title: The paradox of inverted biomass pyramids in kelp forest fish communities.
abstract: Theory predicts that bottom-heavy biomass pyramids or 'stacks' should predominate in real-world communities if trophic-level increases with body size (mean predator-to-prey mass ratio (PPMR) more than 1). However, recent research suggests that inverted biomass pyramids (IBPs) characterize relatively pristine reef fish communities. Here, we estimated the slope of a kelp forest fish community biomass spectrum from underwater visual surveys. The observed biomass spectrum slope is strongly positive, reflecting an IBP. This is incongruous with theory because this steep positive slope would only be expected if trophic position decreased with increasing body size (consumer-to-resource mass ratio, less than 1). We then used δ(15)N signatures of fish muscle tissue to quantify the relationship between trophic position and body size and instead detected strong evidence for the opposite, with PPMR ≈ 1650 (50% credible interval 280-12 000). The natural history of kelp forest reef fishes suggests that this paradox could arise from energetic subsidies in the form of movement of mobile consumers across habitats, and from seasonally pulsed production inputs at small body sizes. There were four to five times more biomass at large body sizes (1-2 kg) than would be expected in a closed steady-state community providing a measure of the magnitude of subsidies.
authors.affiliation: Earth to Ocean Research Group, Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6 Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia rowan.trebilco@utas.edu.au.
authors.forename: Rowan
authors.initials: R
authors.lastname: Trebilco
authors.affiliation: Earth to Ocean Research Group, Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Dulvy
authors.affiliation: Earth to Ocean Research Group, Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Anderson
authors.affiliation: School of Resource and Environmental Management, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Salomon
mesh_terms: D000818:Animals; D018533:Biomass; D005399:Fishes; D020387:Food Chain; D044423:Kelp
keywords: ecosystem baseline; fractionation; habitat complexity; size spectra; species interaction; stable isotope analysis