Regional disparities of phytoplankton in relation to environmental factors in the western Arctic Ocean during summer of 2010

Global warming has caused Arctic sea ice to rapidly retreat,which is affecting phytoplankton,the primary producers at the base of the food chain,as well as the entire ecosystem.However,few studies with large spatial scales related to the Arctic Basin at high latitude have been conducted.This study aimed to investigate the relationship between changes in phytoplankton community structure and ice conditions.Fifty surface and 41 vertically stratified water samples from the western Arctic Ocean（67.0°–88°26′N,152°–178°54′W） were collected by the Chinese icebreaker R/V Xuelong from July 20 to August 30,2010 during China＇s fourth Arctic expedition.Using these samples,the species composition,spatial distribution,and regional disparities of phytoplankton during different stages of ice melt were assessed.A total of 157 phytoplankton taxa（〉5 μm） belonging to 69 genera were identified in the study area.The most abundant species were Navicula pelagica and Thalassiosira nordenskioeldii,accounting for 31.23% and 14.12% of the total phytoplankton abundance,respectively.The average abundance during the departure trip and the return trip were 797.07×10~2 cells/L and 84.94×10~2 cells/L,respectively.The highest abundance was observed at Sta.R09 in the north of Herald Shoal,where Navicula pelagica was the dominant species accounting for 59.42% of the abundance.The vertical distribution of phytoplankton abundance displayed regional differences,and the maximum abundances were confined to the lower layers of the euphotic zone near the layers of the halocline,thermocline,and nutricline.The species abundance of phytoplankton decreased from the low-latitude shelf to the high-latitude basin on both the departure and return trips.The phytoplankton community structure in the shallow continental shelf changed markedly during different stages of ice melt,and there was shift in dominant species from centric to pennate diatoms.Results of canonical correspondence analysis（CCA） showed that there were two distinct communities of phytoplankton in the western Arctic Ocean,and water temperature,ice coverage and silicate concentration were the most important environmental factors affecting phytoplankton distribution in the surveyed sea.These findings will help predict the responses of phytoplankton to the rapid melting of Arctic sea ice.

Community structure and spatial-temporal variation of netzphytoplankton in the Bering Sea in summer

Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species（Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.） and eurychoric species（Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.）, and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species（Th.nordenski？ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.） and eurythermal and euryhaline species（L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.）, and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.

两种方法治疗桡骨远端骨骺骨折的临床疗效比较研究

目的:比较桡骨远端骨骺骨折闭合手法复位夹板外固定与闭合手法复位克氏针内固定的临床疗效差异。方法:回顾性分析2016年2月至2019年2月诊治的107例桡骨远端骨骺骨折患者,按治疗方法不同分为观察组和对照组,分别施行手法复位夹板外固定和手法复位克氏针内固定治疗。末次随访时基于掌倾角和尺偏角对骨折愈合及复位情况进行影像学评估,基于腕关节活动度、Gartland-Werley腕关节评分及家属满意度方面综合评估两组患者的临床疗效和并发症情况。结果:所有病例均获得12~32个月随访(平均18个月),均未发现骨不连、延迟愈合、桡骨远端骨骺早闭等并发症发生。两者在掌倾角、尺偏角、腕关节活动度、Gartland-Werley评分结果优良率方面,组间比较差异均无统计学意义(P>0.05)。但并发症发生率及患者家属对疗效的满意率组间比较,差异均有统计学意义(P<0.05)。结论:手法复位夹板外固定为桡骨远端骨骺骨折患者及临床医师提供了一种并发症少,创伤及痛苦小,简单及时,经济有效,患者家属满意度高的治疗方法选择,值得临床推广。