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POTENTIAL IMPACTS of KELP FOREST HABITAT RESTORATION ALONG the PALOS VERDES PENINSULA Jeremy T

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POTENTIAL IMPACTS of KELP FOREST HABITAT RESTORATION ALONG the PALOS VERDES PENINSULA Jeremy T POTENTIAL IMPACTS OF KELP FOREST HABITAT RESTORATION ALONG THE PALOS VERDES PENINSULA Jeremy T. Claisse1, Jonathan P. Williams1, Laurel A. Zahn1, Daniel J. Pondella1 & Tom Ford2 1 Vantuna Research Group, Department of Biology, Occidental College, Los Angeles, CA 90041 2 The Bay Foundation, Los Angeles, CA 90045 Urchin barrens and kelp forest habitat Urchin barrens effect the invertebrate, kelp, benthic cover and fish communities restoration We sampled 25 sites in both 2012 and High densities of the unfished purple 2013 (Fig. 1) using a standardized Kelp Community giant kelp urchin (Strongylocentrotus purpuratus) comprehensive community monitoring southern result in ‘‘urchin barrens’’ largely survey protocol (for details see Hamilton et sea palm devoid of macroalgae across 61 ha of al. 2010 PNAS 107:18272-18277 and Claisse et rocky reef along the Palos Verdes al. 2012 PLoS ONE 7:e30290). Sites included Peninsula in southern California (Fig. 1; established kelp forests (green), extent of mapped urchin barrens shown urchin barrens (red) and those adjacent to urchin barrens (grey). We only in red). The study presented here is used data from the 5 m depth zone where most barrens occur. Species- focused on evaluating the potential specific site means were calculated by pooling data over both years. For effects of kelp forest habitat restoration fishes, estimated lengths were converted to weights using length-weight Fig. 4. nMDS plot of the kelp community using square by comparing the differences between relationships. root transformed density and a Bray-Curtis similarity ©Tom Boyd Images 2013 urchin barren and kelp forest habitats. matrix. Significant differences were found among site • We found significant community level differences among site categories (R adonis PERMANOVA: F2,16=8.5, categories in nMDS plots (Fig. 2, 4, 7, 8). partial R2=0.52, p=0.001) • Site category differences were then illustrated in selected species Fig. 5. Circles are site-specific kelp densities which made large contributions to the overall community dissimilarity with site category means and SE error bars. between site categories (based on SIMPER analyses; Fig. 3, 5, 6, 9). erect coralline algae Different letters indicate significant Tukey HSD pairwise differences. Fig. 1. Sampling sites • Is some cases these reflect negative impacts of urchin barrens on along the Palos Verdes important fishery species (e.g., lobster and kelp bass; Fig. 3, 9). erect red Peninsula. The extent of nearshore rocky reefs are CCA algae Benthic Cover Type shown in white (Claisse et al. 2012 PLoS ONE 7:e30290) and mapped urchin barrens are Invertebrate Community displayed in red. The Fig. 2. nMDS plot of the boundaries of two “conspicuous, solitary adjacent MPAs in the macroinvertebrate” community study area (SMCAs) are using square root transformed also shown. Note these density and a Bray-Curtis MPAs went into effect similarity matrix. Significant on January 1, 2012 and it differences were found among Fig. 7. nMDS plot of the UPC benthic cover type using is assumed that they had site categories (R adonis arcsine square root transformed ratios and a Bray- not be in existence long PERMANOVA: F2,22=17.1, Curtis similarity matrix. Significant differences were enough to impact the partial R2=0.61, p=0.001) found among site categories (R adonis PERMANOVA: results of this study. 2 F2,22=9.6, partial R =0.47, p=0.001) purple urchin red urchin California sheephead California kelp perch spiny lobster Fig. 6. Circles are site-specific benthic percent cover with site category means and SE error bars. Different letters indicate Over the past 20 years pilot kelp restoration projects significant Tukey HSD pairwise differences. kelp bass in the region have demonstrated re-establishment of giant kelp (Macrocystis pyrifera) after removal of urchins from barrens, with 98% of the urchins removed being the unfished purple urchins. The Fish (Biomass) Community larger red urchin is an important commercial fishery species in California (see section below). Since July 2013, a large scale kelp forest habitat restoration effort (via targeted destruction of purple urchins - right) is being carried out by a coalition including two NGOs (The Bay Foundation and Los Angeles Waterkeeper) and three commercial sea urchin harvesters. The current restoration efforts will Fig. 8 nMDS plot of the fish community using square root transformed biomass density and a Bray-Curtis leave the fished red urchin in place. Community and similarity matrix. Significant differences were found species-specific production effects of restoration will among site categories (R adonis PERMANOVA: Fig. 9. Circles are site-specific fish biomass densities with Fig. 3. Circles are site-specific invertebrate densities with site 2 F2,22=3.12, partial R =0.22, p=0.001) . be monitored over the coming years and compared category means and SE error bars. Different letters indicate site category means and SE error bars. Different letters with the results presented here. ©Tom Boyd Images 2013 significant Tukey HSD pairwise differences. indicate significant Tukey HSD pairwise differences. For more details see: Claisse et al. (2013) Kelp forest habitat Acknowledgments Kelp forest habitat restoration has the potential to increase red sea urchin gonad biomass restoration has the potential to increase sea urchin gonad biomass. Ecosphere 4: art38 Funding: While purple urchins are the primary cause of barrens in the study area, the harvest of the larger red urchin USC Sea Grant under Grant No. 10-069 issued (Strongylocentrotus franciscanus) for their gonads (aka “uni”) is one of the most valuable commercial fisheries in California. by the California Coastal Conservancy. MPA Grant #10-049, California Sea Grant We used Monte Carlo simulations to synthesize the variability in density, size structure, and size-specific gonad weight from Resulting in a 883% increase in red Project # RMPA-27A, through the California empirically collected data to estimate the red urchin gonad biomass available to the fishery (1) currently in urchin barrens urchin gonad biomass available to Marine Protected Areas Baseline Program. NOAA Restoration Center and the Montrose and (2) post-restoration, assuming conditions in restored barrens are similar to those observed in kelp forest habitat. the fishery per unit area restored Settlements Restoration Program. Contributions to the study: http://www.lib.noaa.gov D. Witting, C. Williams, B. Power, B. Meux, L. Protopapadakis, B. Grime, M. Winston, R. Red urchins were 5.2 times Stokes, D. Michels, A. Mikovari, B. Voung, J. more abundant in urchin But red urchin body sizes were Dorsey, S. Luce, J. Lyon, D. Coleman, N. Hall, And red urchins had reduced gonadal tissue production (i.e., the target of the Fig. 14. M. Quill, T. Boyd and the students, volunteers barrens than kelp forests… Gonad biomass smaller in urchin barrens … and employees from The Bay Foundation, Los commercial fishery) in barrens due to reduced availability of algal food resources… available to the fishery (i.e., only Angeles Waterkeeper, the Center for Santa from urchins above Monica Bay Studies at Loyola Marymount University and the Vantuna Research Group. Fig. 10. the legal minimum S. franciscanus size limit) and 95% density in urchin confidence intervals barren or kelp forest estimated from Contact Info: habitat. Error bars Monte Carlo are 95% likelihood simulations. Jeremy T. Claisse profile confidence Adjunct Assistant Prof., Biology Dept. intervals assuming a negative binomial Postdoc, Vantuna Research Group probability Occidental College, Los Angeles, CA distribution. email: [email protected] Fig. 13. Relationship between mean gonad weight and urchin test diameter www.oxy.edu/vantuna-research-group by habitat (barrens: red circles and solid line; kelp forest: green open circles Kelp Fig. 11. S. franciscanus size structure in urchin barren (red) Fig. 12. Representative S. franciscanus gonads (aka “uni”) and dashed line) following Ebert et al. (2011) and assuming a lognormal youtube: VRGMarineBio Barren and kelp forest (green) habitat. collected from kelp forest and urchin barren habitat. distribution of weight on length. facebook: oxymarinebiology .
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