2016 Vol. 38, No. 4
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2016, 38(4): .
Abstract:
2016, 38(4): 1-21.
doi: 10.3969/j.issn.0253-4193.2016.04.001
Abstract:
Oceanic biological pump, as an important component of oceanic carbon cycle, transfers the atmospheric carbon into the deep ocean. In this paper, the processes in oceanic carbon sink and biological pump are discussed, including sinking of phytoplankton cells, zooplankton fecal pellet package effects, transparent exopolymer particles (TEP) sinking, marine snow sinking and carbonate counter pump. Meanwhile, the present paper attempts to state the progress and perspectives of the biological pump in the South China Sea, which contributes to the carbon cycle in China Seas.
Oceanic biological pump, as an important component of oceanic carbon cycle, transfers the atmospheric carbon into the deep ocean. In this paper, the processes in oceanic carbon sink and biological pump are discussed, including sinking of phytoplankton cells, zooplankton fecal pellet package effects, transparent exopolymer particles (TEP) sinking, marine snow sinking and carbonate counter pump. Meanwhile, the present paper attempts to state the progress and perspectives of the biological pump in the South China Sea, which contributes to the carbon cycle in China Seas.
2016, 38(4): 22-30.
doi: 10.3969/j.issn.0253-4193.2016.04.002
Abstract:
The phytoplankton photosynthesis rate is important to understand the variations of oceanic primary production (PP). In this study,we measured sea surface photosynthesis-irradiance (P-E) parameters from in situ experiments during summer and winter cruises,which was carried out in the northern South China Sea (nSCS) in 2004. The results showed that the P-E parameters had obvious seasonal variations in the nSCS. In winter,the P-E parameters were characterized by high α,high β,and high PmB. It indicated that phytoplankton could achieve relatively higher maximum photosynthesis rate,but the light-inhabitation would be significant when the light was supersaturate. In contrast to winter,the P-E parameters,α,β,and PmB, were relatively lower in summer,which indicated that phytoplankton favorites high photosynthetically active radiation environment,and its maximum photosynthesis rate was lower than that in winter but the light-inhabitation was very slight. We found some factors,such as temperature and size structure of phytoplankton,have significant correlation with P-E parameters. This implied that the photosynthesis rate was affected by both the seasonal changes of environment and the phytoplankton groups. The photosynthesis rate (PmodelB),calculated by P-E parameters,had significant linear correlation with the in situ photosynthesis rate (Pin situB) which was derived by PP experiments. However,the PmodelB results also showed overestimation,which was mainly due to the fact that the respiration rate could not be neglected in the P-E experiment. The results are helpful in the understanding of the characters of phytoplankton photosynthesis in the nSCS.
The phytoplankton photosynthesis rate is important to understand the variations of oceanic primary production (PP). In this study,we measured sea surface photosynthesis-irradiance (P-E) parameters from in situ experiments during summer and winter cruises,which was carried out in the northern South China Sea (nSCS) in 2004. The results showed that the P-E parameters had obvious seasonal variations in the nSCS. In winter,the P-E parameters were characterized by high α,high β,and high PmB. It indicated that phytoplankton could achieve relatively higher maximum photosynthesis rate,but the light-inhabitation would be significant when the light was supersaturate. In contrast to winter,the P-E parameters,α,β,and PmB, were relatively lower in summer,which indicated that phytoplankton favorites high photosynthetically active radiation environment,and its maximum photosynthesis rate was lower than that in winter but the light-inhabitation was very slight. We found some factors,such as temperature and size structure of phytoplankton,have significant correlation with P-E parameters. This implied that the photosynthesis rate was affected by both the seasonal changes of environment and the phytoplankton groups. The photosynthesis rate (PmodelB),calculated by P-E parameters,had significant linear correlation with the in situ photosynthesis rate (Pin situB) which was derived by PP experiments. However,the PmodelB results also showed overestimation,which was mainly due to the fact that the respiration rate could not be neglected in the P-E experiment. The results are helpful in the understanding of the characters of phytoplankton photosynthesis in the nSCS.
2016, 38(4): 31-42.
doi: 10.3969/j.issn.0253-4193.2016.04.003
Abstract:
Microzooplankton communities in the northern South China Sea (18°00'-22°00'N,114°00'-116°00'E) were investigated during August and September in 2014. With the analysis by Uterm hl method,a total of 142 taxa which belong to 44 genera of 2 phyla were identified. Tintinnid (28 genera and 78 species were identified) accounted for 54.93% of the species,41.55% were oligotrichs (14 genera and 59 species). Dominant taxa included Strombidium paracalkinsi,Strombidium sulcatum,Strombidium wilberti and the nauplii. Abundance of microzooplankton ranged from 11.43 ind/L to 959.35 ind/L,with an average of 264.99 ind/L. Microzooplankton were mainly concentrated at depths 50 m,and decreased gradually bellow 50 m. Microzooplankton in the surface water were mainly concentrated in the Station J5 and Station I1. Shannon-Wiener diversity index of vertical distributions ranged from 0.92 to 4.18,with an average of 2.77. Pielou's evenness index ranged from 0.63 to 1,with an average of 0.87. According to canonical correspondence analysis (CCA),temperature and salinity are important factors of microzooplankton communities. In the time-series stations (J4 and SEATS),the diurnal fluctuation of microzooplankton communities changed lightly in the upper water but more stable in the lower water. Microzooplankton communities temporal changes are generally coincide with chlorophyll a distributions.
Microzooplankton communities in the northern South China Sea (18°00'-22°00'N,114°00'-116°00'E) were investigated during August and September in 2014. With the analysis by Uterm hl method,a total of 142 taxa which belong to 44 genera of 2 phyla were identified. Tintinnid (28 genera and 78 species were identified) accounted for 54.93% of the species,41.55% were oligotrichs (14 genera and 59 species). Dominant taxa included Strombidium paracalkinsi,Strombidium sulcatum,Strombidium wilberti and the nauplii. Abundance of microzooplankton ranged from 11.43 ind/L to 959.35 ind/L,with an average of 264.99 ind/L. Microzooplankton were mainly concentrated at depths 50 m,and decreased gradually bellow 50 m. Microzooplankton in the surface water were mainly concentrated in the Station J5 and Station I1. Shannon-Wiener diversity index of vertical distributions ranged from 0.92 to 4.18,with an average of 2.77. Pielou's evenness index ranged from 0.63 to 1,with an average of 0.87. According to canonical correspondence analysis (CCA),temperature and salinity are important factors of microzooplankton communities. In the time-series stations (J4 and SEATS),the diurnal fluctuation of microzooplankton communities changed lightly in the upper water but more stable in the lower water. Microzooplankton communities temporal changes are generally coincide with chlorophyll a distributions.
2016, 38(4): 43-53.
doi: 10.3969/j.issn.0253-4193.2016.04.004
Abstract:
The abundance and species composition of phytoplankton community in the northern South China Sea (nSCS) (18°00'-23° 30'N,110°30'-118°00'E) were investigated from 26th October to 24th November 2010. A total of 204 taxa (12 uncertain species included) belonging to 70 genera of 4 phyla were identified. The main phytoplankton group was Bacillariophyta with 146 species,which accounted 93.17% of the total phytoplankton cell abundance,followed by Pyrrophyta with 51 species,which accounted for 0.63% of the total phytoplankton cell abundance. Chrysophyta (3 genera and 4 species) and Cyanophyta (2 genera and 3 species,where Trichodesmium erythraeum was the dominant specie) also had been found. The cell abundance of phytoplankton ranged from 0.06×103 cells/L to 107.50×103 cells/L and the average was 5.00×103 cells/L. The phytoplankton cell abundance in the surface water was high in northeast of Hainan Island and the coasts of east of Guangdong. The vertical profiles of phytoplankton showed that the maximum cell abundance was found in the surface water and 25 m layer. The dominant species were Thalassionema nitzschioides,Navicula spp., Skeletonema costatum,Chaetoceros curvisetus,Guinardia stolterforthii and Paralia sulcata etc. The Shannon-Wiener diversity index and Pielou evenness index were high in the southeast of survey area and relatively low in other area,the average were 3.14 and 0.73 in surface,2.83 and 0.77 in 5 m layer,respectively. These two diversity indices showed a similar distribution. Environmental analysis showed that phytoplankton cells abundance had significant correlation with environmental factors except silicate,and the main dominant factors were the common restriction of nitrogen and phosphate.
The abundance and species composition of phytoplankton community in the northern South China Sea (nSCS) (18°00'-23° 30'N,110°30'-118°00'E) were investigated from 26th October to 24th November 2010. A total of 204 taxa (12 uncertain species included) belonging to 70 genera of 4 phyla were identified. The main phytoplankton group was Bacillariophyta with 146 species,which accounted 93.17% of the total phytoplankton cell abundance,followed by Pyrrophyta with 51 species,which accounted for 0.63% of the total phytoplankton cell abundance. Chrysophyta (3 genera and 4 species) and Cyanophyta (2 genera and 3 species,where Trichodesmium erythraeum was the dominant specie) also had been found. The cell abundance of phytoplankton ranged from 0.06×103 cells/L to 107.50×103 cells/L and the average was 5.00×103 cells/L. The phytoplankton cell abundance in the surface water was high in northeast of Hainan Island and the coasts of east of Guangdong. The vertical profiles of phytoplankton showed that the maximum cell abundance was found in the surface water and 25 m layer. The dominant species were Thalassionema nitzschioides,Navicula spp., Skeletonema costatum,Chaetoceros curvisetus,Guinardia stolterforthii and Paralia sulcata etc. The Shannon-Wiener diversity index and Pielou evenness index were high in the southeast of survey area and relatively low in other area,the average were 3.14 and 0.73 in surface,2.83 and 0.77 in 5 m layer,respectively. These two diversity indices showed a similar distribution. Environmental analysis showed that phytoplankton cells abundance had significant correlation with environmental factors except silicate,and the main dominant factors were the common restriction of nitrogen and phosphate.
2016, 38(4): 54-65.
doi: 10.3969/j.issn.0253-4193.2016.04.005
Abstract:
Phytoplankton community structure was investigated in 11 stations in the northern South China Sea (18°-22°N,114°-116°E) during August 20 to September 6 in 2014,in which 2 stations were time series stations. 68 genera and 229 species (including variety,form and unidentified taxa) belonging to 4 phyla were identified,in which 43 genera and 147 species belonged to Bacillariophyta,and 20 genera and 75 species were Pyrrophyta. The average cells abundance was 16.318×103 cells/L,and diatoms accounted for 89.80% with 14.653×103 cells/L. The distribution of diatoms governed the distribution of phytoplankton. The abundance in neritic area was higher than that in open ocean due to the high nutrition concentration of fresh water in neritic area. The cells abundance increased firstly and later decreased vertically. The dominant species were Trichodesmium thiebautii,Skeletonema costatum,Fragilariopsis sp.,Chaetoceros brevis,Thalassionema nitzschioides,Pseudo-nitzschia delicatissima,Pseudo-nitzschia pungens,Chaetoceros compressus,Chaetoceros lorenzianus and Chaetoceros pelagicus. The distribution patterns of dominant species were similar,the coastal abundance was high in contrast with that in other area. The average Shannon-Weiner diversity index and Pielou evenness values were 2.37 and 0.56 respectively. Phytoplankton diurnal fluctuation was obvious. The result of CCA analysis showed that total nitrogen,silicate,micro-zooplankton and salinity were the main controlling factors in the survey area. Cluster analysis that based on surface cells abundance aggregated stations into coastal group and pelagic group obviously.
Phytoplankton community structure was investigated in 11 stations in the northern South China Sea (18°-22°N,114°-116°E) during August 20 to September 6 in 2014,in which 2 stations were time series stations. 68 genera and 229 species (including variety,form and unidentified taxa) belonging to 4 phyla were identified,in which 43 genera and 147 species belonged to Bacillariophyta,and 20 genera and 75 species were Pyrrophyta. The average cells abundance was 16.318×103 cells/L,and diatoms accounted for 89.80% with 14.653×103 cells/L. The distribution of diatoms governed the distribution of phytoplankton. The abundance in neritic area was higher than that in open ocean due to the high nutrition concentration of fresh water in neritic area. The cells abundance increased firstly and later decreased vertically. The dominant species were Trichodesmium thiebautii,Skeletonema costatum,Fragilariopsis sp.,Chaetoceros brevis,Thalassionema nitzschioides,Pseudo-nitzschia delicatissima,Pseudo-nitzschia pungens,Chaetoceros compressus,Chaetoceros lorenzianus and Chaetoceros pelagicus. The distribution patterns of dominant species were similar,the coastal abundance was high in contrast with that in other area. The average Shannon-Weiner diversity index and Pielou evenness values were 2.37 and 0.56 respectively. Phytoplankton diurnal fluctuation was obvious. The result of CCA analysis showed that total nitrogen,silicate,micro-zooplankton and salinity were the main controlling factors in the survey area. Cluster analysis that based on surface cells abundance aggregated stations into coastal group and pelagic group obviously.
2016, 38(4): 66-75.
doi: 10.3969/j.issn.0253-4193.2016.04.006
Abstract:
Samples for seawater nutrients and chlorophyll a were collected in the western South China Sea from 31 August to 26 September,2014. Results show that coast of IndoChina have cold-core eddy with low temperature,high salinity and warm-core eddy with high temperature,low salinity which is located in the lower right relative to cold-core eddy. Relative to warm-core eddy and other areas,nutrients of cold-core eddy have higher concentration,50 m,75 m and 100 m layer of which is increased remarkably. DIP higher by 0.21 μmol/L,0.39 μmol/L and 0.23 μmol/L respectively,DIN higher by 4.94 μmol/L,7.56 μmol/L and 3.76 μmol/L respectively,and DSi higher by 2.55 μmol/L,5.25 μmol/L and 3.46 μmol/L respectively. It indicates cold-core eddy on improving primary production with significant nutritional advantages and huge potential. DCM layer appear in 50 m layer,maximum value of which is located in coast of Hainan island. Under the influence of nutrients,cold-core eddy increases primary productivity significantly in 25 m layer,while value of Chl a is not high in 75m,100m layer,which may be caused by low temperature with cold-core eddy.
Samples for seawater nutrients and chlorophyll a were collected in the western South China Sea from 31 August to 26 September,2014. Results show that coast of IndoChina have cold-core eddy with low temperature,high salinity and warm-core eddy with high temperature,low salinity which is located in the lower right relative to cold-core eddy. Relative to warm-core eddy and other areas,nutrients of cold-core eddy have higher concentration,50 m,75 m and 100 m layer of which is increased remarkably. DIP higher by 0.21 μmol/L,0.39 μmol/L and 0.23 μmol/L respectively,DIN higher by 4.94 μmol/L,7.56 μmol/L and 3.76 μmol/L respectively,and DSi higher by 2.55 μmol/L,5.25 μmol/L and 3.46 μmol/L respectively. It indicates cold-core eddy on improving primary production with significant nutritional advantages and huge potential. DCM layer appear in 50 m layer,maximum value of which is located in coast of Hainan island. Under the influence of nutrients,cold-core eddy increases primary productivity significantly in 25 m layer,while value of Chl a is not high in 75m,100m layer,which may be caused by low temperature with cold-core eddy.
2016, 38(4): 76-83.
doi: 10.3969/j.issn.0253-4193.2016.04.007
Abstract:
The distribution and controlling factors of diel variation of nutrients and chl a were studied on the basis of 2 continuously measuring stations during the summer (August) in 2013. The results indicated that the thermocline weakened the transportation of nutrients upward. The diel variation of silicate,nitrate,and phosphate on the bottom of nearshore Station S1 appeared a semidiurnal period,but not at offshore Station S2,suggesting that nutrients at nearshore station S1 was influenced by the tidies more obviously. Moreover,the chlorophyll a level at S2 displayed vertical stratification,and low chlorophyll a level at S1 at night reflected the feeding of zooplankton. Our results suggests that the chlorophyll a and nutrients at S1 and at S2 were controlled by the thermocline,tidies,bioglogical effect and light. The tides are more obvious at S1,and the chlorophyll a was also affected by the feeding of zooplankton. It is because chlorophyll a and nutrients are controlled by many environmental factors,making chlorophyll a unrelated to nutrients.
The distribution and controlling factors of diel variation of nutrients and chl a were studied on the basis of 2 continuously measuring stations during the summer (August) in 2013. The results indicated that the thermocline weakened the transportation of nutrients upward. The diel variation of silicate,nitrate,and phosphate on the bottom of nearshore Station S1 appeared a semidiurnal period,but not at offshore Station S2,suggesting that nutrients at nearshore station S1 was influenced by the tidies more obviously. Moreover,the chlorophyll a level at S2 displayed vertical stratification,and low chlorophyll a level at S1 at night reflected the feeding of zooplankton. Our results suggests that the chlorophyll a and nutrients at S1 and at S2 were controlled by the thermocline,tidies,bioglogical effect and light. The tides are more obvious at S1,and the chlorophyll a was also affected by the feeding of zooplankton. It is because chlorophyll a and nutrients are controlled by many environmental factors,making chlorophyll a unrelated to nutrients.
2016, 38(4): 84-94.
doi: 10.3969/j.issn.0253-4193.2016.04.008
Abstract:
The spatial and seasonal variations of diazotrophic cyanobacteria including Trichodesmium population and Richelia intracellularis were investigated in the western South China Sea,Vietnam coastal waters (10°-17°N,108°-115°E). The surveys were performed during the northeast monsoon period in the winter (2006.11.27-12.16) and the southwest monsoon period in the summer (2007.8.11-9.16). Trichodesmium population was mainly composed of Trichodesmium thiebautii,Trichodesmium erythraeum,Trichodesmium hildebrandtii. T. thiebautii was the dominate species,and the dominate symbiont diatom of R. intracellularis was Rhizosolenia spp. in the Western South China Sea. The average abundance of Trichodesmium were 0.194×104 filaments/L and 0.172×106 cells/L,and the average abundance of R. intracellularis was 0.255×104 cells/L in winter. The mainly symbiont specie was Rhizosolenia styliformis. In comparison,the abundance of diazotrophic cyanobacteria was much higher in summer,and symbiont species was more diversified. The average abundance of Trichodesmium were 2.995×104 filaments/L and 6.007×106 cells/L,the average abundance of R. intracellularis was 2.198×104 cells/L,and the dominate symbiont species was R. styliformis in summer. Temperature and cold eddy seemed to have important influence on the distribution of diazotrophic cyanobacteria. The effect of salinity was unconspicuous individually,however,salinity showed certain limitation when combined with temperature.
The spatial and seasonal variations of diazotrophic cyanobacteria including Trichodesmium population and Richelia intracellularis were investigated in the western South China Sea,Vietnam coastal waters (10°-17°N,108°-115°E). The surveys were performed during the northeast monsoon period in the winter (2006.11.27-12.16) and the southwest monsoon period in the summer (2007.8.11-9.16). Trichodesmium population was mainly composed of Trichodesmium thiebautii,Trichodesmium erythraeum,Trichodesmium hildebrandtii. T. thiebautii was the dominate species,and the dominate symbiont diatom of R. intracellularis was Rhizosolenia spp. in the Western South China Sea. The average abundance of Trichodesmium were 0.194×104 filaments/L and 0.172×106 cells/L,and the average abundance of R. intracellularis was 0.255×104 cells/L in winter. The mainly symbiont specie was Rhizosolenia styliformis. In comparison,the abundance of diazotrophic cyanobacteria was much higher in summer,and symbiont species was more diversified. The average abundance of Trichodesmium were 2.995×104 filaments/L and 6.007×106 cells/L,the average abundance of R. intracellularis was 2.198×104 cells/L,and the dominate symbiont species was R. styliformis in summer. Temperature and cold eddy seemed to have important influence on the distribution of diazotrophic cyanobacteria. The effect of salinity was unconspicuous individually,however,salinity showed certain limitation when combined with temperature.
2016, 38(4): 95-108.
doi: 10.3969/j.issn.0253-4193.2016.04.009
Abstract:
The terrestrial vegetation classification in China has attained significant development on the basis of the field investigation and its related research during the past century. Lacking of the observation data,the research situation of insular vegetation classification is diametrical. This article is aiming to fill the vacancy by the conclusive research.Firstly,the article reviews the research experience of Chinese terrestrial vegetation classification and regionalization. Taking the islands of Zhejiang province and Fujian Province as example,it comes up with the exploration of the relationship between insular vegetation classification and climatic limitation factors,and the approach of researching insular vegetation types and its distribution. Secondly,according to the theory of terrestrial classification,the article discusses the possible vegetation types of the islands of Zhejiang province and Fujian Province,and make sure that insular vegetation type should be in the range of terrestrial vegetation.Finally,based on the integrative analysis,a new approach of insular vegetation classification is proposed. Starting from the climatic limitation factors distributions,the vegetation types and their distribution have been being deduced,in consideration of the relationship between vegetation and climatic limitation factors,which differ from method of the land vegetation classification.
The terrestrial vegetation classification in China has attained significant development on the basis of the field investigation and its related research during the past century. Lacking of the observation data,the research situation of insular vegetation classification is diametrical. This article is aiming to fill the vacancy by the conclusive research.Firstly,the article reviews the research experience of Chinese terrestrial vegetation classification and regionalization. Taking the islands of Zhejiang province and Fujian Province as example,it comes up with the exploration of the relationship between insular vegetation classification and climatic limitation factors,and the approach of researching insular vegetation types and its distribution. Secondly,according to the theory of terrestrial classification,the article discusses the possible vegetation types of the islands of Zhejiang province and Fujian Province,and make sure that insular vegetation type should be in the range of terrestrial vegetation.Finally,based on the integrative analysis,a new approach of insular vegetation classification is proposed. Starting from the climatic limitation factors distributions,the vegetation types and their distribution have been being deduced,in consideration of the relationship between vegetation and climatic limitation factors,which differ from method of the land vegetation classification.
2016, 38(4): 109-119.
doi: 10.3969/j.issn.0253-4193.2016.04.010
Abstract:
The current quality standard of ammonia in seawater in China was made based on the foreign water quality criteria and standard,yet it lacked the support of scientific data to verify whether it could effectively protect the resident species in seawater. Study on the seawater aquatic life criteria for ammonia in China mainly applied the species sensitivity rank (SSR) and the mathematic models developed by the United States Environmental Protection Agency (US EPA) in making their ammonia criteria in seawater. The total ammonia criteria were derived by a formula conversion from non-ionized ammonia criteria using toxicity data of 15 seawater species in China. When pH ranges from 7.0 to 9.0,and temperatures from 0℃ to 30℃,as salinity is 10,criteria maximum concentration(CMC) and criteria continuous concentration (CCC) of the total ammonia ranges from (0.089-57.141)mg/L and (0.007-4.365)mg/L,respectively;as salinity is 20,CMC and CCC ranges from (0.092-61.152) mg/L and (0.007-4.671)mg/L respectively;as salinity is 30,CMC and CCC ranges from (0.095-65.446)mg/L and (0.007-4.999)mg/L,respectively. Among these environmental factors,the greatest effect on the total ammonia criteria in seawater is pH,followed by temperatures,and then by salinity. Compared to the US ammonia criteria in seawater,the CMC range narrows 5 times and the CCC range shrinks 10 times. Results showed that the current non-ionized ammonia criteria should be corrected as a lower value of 0.007 mg/L to effectively protect the seawater species. Meanwhile,the total ammonia criteria were suggested to manage the ammonia in seawater. These provide the scientific evidence for making the ammonia standard in seawater in China.
The current quality standard of ammonia in seawater in China was made based on the foreign water quality criteria and standard,yet it lacked the support of scientific data to verify whether it could effectively protect the resident species in seawater. Study on the seawater aquatic life criteria for ammonia in China mainly applied the species sensitivity rank (SSR) and the mathematic models developed by the United States Environmental Protection Agency (US EPA) in making their ammonia criteria in seawater. The total ammonia criteria were derived by a formula conversion from non-ionized ammonia criteria using toxicity data of 15 seawater species in China. When pH ranges from 7.0 to 9.0,and temperatures from 0℃ to 30℃,as salinity is 10,criteria maximum concentration(CMC) and criteria continuous concentration (CCC) of the total ammonia ranges from (0.089-57.141)mg/L and (0.007-4.365)mg/L,respectively;as salinity is 20,CMC and CCC ranges from (0.092-61.152) mg/L and (0.007-4.671)mg/L respectively;as salinity is 30,CMC and CCC ranges from (0.095-65.446)mg/L and (0.007-4.999)mg/L,respectively. Among these environmental factors,the greatest effect on the total ammonia criteria in seawater is pH,followed by temperatures,and then by salinity. Compared to the US ammonia criteria in seawater,the CMC range narrows 5 times and the CCC range shrinks 10 times. Results showed that the current non-ionized ammonia criteria should be corrected as a lower value of 0.007 mg/L to effectively protect the seawater species. Meanwhile,the total ammonia criteria were suggested to manage the ammonia in seawater. These provide the scientific evidence for making the ammonia standard in seawater in China.
2016, 38(4): 120-129.
doi: 10.3969/j.issn.0253-4193.2016.04.011
Abstract:
Exposure of dissolved organic matter (DOM) to irradiation leads to the losses of absorbance (photobleaching) and carbon (photomineralization),thereby impacting the optics and carbon cycle in aquatic environments. In this study,the apparent quantum yields (AQY) of DOM photodegradation in the Changjiang River Estuary and its adjacent sea was investigated to evaluate the variation character of DOM photodegradation in the estuarine and coastal waters. AQY of DOM photodegradation gradually decreases seaward and the photobleaching rate of chromophoric DOM (CDOM) is about ten times that of dissolved organic carbon (DOC) photomineralization along the entire estuary. The significant negative linear correlation between the Φble (solar spectrum-weighted mean apparent quantum yield of CDOM photobleaching, or Φmin:solar spectrum-weighted mean apparent quantum yield of DOC photomineralization) and salinity in the region seaward from the turbidity maximum zone,as well as the significant positive linear correlations between Φble(or Φmin) and SUVA254 indicated the physical mixing process should be the dominant factor in controlling the photoreactivity of DOM along the Changjiang River Estuary and the photoreactivity of terrestrial DOM was higher than that of marine-derived DOM. AQY of DOM photodegradation in the lower section was much lower than that in the upper section. The action spectra of DOM phodegradation was characterized as a non-Gaussian style,with the peak response located around 330 nm. The wavelength integrated result demonstrated UVA is the main contributor to DOM photodegradation. This study will provide help to improve the carbon flux model in the East China Sea.
Exposure of dissolved organic matter (DOM) to irradiation leads to the losses of absorbance (photobleaching) and carbon (photomineralization),thereby impacting the optics and carbon cycle in aquatic environments. In this study,the apparent quantum yields (AQY) of DOM photodegradation in the Changjiang River Estuary and its adjacent sea was investigated to evaluate the variation character of DOM photodegradation in the estuarine and coastal waters. AQY of DOM photodegradation gradually decreases seaward and the photobleaching rate of chromophoric DOM (CDOM) is about ten times that of dissolved organic carbon (DOC) photomineralization along the entire estuary. The significant negative linear correlation between the Φble (solar spectrum-weighted mean apparent quantum yield of CDOM photobleaching, or Φmin:solar spectrum-weighted mean apparent quantum yield of DOC photomineralization) and salinity in the region seaward from the turbidity maximum zone,as well as the significant positive linear correlations between Φble(or Φmin) and SUVA254 indicated the physical mixing process should be the dominant factor in controlling the photoreactivity of DOM along the Changjiang River Estuary and the photoreactivity of terrestrial DOM was higher than that of marine-derived DOM. AQY of DOM photodegradation in the lower section was much lower than that in the upper section. The action spectra of DOM phodegradation was characterized as a non-Gaussian style,with the peak response located around 330 nm. The wavelength integrated result demonstrated UVA is the main contributor to DOM photodegradation. This study will provide help to improve the carbon flux model in the East China Sea.
2016, 38(4): 130-138.
doi: 10.3969/j.issn.0253-4193.2016.04.012
Abstract:
Combined influences of nutrients status and seawater CO2 concentration on microalgae growth and physiology of Gephyrocapsa oceanic was investigated. It was shown that the abundance of G. oceanic significantly increased during CO2 enrichment experiments at different nutrient levels (nitrogen-deficiency vs. nutrient-rich). However,the strongest response was observed in cell density and chlorophyll a concentration of G. oceanic when nitrogen was deficiency,suggesting low nutrients concentration and low N/P ratio might be favor to the cell growth. Besides,electron microscopy results indicated that seawater acidification had significant negative impact on the calcification and cell size distribution (became smaller) of G .oceanic when nitrogen was deficiency. However,in future oligotrophic open ocean,increasing CO2 concentration might stimulate G. oceanic thrive.
Combined influences of nutrients status and seawater CO2 concentration on microalgae growth and physiology of Gephyrocapsa oceanic was investigated. It was shown that the abundance of G. oceanic significantly increased during CO2 enrichment experiments at different nutrient levels (nitrogen-deficiency vs. nutrient-rich). However,the strongest response was observed in cell density and chlorophyll a concentration of G. oceanic when nitrogen was deficiency,suggesting low nutrients concentration and low N/P ratio might be favor to the cell growth. Besides,electron microscopy results indicated that seawater acidification had significant negative impact on the calcification and cell size distribution (became smaller) of G .oceanic when nitrogen was deficiency. However,in future oligotrophic open ocean,increasing CO2 concentration might stimulate G. oceanic thrive.
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