Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples fr...Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.展开更多
The dissolved organic carbon(DOC)in the surface water of Huguangyan Maar Lake was continuously monitored based on once per week sampling frequency of 4 locations from June 2018 to May 2019.The DOC concentrations and i...The dissolved organic carbon(DOC)in the surface water of Huguangyan Maar Lake was continuously monitored based on once per week sampling frequency of 4 locations from June 2018 to May 2019.The DOC concentrations and its seasonal variation were discussed by correlating with the rainfall,water temperature,and p H of lake water.The results showed that the weekly DOC varied from 8.15 to 32.65 mg/L with an annual average concentration of 17.96 mg/L.There was a significant difference in the average DOC concentrations between the rainy and dry seasons as the monthly average DOC concentration was 21.72 mg/L for the wet season compared to the dry season concentration of 14.21 mg/L.The rainfall shows a significant effect on the DOC concentration of lake water,as DOC concentration was much high during the wet season.There were no significant spatial variations in the average monthly concentration among the four sampling locations except occasional variation during the wet season.The reason for the wet season DOC differences among four sampling locations is likely due to the uneven runoff and underground water inputs and the relatively slow circulation of lake water.Finally,the seasonal fluctuation of DOC concentration in this closed lake water suggests that dissolved soil organic matter inputs through the rainfall related to surface runoff and subsurface infiltration from the surrounding watershed land is important to the primary production and organic matter deposition in the lake sediments.展开更多
The Huguangyan Maar Lake（HML）（21°9＇N,110°17＇E）,situated on the Leizhou Peninsula in the southernmost of China's Mainland,is the deepest recent crater lake among the identified volcanic structures i...The Huguangyan Maar Lake（HML）（21°9＇N,110°17＇E）,situated on the Leizhou Peninsula in the southernmost of China's Mainland,is the deepest recent crater lake among the identified volcanic structures in the Leiqiong Volcanic Field.The bi-lobate lake.展开更多
To mark the occasion of the 175th anniversary of the Rheinische Naturforschende Gesellschaft in 2009 and of the centennial of the Mainz Natural History Museum in 2010, we present a short account of our present knowled...To mark the occasion of the 175th anniversary of the Rheinische Naturforschende Gesellschaft in 2009 and of the centennial of the Mainz Natural History Museum in 2010, we present a short account of our present knowledge of the Eckfeld Maar after 20 years of continuous research. This paper does not attempt to include all of the detailed results on the geology of the Eckfeld site or its biota. To date, nearly 250 papers and books have been published since the start of our project. An up-to-date list of these publications can be found at www.eckfeldermaar.de.展开更多
The Barombi Mbo Maar (BMM), which is the largest maar in Cameroon, possesses about 126 m-thick well-preserved pyroclastic deposits sequence in which two successive paleosoil beds have been identified. The maar was tho...The Barombi Mbo Maar (BMM), which is the largest maar in Cameroon, possesses about 126 m-thick well-preserved pyroclastic deposits sequence in which two successive paleosoil beds have been identified. The maar was thought to have been active a million years ago. However, layers stratigraphically separated by the identified paleosoils have been dated to shed lights on its age and to reconstruct the chronology of its past activity. The results showed that the BMM formed through three eruptive cycles: the first ~0.51 Ma ago, the second at ~0.2 Ma and the third ~0.08 Ma B.P. The ages indicate that the BMM maar-forming eruptions were younger than a million years. The findings also suggested that the maar is polygenetic. At a regional scale, the eruptive events would have occurred during some volcanic manifestations at Mt Manengouba and Mt Cameroon. Therefore, with the decrease in the recurrence time of eruptions from ~0.3 Ma to 0.1 Ma, and given the possible relation between its eruptive events and those of its neighboring polygenetic volcanoes, the BMM is expected to erupt within the next 20 ka.展开更多
The Bambili maars are twin contemporaneous maars embedded in trachytic rocks. The two maars are separated by a low lying inter-Maar dome whose inner walls dip towards the Southern Maar. The Bambili Northern Maar (BNM)...The Bambili maars are twin contemporaneous maars embedded in trachytic rocks. The two maars are separated by a low lying inter-Maar dome whose inner walls dip towards the Southern Maar. The Bambili Northern Maar (BNM) contains water and its floor is found at an altitude lower than the Bambili Southern Maar (BSM) (50 m) which is swampy and drains into the BNM. Both maars have very steep vertical walls. Three different units are identified in the area. Unit 1 is 1 m thick sequence, characterize by the presence of matrix supported fine-grained fallouts (ash and lapilli size) with stratified diffused bedding planes. This unit is further subdivided into three different layers: L1, L2 and L3 from bottom to top with increasing sizes of particles respectively. This layer shows reverser grading and its grain sizes rarely exceed 2 cm and this unit shows no depositional structures. Unit 2 is an unstratified unit predominantly made up of tephra deposits. Within these deposits are found blocks of sizes ranging between 2 and 10 cm of different petrographic types. They include scoria, basalts, trachyte, and granite cognate. The last unit, Unit 3 is distinctly stratified characterized by well sorted, heterolithologic, graded bedding layers which are matrix supported. Base on the composition and grain sizes, this unit was subdivided into 7 horizons: h1 - h7. Within this unit, two sequences of deposits are distinguished: U1 and U2. Both sequences are characterized by alternation of lapilli and tuff beds. The clast comprises of juvenile materials, mudstone which are highly vesicular and altered rock fragments. Other products identified within the area are ferolithic volcanic bombs (5 - 20 cm), xenocrystals (2 - 4 cm) within finer deposits. They are elongated and show visible twinned planes. Explosion breccias are equally identified occurring as bolders. Along the inner walls of the maars are also found large basaltic and trachytic blocks which are remnants of pre-maar unit within maar deposits. The model proposed indicates the maars were emplaced simultaneously from adjacent vents followed by a succession of lava flows and pyroclastic ejections.展开更多
Located in Xilin Gol League of Inner Mongolia Autonomous Region,the Xilinhot-Abaga volcanic cluster is in the centre of the Daxing’anling-Datong volcanic eruption belt.More than 300 Quaternary basaltic volcanoes of d...Located in Xilin Gol League of Inner Mongolia Autonomous Region,the Xilinhot-Abaga volcanic cluster is in the centre of the Daxing’anling-Datong volcanic eruption belt.More than 300 Quaternary basaltic volcanoes of different types are developed in the volcanic eruption belt.Maars are found for the first time in the study area,with those in Haotewula in the southeast of Abagaqi,and Chelewula and Esigewula in the northwest of Abagaqi to be the most representative.They all are large in scale,with cone diameters generally 3~4km,with the largest up to 6.5km.The maars show intact structure,a similar two-ringed mountain landscape and obviously phased eruption which contained a vigorous phreatomagmatic explosion at the earlier stage,and weak magmatic explosion at the later stage,and basaltic lava effusion in the last stage.The eruption sequence reflects the interaction between magma and water,the change of intrusive speed and outflow rate of magma.The Middle Pleistocene deposits of sand and gravel in the valley are covered by basal surge deposits.The TL age of sandstone-shale 'xenolith'which was found in the spatter deposits close to the crater is( 0.112 ± 0.0096) Ma,indicating that the eruption time of the Maars was the early Late Pleistocene.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41576123,41706129)the Guangdong Natural Science Foundation(Nos.2015A030313326,2016A030312004)+2 种基金the International Science and Technology Cooperation Project(No.GASI-IPOVI-04)the Project of Enhancing School with Innovation of Guangdong Ocean University(No.GDOU2016050243)the Program for Scientific Research Start-Up Funds of Guangdong Ocean University(No.E15030)
文摘Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.
基金the Special Talent Support Program of Guangdong Ocean University(No.R17001)the Project of Marine geochemistry and climate change of Guangdong Ocean University(No.002026002004)。
文摘The dissolved organic carbon(DOC)in the surface water of Huguangyan Maar Lake was continuously monitored based on once per week sampling frequency of 4 locations from June 2018 to May 2019.The DOC concentrations and its seasonal variation were discussed by correlating with the rainfall,water temperature,and p H of lake water.The results showed that the weekly DOC varied from 8.15 to 32.65 mg/L with an annual average concentration of 17.96 mg/L.There was a significant difference in the average DOC concentrations between the rainy and dry seasons as the monthly average DOC concentration was 21.72 mg/L for the wet season compared to the dry season concentration of 14.21 mg/L.The rainfall shows a significant effect on the DOC concentration of lake water,as DOC concentration was much high during the wet season.There were no significant spatial variations in the average monthly concentration among the four sampling locations except occasional variation during the wet season.The reason for the wet season DOC differences among four sampling locations is likely due to the uneven runoff and underground water inputs and the relatively slow circulation of lake water.Finally,the seasonal fluctuation of DOC concentration in this closed lake water suggests that dissolved soil organic matter inputs through the rainfall related to surface runoff and subsurface infiltration from the surrounding watershed land is important to the primary production and organic matter deposition in the lake sediments.
基金financially supported by the China Geological Survey(grant no.1212011120045)the NSFC(grant no.41274074)
文摘The Huguangyan Maar Lake（HML）（21°9＇N,110°17＇E）,situated on the Leizhou Peninsula in the southernmost of China's Mainland,is the deepest recent crater lake among the identified volcanic structures in the Leiqiong Volcanic Field.The bi-lobate lake.
基金supported by the Government of Rhineland-PalatinateThe German Science Foundation and the Stiftung Rheinland-Pfalz fur Innovation have financially supported several projects and for this we are grateful.
文摘To mark the occasion of the 175th anniversary of the Rheinische Naturforschende Gesellschaft in 2009 and of the centennial of the Mainz Natural History Museum in 2010, we present a short account of our present knowledge of the Eckfeld Maar after 20 years of continuous research. This paper does not attempt to include all of the detailed results on the geology of the Eckfeld site or its biota. To date, nearly 250 papers and books have been published since the start of our project. An up-to-date list of these publications can be found at www.eckfeldermaar.de.
文摘The Barombi Mbo Maar (BMM), which is the largest maar in Cameroon, possesses about 126 m-thick well-preserved pyroclastic deposits sequence in which two successive paleosoil beds have been identified. The maar was thought to have been active a million years ago. However, layers stratigraphically separated by the identified paleosoils have been dated to shed lights on its age and to reconstruct the chronology of its past activity. The results showed that the BMM formed through three eruptive cycles: the first ~0.51 Ma ago, the second at ~0.2 Ma and the third ~0.08 Ma B.P. The ages indicate that the BMM maar-forming eruptions were younger than a million years. The findings also suggested that the maar is polygenetic. At a regional scale, the eruptive events would have occurred during some volcanic manifestations at Mt Manengouba and Mt Cameroon. Therefore, with the decrease in the recurrence time of eruptions from ~0.3 Ma to 0.1 Ma, and given the possible relation between its eruptive events and those of its neighboring polygenetic volcanoes, the BMM is expected to erupt within the next 20 ka.
文摘The Bambili maars are twin contemporaneous maars embedded in trachytic rocks. The two maars are separated by a low lying inter-Maar dome whose inner walls dip towards the Southern Maar. The Bambili Northern Maar (BNM) contains water and its floor is found at an altitude lower than the Bambili Southern Maar (BSM) (50 m) which is swampy and drains into the BNM. Both maars have very steep vertical walls. Three different units are identified in the area. Unit 1 is 1 m thick sequence, characterize by the presence of matrix supported fine-grained fallouts (ash and lapilli size) with stratified diffused bedding planes. This unit is further subdivided into three different layers: L1, L2 and L3 from bottom to top with increasing sizes of particles respectively. This layer shows reverser grading and its grain sizes rarely exceed 2 cm and this unit shows no depositional structures. Unit 2 is an unstratified unit predominantly made up of tephra deposits. Within these deposits are found blocks of sizes ranging between 2 and 10 cm of different petrographic types. They include scoria, basalts, trachyte, and granite cognate. The last unit, Unit 3 is distinctly stratified characterized by well sorted, heterolithologic, graded bedding layers which are matrix supported. Base on the composition and grain sizes, this unit was subdivided into 7 horizons: h1 - h7. Within this unit, two sequences of deposits are distinguished: U1 and U2. Both sequences are characterized by alternation of lapilli and tuff beds. The clast comprises of juvenile materials, mudstone which are highly vesicular and altered rock fragments. Other products identified within the area are ferolithic volcanic bombs (5 - 20 cm), xenocrystals (2 - 4 cm) within finer deposits. They are elongated and show visible twinned planes. Explosion breccias are equally identified occurring as bolders. Along the inner walls of the maars are also found large basaltic and trachytic blocks which are remnants of pre-maar unit within maar deposits. The model proposed indicates the maars were emplaced simultaneously from adjacent vents followed by a succession of lava flows and pyroclastic ejections.
基金sponsored by the Special Fund of Public Research,China Earthquake Administration(200782713)Special Fund of the Geological Heritage Protection,Department of Land and Resources,Inner Mongolia Autonomous Region,China(20101030)
文摘Located in Xilin Gol League of Inner Mongolia Autonomous Region,the Xilinhot-Abaga volcanic cluster is in the centre of the Daxing’anling-Datong volcanic eruption belt.More than 300 Quaternary basaltic volcanoes of different types are developed in the volcanic eruption belt.Maars are found for the first time in the study area,with those in Haotewula in the southeast of Abagaqi,and Chelewula and Esigewula in the northwest of Abagaqi to be the most representative.They all are large in scale,with cone diameters generally 3~4km,with the largest up to 6.5km.The maars show intact structure,a similar two-ringed mountain landscape and obviously phased eruption which contained a vigorous phreatomagmatic explosion at the earlier stage,and weak magmatic explosion at the later stage,and basaltic lava effusion in the last stage.The eruption sequence reflects the interaction between magma and water,the change of intrusive speed and outflow rate of magma.The Middle Pleistocene deposits of sand and gravel in the valley are covered by basal surge deposits.The TL age of sandstone-shale 'xenolith'which was found in the spatter deposits close to the crater is( 0.112 ± 0.0096) Ma,indicating that the eruption time of the Maars was the early Late Pleistocene.
