Simple rules describe bottom‐up and top‐down control in food webs with alternative energy pathways

Wollrab, Sabine; Diehl, Sebastian; Roos, André M. de

doi:10.1111/j.1461-0248.2012.01823.x

Cited by 94 publications

(126 citation statements)

References 79 publications

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“…This can be expected if the system in which a trophic cascade plays out consists of multiple and interconnected trophic chains. For example, in the simple case of two food chains emanating from the same basal species, a topdown effect along one chain will turn into a bottom-up effect along the other chain through the impact on the shared resource 6,33 . In the present study, the bottom-up effect of an initial resource extinction turns into a top-down effect, if consumers have the ability to switch to a new resource.…”

Section: Discussionmentioning

confidence: 99%

Adaptive rewiring aggravates the effects of species loss in ecosystems

2015

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Section: Discussionmentioning

confidence: 99%

Adaptive rewiring aggravates the effects of species loss in ecosystems

2015

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“…trophic control | ecosystem modeling | marine food web functioning | wasp-waist | regime shifts T he question of whether food webs are resource-(bottom-up) or predation-(top-down) controlled is one of the most fundamental research questions in ecology (1)(2)(3). Marine ecosystems, originally thought to be mainly steered by bottom-up control, have recently been shown to exhibit periods of top-down control due to the extraction of large predators through fishing (4-7) or climate oscillations (8).…”

mentioning

confidence: 99%

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

Lynam

Llope

Möllmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

241

169

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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 timeseries 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 bottomup and top-down forces are not necessarily mutually exclusive and together can lead to the emergence of complex patterns of control.trophic control | ecosystem modeling | marine food web functioning | wasp-waist | regime shifts T he question of whether food webs are resource-(bottom-up) or predation-(top-down) controlled is one of the most fundamental research questions in ecology (1-3). Marine ecosystems, originally thought to be mainly steered by bottom-up control, have recently been shown to exhibit periods of top-down control due to the extraction of large predators through fishing (4-7) or climate oscillations (8). Furthermore, experimental evidence shows climate warming may exert a host of indirect effects on aquatic food webs mediated through shifts in the magnitudes of top-down and bottom-up forcing (9, 10). However, for large marine ecosystems that are not amenable to experimentation studies, investigations of how interactions in their complex food webs mediate the influence of both top-down (e.g., fishing) and bottom-up (e.g., climate change) control are lacking or are based on aggregated species complexes. We model an extensive historical dataset for the North Sea (over 45 y) at the lowest possible resolution (often species) to determine key interactions between species and estimate their responses to pressures. The model reveals both simple (direct) and complex (indirect) pathways linking plankton to seabirds and can highlight the wider effects of climate change and potential actions by fishery managers.The North Sea is one of the most anthropogenically impacted marine ecosystem and is thought to be fundamentally driven from the bottom-up through climatic (temperature-related) influences on plankton, planktivorous fish, and the pelagic stages of demersal fish (11-13). Som...

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“…Hence, food web type 1 models with one zoo-PFT (1 trophic link) can only show a direct grazing response, which in most cases would lead to a negative LP,Z-ratio. However, it is possible that changes in grazing pressure on different phytoplankton groups competing for a limiting nutrient will favor certain phytoplankton groups and result in a positive LP,Z-ratio for some (but not all) phyto-PFTs (Wollrab et al 2012). …”

Section: Model Outputmentioning

confidence: 99%

“…anoxia, cannibalism) or complex food web interactions (e.g. bottom-up effects) counterbalancing the top-down effects (Wollrab et al 2012). …”

Section: Top-down Mediated Trophic Cascadesmentioning

confidence: 99%

“…Further, theoretical modelling has produced simple rules for how perturbations at upper trophic levels can affect the strength of potential trophic cascades within specific ecosystems (Mccann et al 1998b, Leibold et al 2004, Wollrab et al 2012, Heath et al 2014. Although these models take into account trophic complexity, they do not account for any local spatio-temporal variability of the ecosystem, which may affect predator-prey interactions and, hence, trophic cascades (Frank et al 2007, Schulz et al 2007.…”

Section: Introductionmentioning

confidence: 99%

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Responses of summer phytoplankton biomass to changes in top-down forcing: Insights from comparative modelling

Maar

Butenschön

Daewel

et al. 2018

Ecological Modelling

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The present study describes the responses of summer phytoplankton biomass to changes in top-down forcing (expressed as zooplankton mortality) in three ecosystems (the North Sea, the Baltic Sea and the Nordic Seas) across different 3D ecosystem models. In each of the model set-ups, we applied the same changes in the magnitude of mortality (±20%) of the highest trophic zooplankton level (Z1). Model results showed overall dampened responses of phytoplankton relative to Z1 biomass. Phytoplankton responses varied depending on the food web structure and trophic coupling represented in the models.Hence, a priori model assumptions were found to influence cascades and pathways in model estimates and, thus, become highly relevant when examining ecosystem pressures such as fishing and climate change. Especially, the different roles and parameterizations of additional zooplankton groups grazed by Z1, and their importance for the outcome, emphasized the need for better calibration data. Spatial variability was high within each model indicating that physics (hydrodynamics and temperature) and nutrient dynamics also play vital roles for ecosystem responses to top-down effects. In conclusion, the model comparison indicated that changes in top-down forcing in combination with the modelled foodweb structure affect summer phytoplankton biomass and, thereby, indirectly influence water quality of the systems.3

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Simple rules describe bottom‐up and top‐down control in food webs with alternative energy pathways

Cited by 94 publications

References 79 publications

Adaptive rewiring aggravates the effects of species loss in ecosystems

Adaptive rewiring aggravates the effects of species loss in ecosystems

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

Responses of summer phytoplankton biomass to changes in top-down forcing: Insights from comparative modelling

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