2016 Vol. 35, No. 10
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2016, 35(10): .
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2016, 35(10): 1-10.
doi: 10.1007/s13131-016-0922-x
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In this study, changes in Arctic sea ice thickness for each ice age category were examined based on satellite observations and modelled results. Interannual changes obtained from Ice, Cloud, and Land Elevation Satellite (ICESat)-based results show a thickness reduction over perennial sea ice (ice that survives at least one melt season with an age of no less than 2 year) up to approximately 0.5-1.0 m and 0.6-0.8 m (depending on ice age) during the investigated winter and autumn ICESat periods, respectively. Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)-based results provide a view of a continued thickness reduction over the past four decades. Compared to 1980s, there is a clear thickness drop of roughly 0.50 m in 2010s for perennial ice. This overall decrease in sea ice thickness can be in part attributed to the amplified warming climate in north latitudes. Besides, we figure out that strongly anomalous southerly summer surface winds may play an important role in prompting the thickness decline in perennial ice zone through transporting heat deposited in open water (primarily via albedo feedback) in Eurasian sector deep into a broader sea ice regime in central Arctic Ocean. This heat source is responsible for enhanced ice bottom melting, leading to further reduction in ice thickness.
In this study, changes in Arctic sea ice thickness for each ice age category were examined based on satellite observations and modelled results. Interannual changes obtained from Ice, Cloud, and Land Elevation Satellite (ICESat)-based results show a thickness reduction over perennial sea ice (ice that survives at least one melt season with an age of no less than 2 year) up to approximately 0.5-1.0 m and 0.6-0.8 m (depending on ice age) during the investigated winter and autumn ICESat periods, respectively. Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)-based results provide a view of a continued thickness reduction over the past four decades. Compared to 1980s, there is a clear thickness drop of roughly 0.50 m in 2010s for perennial ice. This overall decrease in sea ice thickness can be in part attributed to the amplified warming climate in north latitudes. Besides, we figure out that strongly anomalous southerly summer surface winds may play an important role in prompting the thickness decline in perennial ice zone through transporting heat deposited in open water (primarily via albedo feedback) in Eurasian sector deep into a broader sea ice regime in central Arctic Ocean. This heat source is responsible for enhanced ice bottom melting, leading to further reduction in ice thickness.
2016, 35(10): 11-19.
doi: 10.1007/s13131-016-0898-6
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A detailed survey of the reefs in the Nansha Islands' sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager (OLI) images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks, reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm (OTSU method) and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization, simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online (http://www.nansha.org/). Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast. An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution (15 m for OLI image) is expected to provide an optimum satellite based approach to map marine habitats.
A detailed survey of the reefs in the Nansha Islands' sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager (OLI) images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks, reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm (OTSU method) and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization, simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online (http://www.nansha.org/). Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast. An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution (15 m for OLI image) is expected to provide an optimum satellite based approach to map marine habitats.
2016, 35(10): 20-27.
doi: 10.1007/s13131-016-0917-7
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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 SiO3-Si after the late autumn, is one of major reasons inducing the diatom bloom in winter, and the bloom was finally controlled due to SiO3-Si depletion by phytoplankton. The bloom was mainly controlled by SiO3-Si. Before 1998, relatively low level of SiO3-Si kept ecological balance of eutrophication waters in the Jiaozhou Bay. In recent years, however, human activities have increased SiO3-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 SiO3-Si concentration in the Jiaozhou Bay.
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 SiO3-Si after the late autumn, is one of major reasons inducing the diatom bloom in winter, and the bloom was finally controlled due to SiO3-Si depletion by phytoplankton. The bloom was mainly controlled by SiO3-Si. Before 1998, relatively low level of SiO3-Si kept ecological balance of eutrophication waters in the Jiaozhou Bay. In recent years, however, human activities have increased SiO3-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 SiO3-Si concentration in the Jiaozhou Bay.
2016, 35(10): 28-36.
doi: 10.1007/s13131-016-0920-z
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Metal pollution in aquatic ecosystems is of immense importance. Under various environment circumstances, the metal contents of sediments can enter into the overlying water body leading to severe toxicity. This study aims to determine metal concentrations in sediments of Anzali International Wetland in Iran. Chemical partitioning method is used to determine the portion of anthropogenic pollution and the mobility potential of each metal. The intensity of metal pollution in sediments of the wetland is assessed using three reliable indices. The results of chemical partitioning reveal that cadmium bear the highest risk of being released into the aquatic environment and high amount of manganese in sulfide bond phase implies the initiation of redox state in aquatic environment of the Anzali Wetland. The results of chemical partitioning studies show that Pb, Cd, Mn and As have the highest anthropogenic portion. Cluster analysis also confirms the results of chemical partitioning and indicates that the mentioned metals can be originated from anthropogenic sources. Sediment pollution indices, including, Igeo, IPOLL, and m-ERM-Q reveal that metals are in the range of low to moderate pollution and also show that the highest metal pollution is in the eastern and central parts of the wetland. This can be ascribed to rivers which are the recipient of industrial, agricultural and municipal wastewaters and flow into these parts of the wetland.
Metal pollution in aquatic ecosystems is of immense importance. Under various environment circumstances, the metal contents of sediments can enter into the overlying water body leading to severe toxicity. This study aims to determine metal concentrations in sediments of Anzali International Wetland in Iran. Chemical partitioning method is used to determine the portion of anthropogenic pollution and the mobility potential of each metal. The intensity of metal pollution in sediments of the wetland is assessed using three reliable indices. The results of chemical partitioning reveal that cadmium bear the highest risk of being released into the aquatic environment and high amount of manganese in sulfide bond phase implies the initiation of redox state in aquatic environment of the Anzali Wetland. The results of chemical partitioning studies show that Pb, Cd, Mn and As have the highest anthropogenic portion. Cluster analysis also confirms the results of chemical partitioning and indicates that the mentioned metals can be originated from anthropogenic sources. Sediment pollution indices, including, Igeo, IPOLL, and m-ERM-Q reveal that metals are in the range of low to moderate pollution and also show that the highest metal pollution is in the eastern and central parts of the wetland. This can be ascribed to rivers which are the recipient of industrial, agricultural and municipal wastewaters and flow into these parts of the wetland.
2016, 35(10): 37-47.
doi: 10.1007/s13131-016-0923-9
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Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in the current velocity was observed in the South Branch as a result of high river runoff and tide deformation, in which the magnitude and duration of ebb currents were significantly greater than those of flood currents. The suspended sediment concentration (SSC) and suspended median grain size also exhibited remarkable flood-ebb variation; these variables were considerably larger during the ebb than during the flood and increased from neap to spring tide. Affected by the strong asymmetry in the current velocity and SSC between the flood and ebb, suspended sediment flux during the ebb was notably larger than during the flood, and a seaward tidal net flux was observed in each tidal cycle. The balance of sediment flux illustrates that the seaward sediment transport was dominated by river flow and tidal trapping and the landward sediment transport was dominated by the Stokes drift and the shear effect. Notable resuspension occurred during the spring and moderate tides. The critical velocity for the resuspension of bed sediments was estimated based on the correlation between current velocity with SSC and suspended median grain size. The results show that the critical velocity was approximately 40 cm/s during the flood phases and approximately 80 cm/s during the ebb phases because the surficial flood bed sediments located in the lower reach are much finer than the surficial ebb bed sediments located in the upper reach. The flood-ebb variation in the critical erosion velocity has significant effect on the intratidal variation of SSC and sediment transport process, and it is a common phenomenon in many estuaries of the world due to the complicated spatial distribution of bed sediments.
Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in the current velocity was observed in the South Branch as a result of high river runoff and tide deformation, in which the magnitude and duration of ebb currents were significantly greater than those of flood currents. The suspended sediment concentration (SSC) and suspended median grain size also exhibited remarkable flood-ebb variation; these variables were considerably larger during the ebb than during the flood and increased from neap to spring tide. Affected by the strong asymmetry in the current velocity and SSC between the flood and ebb, suspended sediment flux during the ebb was notably larger than during the flood, and a seaward tidal net flux was observed in each tidal cycle. The balance of sediment flux illustrates that the seaward sediment transport was dominated by river flow and tidal trapping and the landward sediment transport was dominated by the Stokes drift and the shear effect. Notable resuspension occurred during the spring and moderate tides. The critical velocity for the resuspension of bed sediments was estimated based on the correlation between current velocity with SSC and suspended median grain size. The results show that the critical velocity was approximately 40 cm/s during the flood phases and approximately 80 cm/s during the ebb phases because the surficial flood bed sediments located in the lower reach are much finer than the surficial ebb bed sediments located in the upper reach. The flood-ebb variation in the critical erosion velocity has significant effect on the intratidal variation of SSC and sediment transport process, and it is a common phenomenon in many estuaries of the world due to the complicated spatial distribution of bed sediments.
2016, 35(10): 48-55.
doi: 10.1007/s13131-016-0919-5
Abstract:
Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30-40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30-40 ka BP spanned a period in the late Marine Isotope Stage 3 (MIS 3) and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level (HS) was defined as the glaciation-climate-forced sea levels, and the relative sea level change (HR) was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago, whereas the simulated relative sea-levels turned out to be-26.3--29.9 m a.s.l. The small error involved in the simulation results of ±(2.5-4.5) m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between-19.2--22.1 m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.
Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30-40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30-40 ka BP spanned a period in the late Marine Isotope Stage 3 (MIS 3) and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level (HS) was defined as the glaciation-climate-forced sea levels, and the relative sea level change (HR) was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago, whereas the simulated relative sea-levels turned out to be-26.3--29.9 m a.s.l. The small error involved in the simulation results of ±(2.5-4.5) m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between-19.2--22.1 m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.
2016, 35(10): 56-62.
doi: 10.1007/s13131-016-0895-9
Abstract:
A study of coccolith assemblages from a box core from the central South Yellow Sea (SYS) was performed revealing fluctuations on their relative abundance (%) that can be related to climatic and hydrographic changes over the last 230 years (1780-2011). Total coccolith abundances ranged from 7.0 to 55.1×106 coccoliths·g-1 sediment. Although the abundance of different species varied widely throughout the core, seven taxa dominated the assemblage. Among these species, Gephyrocapsa oceanica was the most dominant species, and it showed an average percentage of 50.1%. The pattern of G. oceanica (eutrophic species) was opposite to that of the combined percentage of Braarudosphaera bigelowii and Umbilicosphaera sibogae (both oligotrophic species), indicating that in the Yellow Sea (YS), the distribution pattern of G. oceanica might be characteristic of nutrient availability. Similar patterns between G. oceanica and the Siberian High were observed on an inter-decadal time scale, indicating that the East Asian Winter Monsoon (EAWM) may be an important driver of ecological changes in the YS. When the EAWM prevails, both the Yellow Sea Coastal Current (YSCC) and Yellow Sea Warm Current (YSWC) strengthen, and the increasing nutrient availability and warmer water brought by the strengthened YSWC favor eutrophic and warm-water coccolithophore species, such as G. oceanica. This likely mechanism demonstrates that coccolith assemblages can be used as benign and reliable proxy for climate change and surface oceanography.
A study of coccolith assemblages from a box core from the central South Yellow Sea (SYS) was performed revealing fluctuations on their relative abundance (%) that can be related to climatic and hydrographic changes over the last 230 years (1780-2011). Total coccolith abundances ranged from 7.0 to 55.1×10
2016, 35(10): 63-75.
doi: 10.1007/s13131-016-0890-1
Abstract:
Horizontal and vertical distributions of δ18O and δ13C were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ18O and δ13C of these four species were linked to freshwater input. In the Bali Sea, however, depleted δ18O and δ13C for these species may be due to different reasons. Depleted δ18O was a result of freshwater input and as well influenced by along-shore currents while depleted δ13C was more likely due to the Java-Sumatra upwelling. Comparison of shell δ18O records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0-50 m and 20-75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75-125 m water depth. N. dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ13C values of both G. ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.
Horizontal and vertical distributions of δ18O and δ13C were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ18O and δ13C of these four species were linked to freshwater input. In the Bali Sea, however, depleted δ18O and δ13C for these species may be due to different reasons. Depleted δ18O was a result of freshwater input and as well influenced by along-shore currents while depleted δ13C was more likely due to the Java-Sumatra upwelling. Comparison of shell δ18O records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0-50 m and 20-75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75-125 m water depth. N. dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ13C values of both G. ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.
2016, 35(10): 76-82.
doi: 10.1007/s13131-016-0915-9
Abstract:
This study was aimed at examining the phylogenetic and morphometric relationship of frigate tuna (Auxis thazard) and bullet tuna (Auxis rochei) using mtDNA D-loop (control) region sequences and truss measurements, respectively. Maximum-likelihood (ML) tree and median-joining network showed that haplotypes from Auxis populations grouped separately. Discriminant function analyses and non-metric multidimensional scaling of morphometric data showed that bullet and frigate tuna were differed mainly with respect to truss measurements on the anterior region, suggesting adaptation to different diets available in different environments. Historic demographic analyses of sequence data showed that both bullet and frigate tuna had not undergone a significant sudden population expansion recently. Non-significant value of Tajimas's D and Fu's FS were indicated an effective large and stable population size for longer period of both species in South China Sea and Java Sea species. This study gives first report on the complementary relationship between morphometric and genetic analysis in stock discrimination of genus Auxis.
This study was aimed at examining the phylogenetic and morphometric relationship of frigate tuna (Auxis thazard) and bullet tuna (Auxis rochei) using mtDNA D-loop (control) region sequences and truss measurements, respectively. Maximum-likelihood (ML) tree and median-joining network showed that haplotypes from Auxis populations grouped separately. Discriminant function analyses and non-metric multidimensional scaling of morphometric data showed that bullet and frigate tuna were differed mainly with respect to truss measurements on the anterior region, suggesting adaptation to different diets available in different environments. Historic demographic analyses of sequence data showed that both bullet and frigate tuna had not undergone a significant sudden population expansion recently. Non-significant value of Tajimas's D and Fu's FS were indicated an effective large and stable population size for longer period of both species in South China Sea and Java Sea species. This study gives first report on the complementary relationship between morphometric and genetic analysis in stock discrimination of genus Auxis.
2016, 35(10): 83-87.
doi: 10.1007/s13131-016-0888-8
Abstract:
Half-smooth tongue sole (Cynoglossus semilaevis) is a commercially important fish species. There were no reports about accurate genetic parameters of growth traits in C. semilaevis, despite efforts aimed at the culture of this species. Therefore, the main goal of this study was to estimate the parameters for the early growth traits (total length, body depth and body weight) of C. semilaevis based on the data obtained from 80 families. The trait of fish with pure white bottom or not (named as the trait of bottom color) was also analyzed. All the heritabilities estimated for the traits were medium, which varied from 0.210 to 0.362. Genetic correlations among growth traits were highly positive, varying from 0.913 to 0.959, indicating that selection of one of the three traits would result in correlated increase in the others. Also, genetic correlations between bottom color and growth traits were positive and varying from 0.241 to 0.353, suggesting that selection for the bottom color can be utilized to enhance the selection of growth traits. In addition, fish from the top performing 16 full-sib families were selected as broodstock, based on the above analysis and the comparison of family breeding value. This research provides an important basic material to implement selective breeding in C. semilaevis.
Half-smooth tongue sole (Cynoglossus semilaevis) is a commercially important fish species. There were no reports about accurate genetic parameters of growth traits in C. semilaevis, despite efforts aimed at the culture of this species. Therefore, the main goal of this study was to estimate the parameters for the early growth traits (total length, body depth and body weight) of C. semilaevis based on the data obtained from 80 families. The trait of fish with pure white bottom or not (named as the trait of bottom color) was also analyzed. All the heritabilities estimated for the traits were medium, which varied from 0.210 to 0.362. Genetic correlations among growth traits were highly positive, varying from 0.913 to 0.959, indicating that selection of one of the three traits would result in correlated increase in the others. Also, genetic correlations between bottom color and growth traits were positive and varying from 0.241 to 0.353, suggesting that selection for the bottom color can be utilized to enhance the selection of growth traits. In addition, fish from the top performing 16 full-sib families were selected as broodstock, based on the above analysis and the comparison of family breeding value. This research provides an important basic material to implement selective breeding in C. semilaevis.
2016, 35(10): 88-95.
doi: 10.1007/s13131-016-0916-8
Abstract:
Coral transplantation is considered as one of the major tools to increase coral abundance for degraded coral reefs. To investigate the effects of various methods and coral species in transplantation, coral fragments (n=902) of five coral species were transplanted by four methods at Luhuitou, the Sanya Bay, Hainan Province, China, where the reef has been over-exploited and is still threatened by human activities and natural disasters. Ten months after the transplant, the average survivorship of the transplanted corals was 45.5%. Methodologies had different effects on the transplanted corals, but none of them was efficacious for all coral species. Methodology could not change the decreasing trend for Montipora foliosa and Acropora hyacinthus, although it did slow down their decline. All transplants of A. hyacinthus and M. foliosa had high mortalities and significant decrease on survival area, while Porites andrewsi and Galaxea fascicularis had lower mortalities and partial mortalities. Only one method had significant effect on increasing survival area of G. fascicularis, same as P. andrewsi. Out of the five transplanted coral species, Pocillopora damicornis was the only species that had living tissue area increase in all applied methods, while the others had decreased live tissue area in one or more methods. The results of this study suggested that performing coral transplantation in a highly threatened area was not efficient unless the threats were diminished or erased. Moreover, proper species selection for coral transplantation is crucial, especially in a disturbed environment. Methodology, although having limited effects on improving results of coral transplantation, cannot compensate the maladjustment of vulnerable species to the stresses on the Luhuitou Reef. Coral transplantation on Luhuitou Reef should not be performed unless the stresses are under controlled, and corals with good tolerance to the environment should be considered first.
Coral transplantation is considered as one of the major tools to increase coral abundance for degraded coral reefs. To investigate the effects of various methods and coral species in transplantation, coral fragments (n=902) of five coral species were transplanted by four methods at Luhuitou, the Sanya Bay, Hainan Province, China, where the reef has been over-exploited and is still threatened by human activities and natural disasters. Ten months after the transplant, the average survivorship of the transplanted corals was 45.5%. Methodologies had different effects on the transplanted corals, but none of them was efficacious for all coral species. Methodology could not change the decreasing trend for Montipora foliosa and Acropora hyacinthus, although it did slow down their decline. All transplants of A. hyacinthus and M. foliosa had high mortalities and significant decrease on survival area, while Porites andrewsi and Galaxea fascicularis had lower mortalities and partial mortalities. Only one method had significant effect on increasing survival area of G. fascicularis, same as P. andrewsi. Out of the five transplanted coral species, Pocillopora damicornis was the only species that had living tissue area increase in all applied methods, while the others had decreased live tissue area in one or more methods. The results of this study suggested that performing coral transplantation in a highly threatened area was not efficient unless the threats were diminished or erased. Moreover, proper species selection for coral transplantation is crucial, especially in a disturbed environment. Methodology, although having limited effects on improving results of coral transplantation, cannot compensate the maladjustment of vulnerable species to the stresses on the Luhuitou Reef. Coral transplantation on Luhuitou Reef should not be performed unless the stresses are under controlled, and corals with good tolerance to the environment should be considered first.
2016, 35(10): 96-106.
doi: 10.1007/s13131-016-0893-y
Abstract:
A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmental condition. The southeast coast of China is a typical region under the intensive influence of Asia monsoon and freshwater discharge from rivers. The water mass and environmental condition of the Hangzhou Bay, which were influenced by the interaction of currents, freshwater discharge of the Qiantang River and Changjiang River Plume, showed significant seasonal variation. Our results showed that both biomass and abundance were significantly higher in summer ((247.7±148.8) mg/m3 and (350.9±215.6) ind./m3, respectively) than those in other seasons. Four eco-geographical regions were divided based on the cluster analysis of zooplankton community of the Hangzhou Bay throughout the year, except for winter. Monsoon and the dissolved inorganic nitrogen (DIN) input from freshwater discharge of the Qiantang River and Changjiang River resulted in temporal and spatial variations of environmental gradient in the Hangzhou Bay, which significantly influenced the structure of mesozooplankton community. Redundancy analysis (RDA) indicated that the mesozooplankton community structure was strictly correlated with the DIN gradient, while salinity gradient showed a weak influence in the Hangzhou Bay.
A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmental condition. The southeast coast of China is a typical region under the intensive influence of Asia monsoon and freshwater discharge from rivers. The water mass and environmental condition of the Hangzhou Bay, which were influenced by the interaction of currents, freshwater discharge of the Qiantang River and Changjiang River Plume, showed significant seasonal variation. Our results showed that both biomass and abundance were significantly higher in summer ((247.7±148.8) mg/m3 and (350.9±215.6) ind./m3, respectively) than those in other seasons. Four eco-geographical regions were divided based on the cluster analysis of zooplankton community of the Hangzhou Bay throughout the year, except for winter. Monsoon and the dissolved inorganic nitrogen (DIN) input from freshwater discharge of the Qiantang River and Changjiang River resulted in temporal and spatial variations of environmental gradient in the Hangzhou Bay, which significantly influenced the structure of mesozooplankton community. Redundancy analysis (RDA) indicated that the mesozooplankton community structure was strictly correlated with the DIN gradient, while salinity gradient showed a weak influence in the Hangzhou Bay.
2016, 35(10): 107-113.
doi: 10.1007/s13131-016-0894-x
Abstract:
Bacterial abundance, phytoplankton community structure and environmental parameters were investigated to study the relationships between bacteria and phytoplankton during giant jellyfish Nemopilema nomurai blooms in the central Yellow Sea during 2013. N. nomurai appeared in June, increased in August, reached a peak and began to degrade in September 2013. Results showed that phosphate was possible a key nutrient for both phytoplankton and bacteria in June, but it changed to nitrate in August and September. Phytoplankton composition significantly changed that pico-phytoplankton relative biomass significantly increased, whereas other size phytoplankton significantly decreased during jellyfish bloom. In June, a significantly positive correlation was observed between chlorophyll a concentration and bacterial abundance (r=0.67, P<0.001, n=34). During jellyfish outbreak in August, there was no significant correlation between phytoplankton and bacteria (r=0.11, P>0.05, n=25), but the relationship (r=0.71, P<0.001, n=31) was rebuilt with jellyfish degradation in September. In August, small size phytoplankton occupied the mixed layer in offshore stations, while bacteria almost distributed evenly in vertical. chlorophyll a concentration significantly increased from (0.42±0.056) μg/L in June to (0.74±0.174) μg/L in August, while bacterial abundance just slightly increased. Additionally, the negative net community production indicated that community respiration was not entirely determined by the local primary productivity in August. These results indicated that jellyfish blooms potentially affect coupling of phytoplankton and bacteria in marine ecosystems.
Bacterial abundance, phytoplankton community structure and environmental parameters were investigated to study the relationships between bacteria and phytoplankton during giant jellyfish Nemopilema nomurai blooms in the central Yellow Sea during 2013. N. nomurai appeared in June, increased in August, reached a peak and began to degrade in September 2013. Results showed that phosphate was possible a key nutrient for both phytoplankton and bacteria in June, but it changed to nitrate in August and September. Phytoplankton composition significantly changed that pico-phytoplankton relative biomass significantly increased, whereas other size phytoplankton significantly decreased during jellyfish bloom. In June, a significantly positive correlation was observed between chlorophyll a concentration and bacterial abundance (r=0.67, P<0.001, n=34). During jellyfish outbreak in August, there was no significant correlation between phytoplankton and bacteria (r=0.11, P>0.05, n=25), but the relationship (r=0.71, P<0.001, n=31) was rebuilt with jellyfish degradation in September. In August, small size phytoplankton occupied the mixed layer in offshore stations, while bacteria almost distributed evenly in vertical. chlorophyll a concentration significantly increased from (0.42±0.056) μg/L in June to (0.74±0.174) μg/L in August, while bacterial abundance just slightly increased. Additionally, the negative net community production indicated that community respiration was not entirely determined by the local primary productivity in August. These results indicated that jellyfish blooms potentially affect coupling of phytoplankton and bacteria in marine ecosystems.
2016, 35(10): 114-121.
doi: 10.1007/s13131-016-0891-0
Abstract:
Intensive Pyropia aquaculture in the coast of southwestern Yellow Sea and its subsequent waste, including disposed Ulva prolifera, was speculated to be one of the major sources for the large-scale green tide proceeding in the Yellow Sea since 2007. It was, however, unclear how the detached U. prolifera responded and resumed growing after they detached from its original habitat. In this study, we investigated the growth and photosynthetic response of the detached U. prolifera to various temperature, salinity and irradiance in the laboratory. The photosynthetic rate of the detached U. prolifera was significantly higher at moderate temperature levels (14-27℃) and high salinity (26-32), with optimum at 23℃ and 32. Both low (<14℃) and highest temperature (40℃), as well as low salinity (8) had adverse effects on the photosynthesis. Compared with the other Ulva species, U. prolifera showed higher saturated irradiance and no significant photoinhibition at high irradiance, indicating the great tolerance of U. prolifera to the high irradiance. The dense branch and complex structure of floating mats could help protect the thalli and reduce photoinhibition in field. Furthermore, temperature exerted a stronger influence on the growth rate of the detached U. prolifera compared to salinity. Overall, the high growth rate of this detached U. prolifera (10.6%-16.7% d-1) at a wide range of temperature (5-32℃) and salinity (14-32) implied its blooming tendency with fluctuated salinity and temperature during floating. The environmental parameters in the southwestern Yellow Sea at the beginning of green tide were coincident with the optimal conditions for the detached U. prolifera.
Intensive Pyropia aquaculture in the coast of southwestern Yellow Sea and its subsequent waste, including disposed Ulva prolifera, was speculated to be one of the major sources for the large-scale green tide proceeding in the Yellow Sea since 2007. It was, however, unclear how the detached U. prolifera responded and resumed growing after they detached from its original habitat. In this study, we investigated the growth and photosynthetic response of the detached U. prolifera to various temperature, salinity and irradiance in the laboratory. The photosynthetic rate of the detached U. prolifera was significantly higher at moderate temperature levels (14-27℃) and high salinity (26-32), with optimum at 23℃ and 32. Both low (<14℃) and highest temperature (40℃), as well as low salinity (8) had adverse effects on the photosynthesis. Compared with the other Ulva species, U. prolifera showed higher saturated irradiance and no significant photoinhibition at high irradiance, indicating the great tolerance of U. prolifera to the high irradiance. The dense branch and complex structure of floating mats could help protect the thalli and reduce photoinhibition in field. Furthermore, temperature exerted a stronger influence on the growth rate of the detached U. prolifera compared to salinity. Overall, the high growth rate of this detached U. prolifera (10.6%-16.7% d-1) at a wide range of temperature (5-32℃) and salinity (14-32) implied its blooming tendency with fluctuated salinity and temperature during floating. The environmental parameters in the southwestern Yellow Sea at the beginning of green tide were coincident with the optimal conditions for the detached U. prolifera.
