scholarly journals Food Webs

2021 ◽  
Author(s):  
Laura Mondragón-Camarillo ◽  
Salvador Rodríguez Zaragoza
Keyword(s):  
Food Webs ◽  
Aquatic Systems ◽  
Trophic Groups ◽  
Trophic Conditions ◽  
Trophic Networks ◽  
Environmental Perturbations ◽  
Terrestrial Environments ◽  
Anthropogenic Perturbations ◽  
Trophic Webs ◽  
Different Levels

Ciliates are important elements of the trophic networks of aquatic and terrestrial environments, they can be primary producers (myxotrophs), consumers of bacteria, algae, flagellates, even other ciliates and can serve as food for metazoans, for all the above they are the link between different levels of food webs. The structure of the ciliates varies according to the seasons of the year and depending on the trophic conditions of the aquatic systems. Ciliated communities have modifications and adaptations in response to environmental perturbations. The objective of this chapter is to describe the importance of different trophic groups of ciliates in different ecosystems, including anthropogenic perturbations and their impact on trophic webs.

scholarly journals Does metal pollution affect stoichiometry of soil-litter food webs?

2019 ◽  
Author(s):  
Michel Asselman ◽  
Łukasz Sobczyk ◽  
January Weiner ◽  
Stefan Scheu ◽  
Anna Rożen
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Metal Pollution ◽  
Ecological Stoichiometry ◽  
N:P Ratio ◽  
Aquatic Systems ◽  
Trophic Groups ◽  
Elemental Concentrations ◽  
Macro Elements

AbstractTo date the field of ecological stoichiometry has focused mainly on aquatic systems concentrating on macro-elements. We investigated terrestrial systems and included microelements to study the elemental transfer in the detritivorous food web. We compared food webs of six sites differing in the type and degree of metal pollution along two forest transects contaminated with copper or zinc. We measured 11 elements in litter, herbivores, detritivores, predators and omnivores. Based on elemental concentrations of elements differences between trophic groups were visualized using PCA. At all sites litter C:N, C:P, C:K and C:Na ratios were higher than in animals. Invertebrate trophic groups were significantly different from each other in C:Cu, C:Zn and C:Ca ratios. The calculated resource:consumer N:P ratio suggests that invertebrates in studied forests are N limited and not P limited. Similar patterns at all sites suggests that metal pollution at the studied intensity slightly affects the transfer of elements in the terrestrial macro-invertebrate food web.

The structure of a food web in a tropical rain forest in Malaysia based on carbon and nitrogen stable isotope ratios

2010 ◽  
Vol 26 (2) ◽  
pp. 205-214 ◽  
Author(s):  
Fujio Hyodo ◽  
Takashi Matsumoto ◽  
Yoko Takematsu ◽  
Tamaki Kamoi ◽  
Daisuke Fukuda ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Food Web ◽  
Food Webs ◽  
Rain Forest ◽  
Tropical Rain Forest ◽  
Stable Isotope Ratios ◽  
Trophic Groups ◽  
Nitrogen Stable Isotope ◽  
Carbon And Nitrogen ◽  
Below Ground

Abstract:Carbon and nitrogen stable isotope ratios (δ13C and δ15N) have been used to study the structure of food webs. However, few studies have examined how a terrestrial food web can be depicted by this technique. We measured δ13C and δ15N in various consumers of four trophic groups (detritivores, herbivores, omnivores and predators), including vertebrates and invertebrates (14 orders, ≥24 families), as well as canopy and understorey leaves in a tropical rain forest in Malaysia. We found that δ13C and δ15N of the consumers differed significantly among the trophic groups. The predators had significantly higher δ13C than the herbivores, and were similar in δ13C to the detritivores, suggesting that most predators examined depend largely on below-ground food webs. δ15N was higher in predators than detritivores by about 3‰. The comparison of δ13C in plant materials and herbivores suggests that most herbivores are dependent on C fixed in the canopy layers. The vertebrates had significantly higher δ15N and δ13C than the invertebrates of the same trophic group, likely reflecting differences in the physiological processes and/or feeding habits. This study indicates that stable isotope techniques can help better understanding of the terrestrial food webs in terms of both trophic level and the linkage of above- and below-ground systems.

scholarly journals Peculiarities of fish phosphorus balance at a high Cu2+ content in water

2019 ◽  
Vol 77 (1) ◽  
pp. 75-79
Author(s):  
V. Gandziura ◽  
N. Korevo
Keyword(s):  
Feed Efficiency ◽  
Aquatic Environment ◽  
Sharp Increase ◽  
Copper Content ◽  
Phosphorus Content ◽  
The Body ◽  
Trophic Groups ◽  
Trophic Conditions ◽  
Phosphorus Balance ◽  
Phosphorus Excretion

The essential infringements of fish phosphorus balance at elevated concentrations of Cu2+ in water was established – a sharp increase of intensity of phosphorus excretion, which ultimately leads to a significant decrease in its content in the body of fish. The peculiarities of the phosphorus balance of fish of various trophic groups: zooplankton phage, benthophages and ichthyophages have been established. It was found out how trophic conditions effect on the components of the phosphorus balance. It was found out how trophic conditions affect the components of the phosphorus balance. Bentofages and zooplankton- phages at the conditions of higher copper content have more pronounced disorders the phosphorus balance then ichthyophage-predators at the same time, even with an increase in the intensity of phosphorus excretion due to the increased copper content in the aquatic environment, was noted by minimal changes in its content in the body, due to the chemical composition of the food of these trophic groups. It was shown that when the content of Cu2+ in water is 10 µg / l of feed use with a high phosphorus content (3.0 %), it can compensate for its loss due to increased excretion, normalize its natural content in the body and increase the growth rate of fish and their feed efficiency. It is proposed to use the intensity of phosphorus excretion for the diagnosis of toxic pollution of the aquatic environment by heavy metals. At the same time, fish of various trophic groups should be used, with the exception of predators

scholarly journals Parasitism effects on coexistence and stability within simple trophic modules

2018 ◽  
Author(s):  
Loïc Prosnier ◽  
Vincent Médoc ◽  
Nicolas Loeuille
Keyword(s):  
Food Webs ◽  
Species Coexistence ◽  
Prey Species ◽  
Foraging Strategies ◽  
Intrinsic Growth Rate ◽  
Direct Effects ◽  
Trophic Networks ◽  
Stabilizing Effect ◽  
Indirect Impacts ◽  
Infected Prey

AbstractParasites are important components of food webs. Although their direct effects on hosts are well-studied, indirect impacts on trophic networks, thus on non-host species, remain unclear.In this study, we investigate the consequences of parasitism on coexistence and stability within a simple trophic module: one predator consuming two prey species in competition. We test how such effects depend on the infected species (prey or predator). We account for two effects of parasitism: the virulence effect (parasites affect the infected species intrinsic growth rate through direct effects on fecundity or mortality) and the interaction effect (increased vulnerability of infected prey or increased food intake of infected predators).Results show that coexistence is favored when effects have intermediate intensity. We link this result to modifications of direct and apparent competitions among prey species. Given a prey infection, accounting for susceptible-infected population structure highlights that coexistence may also be reduced due to predator-parasite competition.Parasites affect stability by modulating energy transfer from prey to predator. Predator infection therefore has a stabilizing effect due to increased energy fluxes and/or predator mortality.Our results suggest that parasites potentially increase species coexistence. Precise predictions however require an assessment of various parasite effects. We discuss the implications of our results for the functioning of trophic networks and the evolution of foraging strategies within food webs.

scholarly journals Cascading Effects of Moth Outbreaks on Subarctic Soil Food Webs

2021 ◽  
Author(s):  
Irene Calderón-Sanou ◽  
Tamara Münkemüller ◽  
Lucie Zinger ◽  
Heidy Schimann ◽  
Nigel Gilles Yoccoz ◽  
...  
Keyword(s):  
Food Webs ◽  
Large Scale ◽  
Trophic Levels ◽  
Trophic Groups ◽  
Holistic View ◽  
Cascading Effects ◽  
Soil Food Webs ◽  
Network Analyses ◽  
Northern Fennoscandia ◽  
Belowground Diversity

Abstract The increasing severity and frequency of natural disturbances requires a better understanding of their effects on all compartments of biodiversity. In Northern Fennoscandia, recent large-scale moth outbreaks have led to an abrupt change in plant communities from birch forests dominated by dwarf shrubs to grass-dominated systems. However, the indirect effects on the belowground compartment remained unclear. Here, we combined eDNA survey of multiple trophic groups with network analyses to demonstrate that moth defoliation has far-reaching consequences on soil food webs. Following this disturbance, diversity and relative abundance of certain trophic groups declined (e.g. ectomycorrhizal fungi) while many others profited (e.g. bacterivores, omnivores) making soil food webs more diverse and structurally different. Overall, the direct and indirect consequences of moth outbreaks increased belowground diversity at different trophic levels. Our results highlight that a holistic view of ecosystems improves our understanding of cascading effects of major disturbances on soil food webs.

scholarly journals Chironomidae larvae (Diptera) of Neotropical floodplain: overlap niche in different habitats

2014 ◽  
Vol 74 (2) ◽  
pp. 363-370 ◽  
Author(s):  
CMM. Butakka ◽  
FH. Ragonha ◽  
AM. Takeda
Keyword(s):  
Organic Matter ◽  
Alimentary Canal ◽  
Food Resource ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Trophic Groups ◽  
Food Items ◽  
Trophic Networks ◽  
Chironomidae Larvae ◽  
Neotropical Floodplain

The niche overlap between trophic groups of Chironomidae larvae in different habitats was observed between trophic groups and between different environments in Neotropical floodplain. For the evaluation we used the index of niche overlap (CXY) and analysis of trophic networks, both from the types and amount of food items identified in the larval alimentary canal. In all environments, the larvae fed on mainly organic matter such as plants fragments and algae, but there were many omnivore larvae. Species that have high values of food items occurred in diverse environments as generalists with great overlap niche and those with a low amount of food items with less overlap niche were classified as specialists. The largest number of trophic niche overlap was observed among collector-gatherers in connected floodplain lakes. The lower values of index niche overlap were predators. The similarity in the diet of different taxa in the same niche does not necessarily imply competition between them, but coexistence when the food resource is not scarce in the environment even in partially overlapping niches.

scholarly journals On the Use of Stable Hydrogen Isotope Measurements (δ2H) to Discern Trophic Level in Avian Terrestrial Food Webs

Diversity ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 202
Author(s):  
Rien E. van Wijk ◽  
Yahkat Barshep ◽  
Keith A. Hobson
Keyword(s):  
Food Webs ◽  
Hydrogen Isotope ◽  
Trophic Position ◽  
Terrestrial Ecosystems ◽  
Forest Site ◽  
Trophic Enrichment ◽  
Terrestrial Environments ◽  
Closed Canopy ◽  
Stable Hydrogen Isotope ◽  
Δ15n And Δ13c

The measurement of stable hydrogen isotope ratios (δ2H) in animal tissues is a popular means of inferring spatial origins and migratory connections. However, the use of this isotope to infer diet and potentially trophic position remains poorly understood, especially in non-aquatic terrestrial ecosystems. In many animal communities, tissue δ15N values are strongly associated with trophic position. Correlations between tissue δ2H and δ15N are expected, then, if δ2H is affected by trophic enrichment of 2H. In addition, within sites, we would expect higher tissue δ2H values in insectivorous species compared to granivores or nectarivores. We tested these hypotheses for two resident avian communities in Nigeria consisting of 30 species representing a range of dietary guilds (granivores, frugivores, nectarivores, omnivores, insectivores) by comparing feather δ2H, δ15N and δ13C values. We found considerable isotopic overlap among all guilds except granivores, with no clear pattern of enrichment in 2H with trophic position. However, at one of our sites (open scrubland), feather δ2H was positively correlated with feather δ15N (R2 = 0.30) compared to a closed canopy forest site (R2 = 0.09). Our results indicate weak evidence for predictable trophic enrichment in 2H in terrestrial environments and indicate that controlled studies are now required to definitively elucidate the behavior of H isotopes in terrestrial food webs.

scholarly journals Trophic groups and modules: two levels of group detection in food webs

2015 ◽  
Vol 12 (106) ◽  
pp. 20141176 ◽  
Author(s):  
Benoit Gauzens ◽  
Elisa Thébault ◽  
Gérard Lacroix ◽  
Stéphane Legendre
Keyword(s):  
Food Webs ◽  
Expert Knowledge ◽  
Dynamical Analysis ◽  
Trophic Groups ◽  
Food Web Structure ◽  
Trophic Pathways ◽  
Recent Developments ◽  
Functional Consequences ◽  
Group Detection ◽  
Trophic Connections

Within food webs, species can be partitioned into groups according to various criteria. Two notions have received particular attention: trophic groups (TGs), which have been used for decades in the ecological literature, and more recently, modules. The relationship between these two group concepts remains unknown in empirical food webs. While recent developments in network theory have led to efficient methods for detecting modules in food webs, the determination of TGs (groups of species that are functionally similar) is largely based on subjective expert knowledge. We develop a novel algorithm for TG detection. We apply this method to empirical food webs and show that aggregation into TGs allows for the simplification of food webs while preserving their information content. Furthermore, we reveal a two-level hierarchical structure where modules partition food webs into large bottom–top trophic pathways, whereas TGs further partition these pathways into groups of species with similar trophic connections. This provides new perspectives for the study of dynamical and functional consequences of food-web structure, bridging topological and dynamical analysis. TGs have a clear ecological meaning and are found to provide a trade-off between network complexity and information loss.

scholarly journals Does evolution design robust food webs ?

2019 ◽  
Author(s):  
B. Girardot ◽  
M. Gauduchon ◽  
F. Ménard ◽  
JC. Poggiale
Keyword(s):  
Food Webs ◽  
Adaptive Dynamics ◽  
Emergent Properties ◽  
Ecological Communities ◽  
Environmental Perturbations ◽  
Richness Condition ◽  
Trophic Network ◽  
Evolutionary Emergence ◽  
Current Paradigm

Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. In contrast, we propose here to asses the robustness of food webs drawn from ecological and evolutionary processes with the use of community evolution models. In a first part, with the use of Adaptive Dynamics theoretical framework, we generate a variety of diversified food webs by solely sampling different richness levels of the environment as a control parameter, and obtain networks that satisfactory compare with empirical data. This allows us to highlight the complex, structuring role of the environmental richness during the evolutionary emergence of food webs. In a second part, we study the short-term ecological responses of food webs to swift changes in their customary environmental richness condition. We reveal a strong link between the environmental conditions that attended food webs evolutionary constructions and their robustness to environmental perturbations. When focusing on emergent properties of our evolved food webs, especially connectance, we highlight results that seem to contradict the current paradigm. Among these food webs, the most connected appear to be the less robust to sudden depletion of the environmental richness that constituted their evolutionary environment. Otherwise, we appraise the “adaptation” of food webs, by examining how they perform after being suddently immersed in an environment of modified richness level, in comparison with a trophic network that experienced this latter environmental condition all along its evolution.

scholarly journals Chemical Characteristics of Humic Substances in Nature

2021 ◽  
Author(s):  
Claudio Fernando Mahler ◽  
Nicoly Dal Santo Svierzoski ◽  
Cassiano Augusto Rolim Bernardino
Keyword(s):  
Organic Matter ◽  
Soil Erosion ◽  
Humic Substances ◽  
Organic Compounds ◽  
Aquatic Systems ◽  
Chemical Characteristics ◽  
Heterogeneous Mixture ◽  
Terrestrial Environments ◽  
Industrial Use ◽  
Chemical Disinfection

Humic substances are the main constituents of natural organic matter, found in both aquatic and terrestrial environments. Humic substances are a complex, dispersed, and heterogeneous mixture of various organic compounds synthesized from organic matter residues, decomposed by microorganisms. Most scientists indicate that humic substances are as a supramolecular association of small heterogeneous molecules stabilized by weak intermolecular bonds. When these substances are presented in water intended for drinking or industrial use, it can have a significant impact on the treatability of this water and on the success of chemical disinfection processes, due to possible formation of organic compounds harmful to human health. Moreover, the humic substances can be used of several ways such as fertilizer to help in the development of plants, to improve soil erosion and to removal of organic compounds and metals from soils and waters. In addition, humic substances suggest an important role in mitigating areas degraded by the phytoremediation technique. The purpose of chapter is to provide an overview of humic substances and to discuss their concepts, chemical characteristics, ecological effects and technological applications for soils and aquatic systems.

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