The Ecosystem Impacts Of Kelp Forest Habitat Restoration, Including Important Fishery Species
Period: 2/1/2012 -
|Federal Funds:||State Funds:|
Quantify species and community impacts (fish, invertebrates and algae) at restored urchin barren sites due to kelp restoration on rocky reefs in Santa Monica Bay.
Quantify the ecosystem effects of restoration on the scale of a reef (i.e. are reef areas proximate to urchin barrens and recently restored sites different from established kelp forest reference areas?).
Rocky reef sites along the Palos Verdes Peninsula will be sampled annually following a full Before/After, Control/Impact (BACI) sampling design. Sampling of fishes, invertebrates, algae and physical habitat characteristics will be performed following an established comprehensive SCUBA based visual survey methodology. Sites will fall into 3 categories: Barren/Restoration: the urchin barren kelp restoration sites; Kelp Forest Reference: to serve as the controls for both the Barren/Restoration and Restoration Adjacent sites; Restoration Adjacent: to examine reef-scale impacts of kelp restoration, in particular to evaluate the potential that increases/decreases in density inside restored sites are due to immigration/emigration from/to adjacent areas. Control and impact site pairs will be sampled during the summer/fall sampling period prior to the start of restoration efforts at each site, and again during the summer/fall sampling period once each restoration site reaches restored status. Species specific analyses will follow standard BACI methods. Multivariate nMDS and ANOSIM techniques will be used to evaluate community impacts of restoration.
Given the complexity of factors impacting these urban rocky reefs, conservation and resource management efforts demand an equally diverse and proactive suite of strategies. One such endeavor is kelp restoration. These large scale sea urchin relocation projects have successfully enabled the natural re-development of Giant Kelp in demonstration plots on shallow rocky-reefs in Santa Monica Bay. Restoration efforts are now being expanded across a larger impacted region of the Palos Verdes Peninsula. This presents a novel opportunity to develop evaluation tools for habitat restoration in terms of ecosystem response. Understanding the potential of kelp restoration to compliment concurrent management actions to limit fishing pressure (e.g., Marine Protected Areas) and to mitigate the effects of sedimentation and pollution (e.g., watershed management, artificial reefs) will be key to informing the implementation and evaluation of these adaptive and integrative management strategies throughout southern California.
Publications & other print media:
Kelp forest habitat restoration has the potential to increase sea urchin gonad biomass
Jeremy T. Claisse 1,, Jonathan P. Williams 1, Tom Ford 2, Daniel J. Pondella II 1, Brian Meux 3, and Lia Protopapadakis 2
When taking an ecosystem-based approach to marine resource management, managers may be able to implement a combination of management tools in order to mitigate the socioeconomic impacts of implementing any one in isolation, while providing greater overall ecological benefits. The harvest of Strongylocentrotus franciscanus (red sea urchin) for their gonads is one of the most important commercial fisheries in California. However, in some locations, high densities of the unfished Strongylocentrotus purpuratus (purple sea urchin) can clear expanses of kelp forest resulting in urchin barrens. The lack of macroalgal food resources can result in reduced gonad production, making S. franciscanus within barrens less valuable to a fishery. We investigated the potential of kelp forest habitat restoration, which may be achievable primarily by removing S. purpuratus from barrens, to positively impact the local S. franciscanus fishery and offset the losses in fishing grounds within recently established MPAs in our study area. Generalized linear modeling of the relationship between gonad weight and length (test diameter) demonstrated clear size-specific differences in gonad production between urchins collected in barrens and kelp forests. These relationships varied over time, with the maximum observed mean gonad biomass at length being 484% greater in kelp forest than barren habitat for S. franciscanus just above the legal size limit. The variability in S. franciscanus density (5.2 times greater in urchin barrens), size structure (mean test diameters were approximately 50% greater in kelp forest) and gonad production were then incorporated using Monte Carlo simulations. Results indicated that restoration could potentially result in an 864% increase in S. franciscanus gonad biomass available to the fishery, and a 132% increase in reproductive potential per unit area of urchin barren restored to kelp forest. If all 36 ha of urchin barren habitat mapped outside of the new MPAs in the study area were restored, the increase in gonad biomass available to the fishery could potentially offset 52% of which is now protected within the 109 ha of rocky reef in the new MPAs. Kelp restoration has the potential to play a valuable role as one of many integrated tools in an ecosystem-based management approach.
Read More: http://www.esajournals.org/doi/full/10.1890/ES12-00408.1
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