Positive feedback between large-scale disturbance and density-dependent grazing decreases resilience of a kelp bed ecosystem

O’Brien, John; Scheibling, Robert Eric; Krumhansl, Kira A.

doi:10.3354/meps11193

Cited by 16 publications

(11 citation statements)

References 61 publications

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“…Some species of turf algae may also chemically alter the substrate, preventing settlement of kelp spores even after the turf is removed (Kennelly 1987). The turf-algal state can be further reinforced through intensified grazing of remaining kelp blades following defoliation events (Bennett et al 2015, O'Brien et al 2015 and kelp propagule supply-side limitations (O'Brien & Scheibling 2016).…”

Section: Discussionmentioning

confidence: 99%

Wasted effort: recruitment and persistence of kelp on algal turf

Burek¹,

O’Brien²,

Scheibling³

2018

Mar. Ecol. Prog. Ser.

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Section: Discussionmentioning

confidence: 99%

Wasted effort: recruitment and persistence of kelp on algal turf

Burek¹,

O’Brien²,

Scheibling³

2018

Mar. Ecol. Prog. Ser.

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“…The large increase in open space associated with coral mortality greatly expands the foraging area for herbivores and effectively decreases grazing rate per unit area of substratum (Williams et al 2001). Conversely, on temperate reefs a low density of canopy algae can intensify grazing on remaining individuals (O'Brien et al 2015)…”

Section: Relative Importance Of Competition In Mediating Regime Shiftsmentioning

confidence: 99%

Turf wars: competition between foundation and turf-forming species on temperate and tropical reefs and its role in regime shifts

O’Brien¹,

Scheibling²

2018

Mar. Ecol. Prog. Ser.

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Shifts in competitive balance between key functional groups may drive regime shifts in tropical and temperate marine ecosystems. On shallow reefs, regime shifts increasingly involve changes from spatial dominance by foundation species (e.g. reefbuilding corals, canopy-forming algae) to dominance by turf-forming algae differing in structural complexity. To disentangle competitive inter actions from other processes that may contribute to these shifts, we conducted a global meta-analysis of manipulative competition experiments between foundation and turf-forming species. Canopy-forming algae had consistently negative effects on abundance of turfforming algae, particularly on subtidal reefs, but with a tendency towards larger effects on delicate filamentous forms compared to articulated coralline and corticated/ coarsely branching turf. Competitive effects of turf-forming algae on canopy species were limited to early life-history stages, and similarly varied between turf functional groups and between subtidal and intertidal reefs. Conversely, shorter filamentous turf assemblages typical of tropical reefs had no significant effect on settlement and survival of coral larvae. Interactions between turf-forming algae and established coral colonies were negative overall, but variable in magnitude. Mean effect sizes indicated that corals suppress turf abundance, but not vice versa. However, turf-forming algae significantly impacted coral growth and tissue mortality. We suggest reefs with extensive cover of foundation species are resistant to proliferation of turf algae, but competition will inhibit recovery of reefs following disturbances that enable turf algae to establish. Therefore, competitive effects of foundation and turf-forming species must be accounted for to effectively evaluate the stability of these undesirable regime shifts and recovery potential under alternative climate and management scenarios. KEY WORDS: Competition • Turf algae • Coral • Canopy algae • Kelp • Meta-analysis Foundation species such as reef-building corals and canopyforming brown algae face competition with low-lying turf algae on tropical and temperate reefs.

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“…consume cystocarpic tissue of red algae in the genus Iridaea, but in the process tear open cystocarps and release carpospores that might otherwise remain on fronds Santelices 1987, Buschmann 1991). Kilometer-scale variability in overall grazing intensity on kelp by L. vincta arises from negative relationships with both site exposure (Krumhansl and Scheibling 2011b) and kelp abundance (O'Brien et al 2015). While we found most grazing damage on kelp sori consisted of superficial excavations, it is unlikely that L. vincta facilitates the release of spores from sporangia.…”

Section: Effects Of Grazing On Fecundity Reproductive Output and Rementioning

confidence: 50%

“…Because the indirect effects of partial grazing may increase as linear (Poore et al 2014) or stepwise functions of grazing intensity (Krumhansl and Scheibling 2011b), these too are not expected to be uniform among individuals and sites. Kilometer-scale variability in overall grazing intensity on kelp by L. vincta arises from negative relationships with both site exposure (Krumhansl and Scheibling 2011b) and kelp abundance (O'Brien et al 2015). Therefore, we might expect indirect effects to be amplified as kelp abundance wanes, particularly within sheltered sites and embayments.…”

Section: Effects Of Grazing On Fecundity Reproductive Output and Rementioning

confidence: 99%

Nipped in the bud: mesograzer feeding preference contributes to kelp decline

O’Brien

Scheibling

2016

Ecology

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Small invertebrate grazers can disproportionately reduce plant fitness by discriminately consuming valuable tissues, but the context and attendant consequences of this activity at higher levels of ecological organization rarely are considered. To assess the impact of a gastropod mesograzer Lacuna vincta on fecundity and potential reproductive output of the habitat-forming kelp Saccharina latissima, we measured the intensity and distribution of grazing damage on kelp blades at five sites of varying kelp density, during the annual reproductive peak (October-November) in Nova Scotia. We found most grazing damage on reproductive individuals consisted of superficial excavations, and was concentrated on the central sorus (region where sporangia develop) compared to the vegetative blade margins. Grazing intensity on sori (percent grazed) averaged 29.6% across sites and sampling periods. The distribution of grazing on non-reproductive individuals was opposite to that of reproductive ones, indicating that snails shift feeding from blade margins to the center as sori develop. Choice and no-choice feeding assays in the laboratory revealed that focused grazing on sori is likely due to an active feeding preference for sporogenous over vegetative tissue. This preference was correlated with the distribution of chemical defense between tissues (phlorotannin content was ~2.5 times higher in vegetative tissue than sori), but not nutritional quality (no difference in C/N ratio). We deduce, with support from histological observations, that consumption of sorus tissue by L. vincta reduces fecundity of S. latissima. Extrapolating our results to estimate potential reproductive output within kelp beds suggests that spore supply and recruitment limitation may be predominantly imposed by the scarcity of reproductive individuals in the most degraded kelp beds. However, loss of reproductive output to grazing could extend recruitment limitations that impede recovery of waning kelp populations in Nova Scotia.

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Positive feedback between large-scale disturbance and density-dependent grazing decreases resilience of a kelp bed ecosystem

Abstract: Resale or republication not permitted without written consent of the publisherThe mesogastropod Lacuna vincta aggregates on and extensively grazes a solitary kelp blade atop a thick mat of turf-forming algae.

Cited by 16 publications

References 61 publications

Wasted effort: recruitment and persistence of kelp on algal turf

Wasted effort: recruitment and persistence of kelp on algal turf

Turf wars: competition between foundation and turf-forming species on temperate and tropical reefs and its role in regime shifts

Nipped in the bud: mesograzer feeding preference contributes to kelp decline

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