Algae as indicators of environmental change

Despite an increased awareness by governments and the general public of the need for protecting all types of aquatic habitats, human impacts continue to impair the services that these ecosystems provide. Increased monitoring activities that locus on all major biological compartments are needed to quantify the present condition of Earth's aquatic resources and to evaluate the effectiveness of regulations designed to rehabilitate damaged ecosystems. Algae are an ecologically important group in most aquatic ecosystems but are often ignored as indicators of aquatic ecosystem change. We attribute this situation both to an underappreciation of the utility of algal indicators among non-phycologists and to a lack of standardized methods for monitoring with algae.Because of their nutritional needs and their position at the base of aquatic foodwebs, algal indicators provide relatively unique information concerning ecosystem condition compared with commonly used animal indicators. Algae respond rapidly and predictably to a wide range of pollutants and, thus, provide potentially useful early warning signals of deteriorating conditions and the possible causes. Algal assemblages provide one of the few benchmarks for establishing historical water quality conditions and for characterizing the minimally impacted biological condition of many disturbed ecosystems. Preliminary comparisons suggest that algal indicators are a cost-effective monitoring tool as well.Based on available evidence from field studies, we recommend development of taxonomic indicators based on diatoms (Bacillariophyceae) as a standardized protocol for monitoring ecosystem change. Both population- and community-level indices have inherent strengths, and limitations and information from both levels of biological organization should be utilized in tandem. However, further information concerning species tolerances to a variety of anthropogenic stressors is needed if autecological indices are to be used routinely for monitoring purposes. While functional measures (e.g. productivity) may also prove useful as monitoring tools, further investigation is required to characterize the reliability of alternative methodologies and to assess the consistency of these indicators under varying field conditions.Author for correspondence     

Resource-mediated effects of stream pollution on food absorption of Asellus aquaticus (L.) populations

The role of interactions between chemical perturbations and biological constraints on detritivores occurring in polluted streams were investigated by analysing food absorption variation with stress. Absorption rate and efficiency of four Asellus aquaticus (L.) populations from differently polluted habitats were quantified with respect to the microbial guilds colonizing detritus. A twin tracer method was used. Detritus was microbially colonized in standard conditions and on each stream bottom to control for potential resource-independent variations among individuals. The relationship between length and weight was also determined on a random sample of individuals of each population. Differences of 14.6% in potential absorption efficiency and 11.3% in potential absorption rate were observed between populations from the least and the most polluted habitat. Actual (realized) variations were much stronger: from a minimum of a 60.1% reduction in absorption efficiency to a maximum of 93.8% for the rate. The realized food absorption and the individual weight per length showed the same pattern of variation among populations. This suggested that the availability of energy to isopods in nature was related to stream pollution and resource quality. Bottomup interactions appear to be the most relevant pathway through which chemical water pollution affects the Asellus populations studied. The potential resource-independent variations among individuals are also likely to be explained by temporal cascading of resource-mediated effects.     

环境因子对荒漠沙蜥种群密度影响的研究

本文研究人类改造荒漠的活动,植被,潜在的可利用的食物资源,竞争种的密度,土壤理化性质等坏境因子对荒漠沙蜥种群密度的影响。结果说明：人类的活动对沙蜥种群密度没有显著影响;决定沙蜥种群密度的主导因子是潜在的可利用的食物资源,植被,土壤含水量,竞争种的密度。这些因子的任何改变都能改变沙蜥的种群密度,均具有调节种群的作用。     

Elevated ozone decreases the multifunctionality of belowground ecosystems

Elevated tropospheric ozone (O₃) affects the allocation of biomass aboveground and belowground and influences terrestrial ecosystem functions. However, how belowground functions respond to elevated O₃ concentrations ([O₃]) remains unclear at the global scale. Here, we conducted a detailed synthesis of belowground functioning responses to elevated [O₃] by performing a meta-analysis of 2395 paired observations from 222 publications. We found that elevated [O₃] significantly reduced the primary productivity of roots by 19.8%, 16.3%, and 26.9% for crops, trees and grasses, respectively. Elevated [O₃] strongly decreased the root/shoot ratio by 11.3% for crops and by 4.9% for trees, which indicated that roots were highly sensitive to O₃. Elevated [O₃] impacted carbon and nitrogen cycling in croplands, as evidenced by decreased dissolved organic carbon, microbial biomass carbon, total soil nitrogen, ammonium nitrogen, microbial biomass nitrogen, and nitrification rates in association with increased nitrate nitrogen and denitrification rates. Elevated [O₃] significantly decreased fungal phospholipid fatty acids in croplands, which suggested that O₃ altered the microbial community and composition. The responses of belowground functions to elevated [O₃] were modified by experimental methods, root environments, and additional global change factors. Therefore, these factors should be considered to avoid the underestimation or overestimation of the impacts of elevated [O₃] on belowground functioning. The significant negative relationships between O₃-treated intensity and the multifunctionality index for croplands, forests, and grasslands implied that elevated [O₃] decreases belowground ecosystem multifunctionality.     

Interactive effects of rising temperatures and urbanisation on birds across different climate zones: A mechanistic perspective

Climate change and urbanisation are among the most pervasive and rapidly growing threats to biodiversity worldwide. However, their impacts are usually considered in isolation, and interactions are rarely examined. Predicting species' responses to the combined effects of climate change and urbanisation, therefore, represents a pressing challenge in global change biology. Birds are important model taxa for exploring the impacts of both climate change and urbanisation, and their behaviour and physiology have been well studied in urban and non-urban systems. This understanding should allow interactive effects of rising temperatures and urbanisation to be inferred, yet considerations of these interactions are almost entirely lacking from empirical research. Here, we synthesise our current understanding of the potential mechanisms that could affect how species respond to the combined effects of rising temperatures and urbanisation, with a focus on avian taxa. We discuss potential interactive effects to motivate future in-depth research on this critically important, yet overlooked, aspect of global change biology. Increased temperatures are a pronounced consequence of both urbanisation (through the urban heat island effect) and climate change. The biological impact of this warming in urban and non-urban systems will likely differ in magnitude and direction when interacting with other factors that typically vary between these habitats, such as resource availability (e.g. water, food and microsites) and pollution levels. Furthermore, the nature of such interactions may differ for cities situated in different climate types, for example, tropical, arid, temperate, continental and polar. Within this article, we highlight the potential for interactive effects of climate and urban drivers on the mechanistic responses of birds, identify knowledge gaps and propose promising future research avenues. A deeper understanding of the behavioural and physiological mechanisms mediating species' responses to urbanisation and rising temperatures will provide novel insights into ecology and evolution under global change and may help better predict future population responses.     

Detection of Naegleria fowleri cysts in environmental samples by using a DNA probe

Abstract In this study we tried to detect DNA Naegleria fowleri in artificially contaminated environmental samples, with or without sediments, containing 10⁴ cysts of this pathogenic amoeba. We used two assays to extract DNA from samples: first, direct DNA extraction, which gave positive results only for water samples without sediment; second, DNA extraction after sample incubation on agar plates, which allowed us to remove amoeba growing out of the sediments, and which gave positive results for all samples, even those initially with sediments (5, 500 or 500 mg). Thus, this molecular identification appears as a powerful tool to investigate N. fowleri growth in environmental samples.     

Escherichia coli K12 does not colonize the gastrointestinal tract of Fischer-344 rats

Summary The colonizing potential ofEscherichia coli K12 containing a vector coding for somidobove (bovine somatotropin) was determined. Treated male and female Fischer-344 rats were given a single oral gavage inoculum of sucrose with/without tetracycline (15 g/ml). Untreated control animals received similar drinking water regimes. All animals survived until termination. There were no clinical signs of toxicity observed and no treatment-related effect upon body weight, food consumption, or efficiency of food utilization. Fresh fecal samples were collected from each rat every 24 h following inoculation and the population of the marked strain was quantitated until no bacterial colonies were observed for two consecutive days. While all inoculated rats were positive at 24 h, by 72 and 96 h all had become negative for the test (marked) strain, as were the corresponding control group throughout the test. The frozen stock of the marked strain used as the positive control demonstrated that the agar plates were selective for the test strain. Fourteen days following inoculation, all groups of rats were killed and the gastrointestinal tracts removed and treated to recover the marked strain. There was no evidence of the marked strain in the gastrointestinal tract of any rat from any group. Thus, theE. coli K12 host/vector system used in this experiment does not colonize the gastrointestinal tract of Fischer-344 rats.     

微生物在镉污染土壤修复中的应用及其作用机理

土壤中镉（Cd）含量的超标导致了土壤生态系统的恶性发展,微生物作为土壤中的常见组分之一在缓解土壤镉污染中展现出巨大潜力。本文总结了微生物、微生物-植物和微生物-生物炭在镉污染土壤修复中的应用并阐述了相关的作用机理。芽孢杆菌（Bacillus）、不动杆菌（Acinetobacter）、荧光假单胞菌（Pseudomonas fluorescence）、丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）等微生物可以通过吸附、矿化、沉淀、溶解等方式改变镉的生物有效性,从而达到缓解镉污染的目的。pH值、温度、微生物生物量、镉初始浓度以及时间等对微生物降低镉的生物有效性方面有着显著的影响。假单胞菌、伯克霍尔德菌（Burkholderia）、黄杆菌（flavobacterium）等微生物可以通过促生、活化等作用促进超富集植物对Cd²⁺的吸收。生物炭作为一种土壤改良剂,其独有的理化性质可以作为微生物的庇护所。微生物-生物炭联合使用与单用生物炭相比可以进一步促进镉的残渣态的增加,降低土壤中有效态的比例。     

Floral sex ratio variation in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis Ajima et Satomi (Liliaceae)

Intrapopulation and interpopulation variations in floral sex ratio in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis (Liliaceae) were examined. The relative ratio of male flowers to total flowers (male and perfect flowers) decreased with plant size, suggesting size-dependent gender modification. The relative ratio of male flowers per population-basis is negatively correlated with the mean number of perfect flowers. Since the number of perfect flowers proportionally increased with plant size, populations showing low maleness consist of relatively bigger plants and are considered to be in high-quality environment. On the other hand, the relative ratio of male flowers per population basis is independent of female frequency in the population. Plasticity in gender expression probably plays an important role of maintenance of gynodioecy inC. japonica var.kurohimensis.