Algal and grazer responses to trophic skew.

<p>Final A) biomass of experimentally stocked macroalgae, B) colonizing algae (e.g., microalgae) chlorophyll <i>a</i> accumulation C) mesograzer abundance, and the trophic cascade strength on macroalgae (D) and microalgae (E) in experimental mesocosms across trophic skewing treatments after 24 days. Higher values in D and E indicate a stronger positive trophic cascade on the algae. Values are means±1SE.</p

Appendix A. Predator efficiency of prey capture.

Predator efficiency of prey capture

Experimental food webs.

<p>A) Structure of experimental food webs with varying species richness per trophic level, i.e., trophic skew, and B) experimental species pool (predators: <i>Hypleurochilus geminatus, Monacanthus hispidus, Fundulus heteroclitus</i>, swimming crabs (<i>Callinectes sapidus</i> or <i>C. similis</i>), <i>Lagodon rhomboids, Penaeus aztecus, Palaemonetes vulgaris</i>, mud crabs (<i>Panopeus herbstii, Eurypanopeus depressus</i> or <i>Neopanope sayi</i>); grazers: <i>Gammarus mucronatus, Elasmopus levis, Dulichiella appendiculata, Paracerceis caudata</i>; macroalgae: <i>Dictyota menstrualis, Codium fragile, Padina gymnospora, Sargassum filipendula, Ceramium sp., Gracilaria tikvahiae, G. verrucosa, Hypnea musciformis, Ulva lactuca</i>. Species are not drawn to scale.</p

Results of two-factor anova on the effects of trophic skew and food chain length.

<p>The degree of trophic skewing encompassed the presence of upper trophic levels (i.e., food chain length: algae only,+grazers,+grazers+predators) and the distribution of species richness (top-rich, neutral, slightly bottom-rich, bottom-rich skewed) on final A) macroalgal biomass, B) microalgal accumulation, and C) grazer abundance. Only data from replicates in which grazers were initially stocked (all treatments except ‘algae only’) were used in the analysis of food chain length and richness distribution treatment effects on grazer abundance (C).</p

Grazer species responses to trophic skew.

<p>Final grazer abundance per species across trophic skew treatments in the presence and absence of predators. Values are means±1SE.</p

Appendix B. Experimental images.

Experimental images

Net fishing on Aitutaki Island, Cook Islands. Coral reef fisheries like this are threatened by climate change.

<p>Photo: Lauren-Kristine Pryzant.</p

Non-metric multidimensional scaling scores for grazer community response to trophic skew and predator presence.

<p>Plot of the nonmetric multidimensional scaling (NMDS) scores for the two most important axes for all replicates using final grazer species composition data. Circles and stars represent the absence and presence of predators, respectively. Trophic skew treatments are represented from light to dark as follows: top-rich, neutral, slightly bottom-rich, and bottom-rich.</p

Appendix C. Methods for chlorophyll a analysis.

Methods for chlorophyll a analysis

Appendix D. Macroalgal composition.

Macroalgal composition