scholarly journals Effect of a temperature gradient on Sphagnum fallax and its associated living microbial communities: a study under controlled conditions

2011 ◽  
Vol 57 (3) ◽  
pp. 226-235 ◽  
Author(s):  
Vincent E.J. Jassey ◽  
Daniel Gilbert ◽  
Philippe Binet ◽  
Marie-Laure Toussaint ◽  
Geneviève Chiapusio
Keyword(s):  
Climate Change ◽  
Temperature Gradient ◽  
Microbial Communities ◽  
Indirect Effects ◽  
Abiotic Factors ◽  
Testate Amoebae ◽  
Trophic Relationships ◽  
Total Biomass ◽  
Food Web Structure ◽  
Web Structure

Microbial communities living in Sphagnum are known to constitute early indicators of ecosystem disturbances, but little is known about their response (including their trophic relationships) to climate change. A microcosm experiment was designed to test the effects of a temperature gradient (15, 20, and 25 °C) on microbial communities including different trophic groups (primary producers, decomposers, and unicellular predators) in Sphagnum segments (0–3 cm and 3–6 cm of the capitulum). Relationships between microbial communities and abiotic factors (pH, conductivity, temperature, and polyphenols) were also studied. The density and the biomass of testate amoebae in Sphagnum upper segments increased and their community structure changed in heated treatments. The biomass of testate amoebae was linked to the biomass of bacteria and to the total biomass of other groups added and, thus, suggests that indirect effects on the food web structure occurred. Redundancy analysis revealed that microbial assemblages differed strongly in Sphagnum upper segments along a temperature gradient in relation to abiotic factors. The sensitivity of these assemblages made them interesting indicators of climate change. Phenolic compounds represented an important explicative factor in microbial assemblages and outlined the potential direct and (or) indirect effects of phenolics on microbial communities.

scholarly journals Multiple species drive flexible lake food webs with warming

2018 ◽  
Author(s):  
Timothy J. Bartley ◽  
Tyler D. Tunney ◽  
Nigel P. Lester ◽  
Brian J. Shuter ◽  
Robert H. Hanner ◽  
...  
Keyword(s):  
Climate Change ◽  
Temperature Gradient ◽  
Food Webs ◽  
Lake Trout ◽  
Trophic Levels ◽  
Forage Fish ◽  
Food Web Structure ◽  
Web Structure ◽  
Nearshore Habitat ◽  
Multiple Species

AbstractClimate change is rewiring the food webs that determine the fate of diverse ecosystems. Mobile generalist consumers are responding to climate change by rapidly shifting their behaviour and foraging, driving food webs to flex. Although these responsive generalists form a key stabilizing module in food web structure, the extent to which they are present throughout whole food webs is largely unknown. Here, we show that multiple species comprising key trophic roles drive flexible lake food webs with warming. By examining lakes that span a 7°C air temperature gradient, we found significant reductions in nearshore derived carbon and nearshore habitat use with increased temperature in three of four fish species. We also found evidence that the response of lake trout to increased temperatures may reduce their biomass and cascade to release their preferred prey, the pelagic forage fish cisco. Our results suggest that climate warming will shift lake food webs toward increased reliance on offshore habitats and resources. We argue that species across trophic levels broadly couple lake macrohabitats, suggesting that potentially stabilizing responsive consumers are present throughout food webs. However, climate change appears to limit their ability to responsively forage, critically undermining a repeated stabilizing mechanism in food webs.

Invasive rodents have multiple indirect effects on seabird island invertebrate food web structure

2017 ◽  
Vol 27 (4) ◽  
pp. 1190-1198 ◽  
Author(s):  
Joshua J. Thoresen ◽  
David Towns ◽  
Sebastian Leuzinger ◽  
Mel Durrett ◽  
Christa P. H. Mulder ◽  
...  
Keyword(s):  
Food Web ◽  
Indirect Effects ◽  
Food Web Structure ◽  
Web Structure ◽  
Invasive Rodents

scholarly journals Effects of clear-cutting and selective felling in Swedish Boreal coniferous forest: response of invertebrate taxa eaten by birds

1995 ◽  
Vol 6 (2-3) ◽  
pp. 79-90 ◽  
Author(s):  
Ola Atlegrim ◽  
Kjell Sjöberg
Keyword(s):  
Indirect Effects ◽  
Abiotic Factors ◽  
Coniferous Forest ◽  
Bird Species ◽  
Sun Exposure ◽  
Total Biomass ◽  
Insectivorous Birds ◽  
Short Term ◽  
Field Layer ◽  
Clear Cutting

Our aim was to analyse the short-term effects (0-4 years) of selective felling and clear-cutting on the food resources of insectivorous birds. Literature data on bird diets showed that herbivorous larvae (Lepidoptera and Hymenoptera: Symphyta) and spiders (Araneae) were used by 81 and 50%, respectively, of 16 bird species breeding in the Swedish boreal coniferous forest. A field study comparing selective fellings, clear-cuttings and uncut controls showed considerable effects of clear-cutting on both terricolous and field layer invertebrates. Clear-cuttings had significantly lower abundance and biomass, and a different composition of herbivorous larvae and spiders, as well as a lower total biomass of invertebrates in the field layer than controls. Drastic changes of abiotic factors (like increased temperature range) following clear-cutting may directly affect the occurrence of invertebrates. However, indirect effects (like increased sun exposure, affecting food plant quality for herbivorous larvae) are probably also responsible. Selective fellings did not differ from controls in the occurrence of herbivorous larvae and spiders. Therefore, over the four-year term of our study, selective felling seems to provide birds with conditions similar to uncut forest for invertebrates used by birds.

Changes in food web structure of fish assemblages along a river-to-ocean transect of a coastal subtropical system

2019 ◽  
Vol 70 (3) ◽  
pp. 402 ◽  
Author(s):  
Adna F. S. Garcia ◽  
Mauricio L. Santos ◽  
Alexandre M. Garcia ◽  
João P. Vieira
Keyword(s):  
Food Web ◽  
Fish Assemblages ◽  
Human Impacts ◽  
Environmental Gradients ◽  
Stomach Contents ◽  
Trophic Relationships ◽  
Food Sources ◽  
Bipartite Networks ◽  
Food Web Structure ◽  
Web Structure

There is an urgent need to understand how food web structure changes along environmental gradients. In this study we investigated changes in trophic organisation and the relative importance of autotrophic sources sustaining fish assemblages along a transect from river to ocean. In order to address these topics, we analysed fish stomach contents and isotopic composition of consumers and food sources. The findings revealed a greater number of autotrophic sources sustaining fish assemblages in the continental systems (especially in the river) than in the adjacent marine system. Bipartite networks depicting trophic relationships between fish and prey also changed along the transect, showing comparatively higher complexity in the estuary. These findings could be explained by the greater number of food web components (autotrophic sources, fish trophic guilds and prey) associated with pelagic and benthic food chains within the estuary compared with the adjacent systems studied. The findings of this study highlight the need to take into account river-to-ocean changes in food web structure of fish assemblages in management plans to mitigate human impacts in coastal systems.

Direct and Indirect Effects of Resource Quality on Food Web Structure

Science ◽  
2008 ◽  
Vol 319 (5864) ◽  
pp. 804-807 ◽  
Author(s):  
T. Bukovinszky ◽  
F. J. F. van Veen ◽  
Y. Jongema ◽  
M. Dicke
Keyword(s):  
Food Web ◽  
Indirect Effects ◽  
Direct And Indirect Effects ◽  
Food Web Structure ◽  
Resource Quality ◽  
Web Structure

Forecasting fine-scale changes in the food-web structure of coastal marine communities under climate change

Ecography ◽  
2016 ◽  
Vol 39 (12) ◽  
pp. 1227-1237 ◽  
Author(s):  
Tarek Hattab ◽  
Fabien Leprieur ◽  
Frida Ben Rais Lasram ◽  
Dominique Gravel ◽  
François Le Loc'h ◽  
...  
Keyword(s):  
Climate Change ◽  
Food Web ◽  
Fine Scale ◽  
Food Web Structure ◽  
Marine Communities ◽  
Web Structure ◽  
Coastal Marine

scholarly journals Phagotrophic Protists and Their Associates: Evidence for Preferential Grazing in an Abiotically Driven Soil Ecosystem

2021 ◽  
Vol 9 (8) ◽  
pp. 1555
Author(s):  
Andrew R. Thompson ◽  
Andrea J. Roth-Monzón ◽  
Zachary T. Aanderud ◽  
Byron J. Adams
Keyword(s):  
Species Interactions ◽  
Abiotic Factors ◽  
Wall Structure ◽  
Dry Valleys ◽  
Food Web Structure ◽  
Soil Biodiversity ◽  
Soil Food Webs ◽  
Web Structure ◽  
Starting Point ◽  
Occurrence Patterns

The complex relationship between ecosystem function and soil food web structure is governed by species interactions, many of which remain unmapped. Phagotrophic protists structure soil food webs by grazing the microbiome, yet their involvement in intraguild competition, susceptibility to predator diversity, and grazing preferences are only vaguely known. These species-dependent interactions are contextualized by adjacent biotic and abiotic processes, and thus obfuscated by typically high soil biodiversity. Such questions may be investigated in the McMurdo Dry Valleys (MDV) of Antarctica because the physical environment strongly filters biodiversity and simplifies the influence of abiotic factors. To detect the potential interactions in the MDV, we analyzed the co-occurrence among shotgun metagenome sequences for associations suggestive of intraguild competition, predation, and preferential grazing. In order to control for confounding abiotic drivers, we tested co-occurrence patterns against various climatic and edaphic factors. Non-random co-occurrence between phagotrophic protists and other soil fauna was biotically driven, but we found no support for competition or predation. However, protists predominately associated with Proteobacteria and avoided Actinobacteria, suggesting grazing preferences were modulated by bacterial cell-wall structure and growth rate. Our study provides a critical starting-point for mapping protist interactions in native soils and highlights key trends for future targeted molecular and culture-based approaches.

scholarly journals Thermal preference influences depth use but not biomass of predatory fishes in response to lake morphometry

2019 ◽  
Author(s):  
Timothy J. Bartley ◽  
Matthew M. Guzzo ◽  
Kevin Cazelles ◽  
Alex Verville ◽  
Bailey C. McMeans ◽  
...  
Keyword(s):  
Food Web ◽  
Abiotic Factors ◽  
Thermal Preference ◽  
Lake Morphometry ◽  
Top Predator ◽  
Food Web Structure ◽  
Web Structure ◽  
Top Predators ◽  
Thermal Preferences ◽  
Depth Use

ABSTRACTTop predators’ responses to environmental conditions shape food web architecture and influence ecosystem structure and stability. Yet the impacts of fundamental properties like ecosystem size and morphometry on top predators’ behaviour are poorly understood. We examined how lake morphometry impacts the behaviour (inferred by depth use) of three key fish top predators—the cold-adapted lake trout, the cool-adapted walleye, and the warm-adapted smallmouth bass— which can each strongly impact local food web structure. We used catch-per-unit-effort data from nearly 500 boreal lakes of Ontario, Canada to evaluate the role of thermal preference in dictating mean depth of capture and biomass index in response to lake morphometry. We found evidence that thermal preferences influence how species’ depth use and biomass changed with lake size, proportion of littoral area, and maximum lake depth, although we found no relationship with lake shape. However, found no strong evidence that lake morphology influences these species’ biomasses, despite theory that predicts such a relationship. Our results suggest that some aspects of lake morphometry can alter habitat accessibility and productivity in ways that influence the behaviour and biomass of these top predator species depending on their thermal preferences. Our results have implications for how lake food webs expand and contract with lake morphometry and other key abiotic factors. We argue that several key abiotic factors likely drive top predator depth use in ways that may shape local food web structure and play an important role in determining the ultimate fate of ecosystems with environmental change.

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