2013 Vol. 32, No. 4
Display Method:
2013, 32(4): 1-10.
doi: 10.1007/s13131-013-0293-5
Abstract:
Temporal and spatial distribution of biogenic (BSi) and lithogenic (LSi) silica were studied in the Changjiang (Yangtze River) Estuary and its adjacent area. The annual average BSi and LSi concentrations were (1.71±1.79) μmol/L and (0.56±1.41) mmol/L, respectively. Both BSi and LSi were high in the inshore areas, where they received terrigenous discharge from the Changjiang, and decreased towards the offshore region. BSi and LSi were most abundant at the near bottom layer due to the high sedimentation rates and resuspension of sediment. Diatom blooms occurred in summer with high Chl a concentration in the surface layer, which induced that BSi in the surface layer during summer was obviously higher than that in the surface layer of other seasons. LSi concentration was maximal in autumn and spring and minimum in summer, associated with the seasonal variation of SPM values. Drifting investigation and mesocosm experiments were conducted during dinoflagellate bloom, aiming to understand the effect of nutrients on BSi by changing the phytoplankton composition. The results show that the low dissolved inorganic phosphorus concentration and high molar ratio of N/P (dissolved inorganic nitrogen vs. dissolved inorganic phosphorus), were the important factors for decreasing diatom biomass in the study area, and it would subsequently decrease the BSi concentration in aquatic ecosystem.
Temporal and spatial distribution of biogenic (BSi) and lithogenic (LSi) silica were studied in the Changjiang (Yangtze River) Estuary and its adjacent area. The annual average BSi and LSi concentrations were (1.71±1.79) μmol/L and (0.56±1.41) mmol/L, respectively. Both BSi and LSi were high in the inshore areas, where they received terrigenous discharge from the Changjiang, and decreased towards the offshore region. BSi and LSi were most abundant at the near bottom layer due to the high sedimentation rates and resuspension of sediment. Diatom blooms occurred in summer with high Chl a concentration in the surface layer, which induced that BSi in the surface layer during summer was obviously higher than that in the surface layer of other seasons. LSi concentration was maximal in autumn and spring and minimum in summer, associated with the seasonal variation of SPM values. Drifting investigation and mesocosm experiments were conducted during dinoflagellate bloom, aiming to understand the effect of nutrients on BSi by changing the phytoplankton composition. The results show that the low dissolved inorganic phosphorus concentration and high molar ratio of N/P (dissolved inorganic nitrogen vs. dissolved inorganic phosphorus), were the important factors for decreasing diatom biomass in the study area, and it would subsequently decrease the BSi concentration in aquatic ecosystem.
2013, 32(4): 11-17.
doi: 10.1007/s13131-013-0294-4
Abstract:
The Changjiang Estuary has been considered as one of the most polluted estuaries in the world due to high nitrate (NO3-) input, especially in spring and summer. In this study, δ15N and δ18O of NO3-, along with other chemical parameters in this area, were measured in spring to evaluate NO3- biogeochemical processes. A simple two end-members mixing model was used to examine the relative contribution of the Changjiang River Diluted Water and marine water to NO3- sources in the Changjiang Estuary and the adjacent East China Sea. The isotopic signals show that NO3- behaved relatively and conservatively in Transect F and Transect P where assimilation was weak possibly due to vertical mixing, while active assimilation and weak nitrification occurred in Transect D. Spatial difference in assimilation was indicated by the ~1:1 enrichment of δ15N and δ18O in the three transects, while spatial difference in nitrification was reflected by deviations of δ15N and δ18O from assimilation line. Our results suggest that the input of the Changjiang River Diluted Water promoted NO3- assimilation possibly by stratifying the water column which favored the phytoplankton growth.
The Changjiang Estuary has been considered as one of the most polluted estuaries in the world due to high nitrate (NO3-) input, especially in spring and summer. In this study, δ15N and δ18O of NO3-, along with other chemical parameters in this area, were measured in spring to evaluate NO3- biogeochemical processes. A simple two end-members mixing model was used to examine the relative contribution of the Changjiang River Diluted Water and marine water to NO3- sources in the Changjiang Estuary and the adjacent East China Sea. The isotopic signals show that NO3- behaved relatively and conservatively in Transect F and Transect P where assimilation was weak possibly due to vertical mixing, while active assimilation and weak nitrification occurred in Transect D. Spatial difference in assimilation was indicated by the ~1:1 enrichment of δ15N and δ18O in the three transects, while spatial difference in nitrification was reflected by deviations of δ15N and δ18O from assimilation line. Our results suggest that the input of the Changjiang River Diluted Water promoted NO3- assimilation possibly by stratifying the water column which favored the phytoplankton growth.
2013, 32(4): 18-26.
doi: 10.1007/s13131-013-0295-3
Abstract:
The sources and distributions of terrigenous organic matter (OM) were investigated in a small tropical estuary in the Hainan Island, South China. Plants, suspended particulate matter (SPM), and surface sediments samples in the estuary and coast were collected. Bulk properties [organic carbon (OC%), total nitrogen (TN%), stable carbon isotope (δ13C) and grain size] and lignin phenol concentrations were measured. OC% of mangrove plants was (43.4±2.1)%, which is similar to the values reported for mangrove plants in other regions. OC% of sediment samples ranged from 0.07% to 1.42%, and they were related to the sediment texture. Lignin phenols in the sediment ranged from 5.16 mg/100 mg OC in the uppermost station to 0.51 mg/100 mg OC in the coast. The molar ratio of organic carbon to total nitrogen (C/N) (~7) and δ13C (~-31.1×10-3) of riverine SPM revealed that the major OM sources of riverine SPM were aquatic OM (phytoplankton and/or bacteria). Moreover, the lower lignin concentration (Λ8) and higher (Ad/Al)v of lignin phenols suggest that terrestrial OM in riverine SPM were mainly from soil. Furthermore, C/N ratio, δ13C and lignin phenols reveal that mangrove plants were the predominant OM sources of mangrove surface sediment. Based on the δ13C and lignin phenols, it can be concluded that the major OM sources in estuarine and coastal surface sediments were marine phytoplankton, riverine SPM and mangrove surface sediment. In addition, the higher (Ad/Al)v of lignin phenols in those coastal sediments indicate that seagrass might be a potential OM source in coastal sediments, however, the lower (Ad/Al)v in the estuarine sediments in turn suggests that seagrass could not be transported to the mangrove fringed region. A three-end-member model which is based on lignin concentrations and δ13C was applied to evaluate the contribution of mangroves to the organic matter preserved in the surface sediments. Around the mangrove fringed region, mangrove could contribute more than 50% to the sedimentary OM, and this value is much higher than riverine OM. Nevertheless, mangrove OM could not be efficiently transported to the coastal region. Our study suggests that mangrove forest is an important OM source in this small estuary.
The sources and distributions of terrigenous organic matter (OM) were investigated in a small tropical estuary in the Hainan Island, South China. Plants, suspended particulate matter (SPM), and surface sediments samples in the estuary and coast were collected. Bulk properties [organic carbon (OC%), total nitrogen (TN%), stable carbon isotope (δ13C) and grain size] and lignin phenol concentrations were measured. OC% of mangrove plants was (43.4±2.1)%, which is similar to the values reported for mangrove plants in other regions. OC% of sediment samples ranged from 0.07% to 1.42%, and they were related to the sediment texture. Lignin phenols in the sediment ranged from 5.16 mg/100 mg OC in the uppermost station to 0.51 mg/100 mg OC in the coast. The molar ratio of organic carbon to total nitrogen (C/N) (~7) and δ13C (~-31.1×10-3) of riverine SPM revealed that the major OM sources of riverine SPM were aquatic OM (phytoplankton and/or bacteria). Moreover, the lower lignin concentration (Λ8) and higher (Ad/Al)v of lignin phenols suggest that terrestrial OM in riverine SPM were mainly from soil. Furthermore, C/N ratio, δ13C and lignin phenols reveal that mangrove plants were the predominant OM sources of mangrove surface sediment. Based on the δ13C and lignin phenols, it can be concluded that the major OM sources in estuarine and coastal surface sediments were marine phytoplankton, riverine SPM and mangrove surface sediment. In addition, the higher (Ad/Al)v of lignin phenols in those coastal sediments indicate that seagrass might be a potential OM source in coastal sediments, however, the lower (Ad/Al)v in the estuarine sediments in turn suggests that seagrass could not be transported to the mangrove fringed region. A three-end-member model which is based on lignin concentrations and δ13C was applied to evaluate the contribution of mangroves to the organic matter preserved in the surface sediments. Around the mangrove fringed region, mangrove could contribute more than 50% to the sedimentary OM, and this value is much higher than riverine OM. Nevertheless, mangrove OM could not be efficiently transported to the coastal region. Our study suggests that mangrove forest is an important OM source in this small estuary.
2013, 32(4): 27-40.
doi: 10.1007/s13131-013-0296-2
Abstract:
Bedload sediment transport was estimated by the SEDTRANS96 model based on three-day hydrodynamics data obtained off the Dongfang coast in the Beibu Gulf during Typhoon Ketsana in September 2009. Bedforms on the sea floor off the Dongfang coast and internal structures of a typical dune were interpreted to evaluate storm influences on individual dunes and the dune field. Results indicated that flow forcings and related bedload transport were both strengthened significantly due to Typhoon Ketsana. The measurements and modeling results, which mainly included three different stages, presented noticeable phasic variation. The three stages were dominated by tidal current (Period I), tidal current combined with wind-induced waves (Period Ⅱ), and swells combined with tidal current and seaward flows (Period Ⅲ). This phasic variation could be a common trait of hydrodynamics due to typhoons moving westwardly to the south of Hainan Island and Beibu Gulf in South China Sea. Results indicated that the maximum bedload transport rate for every burst in Period Ⅲ was almost 100 times larger than that in Period I and was ten times larger than that in Period Ⅱ. However, the short-term increase in bedload transport induced by storms like Ketsana did not change the long-term evolution of dune morphology. Evidence was given by the internal structures of a typical dune, which revealed renewed modification under subsequent moderate conditions after storm erosion. Instead, storms may influence at different scales and regional allocation of sand dunes in some large areas because changes of the sea floor in large scales can hardly be recovered. More surveys during and after storm passage are also needed to document the level of positive contribution to forward migration.
Bedload sediment transport was estimated by the SEDTRANS96 model based on three-day hydrodynamics data obtained off the Dongfang coast in the Beibu Gulf during Typhoon Ketsana in September 2009. Bedforms on the sea floor off the Dongfang coast and internal structures of a typical dune were interpreted to evaluate storm influences on individual dunes and the dune field. Results indicated that flow forcings and related bedload transport were both strengthened significantly due to Typhoon Ketsana. The measurements and modeling results, which mainly included three different stages, presented noticeable phasic variation. The three stages were dominated by tidal current (Period I), tidal current combined with wind-induced waves (Period Ⅱ), and swells combined with tidal current and seaward flows (Period Ⅲ). This phasic variation could be a common trait of hydrodynamics due to typhoons moving westwardly to the south of Hainan Island and Beibu Gulf in South China Sea. Results indicated that the maximum bedload transport rate for every burst in Period Ⅲ was almost 100 times larger than that in Period I and was ten times larger than that in Period Ⅱ. However, the short-term increase in bedload transport induced by storms like Ketsana did not change the long-term evolution of dune morphology. Evidence was given by the internal structures of a typical dune, which revealed renewed modification under subsequent moderate conditions after storm erosion. Instead, storms may influence at different scales and regional allocation of sand dunes in some large areas because changes of the sea floor in large scales can hardly be recovered. More surveys during and after storm passage are also needed to document the level of positive contribution to forward migration.
2013, 32(4): 41-48.
doi: 10.1007/s13131-013-0297-1
Abstract:
The AHP-GDM model is used for the assessment of structural stability, with the Bohai Sea area as an example. In this model, the credit degree of each expert is calculated through the assessment matrix based on the similarity and diversity of vector. The comprehensive opinions of expert panel are quantitatively obtained by considering the effect of credit degree. According to the geological structural setting, the Bohai Sea is divided into twelve assessment zones of structural stability by non-uniform element method. The structural stability grade of each zone is obtained on the basis of the latest geophysical data, earthquake statistical data, and the information of fault activities, current stress field and crustal deformation. The results show that there are one relatively stable area, three relatively sub-stable areas, six relatively sub-unstable areas and two relatively unstable areas. The assessment results of non-uniform element method are very close with those of uniform grid method with size of 0.25° in longitude direction and 0.14° in latitude direction. However the workload of non-uniform element method is only 1/16 of the latter. Compared with traditional assessment methods of structural stability, a more objective and reliable assessment result can be obtained by combining non-uniform element method and AHP-GDM model.
The AHP-GDM model is used for the assessment of structural stability, with the Bohai Sea area as an example. In this model, the credit degree of each expert is calculated through the assessment matrix based on the similarity and diversity of vector. The comprehensive opinions of expert panel are quantitatively obtained by considering the effect of credit degree. According to the geological structural setting, the Bohai Sea is divided into twelve assessment zones of structural stability by non-uniform element method. The structural stability grade of each zone is obtained on the basis of the latest geophysical data, earthquake statistical data, and the information of fault activities, current stress field and crustal deformation. The results show that there are one relatively stable area, three relatively sub-stable areas, six relatively sub-unstable areas and two relatively unstable areas. The assessment results of non-uniform element method are very close with those of uniform grid method with size of 0.25° in longitude direction and 0.14° in latitude direction. However the workload of non-uniform element method is only 1/16 of the latter. Compared with traditional assessment methods of structural stability, a more objective and reliable assessment result can be obtained by combining non-uniform element method and AHP-GDM model.
2013, 32(4): 49-58.
doi: 10.1007/s13131-013-0281-9
Abstract:
The previous studies of the sedimentology and chronology of sediment core SYS-0701, which was recovered from the western South Huanghai Sea (Yellow Sea), have revealed the changes in the sea-level and sedimentary evolution during the late Quaternary in the region. The present study used mineralogical data from the section of the core deposited since Marine Isotope Stage (MIS) 3, to decipher the provenance of sediments of the paleo-delta deposited during MIS 3 and MIS 1. Based on the lithologic features and the variations with depth of the concentrations of carbonates and both heavy and light minerals in bulk samples, the upper part of Core SYS-0701 can be divided into three units designated DU1, DU4, and DU5, in accord with previously used terminology. Sub-units of units DU1 (DU1-1 and DU1-2) and DU4 (DU4-1 and DU4-2) have also been identified. DU1 was deposited during MIS 1, and DU4 and DU 5 were formed during MIS 3. All data pertaining to dominant heavy mineral assemblages, diagnostic minerals, ratios of diagnostic minerals, light mineral associations, textural maturities, and carbonate contents, indicate that the sediments of Core SYS-0701 are comparable with Huanghe River (Yellow River) sediments. Moreover, the mineralogy of the sediment evidenced its dependence on supply rates and hydrodynamic conditions. Weak hydrodynamics (DU5 and DU4-2) and/or low sediment supply (DU1-2) led to sediment containing less hornblende and epidote, with a large specific gravity and high content of flaky minerals, and vice versa in cases of strong hydrodynamics (DU4-1) and very large sediment supply (DU1-1).
The previous studies of the sedimentology and chronology of sediment core SYS-0701, which was recovered from the western South Huanghai Sea (Yellow Sea), have revealed the changes in the sea-level and sedimentary evolution during the late Quaternary in the region. The present study used mineralogical data from the section of the core deposited since Marine Isotope Stage (MIS) 3, to decipher the provenance of sediments of the paleo-delta deposited during MIS 3 and MIS 1. Based on the lithologic features and the variations with depth of the concentrations of carbonates and both heavy and light minerals in bulk samples, the upper part of Core SYS-0701 can be divided into three units designated DU1, DU4, and DU5, in accord with previously used terminology. Sub-units of units DU1 (DU1-1 and DU1-2) and DU4 (DU4-1 and DU4-2) have also been identified. DU1 was deposited during MIS 1, and DU4 and DU 5 were formed during MIS 3. All data pertaining to dominant heavy mineral assemblages, diagnostic minerals, ratios of diagnostic minerals, light mineral associations, textural maturities, and carbonate contents, indicate that the sediments of Core SYS-0701 are comparable with Huanghe River (Yellow River) sediments. Moreover, the mineralogy of the sediment evidenced its dependence on supply rates and hydrodynamic conditions. Weak hydrodynamics (DU5 and DU4-2) and/or low sediment supply (DU1-2) led to sediment containing less hornblende and epidote, with a large specific gravity and high content of flaky minerals, and vice versa in cases of strong hydrodynamics (DU4-1) and very large sediment supply (DU1-1).
2013, 32(4): 59-65.
doi: 10.1007/s13131-013-0298-0
Abstract:
The complete mitochondrial genome of the grey bamboo shark, Chiloscyllium griseum (Orectolobiformes:Hemiscylliidae) was obtained, with a total of 16 755 base pairs (bp). The mitogenome encoded 13 proteincoding genes, two ribosomal RNAs, 22 transfer RNAs and a noncoding control region, a gene arrangement identical to the most common type found in vertebrates. All tRNA sequences were folded into typical cloverleaf secondary structure with the exception of tRNA-Ser2, in which the DHU arm stem was replaced with 12 unpaired nucleotides and formed a simple loop. In the control region, the putative termination-associated sequences (TAS) with hairpin-loop structure and the conserved sequence blocks (CSB) I-Ⅲ were identified and considered to be associated with the replication and transcription of mtDNA. No repeat motifs were found in the mitogenome of C. griseum. On the basis of the mitogenomic data available in the Class Chondrichthyes from both Genbank and this study, and the phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) methods, the results strongly support the basal division between batoids and sharks and the monophyly of the Superorder Galeomorphii, and confirm the phylogenetic position of C. griseum in the Subclass Elasmobranchii. This study suggests that the mitogenomic data are more robust for reconstructing phylogenetic relationships than individual genes in the Elasmobranchii.
The complete mitochondrial genome of the grey bamboo shark, Chiloscyllium griseum (Orectolobiformes:Hemiscylliidae) was obtained, with a total of 16 755 base pairs (bp). The mitogenome encoded 13 proteincoding genes, two ribosomal RNAs, 22 transfer RNAs and a noncoding control region, a gene arrangement identical to the most common type found in vertebrates. All tRNA sequences were folded into typical cloverleaf secondary structure with the exception of tRNA-Ser2, in which the DHU arm stem was replaced with 12 unpaired nucleotides and formed a simple loop. In the control region, the putative termination-associated sequences (TAS) with hairpin-loop structure and the conserved sequence blocks (CSB) I-Ⅲ were identified and considered to be associated with the replication and transcription of mtDNA. No repeat motifs were found in the mitogenome of C. griseum. On the basis of the mitogenomic data available in the Class Chondrichthyes from both Genbank and this study, and the phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) methods, the results strongly support the basal division between batoids and sharks and the monophyly of the Superorder Galeomorphii, and confirm the phylogenetic position of C. griseum in the Subclass Elasmobranchii. This study suggests that the mitogenomic data are more robust for reconstructing phylogenetic relationships than individual genes in the Elasmobranchii.
2013, 32(4): 66-70.
doi: 10.1007/s13131-013-0299-z
Abstract:
Ciliates play a curial role in energy transfer from pico-and nano-phytoplankton to mesozooplankton in marine ecosystems. In order to visualize their geographical distributions from the Java Sea to the South China Sea (6°S to 20°N), the authors investigated the ciliate abundance and species composition in surface waters during May 18 to 27 of 2010. The ciliate abundance decreased latitudinally from 3 080 ind./L (~6°S) to 40 ind./L (~3°N), and then increased to 1 180 ind./L (~16°N) at the end of the survey. A total of 22 ciliates belonging to 15 genera were identified with the tintinnids accounted for 50% (11 species); and the species number showed a same spatial change as the ciliate abundance. Moreover, the Strombidium occupied over 50% of total ciliate abundance in most stations and Mesodinium and Tintinnopsis contributed to about 18.7% and 11.4%, respectively. In particular, our results indicate that the geographical changes in ciliate abundance were positively regulated by larger nano-and micro-phytoplankton biomass, rather than smaller pico-phytoplankton in the investigated waters.
Ciliates play a curial role in energy transfer from pico-and nano-phytoplankton to mesozooplankton in marine ecosystems. In order to visualize their geographical distributions from the Java Sea to the South China Sea (6°S to 20°N), the authors investigated the ciliate abundance and species composition in surface waters during May 18 to 27 of 2010. The ciliate abundance decreased latitudinally from 3 080 ind./L (~6°S) to 40 ind./L (~3°N), and then increased to 1 180 ind./L (~16°N) at the end of the survey. A total of 22 ciliates belonging to 15 genera were identified with the tintinnids accounted for 50% (11 species); and the species number showed a same spatial change as the ciliate abundance. Moreover, the Strombidium occupied over 50% of total ciliate abundance in most stations and Mesodinium and Tintinnopsis contributed to about 18.7% and 11.4%, respectively. In particular, our results indicate that the geographical changes in ciliate abundance were positively regulated by larger nano-and micro-phytoplankton biomass, rather than smaller pico-phytoplankton in the investigated waters.
2013, 32(4): 71-76.
doi: 10.1007/s13131-013-0300-x
Abstract:
The diversity and distribution of Pronoctiluca, a marine dinoflagellate of enigmatic systematic position, was studied in the vicinity of the Kuroshio and Oyashio Currents, the Philippines, Celebes, Sulu and South China Seas, western and central equatorial and southeast Pacific Ocean. The abundance of Pronoctiluca was higher, with a wide vertical distribution, in eutrophic temperate regions, whereas it was nearly absent in surface waters of oligotrophic tropical regions. Most of the specimens corresponded to P. spinifera. Pronoctiluca pelagica, covered by hyaline layers and with no flagella, is considered as an encysted form. The bipartition was only observed in P. acuta-P. spinifera forms, that together with the occurrence of intermediate forms between P. spinifera and P. pelagica suggest that they may correspond to developmental stages of a single species. Pronoctiluca is essential to understanding the evolutionary history of the alveolates.
The diversity and distribution of Pronoctiluca, a marine dinoflagellate of enigmatic systematic position, was studied in the vicinity of the Kuroshio and Oyashio Currents, the Philippines, Celebes, Sulu and South China Seas, western and central equatorial and southeast Pacific Ocean. The abundance of Pronoctiluca was higher, with a wide vertical distribution, in eutrophic temperate regions, whereas it was nearly absent in surface waters of oligotrophic tropical regions. Most of the specimens corresponded to P. spinifera. Pronoctiluca pelagica, covered by hyaline layers and with no flagella, is considered as an encysted form. The bipartition was only observed in P. acuta-P. spinifera forms, that together with the occurrence of intermediate forms between P. spinifera and P. pelagica suggest that they may correspond to developmental stages of a single species. Pronoctiluca is essential to understanding the evolutionary history of the alveolates.
2013, 32(4): 77-81.
doi: 10.1007/s13131-013-0301-9
Abstract:
The Strait of Malacca (SoM), the world's busiest sea-route, is increasingly polluted as the rapid development of world trades, affecting phytoplankton primary productivity therein. The variations of surface phytoplankton biomass, size-structure and carbon fixation were investigated across the SoM during the spring period (May 4 to 9, 2011). Chlorophyll a concentration increased from 0.12 μg/L at the northwest entrance of the SoM to a maximal 0.63 μg/L at narrowest section, and decreased to 0.10 μg/L at the southeast entrance. Photosynthetic carbon fixation by phytoplankton coincided well with Chl a biomass, and increased from 10.8 to 22.3 μg C/(L·d), then decreased to 9.21 μg C/(L·d); while the carbon fixation rate showed an inverse pattern to the changes of Chl a, and decreased from 87.1 to 35.5 μg C/(μg Chl a·d) and increased thereafter to 95.3 μg C/(μg Chl a·d). Picophytoplankton cells (<3 μm) contributed to more than 60% and 50% of the total Chl a and carbon fixation at both the entry waters; while the contributions of pico-cells decreased sharply to the minimum of 18.3% and 27.5% at the narrowest part of the SoM. In particular, our results showed that the silicate concentration positively regulated Chl a biomass and carbon fixation, reflecting that the higher silicate favoured the growth of phytoplankton and thus led to higher primary production in this strait.
The Strait of Malacca (SoM), the world's busiest sea-route, is increasingly polluted as the rapid development of world trades, affecting phytoplankton primary productivity therein. The variations of surface phytoplankton biomass, size-structure and carbon fixation were investigated across the SoM during the spring period (May 4 to 9, 2011). Chlorophyll a concentration increased from 0.12 μg/L at the northwest entrance of the SoM to a maximal 0.63 μg/L at narrowest section, and decreased to 0.10 μg/L at the southeast entrance. Photosynthetic carbon fixation by phytoplankton coincided well with Chl a biomass, and increased from 10.8 to 22.3 μg C/(L·d), then decreased to 9.21 μg C/(L·d); while the carbon fixation rate showed an inverse pattern to the changes of Chl a, and decreased from 87.1 to 35.5 μg C/(μg Chl a·d) and increased thereafter to 95.3 μg C/(μg Chl a·d). Picophytoplankton cells (<3 μm) contributed to more than 60% and 50% of the total Chl a and carbon fixation at both the entry waters; while the contributions of pico-cells decreased sharply to the minimum of 18.3% and 27.5% at the narrowest part of the SoM. In particular, our results showed that the silicate concentration positively regulated Chl a biomass and carbon fixation, reflecting that the higher silicate favoured the growth of phytoplankton and thus led to higher primary production in this strait.
2013, 32(4): 82-88.
doi: 10.1007/s13131-013-0302-8
Abstract:
Being a primary producer, Microphytobenthos (MPB) play an important role in the benthic ecosystem of mangrove swamps. The temporal and vertical distribution of MPB biomass, expressed as chlorophyll a (Chl a), was investigated in mangrove swamps on the Qi'ao island and the Futian Mangrove Nature Reserve, Guangdong Province, South China. Both locations are situated in the Zhujiang (Pearl River) Estuary. For each location, bi-monthly sampling was carried out at four sites during low tide period. Except one site on the Qi'ao Island, which was in Phragmites australis marsh, all sites were in mangrove swamps. The Chl a concentration in surface (0-1 cm) sediment ranged from 0.2 μg/cm3 to 8.3 μg/cm3 in the Qi'ao Island and from 2.1 μg/cm3 to 15.6 μg/cm3 in the Futian Mangrove Reserve. The peak Chl a concentration occurred in winter or early spring, while the lowest Chl a concentration, with a value of about one quarter of the peak, was observed in summer or early autumn. The vertical distribution of Chl a concentration exhibited an exponential decline with depth, which indicated a muddy sediment with high organic matter, and the slope of the curve was positively related to Chl a concentration in the surface sediment. The MPB biomass of the Qi'ao Island was significantly lower than that of the Futian Mangrove Reserve. Our results suggest that the overlaying water quality might influence the MPB biomass in surface sediments.
Being a primary producer, Microphytobenthos (MPB) play an important role in the benthic ecosystem of mangrove swamps. The temporal and vertical distribution of MPB biomass, expressed as chlorophyll a (Chl a), was investigated in mangrove swamps on the Qi'ao island and the Futian Mangrove Nature Reserve, Guangdong Province, South China. Both locations are situated in the Zhujiang (Pearl River) Estuary. For each location, bi-monthly sampling was carried out at four sites during low tide period. Except one site on the Qi'ao Island, which was in Phragmites australis marsh, all sites were in mangrove swamps. The Chl a concentration in surface (0-1 cm) sediment ranged from 0.2 μg/cm3 to 8.3 μg/cm3 in the Qi'ao Island and from 2.1 μg/cm3 to 15.6 μg/cm3 in the Futian Mangrove Reserve. The peak Chl a concentration occurred in winter or early spring, while the lowest Chl a concentration, with a value of about one quarter of the peak, was observed in summer or early autumn. The vertical distribution of Chl a concentration exhibited an exponential decline with depth, which indicated a muddy sediment with high organic matter, and the slope of the curve was positively related to Chl a concentration in the surface sediment. The MPB biomass of the Qi'ao Island was significantly lower than that of the Futian Mangrove Reserve. Our results suggest that the overlaying water quality might influence the MPB biomass in surface sediments.
