Coupled energy pathways and the resilience of size-structured food webs |
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Authors: | Julia L Blanchard Richard Law Matthew D Castle Simon Jennings |
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Institution: | (1) Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Lowestoft, NR33 0HT, UK;(2) Biology Department, University of York, PO Box 373, York, YO1 5YW, UK;(3) Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK;(4) Present address: Division of Biology, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK |
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Abstract: | Size-based food-web models, which focus on body size rather than species identity, capture the generalist and transient feeding
interactions in most marine ecosystems and are well-supported by data. Here, we develop a size-based model that incorporates
dynamic interactions between marine benthic (detritus-based) and pelagic (primary producer based) pathways to investigate
how the coupling of these pathways affects food web stability and resilience. All model configurations produced stable steady-state
size spectra. Resilience was measured by the return speed obtained from local stability analysis. Return times following large
perturbations away from steady-state were also measured. Resilience varied nonlinearly with both predator and detrital coupling,
and high resilience came from predators (1) feeding entirely in the slow benthic zone or (2) feeding across the two energy
pathways, with most food coming from the fast pelagic pathway. When most of the energy flowed through the pelagic pathway,
resilience was positively related to turnover rate. When most of the energy flowed through the benthic pathway, resilience
was negatively related to turnover rate. Analysis of the effects of large perturbations revealed that resilience for pelagic
ecosystems depended on the nature of the perturbation and the degree of benthic–pelagic coupling. Areas with very little or
no benthic–pelagic coupling (e.g. deep seas or highly stratified water columns) may return more quickly following pulses of
detrital fallout or primary production but could be much less resilient to the effects of human-induced mortality (harvesting). |
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