Activity profiles of bacterioplankton in a eutrophic river

1. The significance of microbial diversity in processing dissolved organic matter (DOM) is largely unknown. We investigated the range of functional diversity in the bacterioplankton from a eutrophic river by profiling extracellular enzyme activities (EEA) and substrate-induced respiration (SIR) patterns.
2. The EEA profiles consisted of assays for 21 hydrolases, measured using fluorogenic substrates arrayed on 96-well microplates. Commercially available BiOLOG^® GN and ECO plates, which contained 120 different substrates, were used for the SIR profiles.
3. The EEA data were more dynamic than the SIR. Five enzymes, leucine aminopeptidase, alkaline phosphatase, alanine aminopeptidase, arginine aminopeptidase and β-glucosidase, showed consistently high activity; ten others were ubiquitous at lower activity levels; the remainder were detected intermittently. The SIR data showed less temporal variability. With one exception (citrate), the 20 substrates that generated the largest responses were all saccharides or their derivatives.
4. The EEA and SIR data did not generally correlate. Both methods were effective for ordinating bacterioplankton although, unlike the SIR, the EEA ordination followed a clear temporal trajectory.
5. Because the SIR profiles are based on a culture response, whilst the EEA profiles measure activity of the extant community, the latter appear to be more directly linked to the mechanics of DOM processing.     

荒漠河岸林植物木质部导水与栓塞特征及其对干旱胁迫的响应

 以同处于干旱区的塔里木河下游(铁干里克)和黑河下游(乌兰图格)断面为研究区, 比较了荒漠河岸林主要建群种胡杨(Populus euphratica)、柽柳(Tamarix spp.)、疏叶骆驼刺(Alhagi sparsifolia)和花花柴(Karelinia caspia)在长期遭受不同干旱胁迫下的根、枝条木质部导水力和栓塞化程度的变化特征, 并分析了木质部导水对干旱胁迫的响应及适应策略。结果表明: 1) 黑河下游荒漠河岸林植物的导水能力显著高于塔里木河下游, 其中柽柳、胡杨、疏叶骆驼刺和花花柴根木质部的初始比导率(K_s0)分别高11.97、6.74、7.10和3.73倍, 枝条的K_s0分别高9.48、3.65、2.07和1.88倍, 地下水埋深导致的干旱胁迫程度不同是诱发荒漠植物导水能力差异的根本原因; 2)柽柳耐干旱能力最强, 适应范围较宽, 而花花柴、疏叶骆驼刺的耐旱性相对较弱, 适生范围较窄, 这可能与植物的根系分布有关; 3)干旱胁迫较轻时, 枝条木质部是荒漠河岸林植物水分传输的主要阻力部位, 干旱胁迫严重时, 根木质部是限制植株水流的最大阻碍部位; 4)荒漠河岸林植物主要通过调节枝条木质部的水流阻力来适应干旱胁迫, 且其适应策略与干旱胁迫程度有关, 干旱胁迫轻时, 植物通过限制枝条木质部水流来协调整株植物的均匀生长; 干旱胁迫严重时, 植物通过牺牲劣势枝条、增强优势枝条水流来提高植株整体生存的机会。     

珠三角河网区典型生境植物群落构成特征及生态修复

如何实现生态文明建设与三生空间高度混杂地区的高质量协同发展是珠三角河网区新时期面对的重要难题。以2018—2021年间积累的第一手田野调查资料为基础,针对广佛地区20处样地202个样点,综合生态学数量分析与风景园林学空间分析方法,研究河网区典型生境的植物群落构成特征及应用。结果表明：(1)珠三角河网区植物物种丰富,维管束植物共122科382属551种;植物群落“乔、灌、草、藤本”垂直结构完整,但乡土植物占比较低、外来入侵较严重;(2)动物友好植物种类丰富,共有鸟类友好植物88种、昆虫类友好植物90种、鱼类两栖类友好植物34种,但缺乏针对动物友好生境的科学配置;(3)河网区包括滨水、坑塘、农田、聚落四类典型生境以及9个稳定的植物群系,但在长期人为干扰下其生态功能和水乡风貌特征被严重削弱。最后,以佛山大美公园为例,探讨了以恢复河网区生物多样性和特色景观风貌为目标的生态修复实践。研究为珠三角河网区地域性景观恢复和三生空间混杂区域的近自然生态修复提供了重要的规划设计蓝本和实践示范。     

Self-Organizing Maps in Revealing Variation in Non-obligatory Riverine Fish in Long-term Data

Sensitiveness to the overall influence of the river channel regulation, impoundment and pollution was studied for 12 non-obligatory riverine (NOR) fish species in the Warta River, Poland, over the period of 1963–1998. Their total abundance has not considerably changed unlike the structure of their aggregation, which was revealed by a self-organizing map (SOM, Kohonen unsupervised artificial neural network) almost perfectly separating 1960s samples from 1990s ones. The greatest changes in proportion were recorded for the dominant roach Rutilus rutilus (from 28.6 to 60.0%), perch Perca fluviatilis (1.9 to 9.5%), pike Esox lucius (2.9 to 4.9%), and the former codominant bleak Alburbus alburnus (22.9 to 1.8%). They resulted from highly significant (p < 0.001), reaching even one order of magnitude, differences in the abundance of these species. Such remarkable alternations in dominant NOR ichthyofauna obviously influenced the whole fish assemblage structure, which was best illustrated by a clear vertical gradient over SOM in Simpson and Shannon indices. Thus, NOR species, both studied together and separately, can supply valuable information on the fish assemblage dynamics and should not be neglected in temporal analyses, often focused only on vulnerable obligatory riverine, migratory and/or endemic species.     

Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA

One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm⁻³ at 1–3 cm depth in September 1993. New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed.     

Predicting the unexpected: using a qualitative model of a New Zealand dryland ecosystem to anticipate pest management outcomes

Pest management is expensive and there is often uncertainty about the benefits for the resources being protected. There can also be unintended consequences for other parts of the ecosystem, especially in complex food webs. In making decisions managers generally have to rely on qualitative information collected in a piecemeal fashion. A method to assist decision making is a qualitative modelling approach using fuzzy cognitive maps, a directed graphical model related to neural networks that can take account of interactions between pests and conservation assets in complex food webs. Using all available information on relationships between native and exotic resources and consumers, we generated hypotheses about potential consequences of single‐species and multi‐species pest control on the long‐term equilibrium abundances of other biotic components of an ecosystem. We applied the model to a dryland ecosystem in New Zealand because we had good information on its trophic structure, but the information on the strength of species interactions was imprecise. Our model suggested that pest control is unlikely to significantly boost native invertebrates and lizards in this ecosystem, suggesting that other forms of management may be required for these groups. Most of the pest control regimes tested resulted in greater abundances of at least one other pest species, which could potentially lead to other management problems. Some of the predictions were unexpected, such as more birds resulting from possum and mouse control. We also modelled the effects of an increase in invasive rabbits, which led to unexpected declines of stoats, weasels, mice and possums. These unexpected outcomes resulted from complex indirect pathways in the food web. Fuzzy cognitive maps allow rapid construction of prototype models of complex food webs using a wide range of data and expert opinion. Their utility lies in providing direction for future monitoring efforts and generating hypotheses that can be tested with field experiments.     

土壤抑真菌作用与细菌群落结构的关系

自然清洁土壤所具有的抑真菌作用,是健康土壤的一种自然属性,也是土壤质量的重要指标之一,对控制农作物土传病原真菌的爆发具有积极的生态学意义.本试验以中国科学院沈阳生态实验站近10年未受农药和肥料影响的撂荒地土壤作为自然清洁土壤样品,通过高温（对照、100 ℃、110 ℃、121 ℃）处理得到具有不同抑真菌作用的土壤模型,采用PCR DGGE(变性梯度凝胶电泳)方法对上述土壤样品的细菌群落结构进行分析.结果表明：土壤抑真菌作用与土壤细菌群落结构紧密相关;对照清洁土壤抑真菌作用最强,处理后土壤细菌群落结构偏离自然清洁土壤愈远,土壤抑真菌能力愈差;DGGE特异性条带切胶测序结果表明,Sphingomonas asaccharolytica、Nitrospira sp.、Hyphomicrobiaceae sp.、Bacillus megaterium和Micrococcus sp.可能与土壤抑真菌作用密切相关.     

Rotifer Nervous System Visualized by FMRFamide and 5-HT Immunocytochemistry and Confocal Laser Scanning Microscopy

The characteristic ecology of floodplain lakes is in part due to their relatively strong water-level fluctuations. We analyzed the factors determining water-level fluctuations in 100 floodplain lakes (during non-flooded conditions) in the active floodplains of the Lower Rhine in the Netherlands. Furthermore, we explored the relationship between water-level fluctuations and macrophyte species richness, and analyzed the suitability of artificially created lakes for macrophyte vegetation. During non-flooded conditions along the Rhine, lake water-level fluctuations are largely driven by groundwater connection to the river. Hence, water-level fluctuations are largest in lakes close to the main channel in strongly fluctuating sectors of the river and smallest in isolated lakes. Additionally, water-level fluctuations are usually small in old lakes, mainly due to reduced groundwater hydraulic conductivity resulting from accumulated clay and silt on the bottom. Species richness of floating-leaved and emergent macrophytes was reduced at both small and large water-level fluctuations, whereas species richness of submerged macrophytes was reduced at small water-level fluctuations only. In addition, species richness of submerged macrophytes was higher in lakes that experienced drawdown, whereas no similar pattern was detected for floating-leaved and emergent macrophytes. The decline in amplitude of lake water-level with lake age implies that the number of hydrologically dynamic lakes will decrease over time. Therefore, we suggest that excavation of new lakes is essential to conserve the successional sequence of floodplain water bodies including conditions of high biodiversity. Shallow, moderately isolated, lakes with occasional bottom exposure have the highest potential for creating macrophyte-rich floodplain lakes along large lowland rivers. The water-level regime of such lakes can in part be designed, through choice of the location along the river, the distance away from the river and the depth profile of the lake.     

Native fish entrapment in irrigation systems: A step towards understanding the significance of the problem

Summary   The Australian irrigation industry diverts significant volumes of water from our rivers, and as such, may also divert and entrain riverine fish. Although it is widely acknowledged that our native fish fauna have been greatly affected by a variety of anthropogenic changes, little is known about the extent or significance of fish entrainment in irrigation systems. This paper presents results from a preliminary investigation into the diversion of fish into irrigation channels undertaken in the Goulburn-Murray Irrigation Network, Victoria, Australia. The case study and our knowledge of the life-history strategies of the Basin's fish fauna suggest that the loss of native fish into irrigation networks may be a substantial problem, which, up until recently, has been largely ignored. We strongly suggest that the impact of diversions on native fish populations requires urgent further investigation and quantification, through the cooperation of water management authorities and fish biologists.     

Life history and production of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) in the lower Ebro river: a comparison after 18 years

The life history of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) was studied during spring and summer 2005 in the lower Ebro river (Catalonia) and compared to a previous study performed in 1987 (Ibáñez, Escosa, Muñoz and Prat 1991). The results showed an advancement of Ephoron virgo life cycle and an increase of production estimates. In 2005 larval development reached the maximum size one month earlier than in 1987, and adult emergence peak began three weeks earlier. Comparing adult sex ratios (F:M), there was a major presence of females in 2005 (1:4), while the opposite was observed in 1987 (2:1). Secondary production was higher in 2005 than in 1987, obtaining 950 mg dry weight/m²/year with the increment summation method and 1080 mg dry weight/m²/year using the removal summation method. Higher water temperatures were measured for the entire 2005 larval growth period, which were related to higher air temperatures. Therefore, that temperature increment was likely the main cause of changes observed in the Ephoron virgo life cycle.