Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their di- versity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S...Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their di- versity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S and K4S where sea ice was melting obviously. The analysis of water samples with fluorescence in situ hybridization （FISH） showed that DMSP-degrading bacteria accounted for 13% of the total bacteria at the station K2S. No aerobic anoxygenic phototrophic （AAP） bacteria were detected in both samples. The bacterial communities were characterized by two 16S rRNA gene clone libraries. Sequences fell into four major lineages of the domain Bacteria, including Proteobacteria （Alpha, Beta and Gamma subclasses）, Bac- teroidetes, Actinobacteria and Firmicutes. No significant difference was found between the two clone li- braries. SAR11 and Rhodobacteraceae clades of Alphaproteobacteria and Pseudoalteromonas of Gammapro- teobacteria constituted three dominant fractions in the clone libraries. A total of 191 heterotrophic bacterial strains were isolated and 76% showed extracellular proteolytic activity. Phylogenetic analysis reveals that the isolates fell into Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. UniFrac data showed suggestive differences in bacterial communities between the Chukchi Borderland and the northern Bering Sea.展开更多
This study presents an analysis of the CTD data and the turbulent microstructure data collected in 2014, the turbulent mixing environment above the Atlantic Water（AW） around the Chukchi Borderland region is studied....This study presents an analysis of the CTD data and the turbulent microstructure data collected in 2014, the turbulent mixing environment above the Atlantic Water（AW） around the Chukchi Borderland region is studied.Surface wind becomes more efficient in driving the upper ocean movement along with the rapid decline of sea ice,thus results in a more restless interior of the Arctic Ocean. The turbulent dissipation rate is in the range of4.60×10–10（–3.31×10–9 W/kg with a mean value of 1.33×10–9 W/kg, while the diapycnal diffusivity is in the range of1.45×10–6–1.46×10–5m2/s with a mean value of 4.84×10–6 m2/s in 200–300 m（above the AW）. After investigating on the traditional factors（i.e., wind, topography and tides） that may contribute to the turbulent dissipation rate, the results show that the tidal kinetic energy plays a dominating role in the vertical mixing above the AW. Besides, the swing of the Beaufort Gyre（BG） has an impact on the vertical shear of the geostrophic current and may contribute to the regional difference of turbulent mixing. The parameterized method for the double-diffusive convection flux above the AW is validated by the direct turbulent microstructure results.展开更多
A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedit...A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedition(CHINARE-Arc9)in 2018 and previously published data.The new data reveal scours that developed at water depths of 850–1030 m with an orientation of about 75°/255°.The maximum water depth occurs in the southernmost scour and is deeper than that from previous investigations,which showed a maximum scouring depth of about 900 m on the seamount.The topographic and geomorphological characteristics suggest that these scours resulted from erosion by the ice shelf extending from the Chukchi margin and/or Laurentide Ice Sheet that grounded on the crest of the seamount and moved in a NE–SW direction.Other possibilities of their genesis include armadas of large icebergs/multi-keel icebergs calved from the Chukchi Shelf or the Laurentide Ice Sheet.The new data provide new constraints for assessing the extent and volume of the ice sheet in the Chukchi area during glacial maxima.展开更多
Among the nine sub-species of giraffes, the Maasai giraffe is the most widespread and common in Northern and Southern Kenya. Although it’s considered by the IUCN to be a species of no conservation concern, they have ...Among the nine sub-species of giraffes, the Maasai giraffe is the most widespread and common in Northern and Southern Kenya. Although it’s considered by the IUCN to be a species of no conservation concern, they have been reported to have declined in some of their range areas mostly due to bush meat activities, habitat fragmentation and loss. There are also concerns recent climatic changes especially prevalence of droughts is increasingly becoming another threat to their survival. In this regard, this study examined the status and trend of the Maasai giraffe in the Kenya-Tanzania border after the 2007 to 2009 drought. Amboseli had the highest giraffe number (averaging 2, 062.5 ± 534.7 giraffes), followed by a distant Lake Natron area (725.8 ± 129.4 giraffes), Magadi/Namanga (669.5 ± 198.0 giraffes), and lastly West Kilimanjaro area (236.5 ± 47.8 giraffes). Further, the proportion of giraffes were highest in Amboseli (55.09% ± 5.65%) followed by Lake Natron area (20.98% ± 3.42%), Magadi/Namanga area (16.35% ± 3.83%), and lastly West Kilimanjaro (7.58% ± 2.12%). But in terms of population growth after droughts, giraffe had positive growth in all locations in the borderland, with Magadi leading (+339.82 ± 329.99) followed Lake Natron area (+37.62 ± 83.27), Amboseli area (+38.11 ± 7.09), and lastly West Kilimanjaro (+3.21 ± 57.95.27). Their wet season population and density was much higher than that of the dry season. However, though the species was widely spread in the borderland, they seemed to avoid the region between Lake Magadi and Amboseli which is traversed by the Nairobi-Namanga highway both in wet and dry season. There is a need to develop a collaborative management framework for cross-border conservation to enhance their protection, conservation and genetic linkage.展开更多
Even though over many years the IUCN has considered the African buffalo and waterbuck and abundant species in Africa with no conservation concern, the situation is rapidly changing. Using aerial counts in wet and dry ...Even though over many years the IUCN has considered the African buffalo and waterbuck and abundant species in Africa with no conservation concern, the situation is rapidly changing. Using aerial counts in wet and dry season in 2010 and 2013, this study assessed the trend, population status and distribution of the African buffalo and common waterbuck in the Northern Tanzania and Southern Kenya borderland. Both species were rare in the borderland, with the Amboseli region had the highest number of buffalo (241.5 ± 29.9), followed by Magadi/Namanga (58.0 ± 22.0), West Kilimanjaro (38.8 ± 34.9), and lastly Lake Natron (14.5 ± 9.0) areas. In terms of density, Amboseli also led with 0.03 ± 0.00 (buffalo per km2), but rest had similar densities of 0.01 ± 0.00 buffalo per km2. In terms of percent changes in buffalo, Amboseli area had a positive increase (+10.59 ± 27.71), but with a negative growth of -17.12 in the dry season. All other changes in all locations had negative (decline) buffalo numbers over time. For waterbuck numbers, Amboseli area also led with 12.3 ± 3.9 waterbuck), followed by Magadi/Namanga (10.3 ± 3.7.0), Lake Natron (3.8 ± 3.4), and lastly West Kilimanjaro (0.5 ± 0.5) areas. In terms of waterbuck density, they were low and less than 0.00 ± 0.00 per km2. For percent changes in waterbuck numbers, Magadi/Namanga had higher positive change (+458.33 ± 291.67), but all other locations had negative (decline) changes with the worst being West Kilimanjaro and Lake Natron areas. Further, buffalo number was dependent (p = 0.008) on the season, with numbers being higher in the wet season than dry season. For waterbuck, numbers were independent (p = 0.72) of the season, with numbers being similar across seasons. The findings of this study showed that both species were negatively affected by drought. We recommend a constant joint monitoring program between Kenya and Tanzania, and jointly combat poaching, habitat fragmentation and encroachment to build viable populations in the borderland.展开更多
基金The National Natural Science Foundation of China under contract No.41076131the Youth Marine Science Foundation of State Oceanic Administration under contract No.2011104+3 种基金the Public Science and Technology Research Funds Projects of Ocean under contract No.201105022the Chinese Polar Environment Comprehensive Investigation and Assessment Program under contract No.CHINARE2012-02-01the National High-Tech Research and Development Program of China under contract No.2012AA021706supports for SH Lee were provided by grants for the Polar Academic Program(PAP)and Korea Polar Research Institute(KOPRI)under contract No.PM11080
文摘Planktonic bacteria are abundant in the Chukchi Borderland region. However, little is known about their di- versity and the roles of various bacteria in the ocean. Seawater samples were collected from two stations K2S and K4S where sea ice was melting obviously. The analysis of water samples with fluorescence in situ hybridization （FISH） showed that DMSP-degrading bacteria accounted for 13% of the total bacteria at the station K2S. No aerobic anoxygenic phototrophic （AAP） bacteria were detected in both samples. The bacterial communities were characterized by two 16S rRNA gene clone libraries. Sequences fell into four major lineages of the domain Bacteria, including Proteobacteria （Alpha, Beta and Gamma subclasses）, Bac- teroidetes, Actinobacteria and Firmicutes. No significant difference was found between the two clone li- braries. SAR11 and Rhodobacteraceae clades of Alphaproteobacteria and Pseudoalteromonas of Gammapro- teobacteria constituted three dominant fractions in the clone libraries. A total of 191 heterotrophic bacterial strains were isolated and 76% showed extracellular proteolytic activity. Phylogenetic analysis reveals that the isolates fell into Gammaproteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. UniFrac data showed suggestive differences in bacterial communities between the Chukchi Borderland and the northern Bering Sea.
基金The Key Project of Chinese Natural Science Foundation under contract No.41330960the National Basic Research Program(973 Program)of China under contract No.2015CB953902+1 种基金the PhD Programs Foundation of Ministry of Education of China under contract No.20130132110021the National Natural Science Foundation of China under contract No.41706211
文摘This study presents an analysis of the CTD data and the turbulent microstructure data collected in 2014, the turbulent mixing environment above the Atlantic Water（AW） around the Chukchi Borderland region is studied.Surface wind becomes more efficient in driving the upper ocean movement along with the rapid decline of sea ice,thus results in a more restless interior of the Arctic Ocean. The turbulent dissipation rate is in the range of4.60×10–10（–3.31×10–9 W/kg with a mean value of 1.33×10–9 W/kg, while the diapycnal diffusivity is in the range of1.45×10–6–1.46×10–5m2/s with a mean value of 4.84×10–6 m2/s in 200–300 m（above the AW）. After investigating on the traditional factors（i.e., wind, topography and tides） that may contribute to the turbulent dissipation rate, the results show that the tidal kinetic energy plays a dominating role in the vertical mixing above the AW. Besides, the swing of the Beaufort Gyre（BG） has an impact on the vertical shear of the geostrophic current and may contribute to the regional difference of turbulent mixing. The parameterized method for the double-diffusive convection flux above the AW is validated by the direct turbulent microstructure results.
基金The National Natural Science Foundation of China under contract No.41976079the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract No.CHINARE-03-03。
文摘A series of sub-parallel linear glacial scours are identified on the crest of the Baoshi Seamount in the Northwind Abyssal Plain by compiling new multibeam data acquired during the 9 th Chinese Arctic Research Expedition(CHINARE-Arc9)in 2018 and previously published data.The new data reveal scours that developed at water depths of 850–1030 m with an orientation of about 75°/255°.The maximum water depth occurs in the southernmost scour and is deeper than that from previous investigations,which showed a maximum scouring depth of about 900 m on the seamount.The topographic and geomorphological characteristics suggest that these scours resulted from erosion by the ice shelf extending from the Chukchi margin and/or Laurentide Ice Sheet that grounded on the crest of the seamount and moved in a NE–SW direction.Other possibilities of their genesis include armadas of large icebergs/multi-keel icebergs calved from the Chukchi Shelf or the Laurentide Ice Sheet.The new data provide new constraints for assessing the extent and volume of the ice sheet in the Chukchi area during glacial maxima.
文摘Among the nine sub-species of giraffes, the Maasai giraffe is the most widespread and common in Northern and Southern Kenya. Although it’s considered by the IUCN to be a species of no conservation concern, they have been reported to have declined in some of their range areas mostly due to bush meat activities, habitat fragmentation and loss. There are also concerns recent climatic changes especially prevalence of droughts is increasingly becoming another threat to their survival. In this regard, this study examined the status and trend of the Maasai giraffe in the Kenya-Tanzania border after the 2007 to 2009 drought. Amboseli had the highest giraffe number (averaging 2, 062.5 ± 534.7 giraffes), followed by a distant Lake Natron area (725.8 ± 129.4 giraffes), Magadi/Namanga (669.5 ± 198.0 giraffes), and lastly West Kilimanjaro area (236.5 ± 47.8 giraffes). Further, the proportion of giraffes were highest in Amboseli (55.09% ± 5.65%) followed by Lake Natron area (20.98% ± 3.42%), Magadi/Namanga area (16.35% ± 3.83%), and lastly West Kilimanjaro (7.58% ± 2.12%). But in terms of population growth after droughts, giraffe had positive growth in all locations in the borderland, with Magadi leading (+339.82 ± 329.99) followed Lake Natron area (+37.62 ± 83.27), Amboseli area (+38.11 ± 7.09), and lastly West Kilimanjaro (+3.21 ± 57.95.27). Their wet season population and density was much higher than that of the dry season. However, though the species was widely spread in the borderland, they seemed to avoid the region between Lake Magadi and Amboseli which is traversed by the Nairobi-Namanga highway both in wet and dry season. There is a need to develop a collaborative management framework for cross-border conservation to enhance their protection, conservation and genetic linkage.
文摘Even though over many years the IUCN has considered the African buffalo and waterbuck and abundant species in Africa with no conservation concern, the situation is rapidly changing. Using aerial counts in wet and dry season in 2010 and 2013, this study assessed the trend, population status and distribution of the African buffalo and common waterbuck in the Northern Tanzania and Southern Kenya borderland. Both species were rare in the borderland, with the Amboseli region had the highest number of buffalo (241.5 ± 29.9), followed by Magadi/Namanga (58.0 ± 22.0), West Kilimanjaro (38.8 ± 34.9), and lastly Lake Natron (14.5 ± 9.0) areas. In terms of density, Amboseli also led with 0.03 ± 0.00 (buffalo per km2), but rest had similar densities of 0.01 ± 0.00 buffalo per km2. In terms of percent changes in buffalo, Amboseli area had a positive increase (+10.59 ± 27.71), but with a negative growth of -17.12 in the dry season. All other changes in all locations had negative (decline) buffalo numbers over time. For waterbuck numbers, Amboseli area also led with 12.3 ± 3.9 waterbuck), followed by Magadi/Namanga (10.3 ± 3.7.0), Lake Natron (3.8 ± 3.4), and lastly West Kilimanjaro (0.5 ± 0.5) areas. In terms of waterbuck density, they were low and less than 0.00 ± 0.00 per km2. For percent changes in waterbuck numbers, Magadi/Namanga had higher positive change (+458.33 ± 291.67), but all other locations had negative (decline) changes with the worst being West Kilimanjaro and Lake Natron areas. Further, buffalo number was dependent (p = 0.008) on the season, with numbers being higher in the wet season than dry season. For waterbuck, numbers were independent (p = 0.72) of the season, with numbers being similar across seasons. The findings of this study showed that both species were negatively affected by drought. We recommend a constant joint monitoring program between Kenya and Tanzania, and jointly combat poaching, habitat fragmentation and encroachment to build viable populations in the borderland.
