近年来乌梁素海疣鼻天鹅种群数量变化及原因分析

为查清内蒙古乌梁素海湖泊湿地疣鼻天鹅(Cygnus olor)繁殖期和秋季迁徙前期种群数量,2014至2017年采用路线统计法和样点统计法对其进行精确计数统计,结合近十余年来的文献数据和监测记录,探讨了种群数量的变化及原因。结果显示,2015至2017年春季繁殖成鸟数量依次为84只、92只、80只,基本稳定;2014至2017年,秋季种群数量依次为411只、302只、281只、153只,逐年减少;近几年适宜繁殖地和觅食地面积不断缩小、天敌偷袭、捡蛋和投毒等因素影响亚成鸟和幼鸟的生存。根据文献和保护区监测数据,1996至2004年种群数量逐年增多,与自然保护区的建立、严禁捡蛋和没收猎枪有关,而2005至2013年因干旱缺水、水域被开发利用、芦苇(Phragmites australis)和宽叶香蒲(Typhalatifolia)面积扩增、水质恶化、富营养化加重等原因种群数量下降。研究表明,近几年乌梁素海被过度开发利用,人为干扰频繁,影响疣鼻天鹅正常繁殖栖息;栖息地的科学管理和严禁捡蛋及投毒行为,对该种群的生存及增长至关重要。     

大型浅水湖泊鄱阳湖湿地微生物的研究现状

鄱阳湖是我国第一大淡水湖泊,同时也是一个典型的季节性通江浅水湖泊,独特的水文特征和多样的湿地景观类型形成了复杂多样的微生物群落。本文综述了鄱阳湖水文节律、营养盐及重金属含量对湖泊微生物群落组成的影响,以及水位高程和湿地围垦对鄱阳湖湿地土壤微生物分布特征的影响,同时还探讨了未来湖泊湿地微生物的研究方向和鄱阳湖所拥有的独特研究条件,以期为未来湖泊微生物研究提供重要参考。     

艾比湖湿地芦苇根际土壤氨氧化古菌的多样性和群落结构

【目的】旨在揭示耐盐植物芦苇根际与非根际土壤AOA群落结构间的差异,为深入研究盐生植物根际土壤微生物与耐盐性之间的关系提供理论基础。【方法】应用高通量测序技术以氨单加氧酶基因(amoA)为分子标记,对新疆艾比湖湿地荒漠生态系统不同季节(春、夏、秋)芦苇根际与非根际土壤氨氧化古菌(AOA)的多样性和群落结构进行研究。【结果】结果表明,不同季节芦苇根际土壤AOA多样性和丰富度存在差异,相比非根际土壤,夏季和秋季芦苇根际土壤AOA多样性较低丰富度较高,春季多样性较高丰富度较低。芦苇根际土壤中AOA的多样性为春季夏季秋季。AOA群落组成分析表明,土壤样品中AOA群落主要集中在泉古菌门(Crenarchaeota)和奇古菌门(Thaumarchaeota),其中泉古菌门为主要优势菌门。RDA分析表明,含水量(SM)、有机质(SOM)、总氮(TN)和pH是影响芦苇根际土壤AOA群落多样性和丰富度的主要环境因子。【结论】不同季节芦苇根际土壤AOA多样性及丰富度存在差异,相比非根际土壤,芦苇根际土壤AOA更丰富。     

Visual performance impaired by elevated sedimentary and algal turbidity in walleye Sander vitreus and emerald shiner Notropis atherinoides

The objectives of this study were to determine the effects of different forms of elevated turbidity on the visual acuity of two native Lake Erie fishes and to assess the response of fishes from different trophic levels to elevated turbidity. Additionally, the role of visual morphology (e.g., eye and optic lobe size) on visual acuity was evaluated across visual environments. Reaction distance, a behavioural proxy for measures of visual acuity, was measured for a top predator, walleye Sander vitreus and a forage fish, emerald shiner Notropis atherinoides. In both S. vitreus (n = 27) and N. atherinoides (n = 40) reaction distance across all types of turbidity (sedimentary, algal, sedimentary + algal; 20 NTU) was approximately 50% lower relative to the clear treatment. Reaction distance was further reduced in algal compared with sedimentary turbidity for wild-caught S. vitreus. Eye and brain morphology also influenced reaction distance across turbidity treatments, such that larger relative eye and brain metrics were positively correlated with reaction distance. This study provides evidence for disrupted visual acuity as a potential mechanism underlying fish responses, such as decreased foraging efficiency, to increased turbidity and further indicates that algal turbidity will probably be more detrimental to visual processes than sedimentary turbidity. With the increasing occurrence and severity of harmful algal blooms due to cultural eutrophication globally, this could have significant implications for predator–prey relationships in aquatic systems.     

青海赖草属一新种

报道了青海赖草属植物一新种：圆稃赖草(Leymus oblongolenmatus L. Zhi et L.B. Cai)。该种的主要特征如下：多年生草本,杆直立、光滑、疏丛,高60～90 cm。叶鞘粗糙,边缘膜质,长于或短于节间,叶舌膜质;叶片边缘内卷。穗状花序直立、密集、黄绿色,长10～15 cm,宽5～15 mm,穗轴粗糙,小穗常3～4枚生于每节,含3～6小花;颖披针形,长4～7 mm,具3～5脉,边缘膜质;外稃长圆状披针形,不明显3脉,背部疏生短柔毛;花药黄色,长4～5 mm。该种与L. paboahus相似。     

Schistosomiasis in Lake Malawi: Relationship of Fish and Intermediate Host Density to Prevalence of Human Infection

Prior to 1985, the open waters of Lake Malawi were free from schistosome transmission. Over the past decades, however, the prevalence of urinary schistosomiasis has increased dramatically in the southern part of the lake. We found the prevalence of human schistosomiasis in school-aged children to be negatively correlated with the density of molluscivorous fishes. Specifically, the increased infection rate in southern Lake Malawi between 1978 and 1991 is coincident with the reduction in numbers of snail-eating fishes. During 2003, we determined the relative abundance of molluscivorous fishes and snail density at 18 sites throughout the lake and schistosome infection in school-aged children living in selected lakeshore communities of Lake Malawi. At the 18 sites sampled in 2003, we found that snail abundance decreased with an increase in abundance of snail-eating fishes. Furthermore, the 2003 samples showed that the abundance of snail-eating fishes increased and there was a reduction in schistosomiasis in school-aged children in Chembe Village. We believe that we will not observe a return to the 1978 infection rates until these fishes continue to increase and inhabit shallower waters.     

中国虎耳草属(虎耳草科)二新种————班玛虎耳草和丁青虎耳草

记载了中国虎耳草属Saxifraga二新种, 即班玛虎耳草S. banmaensis J. T. Pan和丁青虎耳草S. dingqingensis J. T. Pan。其中, 班玛虎耳草仅见于青海班玛, 与小伞虎耳草S. umbellulata Hook. f. &; Thoms.近缘, 但其萼片先端具软骨质短尖头, 花瓣线形, 非提琴状长圆形至提琴形, 基部无爪, 可资区别。丁青虎耳草见于西藏丁青, 与近加拉虎耳草S. llonakhensis W. W. Smith相似, 但其萼片3脉, 于先端汇合成1疣点, 花瓣具8痂体和4-5脉, 基部截形或近耳形, 可以区别。此两种均系中国特有种, 隶属于莲座状亚组subsect. Rosulares Gornall。     

Alternation between clear,high-vegetation and turbid,low-vegetation states in a shallow lake: the role of birds

External phosphorus load to a wetland with two shallow lakes in the Botshol Nature Reserve, the Netherlands, was reduced since 1989, resulting in a rapid reduction of phosphorus levels, phytoplankton biomass and turbidity, and after 4 years, explosive growth of Characeae. The clear water state was unstable, however, and the ecosystem subsequently alternated between clear, high-vegetation and turbid, low-vegetation states. The switch from clear to turbid states occurred at a higher phosphorus level than the switch from turbid to clear states and area covered by macrophytes was significantly correlated to Secchi disc depth (r = 0.86, p < 0.001). Beginning in 1997, phosphorus input from droppings of greylag geese and black-headed gulls increased. The hypothesis that grazing prevented the return of Characeae populations was tested during 1996–1997 using large-scale exclosure experiments. The biomass and cover of Characeae were monitored in 17 exclosures for 2 years. The experiments showed no significant increase in Characeae in the absence of grazers compared with the controls. During the course of the experiments, the entire lake switched from turbid water to clear water and high Chara biomass. These ecosystem developments suggest that light limitation was the main factor controlling the collapse and return of Characeae in Botshol.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal have been first studied after exposure to extremely low temperatures (freeze-thawing) for different lengths of time. It has been shown that short-term freezing (1–3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7-and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7-and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.