Sedentary urchins influence benthic community composition below the macroalgal zone

Lowe, Alexander T.; Whippo, Ross; Galloway, Aaron W. E.; Britton‐Simmons, Kevin H.; Dethier, Megan N.

doi:10.1111/maec.12124

Cited by 18 publications

(26 citation statements)

References 44 publications

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“…1). Red urchins can capture > 20 g drift algae urchin −1 d −1 in the San Juan Archipelago (Lowe et al 2014), an amount greater than they consumed in this study. The captured drift algae are composed of many species, among which Agarum is common, while Nereocystis is less frequently observed (Britton-Simmons et al 2009).…”

Section: Discussionmentioning

confidence: 67%

“…Through wave action, tidal currents, and storms, drift algae are transported to neighboring ecosystems in both shallow photic and deep aphotic habitats (Duggins et al 1989, Krumhansl & Scheibling 2012a, where they support substantial secondary production and diversity (Vetter & Dayton 1998). This carbon subsidy from shallow to deep regions constitutes an essential food source for primary consumers and affects many aspects of ecosystem dynamics (Britton-Simmons et al 2009, Lowe et al 2014.…”

Section: Introductionmentioning

confidence: 99%

“…In the San Juan Islands Archipelago, USA, red urchins (Mesocentrotus [=Strongylocentrotus] franciscanus) are common from the shallow subtidal to depths well beyond the photosynthetic limit of kelps (>100 m; Britton-Simmons et al 2012). Urchins in this system feed primarily on drift algae (Britton-Simmons et al 2009) and can remain sedentary owing to the abundance of drift algae throughout their depth range , Lowe et al 2014. Urchins (Mesocentrotus spp.…”

Section: Introductionmentioning

confidence: 99%

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Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Raymond¹,

Lowe²,

Galloway³

2014

Mar. Ecol. Prog. Ser.

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Kelps in temperate marine ecosystems produce substantial detrital biomass that provides a carbon subsidy to consumers. After detachment, detrital kelp degrades and potentially changes in nutritional quality. Red sea urchins Mesocentrotus franciscanus are an abundant consumer of drift algae, but little is known about the effects of kelp degradation on feeding preferences or nutritional value to urchins. We compared the response of gonad index (GI), carbon and nitrogen stable isotope (SI) content, and fatty acid (FA) composition in the gonads of red urchins fed 2 species of fresh or degraded kelp for 17 wk. We found significant effects of kelp species but not kelp degradation state on urchin GI and SI, but also significant interactions between kelp species and degradation state. Urchins with greater gonad growth had δ 13 C values more similar to those of their diet than did urchins with low gonad growth. Multivariate FA composition of the kelp diets (both in terms of species and degradation state) and the gonads of urchins fed those diets differed significantly. Several polyunsaturated essential FA (including SDA, EPA, and ARA) and FA summary classes were important for differentiating urchin gonads among treatments, suggesting kelp species-dependent effects of diet degradation. The total concentration of ω-3 and ω-6 FA declined with degradation state in both diets but did not differ in the gonads of urchins fed these diets. Thus, even if diets are depleted in certain FA, urchins are able to maintain concentrations of these FA in their gonads. KEY WORDS: Fatty acids · Stable isotopes · Gonad index · Food availability · Red urchins · Drift algaeResale or republication not permitted without written consent of the publisher

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Section: Discussionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Raymond¹,

Lowe²,

Galloway³

2014

Mar. Ecol. Prog. Ser.

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“…In the present study, we demonstrated that even though there were no significant differences in the FA profiles between algae consumed and egested, the urchins increased the nutritive quality of egesta in the form of increased total lipid content. This has significant implications for marine food webs, because increased lipid content in a food source is likely to benefit consumers, and suggests a mechanism for why macrophyte-derived carbon (generally) and kelpderived carbon (more specifically) may be a valuable trophic subsidy (Sauchyn and Scheibling, 2009;Sauchyn et al, 2011;Britton-Simmons et al, 2012;Lowe et al, 2015) to benthic organisms that might not otherwise utilize these sources directly.…”

Section: Discussionmentioning

confidence: 99%

Trophic Transfer of Macroalgal Fatty Acids in Two Urchin Species: Digestion, Egestion, and Tissue Building

et al. 2018

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Sea urchins are ecosystem engineers of nearshore benthic communities because of their influence on the abundance and distribution of macroalgal species. Urchins are notoriously inefficient in assimilation of their macroalgal diets, so their fecal production can provide a nutritional subsidy to benthic consumers that cannot capture and handle large macroalgae. We studied the assimilation of macroalgal diets by urchins by analyzing the profiles of trophic biomarkers such as fatty acids (FAs). We tracked macroalgal diet assimilation in both Strongylocentrotus droebachiensis and S. purpuratus. Juvenile S. droebachiensis and adult S. purpuratus were maintained for 180 and 70 days, respectively, on one of three monoculture diets from three algal phyla: Nereocystis luetkeana, Pyropia sp., or Ulva sp. We then analyzed FA profiles of the macroalgal tissue fed to urchins as well as urchin gonad, gut, digesta, and egesta (feces) to directly evaluate trophic modification and compare nutritional quality of urchin food sources, urchin tissues, and fecal subsidies. In the S. purpuratus assay, there were significantly more total lipids in the digesta and egesta than in the algae consumed. The FA profiles of urchin tissues differed among urchin species, all diets, and tissue types. Despite these differences, we observed similar patterns in the relationships between the urchin and macroalgal tissues for both species. Egesta produced by urchins fed each of the three diets were depleted with respect to the concentration of important long chain polyunsaturated fatty acids (LCPUFAs), but did not differ significantly from the source alga consumed. Both urchin species were shown to synthesize and selectively retain both the precursor and resulting LCPUFAs involved in the synthesis of the LCPUFAs 20:4ω6 and 20:5ω3. S. droebachiensis and S. purpuratus exhibited consistent patterns in the respective depletion and retention of precursor FAs and resulting LCPUFAs of Pyropia and Ulva tissues, suggesting species level control of macroalgal digestion or differential tissue processing by gut microbiota. For both S. droebachiensis and S. purpuratus, macroalgal diet was a surprisingly strong driver of urchin tissue fatty acids; this indicates the potential of fatty acids for future quantitative trophic estimates of urchin assimilation of algal phyla in natural settings.

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“…This large kelp provides abundant food, including detrital material, to food webs within and below the photic zone ( Duggins & Eckman, 1994 ), as well as habitat and nursery space for a variety of fish species ( Carr, 1991 ). Red urchins playa smaller role in structuring these bull kelp forests than in many other habitats because of the high availability of drift kelp that limits their need to search for food ( Britton-Simmons, Foley & Okamoto, 2009 ; Lowe et al, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

Dobkowski

2017

PeerJ

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The Northern kelp crab (Pugettia producta) and the graceful kelp crab (Pugettia gracilis) are common primary consumers in bull kelp beds near the San Juan Islands (Salish Sea, NE Pacific). In this system, urchins (often considered the most voracious herbivores exerting top-down control on kelp beds) tend to remain sedentary because of the high availability of detrital macroalgae, but the extent to which kelp crabs consume kelp (and other food options) is largely unknown. I conducted four types of laboratory feeding experiments to evaluate kelp crab feeding patterns: (1) feeding electivity between bull kelp (Nereocystis luetkeana) and seven species of co-occurring local macroalgae; (2) feeding electivity on aged vs. fresh bull kelp; (3) feeding preference between N. luetkeana and small snails (Lacuna sp.); and (4) scaling of feeding rate with body size in P. producta and P. gracilis. In choice experiments, P. producta consumed greater mass of N. luetkeana than of other macroalgal species offered and elected to eat fresh bull kelp over aged. However, P. producta also consumed snails (Lacuna sp.), indicating more generalized feeding than previously suspected. Feeding rates for P. producta exceeded the expected 3∕4 scaling rule of metabolic rates, indicating that larger P. producta may have a disproportionately large impact on bull kelp. A subtidal field experiment, designed to assess the influence of consumers on juvenile bull kelp net tissue gain, found that only fully enclosed (protected) bull kelp increased in wet mass and blade length. Herbivory by kelp crabs, among other consumers, is likely to play a previously unrecognized role in mediating the growth and survival of this annual kelp species within the Salish Sea.

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Sedentary urchins influence benthic community composition below the macroalgal zone

Cited by 18 publications

References 44 publications

Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Trophic Transfer of Macroalgal Fatty Acids in Two Urchin Species: Digestion, Egestion, and Tissue Building

The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

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