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Abstract

Trophic cascades occur in many ecosystems, but the factors regulating them are still elusive. We suggest that an overlooked factor is that trophic interactions (TIs) are often scale-dependent and possibly interact across spatial scales. To explore the role of spatial scale for trophic cascades, and particularly the occurrence of cross-scale interactions (CSIs), we collected and analysed food-web data from 139 stations across 32 bays in the Baltic Sea. We found evidence of a four-level trophic cascade linking TIs across two spatial scales: at bay scale, piscivores (perch and pike) controlled mesopredators (three-spined stickleback), which in turn negatively affected epifaunal grazers. At station scale (within bays), grazers on average suppressed epiphytic algae, and indirectly benefitted habitat-forming vegetation. Moreover, the direction and strength of the grazer-algae relationship at station scale depended on the piscivore biomass at bay scale, indicating a cross-scale interaction effect, potentially caused by a shift in grazer assemblage composition. In summary, the trophic cascade from piscivores to algae appears to involve TIs that occur at, but also interact across, different spatial scales. Considering scale-dependence in general, and CSIs in particular, could therefore enhance our understanding of trophic cascades.

Keywords

trophic cascade; cross-scale interaction; piecewise structural equation model; algal bloom; piscivorous fish; Baltic Sea

Published in

Proceedings of the Royal Society B: Biological Sciences
2017, volume: 284, number: 1859, article number: 20170045

SLU Authors

Global goals (SDG)

SDG14 Life below water

UKÄ Subject classification

Ecology

Publication identifier

  • DOI: https://doi.org/10.1098/rspb.2017.0045

Permanent link to this page (URI)

https://res.slu.se/id/publ/83793