scholarly journals Lake Bacterial Assemblage Composition Is Sensitive to Biological Disturbance Caused by an Invasive Filter Feeder

mSphere ◽  
2017 ◽  
Vol 2 (3) ◽  
Author(s):  
Vincent J. Denef ◽  
Hunter J. Carrick ◽  
Joann Cavaletto ◽  
Edna Chiang ◽  
Thomas H. Johengen ◽  
...  
Keyword(s):  
Global Change ◽  
Functional Group ◽  
Group Representation ◽  
Taxonomic Composition ◽  
Direct Effects ◽  
Dreissenid Mussels ◽  
Elemental Cycling ◽  
Anthropogenic Global Change ◽  
Bacterial Assemblages ◽  
The Impact

ABSTRACT Freshwater bacteria play fundamental roles in global elemental cycling and are an intrinsic part of local food webs. Human activities are altering freshwater environments, and much has been learned regarding the sensitivity of bacterial assemblages to a variety of these disturbances. Yet, relatively few studies have focused on how species invasion, which is one of the most important aspects of anthropogenic global change, affects freshwater bacterial assemblages. This study focuses on the impact of invasive dreissenid mussels (IDMs), a globally distributed group of invasive species with large impacts on freshwater phyto- and zooplankton assemblages. We show that IDMs have direct effects on lake bacterioplankton abundance, taxonomic composition, and inferred bacterial functional group representation. One approach to improve forecasts of how global change will affect ecosystem processes is to better understand how anthropogenic disturbances alter bacterial assemblages that drive biogeochemical cycles. Species invasions are important contributors to global change, but their impacts on bacterial community ecology are rarely investigated. Here, we studied direct impacts of invasive dreissenid mussels (IDMs), one of many invasive filter feeders, on freshwater lake bacterioplankton. We demonstrated that direct effects of IDMs reduced bacterial abundance and altered assemblage composition by preferentially removing larger and particle-associated bacteria. While this increased the relative abundances of many free-living bacterial taxa, some were susceptible to filter feeding, in line with efficient removal of phytoplankton cells of <2 μm. This selective removal of particle-associated and larger bacteria by IDMs altered inferred bacterial functional group representation, defined by carbon and energy source utilization. Specifically, we inferred an increased relative abundance of chemoorganoheterotrophs predicted to be capable of rhodopsin-dependent energy generation. In contrast to the few previous studies that have focused on the longer-term combined direct and indirect effects of IDMs on bacterioplankton, our study showed that IDMs act directly as a biological disturbance to which freshwater bacterial assemblages are sensitive. The negative impacts on particle-associated bacteria, which have been shown to be more active than free-living bacteria, and the inferred shifts in functional group representation raise the possibility that IDMs may directly alter bacterially mediated ecosystem functions. IMPORTANCE Freshwater bacteria play fundamental roles in global elemental cycling and are an intrinsic part of local food webs. Human activities are altering freshwater environments, and much has been learned regarding the sensitivity of bacterial assemblages to a variety of these disturbances. Yet, relatively few studies have focused on how species invasion, which is one of the most important aspects of anthropogenic global change, affects freshwater bacterial assemblages. This study focuses on the impact of invasive dreissenid mussels (IDMs), a globally distributed group of invasive species with large impacts on freshwater phyto- and zooplankton assemblages. We show that IDMs have direct effects on lake bacterioplankton abundance, taxonomic composition, and inferred bacterial functional group representation.

scholarly journals Transitions in oral and gut microbiome of HPV+ oropharyngeal squamous cell carcinoma following definitive chemoradiotherapy (ROMA LA-OPSCC study)

2021 ◽  
Author(s):  
Marc Oliva ◽  
Pierre H. H. Schneeberger ◽  
Victor Rey ◽  
Matthew Cho ◽  
Rachel Taylor ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
Cell Carcinoma ◽  
Squamous Cell ◽  
Taxonomic Composition ◽  
Oropharyngeal Squamous Cell Carcinoma ◽  
Oral Microbiome ◽  
Metagenomic Sequencing ◽  
Α Diversity ◽  
16S Rna ◽  
The Impact

Abstract Background Oral and gut microbiomes have emerged as potential biomarkers in cancer. We characterised the oral and gut microbiomes in a prospective observational cohort of HPV+ oropharyngeal squamous cell carcinoma (OPSCC) patients and evaluated the impact of chemoradiotherapy (CRT). Methods Saliva, oropharyngeal swabs over the tumour site and stool were collected at baseline and post-CRT. 16S RNA and shotgun metagenomic sequencing were used to generate taxonomic profiles, including relative abundance (RA), bacterial density, α-diversity and β-diversity. Results A total of 132 samples from 22 patients were analysed. Baseline saliva and swabs had similar taxonomic composition (R2 = 0.006; p = 0.827). Oropharyngeal swabs and stool taxonomic composition varied significantly by stage, with increased oral RA of Fusobacterium nucleatum observed in stage III disease (p < 0.05). CRT significantly reduced the species richness and increased the RA of gut-associated taxa in oropharyngeal swabs (p < 0.05), while it had no effect in stool samples. These findings remained significant when adjusted by stage, smoking status and antibiotic use. Conclusions Baseline oral and gut microbiomes differ by stage in this HPV+ cohort. CRT caused a shift towards a gut-like microbiome composition in oropharyngeal swabs. Stage-specific features and the transitions in oral microbiome might have prognostic and therapeutic implications.

scholarly journals Resilience of Epiphytic Lichens to Combined Effects of Increasing Nitrogen and Solar Radiation

2021 ◽  
Vol 7 (5) ◽  
pp. 333
Author(s):  
Lourdes Morillas ◽  
Javier Roales ◽  
Cristina Cruz ◽  
Silvana Munzi
Keyword(s):  
Global Change ◽  
Solar Radiation ◽  
Functional Groups ◽  
Physiological Response ◽  
Functional Group ◽  
Environmental Drivers ◽  
Combined Effects ◽  
Environmental Stressor ◽  
Comprehensive Understanding ◽  
Direct Sunlight

Lichens are classified into different functional groups depending on their ecological and physiological response to a given environmental stressor. However, knowledge on lichen response to the synergistic effect of multiple environmental factors is extremely scarce, although vital to get a comprehensive understanding of the effects of global change. We exposed six lichen species belonging to different functional groups to the combined effects of two nitrogen (N) doses and direct sunlight involving both high temperatures and ultraviolet (UV) radiation for 58 days. Irrespective of their functional group, all species showed a homogenous response to N with cumulative, detrimental effects and an inability to recover following sunlight, UV exposure. Moreover, solar radiation made a tolerant species more prone to N pollution’s effects. Our results draw attention to the combined effects of global change and other environmental drivers on canopy defoliation and tree death, with consequences for the protection of ecosystems.

The impact of global change on the hydropower potential of Europe: a model-based analysis

Energy Policy ◽  
2005 ◽  
Vol 33 (7) ◽  
pp. 839-855 ◽  
Author(s):  
Bernhard Lehner ◽  
Gregor Czisch ◽  
Sara Vassolo
Keyword(s):  
Global Change ◽  
Model Based ◽  
Hydropower Potential ◽  
The Impact ◽  
Model Based Analysis

scholarly journals The influence of hypercapnia and the infaunal brittlestar <i>Amphiura filiformis</i> on sediment nutrient flux – will ocean acidification affect nutrient exchange?

2009 ◽  
Vol 6 (10) ◽  
pp. 2015-2024 ◽  
Author(s):  
H. L. Wood ◽  
S. Widdicombe ◽  
J. I. Spicer
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Marine Invertebrates ◽  
Nutrient Flux ◽  
Additional Treatment ◽  
Direct Effects ◽  
Exposure Study ◽  
Physicochemical Changes ◽  
Amphiura Filiformis ◽  
The Impact

Abstract. Rising levels of atmospheric carbon dioxide and the concomitant increased uptake of this by the oceans is resulting in hypercapnia-related reduction of ocean pH. Research focussed on the direct effects of these physicochemical changes on marine invertebrates has begun to improve our understanding of impacts at the level of individual physiologies. However, CO2-related impairment of organisms' contribution to ecological or ecosystem processes has barely been addressed. The burrowing ophiuroid Amphiura filiformis, which has a physiology that makes it susceptible to reduced pH, plays a key role in sediment nutrient cycling by mixing and irrigating the sediment, a process known as bioturbation. Here we investigate the role of A. filiformis in modifying nutrient flux rates across the sediment-water boundary and the impact of CO2- related acidification on this process. A 40 day exposure study was conducted under predicted pH scenarios from the years 2100 (pH 7.7) and 2300 (pH 7.3), plus an additional treatment of pH 6.8. This study demonstrated strong relationships between A. filiformis density and cycling of some nutrients;

scholarly journals Prevention of UVI Precipitation in Alkaline Aqueous Solutions by the Siderophore Desferrioxamine B

2020 ◽  
Author(s):  
Matthew Kirby ◽  
Jason Louis Sonnenberg ◽  
Jonathan S. Watson ◽  
Dominik Weiss
Keyword(s):  
Functional Group ◽  
Experimental Studies ◽  
Binding Mode ◽  
Batch Experiments ◽  
Desferrioxamine B ◽  
Waste Storage ◽  
Contaminant Sources ◽  
Waste Repositories ◽  
Saline Solutions ◽  
The Impact

<p>In alkaline and saline solutions, uranium VI (U<sup>VI</sup>)<sup> </sup>forms uranyl salts, limiting its mobility in leachates released from nuclear waste repositories into groundwater. However, recent experimental and computational work suggested that natural organic molecules widely present in groundwater such as siderophores could potentially prevent solid precipitation because of the formation of stable UVI-siderophore complexes. It is important we assess the impact of siderophores on aqueous U<sup>VI</sup> chemistry as they could mobilise U<sup>VI </sup>from contaminated land and radioactive waste storage and disposal sites. Here we test this hypothesis by combining for the first time experimental studies on uranium precipitation in alkaline pH in the presence of desferrioxamine B (DFOB) and electron structure method calculation of uranyl – hydroxamate complexes to assess their stability. Stirred batch experiments containing 0 to 420 µM DFOB, 42 µM U<sup>VI</sup> and 0.1 M NaCl were conducted at pH 11.5. DFT was employed to explore the relative stability of different U<sup>VI</sup>-hydroxamate complexes, representative of the local binding mode of DFOB. During the stirred batch experiments, 5%, 11-12%, 41-53%, 95-96% and 100% of U<sup>VI</sup> passes through the filter membranes (0.2-1 µm pore diameter) after 24 hours when 0, 4.2, 42, 130 and 420 µM DFOB was added to solution. The DFT results suggest one hydroxamate functional group is most likely to complex with U<sup>VI</sup> with ∆<sub>r</sub>G calculated as +3 kJ/mol and -9 kJ/mol for [UO<sub>2</sub>(OH)<sub>3</sub>(L<sub>mono</sub>)]<sup>2- </sup>and [UO<sub>2</sub>(OH)<sub>2</sub>(L)]<sup>-</sup> respectively. Conversion of the experimentally derived log β (-1.2 ± 0.3) through the equation ∆<sub>r</sub>G = -2.303RTlogβ provides ∆<sub>r</sub>G of +7 kJ/mol, similar to the ∆<sub>r</sub>G of these two complexes. The results of our study confirm that U<sup>VI</sup> precipitation could be hindered by the formation of a DFOB complex with U<sup>VI</sup> complexation through a single hydroxamate functional group as a likely mechanism. These results highlight the mobilising effect siderophores have on U<sup>VI</sup> from contaminant sources and need to be incorporated in environmental risk assessment studies.</p>

ZOOBENTHOS OF WATERCOURSES IN THE BUKHTARMA RIVER BASIN (UPPER IRTYSH, SOUTH-WESTERN ALTAI) AT REFERENCE SITES AND IN THE IMPACT ZONE

2021 ◽  
pp. 66-83
Author(s):  
A. Evseeva
Keyword(s):  
River Basin ◽  
Cold Water ◽  
Taxonomic Composition ◽  
Anthropogenic Factors ◽  
Impact Zone ◽  
High Oxygen Content ◽  
Water Courses ◽  
Cold Water Temperature ◽  
Composition Structure ◽  
The Impact

The composition, structure, and spatial distribution of zoobenthos in streams of the Bukhtarma River basin are described and quantitative indicators of benthos in the lower course of the Bukhtarma River are given. The predominance of insects from the orders of mayflies, caddisflies, and freckles is characteristic of the water-courses in the Bukhtarma River basin and is associated with the presence of stony soils in the rivers, rapid flow, moderate-cold-water temperature regime, and high oxygen content in the water – factors that are most favorable for these groups of invertebrates. To assess the ecological state of surface waters in the streams under study by bioindication methods, TBI, BMWP, ASPT, and ERT biotic indices are used. The taxonomic composition of each of the studied watercourses and river sections is formed in accordance with specific environmental conditions associated with natural and anthropogenic factors. It is established that watercourses in the reference areas can be used as reference ones in accordance with the requirements of the EU Framework Water Directive, and the characteristics of invariant States of biocenoses of the lower course of the Bukhtarma River in the impact zone are also given using the criteria of the V. A. Abakumov system of ecological modulations.

The Impact of Inertia as Mediator and Antecedent on Consumer Loyalty and Continuance Intention

2018 ◽  
pp. 960-981 ◽  
Author(s):  
Donald Louis Amoroso ◽  
Pajaree Ackaradejruangsri ◽  
Ricardo A. Lim
Keyword(s):  
Information Systems ◽  
Relationship Marketing ◽  
Structural Equation ◽  
Structural Equation Models ◽  
Explanatory Power ◽  
Consumer Attitudes ◽  
Consumer Loyalty ◽  
Direct Effects ◽  
Continuance Intention ◽  
The Impact

This study builds on existing loyalty literature and theories, and extends to include consumer attitudes impact on continuous intention and loyalty based on relationship marketing and information systems. Three structural equation models built from a survey of 458 mobile Thai consumers revealed that inertia was the strongest factor among all constructs in predicting consumer loyalty and continuance intention, either as mediator or antecedent. Support was found for all of the hypothesized relationships for consumers using mobile wallet apps, except for the path between loyalty and continuance intention. Though the direct effects of consumer attitudes were more or less constant, satisfaction became insignificant when inertia acted as a mediator. As an antecedent to both consumer attitudes and satisfaction, inertia significantly increased the explanatory power of continuance intention and loyalty. This study provides new insights into factors that influence loyalty and continuance intention in the context of mobile wallet applications.

scholarly journals Interactions between Climate and Nutrient Cycles on Forest Response to Global Change: The Role of Mixed Forests

Forests ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 609 ◽  
Author(s):  
Ester González de Andrés
Keyword(s):  
Climate Change ◽  
Global Change ◽  
Environmental Conditions ◽  
Species Interactions ◽  
N Deposition ◽  
Elemental Ratios ◽  
Nutrient Mineralization ◽  
Carbon Dioxide Co2 ◽  
The Impact

Forest ecosystems are undergoing unprecedented changes in environmental conditions due to global change impacts. Modification of global biogeochemical cycles of carbon and nitrogen, and the subsequent climate change are affecting forest functions at different scales, from physiology and growth of individual trees to cycling of nutrients. This review summarizes the present knowledge regarding the impact of global change on forest functioning not only with respect to climate change, which is the focus of most studies, but also the influence of altered nitrogen cycle and the interactions among them. The carbon dioxide (CO2) fertilization effect on tree growth is expected to be constrained by nutrient imbalances resulting from high N deposition rates and the counteractive effect of increasing water deficit, which interact in a complex way. At the community level, responses to global change are modified by species interactions that may lead to competition for resources and/or relaxation due to facilitation and resource partitioning processes. Thus, some species mixtures can be more resistant to drought than their respective pure forests, albeit it depends on environmental conditions and species’ functional traits. Climate change and nitrogen deposition have additional impacts on litterfall dynamics, and subsequent decomposition and nutrient mineralization processes. Elemental ratios (i.e., stoichiometry) are associated with important ecosystem traits, including trees’ adaptability to stress or decomposition rates. As stoichiometry of different ecosystem components are also influenced by global change, nutrient cycling in forests will be altered too. Therefore, a re-assessment of traditional forest management is needed in order to cope with global change. Proposed silvicultural systems emphasize the key role of diversity to assure multiple ecosystem services, and special attention has been paid to mixed-species forests. Finally, a summary of the patterns and underlying mechanisms governing the relationships between diversity and different ecosystems functions, such as productivity and stability, is provided.

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