events in the coastal waters of Guangdong from 1980–2016. We analyzed distribution patterns and characteristics of HABs by dividing the coast of Guangdong into well-known bays, estuary and coastal waters. Results showed that there were a total of 337 HABs recorded in Guangdong coastal waters. Spatial and temporal distributions varied among diff erent regions. Most HABs occurred in the Mirs Bay, followed by the west coast of Daya Bay, while a few occurred in the west and east coasts of Guangdong but with an increasing trend in the past two decades. HABs occurred mostly in warmer months of March to May in the western coast of Guangdong, March and April in Mirs Bay, April in Zhujiang (Pearl) River estuary, November in eastern coast of Guangdong. For Daya Bay, most HABs were reported between March and September. The most frequently occurring HABs species were Noctiluca scintillans , Phaeocystis globosa , Skeletonema costatum and Scrippsiella trochoidea , occurring mostly in Mirs Bay, western Guangdong coast area, eastern Guangdong coast area and Zhujiang River estuary and Daya Bay, respectively. Ichthyotoxic blooms were more common than toxic blooms, and Heterosigma akashiwo , Chattonella marina , Karenia mikimotoi and P haeocystis globosa were the most common ichthyotoxic species. Our results provide baseline information useful for policy making and management of HABs in the region.
基金The National Natural Science Foundation of China under contract No.40776043
文摘The variations in nutrients（molar ratios） and chlorophyll a in the Jiaozhou Bay were examined before and after a diatom bloom in a period that lasted from November 2003 to March 2004. Negative relationships between nutrient concentrations, Si/P, Si/N ratios and chlorophyll a content were found during the bloom, which reflected the relationship between nutrient concentrations, phytoplankton biomass and growth. Large increase in nutrient concentrations, particularly SiO_3-Si after the late autumn, is one of major reasons inducing the diatom bloom in winter, and the bloom was finally controlled due to SiO_3-Si depletion by phytoplankton. The bloom was mainly controlled by SiO_3-Si. Before 1998, relatively low level of SiO_3-Si kept ecological balance of eutrophication waters in the Jiaozhou Bay. In recent years, however, human activities have increased SiO_3-Si concentration, which is likely one of the primary cause for the increased diatom blooms in the Jiaozhou Bay. Therefore, it is necessary to control SiO_3-Si concentration in the Jiaozhou Bay.
基金The National Basic Research Program of China (973 Program) under contract No.2013CB430302the National High Technology Research and Development Program of China (863 Program) under contract No.2007AA092002+2 种基金the National Natural Science Foundation of China under contract No.41206170the public science and technology research funds projects of the ocean under contract No.201005030scientific research fund of the Second Institute of Oceanography,SOA under contract No.JG1212
文摘Prorocentrum donghaiense is one of the most common red tide causative dinoflagellates in the Changjiang （Yangtze） River Estuary and the adjacent area of the East China Sea. It causes large-scale blooms in late spring and early summer that lead to widespread ecologic and economic damage. A means for distinguish- ing dinoflagellate blooms from diatom （Skeletonema costatum） blooms is desired. On the basis of measure- ments of remote sensing refectance [Rrs（λ）] and inherent optical parameters, the potential of using a mul- tispectral approach is assessed for discriminating the algal blooms due to P. donghaiense from those due to S. costatum. The behavior of two reflectance ratios [R1 = Rrs（560）/Rrs（532） and Re = Rrs（708）/Rrs（665）], suggests that differentiation of P. donghaiense blooms from diatom bloom types is possible from the current band setup of ocean color sensors. It is found that there are two reflectance ratio regimes that indicate a bloom is dominated by P. donghaiense; （1） R1 〉 1.55 and R2 〈 1.0 or （2） R1 〉 1.75 and R2 ≥ 1.0. Various sensitivity analyses are conducted to investigate the effects of the variation in varying levels of chlorophyll concentration and colored dissolved organic matter （CDOM） as well as changes in the backscattering ratio （bbp/bp） on the efficacy of this muitispectral approach. Results indicate that the intensity and inherent op- tical properties of the algal species explain much of the behavior of the two ratios. Although backscattering influences the amplitude of Rrs（λ）, especially in the 530 and 560 nm bands, the discrimination between P. donghaiense and diatoms is not significantly affected by the variation of bbp/bp. Since aCDOM （440） in coastal areas of the ECS is typically lower than 1.0 m-1 in most situations, the presence of CDOM does not interfere with this discrimination, even as SCDOM varies from 0.01 to 0.026 nm-1. Despite all of these effects, the dis- crimination of P. donghaiense blooms from diatom blooms based on multispectral measurements of Rrs（λ） is feasible.
文摘After water storage in the Three Gorges Reservoir Region,there are no outbreaks of algal blooms in the main stream of the reservoir region,but the density of algae increases obviously. Outbreaks of algal blooms mainly appeared in the tributaries of the reservoir region such as the Xiangxi River,Daning River,Shennong River and Xiaojiang River,but they did not occur every year. The reasons for outbreaks of algal blooms in the tributaries are shown as follows: the existence of sources of algae(blue-green algae) in the Three Gorges Reservoir is the root cause,and the sources include sources existing and being produced in the reservoir and sources from upstream main stream and its tributaries and other related lakes and reservoirs,of which the sources are mainly from the Dianchi Lake; slight or moderate eutrophication of water is the basic condition;hydrologic and hydrodynamic conditions and suitable temperature are conducive to proliferation and aggregation of algae(blue-green algae) after the operation of the Three Gorges Reservoir until outbreaks of algal blooms appear. Outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region mainly appear in backwater reaches; they mainly occur in the tributaries in the north of the reservoir region and near to the dam;they mainly appear from March to July; the dominant species of algae( blue-green algae) in the Three Gorges Reservoir are Pyrrophyta,Bacillariophyta and Chlorophyta,but they tend to change into blue-green algae and other algae. To control outbreaks of algal blooms in the tributaries of the Three Gorges Reservoir Region,it is needed to prevent water containing blue-green algae collected from the Dianchi Lake and other lakes and reservoirs from being input into the lower reaches,reduce pollution load flowing into the Three Gorges Reservoir,use enclosures to change hydrodynamic conditions of backwater reaches of the tributaries appropriately,and adopt biological measures such as culturing fish and planting plants to improve ecosystem of the tributaries and other measures to inhibit and eliminate algae and decrease eutrophication level.
基金Supported by the National Natural Science Foundation of China(No.41576119)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA11020302)the Public Science and Technology Research Funds Projects of Ocean(No.201305003-3)
文摘Blooms of some pico/nanophytoplankton have occurred frequently along the Qinhuangdao coast since 2009, and it is necessary to identify the critical environmental factors inducing them. In this study, variations in the physical and nutrient characteristics of the seawater were analyzed following the development of local blooms in 2013. The local environmental characteristics were also compared with those of the Changjiang River estuary, China, and the Long Island estuaries in the USA, which are also prone to blooms of special algal species. In Qinhuangdao the local water temperature varied seasonally and rose above 15°C in 2013 early summer, coincident with the water discoloration. The salinity was more than 28 with a variation range of <3 throughout the year. Our results suggest that the physical conditions of the Qinhuangdao coastal area were suitable for the explosive proliferation of certain pico/nanophytoplankton, e.g. Aureococcus anophageff erens. The water supporting the bloom was not in a condition of serious eutrophication, but there were relatively high concentrations of reduced nitrogen(especially ammonium), which acted as an important nitrogen source for the pico/nanophytoplankton bloom. There was also a large gap between total nitrogen(TN) and dissolved inorganic nitrogen(DIN). Although the phosphate concentration was relatively low, there was no evidence of phosphorus limitation to the growth of pico/nanophytoplankton during bloom events.
文摘Harmful algal blooms (HABs) are a serious worldwide issue which has posed great risks on marine ecosystems and public health by directly releasing toxins or indirectly leading to anoxia in marine environment. In recent years HABs have caused huge economic losses in China, particularly in the Yangtze Estuary and the adjacent East China Sea (ECS). The present study investigated the spatial-temporal and species characteristics of large-scale HABs in this area using geographic information system (GIS) Kernel Density Estimation (KDE) spatial analysis, statistical methods and satellite image interpretation. Results revealed that the Yangtze Estuary, Zhoushan island, Xiangshan bay and Jiushan island are the regions with highest frequency of large-scale HABs. HABs in the ECS reached a peak in terms of total number and area in 2003 to 2005 and occupied a high percentage (around 70% in area and 60% in occurrence) in the four Chinese coastal waters. The number of large-scale HABs (> 1000 km2) in the Yangtze Estuary and the adjacent ECS declined after 2005 while that of HABs (> 100 km2) declined after 2008. Large-scale HABs occurrences concentrated in summer (May to July), and the averaged duration increased continually from the shortest time (1.3 days) in 2001 to the longest (10.9 days) in 2010 for each HAB. 17 causative species were found with Prorocentrum dentutam as the most frequent dominant species, followed by Skeletonema costatum, Karenia mikimotoi, and Chaetoceros curvisetus. Water discoloration observed in MODIS satellite true color images was well consistent with the corresponding HABs reported by State Oceanic Administration of China (SOA). Multiple factors involving eutrophication, physical dynamics, topography and deposition conditions contributed to the formation of frequent HABs in the ECS. Three strategies including establishing a synthesized system, improving the previous database and investigating multiple contributors were proposed for future HABs monitoring and management.
基金funded by the Ministry of Science and Technology of China (No. 2016YFA0601302)the National Natural Science Foundation of China (No. 41521064)+1 种基金supported by the Taishan Scholars Program of Shandong Provincethe Aoshan Talents Program of the Qingdao National Laboratory for Marine Science and Technology (No. 2015ASTP-OS08)
文摘Methane (CH4) is an important greenhouse gas and oceans are net sources of atmospheric CH4. The effects of environ- mental factors on the CH4 variation during different phases of the spring algal blooms were examined during two cruises conducted in the Yellow Sea (YS) from February to April of 2009. During the pre-bloom period from February to March, low CH4 saturation (< 134%) was observed in the surface water, except at two nearshore stations where the CH4 levels were above 140% in March due to mixing with the coastal water. During the bloom period, CH4 increased obviously at two bloom-tracking stations, especially at the surface with mean saturations of 140% and 170%. The increase in CH4 concentration/saturation is thought to be the result of in situ CH4 production. The particulate organic carbon (POC) and chlorophyll a contents were believed to be important factors that influ- enced the CH4 production. In addition, the presence of different dominant phytoplankton species and the grazing pressure may have stimulated the CH4 production by supplying potential methanogenic substrates (such as dimethylsulphoniopropionate (DMSP)). Both the incubation data and the in situ estimations further evidenced the significant influence of the spring blooms on the CH4 production. The calculated sea-to-air CH4 fluxes during the bloom period were not significantly higher than those during the pre-bloom period despite the bloom-increased CH4 saturation. This is due to the variation in physical forcing (such as wind speed), which is the main driver for determining the CH4 flux. Finally, we estimated the annual CH4 flux in the YS as 9.0 μmol m 2 d 1;the findings suggest that the YS is a natural source of atmospheric CH4.
