Food chains and food webs: controlling factors and cascading effects

2019 ◽  
pp. 206-230
Author(s):  
Gary G. Mittelbach ◽  
Brian J. McGill
Keyword(s):  
Trophic Level ◽  
Resource Limitation ◽  
Trophic Levels ◽  
Joint Control ◽  
Top Down ◽  
Bottom Up ◽  
Cascading Effects ◽  
Natural Systems ◽  
Ecosystem Size ◽  
Community Theory

This chapter uses simple theory and experiments to address the fundamental question of what determines the biomass (abundance) of different trophic levels (plants, herbivores, carnivores) in a community. Theory predicts joint control of trophic-level abundance by bottom-up effects (resources) and top-down effects (predation), with the relative strengths of top-down and bottom-up effects depending on the number of trophic levels and species composition within a trophic level. Observations and experiments support these predictions. Trophic cascades provide evidence for the importance of top-down processes, but the existence of a trophic cascade says little about the relative importance of predator limitation versus resource limitation. Cascading effects result from either the consumptive or non-consumptive effects of predators, or both. Natural systems contain as few as three and as many as six trophic levels, but what determines this number is unknown. Evidence suggests that both productivity and ecosystem size, perhaps in combination, are the primary factors.

scholarly journals Interaction between top-down and bottom-up control in marine food webs

2017 ◽  
Vol 114 (8) ◽  
pp. 1952-1957 ◽  
Author(s):  
Christopher Philip Lynam ◽  
Marcos Llope ◽  
Christian Möllmann ◽  
Pierre Helaouët ◽  
Georgia Anne Bayliss-Brown ◽  
...  
Keyword(s):  
Food Webs ◽  
North Sea ◽  
Time Series Data ◽  
Trophic Levels ◽  
Series Data ◽  
Resource Exploitation ◽  
Top Down ◽  
Bottom Up ◽  
Cascading Effects ◽  
Complex Patterns

Climate change and resource exploitation have been shown to modify the importance of bottom-up and top-down forces in ecosystems. However, the resulting pattern of trophic control in complex food webs is an emergent property of the system and thus unintuitive. We develop a statistical nondeterministic model, capable of modeling complex patterns of trophic control for the heavily impacted North Sea ecosystem. The model is driven solely by fishing mortality and climatic variables and based on time-series data covering >40 y for six plankton and eight fish groups along with one bird group (>20 y). Simulations show the outstanding importance of top-down exploitation pressure for the dynamics of fish populations. Whereas fishing effects on predators indirectly altered plankton abundance, bottom-up climatic processes dominate plankton dynamics. Importantly, we show planktivorous fish to have a central role in the North Sea food web initiating complex cascading effects across and between trophic levels. Our linked model integrates bottom-up and top-down effects and is able to simulate complex long-term changes in ecosystem components under a combination of stressor scenarios. Our results suggest that in marine ecosystems, pathways for bottom-up and top-down forces are not necessarily mutually exclusive and together can lead to the emergence of complex patterns of control.

Can top-down and bottom-up forces explain phytoplankton structure in a subtropical and shallow groundwater-connected lake?

2015 ◽  
Vol 66 (12) ◽  
pp. 1106 ◽  
Author(s):  
Diego Frau ◽  
Melina Devercelli ◽  
Susana José de Paggi ◽  
Pablo Scarabotti ◽  
Gisela Mayora ◽  
...  
Keyword(s):  
Shallow Groundwater ◽  
Resource Limitation ◽  
River System ◽  
High Water ◽  
Taxonomic Resolution ◽  
Dominant Group ◽  
Top Down ◽  
Bottom Up ◽  
Physico Chemical ◽  
Phytoplankton Structure

Bottom-up and top-down control of phytoplankton is one of the most important hypothesis that explains and predicts the structure of aquatic community. Our aim was to elucidate whether predation and resource limitation can control phytoplankton composition and abundance in a subtropical shallow lake with groundwater connection to the river system. During 12 months, the lake was sampled at three points. Physico-chemical parameters, phytoplankton and zooplankton were sampled fortnightly, whereas fish were sampled every 3 months. The results showed that Euglenophyta dominated the total biovolume, followed by Dinophyta and Cryptophyta. As for the species composition, Chlorophyta was the dominant group (80 species recorded), followed by phylum Cyanobacteria (26 species recorded). Redundancy analysis (RDA) indicated that temperature and nitrate + nitrite concentration mainly explained biovolume changes, with zooplankton predation not having any measurable effect on phytoplankton during the high-water (HW) period. During low-water (LW) period top-down by fish was more important. At higher taxonomic resolution (species biovolume), phosphorus was another controlling factor. We concluded that phytoplankton in this lake is mainly regulated by hydrological changes as a macrofactor that affects nutrient availability and other environmental conditions. Even though bottom-up top-down forces do not have a central effect, we found evidence of positive nutrient influences at the HW period and fish effect at the LW period.

Large mammals generate both top-down effects and extended trophic cascades on floral-visitor assemblages

2019 ◽  
Vol 35 (4) ◽  
pp. 185-198 ◽  
Author(s):  
Allison Louthan ◽  
Emily Valencia ◽  
Dino J. Martins ◽  
Travis Guy ◽  
Jacob Goheen ◽  
...  
Keyword(s):  
Trophic Cascade ◽  
Structural Equation ◽  
Trophic Cascades ◽  
Trophic Levels ◽  
Large Mammals ◽  
Top Down ◽  
Cascading Effects ◽  
Floral Visitor ◽  
Show Evidence ◽  
Floral Visitors

AbstractCascading effects of high trophic levels onto lower trophic levels have been documented in many ecosystems. Some studies also show evidence of extended trophic cascades, in which guilds dependent on lower trophic levels, but uninvolved in the trophic cascade themselves, are affected by the trophic cascade due to their dependence on lower trophic levels. Top-down effects of large mammals on plants could lead to a variety of extended trophic cascades on the many guilds dependent on plants, such as pollinators. In this study, floral-visitor and floral abundances and assemblages were quantified within a series of 1-ha manipulations of large-mammalian herbivore density in an African savanna. Top-down effects of large mammals on the composition of flowers available for floral visitors are first shown, using regressions of herbivore activity on metrics of floral and floral-visitor assemblages. An extended trophic cascade is also shown: the floral assemblage further altered the assemblage of floral visitors, according to a variety of approaches, including a structural equation modelling approach (model with an extended trophic cascade was supported over a model without, AICc weight = 0.984). Our study provides support for extended trophic cascades affecting floral visitors, suggesting that trophic cascades can have impacts throughout entire communities.

Site-specific effects on productivity of an upper trophic-level marine predator: Bottom-up, top-down, and mismatch effects on reproduction in a colonial seabird

2006 ◽  
Vol 68 (2-4) ◽  
pp. 303-328 ◽  
Author(s):  
Robert M. Suryan ◽  
David B. Irons ◽  
Evelyn D. Brown ◽  
Patrick G.R. Jodice ◽  
Daniel D. Roby
Keyword(s):  
Trophic Level ◽  
Top Down ◽  
Bottom Up ◽  
Site Specific ◽  
Marine Predator ◽  
Specific Effects ◽  
Colonial Seabird

scholarly journals Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

2013 ◽  
Vol 71 (2) ◽  
pp. 406-416 ◽  
Author(s):  
T. O. M. Reilly ◽  
H. M. Fraser ◽  
R. J. Fryer ◽  
J. Clarke ◽  
S. P. R. Greenstreet
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Levels ◽  
Top Down ◽  
Bottom Up ◽  
Control Processes ◽  
Top Predators ◽  
Environmental Status ◽  
Fish Predators ◽  
Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

scholarly journals Adaptive genetic variation mediates bottom-up and top-down control in an aquatic ecosystem

2015 ◽  
Vol 282 (1812) ◽  
pp. 20151234 ◽  
Author(s):  
Seth M. Rudman ◽  
Mariano A. Rodriguez-Cabal ◽  
Adrian Stier ◽  
Takuya Sato ◽  
Julian Heavyside ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Intraspecific Variation ◽  
Phenotypic Variation ◽  
Evolutionary Dynamics ◽  
Trophic Levels ◽  
Community Genetics ◽  
Top Down ◽  
Black Cottonwood ◽  
Bottom Up

Research in eco-evolutionary dynamics and community genetics has demonstrated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubiquitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an ecosystem impacts its ecology. Using two species that co-occur and demonstrate adaptation to their natal environments, black cottonwood ( Populus trichocarpa ) and three-spined stickleback ( Gasterosteus aculeatus ), we investigated the effects of intraspecific phenotypic variation on both top-down and bottom-up forces using a large-scale aquatic mesocosm experiment. Black cottonwood genotypes exhibit genetic variation in their productivity and consequently their leaf litter subsidies to the aquatic system, which mediates the strength of top-down effects from stickleback on prey abundances. Abundances of four common invertebrate prey species and available phosphorous, the most critically limiting nutrient in freshwater systems, are dictated by the interaction between genetic variation in cottonwood productivity and stickleback morphology. These interactive effects fit with ecological theory on the relationship between productivity and top-down control and are comparable in strength to the effects of predator addition. Our results illustrate that intraspecific variation, which can evolve rapidly, is an under-appreciated driver of community structure and ecosystem function, demonstrating that a multi-trophic perspective is essential to understanding the role of evolution in structuring ecological patterns.

Transient top‐down and bottom‐up effects of resources pulsed to multiple trophic levels

Ecology ◽  
2020 ◽  
Author(s):  
Matthew A. McCary ◽  
Joseph S. Phillips ◽  
Tanjona Ramiadantsoa ◽  
Lucas A. Nell ◽  
Amanda R. McCormick ◽  
...  
Keyword(s):  
Trophic Levels ◽  
Top Down ◽  
Bottom Up

scholarly journals The trophic spectrum: theory and application as an ecosystem indicator

2005 ◽  
Vol 62 (3) ◽  
pp. 443-452 ◽  
Author(s):  
Didier Gascuel ◽  
Yves-Marie Bozec ◽  
Emmanuel Chassot ◽  
Audrey Colomb ◽  
Martial Laurans
Keyword(s):  
Trophic Level ◽  
Trophic Structure ◽  
Fish Assemblages ◽  
Marine Protected Area ◽  
New Caledonia ◽  
Theoretical Background ◽  
Trophic Levels ◽  
Total Biomass ◽  
Ecosystem Structure ◽  
Top Down

Abstract Trophic spectra represent the distribution of biomass, abundance, or catch by trophic level, and may be used as indicators of the trophic structure and functioning of aquatic ecosystems in a fisheries context. As a theoretical background, we present a simple ecosystem model of biomass flow reflecting predation and ontogenetic processes. Biomass trophic spectrum of total biomass can be modelled as the result of three major factors and processes: trophic efficiency, transfer kinetics, and extent of top-down control. In the simulations, changes in the spectrum highlight fishing impacts on trophic structure and reveal some functional characteristics of the underlying ecosystem. As examples of potential applications, three case studies of trophic spectra are presented. Catch trophic spectra allow description of structural differences among European fishing areas and periods. Abundance trophic spectra of coral-reef fish assemblages display different trophic signatures, characterizing different reef habitats in New Caledonia and highlighting fishing effects in a marine protected area context. Biomass trophic spectra of demersal resources off Northwest Africa show a shift in ecosystem structure that can be attributed to the rapid increase in fishing pressure during the past few decades. Off Senegal, total biomass remained fairly constant, suggesting a strong top-down control linked to fisheries targeting high trophic level species. Off Guinea, exploitation rates are spread over a wider range of trophic levels, and the total biomass of demersal resources tended to decrease. The trophic spectrum is concluded to be a useful indicator describing and comparing systems in time and space, detecting phase shifts linked to natural or anthropogenic perturbations, and revealing differences in ecosystem functioning.

scholarly journals Common carp disrupt ecosystem structure and function through middle-out effects

2017 ◽  
Vol 68 (4) ◽  
pp. 718 ◽  
Author(s):  
Mark A. Kaemingk ◽  
Jeffrey C. Jolley ◽  
Craig P. Paukert ◽  
David W. Willis ◽  
Kjetil Henderson ◽  
...  
Keyword(s):  
Common Carp ◽  
Trophic Ecology ◽  
Experimental Studies ◽  
Structure And Function ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Top Down ◽  
Bottom Up ◽  
And Function ◽  
Ecosystem Structure And Function

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

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