A cross-scale trophic cascade from large predatory fish to algae in coastal ecosystems. Issue 1859 (19th July 2017)

• Record Type: Journal Article
• Authors: Donadi, S.; Austin, Å. N.; Bergström, U.; Eriksson, B. K.; Hansen, J. P.; Jacobson, P.; Sundblad, G.; van Regteren, M.; Eklöf, J. S.
• Is Part Of: Proceedings. Volume 284:Issue 1859(2017)
• Publication Date: 2017-07-19
• Subjects: trophic cascade -- cross-scale interaction -- piecewise structural equation model -- algal bloom -- piscivorous fish -- Baltic Sea; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2017.0045
• Languages: English
• ISSNs: 0962-8452

Abstract

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.