scholarly journals Diatoms as indicators of the effects of river impoundment at multiple spatial scales

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e8092 ◽  
Author(s):  
Hendrik J. Krajenbrink ◽  
Mike Acreman ◽  
Michael J. Dunbar ◽  
Libby Greenway ◽  
David M. Hannah ◽  
...  
Keyword(s):  
Water Supply ◽  
Anthropogenic Impacts ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Regional Scale ◽  
Assemblage Structure ◽  
Diatom Assemblage ◽  
Diatom Assemblages ◽  
National Scale ◽  
Water Supply Reservoirs

River impoundment constitutes one of the most important anthropogenic impacts on the World’s rivers. An increasing number of studies have tried to quantify the effects of river impoundment on riverine ecosystems over the past two decades, often focusing on the effects of individual large reservoirs. This study is one of the first to use a large-scale, multi-year diatom dataset from a routine biomonitoring network to analyse sample sites downstream of a large number of water supply reservoirs (n = 77) and to compare them with paired unregulated control sites. We analysed benthic diatom assemblage structure and a set of derived indices, including ecological guilds, in tandem with multiple spatio-temporal variables to disclose patterns of ecological responses to reservoirs beyond the site-specific scale. Diatom assemblage structure at sites downstream of water supply reservoirs was significantly different to control sites, with the effect being most evident at the regional scale. We found that regional influences were important drivers of differences in assemblage structure at the national scale, although this effect was weaker at downstream sites, indicating the homogenising effect of river impoundment on diatom assemblages. Sites downstream of reservoirs typically exhibited a higher taxonomic richness, with the strongest increases found within the motile guild. In addition, Trophic Diatom Index (TDI) values were typically higher at downstream sites. Water quality gradients appeared to be an important driver of diatom assemblages, but the influence of other abiotic factors could not be ruled out and should be investigated further. Our results demonstrate the value of diatom assemblage data from national-scale biomonitoring networks to detect the effects of water supply reservoirs on instream communities at large spatial scales. This information may assist water resource managers with the future implementation of mitigation measures such as setting environmental flow targets.

Multi-scale and multi-system perspectives of zooplankton structure and function in Canadian freshwaters

2021 ◽  
Author(s):  
Bernadette Pinel-Alloul ◽  
Alain Patoine ◽  
Jérôme Marty
Keyword(s):  
Environmental Changes ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Regional Scale ◽  
Ecological Integrity ◽  
Future Research ◽  
Freshwater Zooplankton ◽  
Anthropogenic Stressors ◽  
Wide Range ◽  
And Function

This review provides a Canadian perspective on freshwater zooplankton diversity and ecology across scales and systems. It aims at describing how zooplankton is a source of biodiversity in forms and functions, a key component of plankton food web, a model for ecological theories and a sentinel for monitoring lake ecological integrity and function facing environmental changes and anthropogenic stressors. These objectives are addressed across a continuum of spatial scales and ecosystem types. Zooplankton communities demonstrated a wide range of responses to anthropogenic disturbances across scales and systems due to interactions with watershed biogeochemistry and climate. This review supports the Multiple Forces hypothesis where forcing by abiotic factors have a primordial role at global scale over Canadian ecoregions, and at regional scale in the Boreal ecozones. In contrast, forcing by biotic factors is more influential at local scale, in resort and urban regions. Future research challenge will be to combine all new concepts and approaches in a holistic perspective to examine the response of freshwater zooplankton to multiple environmental changes and anthropogenic stressors.

scholarly journals Parasitism without frontiers: Infection variability of an intermediate host across multiple spatial scales

2018 ◽  
Author(s):  
Sara M Rodríguez ◽  
Fernando C Aliaga ◽  
Nelson Valdivia
Keyword(s):  
Spatial Variability ◽  
Intermediate Host ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Regional Scale ◽  
Spatiotemporal Variability ◽  
Mixed Effect ◽  
Sandy Shores ◽  
Host Parasite ◽  
Meso Scale

Background. Parasites are heterogeneously distributed in intermediate host populations, but how this variability changes between multiple geographic scales remain unclear. Here, we test whether in a complex host-parasite system developing in sandy shores, the high spatiotemporal variability in the physical structure of these habitats will lead to comparatively high variability in parasitosis observed at the local- (i.e. few metres) and meso-scale (i.e. tens of km), relative to the regional scale (several 100s of km). Methods. Here, we analyse the spatial variability of acanthocephalan parasites infecting decapod molecrabs according to a hierarchical design spanning more than 500 km of the southern-central shore of Chile. We predicted that the local effects could potentially influence the host-parasite interaction by generating a large amount of between-site heterogeneity in parasitosis and thus, to improve our understanding of the development of epidemic and infectious processes. Results. The analysis of generalized mixed-effect models showed that the spatial variability in parasitosis (i.e. probability of infection, parasite burden, prevalence, mean intensity, and mean abundance) was smallest at the regional scale. On the other hand, the largest amount of spatial variability of most measures of parasitosis was observed at the meso-scale. Prevalence, however, displayed similar (and high) levels of variation at meso- and local-scales. Conclusions. We suggest that parasite infection could be related with abiotic factors that determine habitat physical stability, such as seasonal morphodynamic of sandy shores. Thus, local environmental filters can have strong and deterministic effects on the regulation of this complex host-parasite system across spatial scales.

scholarly journals Exploring the Interplay Between Local and Regional Drivers of Distribution of a Subterranean Organism

Diversity ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 119 ◽  
Author(s):  
Stefano Mammola ◽  
Shlomi Aharon ◽  
Merav Seifan ◽  
Yael Lubin ◽  
Efrat Gavish-Regev
Keyword(s):  
Species Distribution ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Regional Scale ◽  
Regional Distribution ◽  
Ecological Factors ◽  
Local Scale ◽  
Model Systems ◽  
Mean Annual Temperature ◽  
Distribution Models

Caves are excellent model systems to study the effects of abiotic factors on species distributions due to their selective conditions. Different ecological factors have been shown to affect species distribution depending on the scale of analysis, whether regional or local. The interplay between local and regional factors in explaining the spatial distribution of cave-dwelling organisms is poorly understood. Using the troglophilic subterranean spider Artema nephilit (Araneae: Pholcidae) as a model organism, we investigated whether similar environmental predictors drive the species distribution at these two spatial scales. At the local scale, we monitored the abundance of the spiders and measured relevant environmental features in 33 caves along the Jordan Rift Valley. We then extended the analysis to a regional scale, investigating the drivers of the distribution using species distribution models. We found that similar ecological factors determined the distribution at both local and regional scales for A. nephilit. At a local scale, the species was found to preferentially occupy the outermost, illuminated, and warmer sectors of caves. Similarly, mean annual temperature, annual temperature range, and solar radiation were the most important drivers of its regional distribution. By investigating these two spatial scales simultaneously, we showed that it was possible to achieve an in-depth understanding of the environmental conditions that governs subterranean species distribution.

scholarly journals Parasitism without frontiers: Infection variability of an intermediate host across multiple spatial scales

2018 ◽  
Author(s):  
Sara M Rodríguez ◽  
Fernando C Aliaga ◽  
Nelson Valdivia
Keyword(s):  
Spatial Variability ◽  
Intermediate Host ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Regional Scale ◽  
Spatiotemporal Variability ◽  
Mixed Effect ◽  
Sandy Shores ◽  
Host Parasite ◽  
Meso Scale

Background. Parasites are heterogeneously distributed in intermediate host populations, but how this variability changes between multiple geographic scales remain unclear. Here, we test whether in a complex host-parasite system developing in sandy shores, the high spatiotemporal variability in the physical structure of these habitats will lead to comparatively high variability in parasitosis observed at the local- (i.e. few metres) and meso-scale (i.e. tens of km), relative to the regional scale (several 100s of km). Methods. Here, we analyse the spatial variability of acanthocephalan parasites infecting decapod molecrabs according to a hierarchical design spanning more than 500 km of the southern-central shore of Chile. We predicted that the local effects could potentially influence the host-parasite interaction by generating a large amount of between-site heterogeneity in parasitosis and thus, to improve our understanding of the development of epidemic and infectious processes. Results. The analysis of generalized mixed-effect models showed that the spatial variability in parasitosis (i.e. probability of infection, parasite burden, prevalence, mean intensity, and mean abundance) was smallest at the regional scale. On the other hand, the largest amount of spatial variability of most measures of parasitosis was observed at the meso-scale. Prevalence, however, displayed similar (and high) levels of variation at meso- and local-scales. Conclusions. We suggest that parasite infection could be related with abiotic factors that determine habitat physical stability, such as seasonal morphodynamic of sandy shores. Thus, local environmental filters can have strong and deterministic effects on the regulation of this complex host-parasite system across spatial scales.

Spatial regularities between non-immigrant and immigrant numbers in Canada

2014 ◽  
Vol 11 (1) ◽  
pp. 90-100
Author(s):  
Yigit Aydede
Keyword(s):  
Fixed Effects ◽  
Spatial Scales ◽  
National Scale ◽  
Pooled Data

The present study intends to reveal spatial regularities between non-immigrant and immigrant numbers in two different ways. First, it questions the existence of those regularities when spatial scales get finer. Second, it uses pooled data over four population censuses covering the period from 1991 to 2006, which enabled us to apply appropriate techniques to remove those unobserved fixed effects so that the estimations would accurately identify the linkage between local immigrant and non-immigrant numbers. The results provide evidence about the existence of negative spatial regularities between non-immigrant and immigrant numbers in Canada at national scale.

Source characterization of disinfection byproduct precursors in two Arkansas water-supply reservoirs

Fact Sheet ◽  
1997 ◽  
Author(s):  
Michael L. Pomes ◽  
W.R. Green ◽  
E.M. Thurman ◽  
W.H. Orem ◽  
H.T. Lerch
Keyword(s):  
Water Supply ◽  
Source Characterization ◽  
Disinfection Byproduct ◽  
Water Supply Reservoirs

Susceptibility of Water Supply Reservoirs to Drought Conditions

1998 ◽  
Vol 3 (2) ◽  
pp. 140-148 ◽  
Author(s):  
Antonino Cancelliere ◽  
Alessandro Ancarani ◽  
Giuseppe Rossi
Keyword(s):  
Water Supply ◽  
Drought Conditions ◽  
Water Supply Reservoirs

scholarly journals Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mulalo M. Muluvhahothe ◽  
Grant S. Joseph ◽  
Colleen L. Seymour ◽  
Thinandavha C. Munyai ◽  
Stefan H. Foord
Keyword(s):  
Climate Change ◽  
Species Composition ◽  
High Altitude ◽  
Functional Diversity ◽  
Large Scale ◽  
Climate Models ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Composition Analysis ◽  
Fine Scale

AbstractHigh-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.

scholarly journals Setting the Flow Accumulation Threshold Based on Environmental and Morphologic Features to Extract River Networks from Digital Elevation Models

2021 ◽  
Vol 10 (3) ◽  
pp. 186
Author(s):  
HuiHui Zhang ◽  
Hugo A. Loáiciga ◽  
LuWei Feng ◽  
Jing He ◽  
QingYun Du
Keyword(s):  
Spatial Scales ◽  
Digital Elevation Models ◽  
Regional Scale ◽  
Drainage Density ◽  
River Network ◽  
Landscape Patterns ◽  
Estimation Methods ◽  
River Networks ◽  
Flow Accumulation ◽  
Digital Elevation

Determining the flow accumulation threshold (FAT) is a key task in the extraction of river networks from digital elevation models (DEMs). Several methods have been developed to extract river networks from Digital Elevation Models. However, few studies have considered the geomorphologic complexity in the FAT estimation and river network extraction. Recent studies estimated influencing factors’ impacts on the river length or drainage density without considering anthropogenic impacts and landscape patterns. This study contributes two FAT estimation methods. The first method explores the statistical association between FAT and 47 tentative explanatory factors. Specifically, multi-source data, including meteorologic, vegetation, anthropogenic, landscape, lithology, and topologic characteristics are incorporated into a drainage density-FAT model in basins with complex topographic and environmental characteristics. Non-negative matrix factorization (NMF) was employed to evaluate the factors’ predictive performance. The second method exploits fractal geometry theory to estimate the FAT at the regional scale, that is, in basins whose large areal extent precludes the use of basin-wide representative regression predictors. This paper’s methodology is applied to data acquired for Hubei and Qinghai Provinces, China, from 2001 through 2018 and systematically tested with visual and statistical criteria. Our results reveal key local features useful for river network extraction within the context of complex geomorphologic characteristics at relatively small spatial scales and establish the importance of properly choosing explanatory geomorphologic characteristics in river network extraction. The multifractal method exhibits more accurate extracting results than the box-counting method at the regional scale.

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