Abstract
Kelp and macroalgal forests provide the ecological foundations of many temperate rocky reef ecosystems, but have regionally declined, often due to sea urchin overgrazing and the formation of urchin barrens. Sea urchin removal has long been used to investigate kelp-sea urchin dynamics and is increasingly being promoted for kelp forest restoration. In this review, we assess the methods and outcomes of sea urchin removal experiments to evaluate their potential use and feasibility as a tool for restoring macroalgal forests. Seventy-nine sea urchin removal projects were reviewed from temperate subtidal rocky reef systems between 1975 and 2020. Removal methods were often not reported (35%), but included manual culling, including crushing (25%) and chemical application (quicklime, 9%), or relocating sea urchins (13%). Only a small percentage of removals were large in scale (16% > 10 ha) and 92% of these utilized culling. Culling is often the most practical method of urchin removal, but all methods can be effective and we encourage development of new approaches that harvest and utilize low-quality urchins. Urchin removal led to an increase in macroalgae in 70% of studies, and a further 21% showed partial increases (e.g., at one or more sites or set of conditions). Restoration effectiveness is increased by removing essentially all sea urchins from discrete areas of urchin barrens. Sea urchin removal provides a simple, relatively cheap, and effective method that promotes kelp recovery within urchin barrens. However, sea urchin removal does not address the underlying cause of elevated sea urchin populations and is unlikely to provide a long-term solution to restore kelp forests and full ecosystem function on its own. We therefore suggest that if sea urchin removal is considered as a tool for kelp forest restoration, it should be incorporated with other management measures that aim to increase kelp forest resilience and biodiversity (e.g., marine protected areas, predator protection or enhancement). This will ensure that kelp restoration efforts have the greatest ecological, socio-economic and cultural outcomes in the long-term.
Highlights
“I will briefly summarize our labors by saying that the aforesaid Quicklime did grievously smite the spiny enemies of Your glorious empire in such a fashion that most of them perished as they so richly deserved.”—Brock Bernstein Letter of Transmittal to Queen Elizabeth II, 30 October 1981, cover letter of Bernstein and Welsford (1982)
This review found sea urchin removal to be generally effective in promoting recovery of macroalgal forests, and that several removal methods are feasible to conduct on large-scales for restoration purposes
Most of the research reviewed here found that essentially all accessible urchins needed to be removed in order to promote macroalgal regrowth. This is consistent with other reviews on urchin barrens and kelp forest dynamics, which included urchin declines resulting from manual removals, storms, disease die-offs, and marine reserve establishment (Filbee-Dexter and Scheibling, 2014; Ling et al, 2015)
Summary
“I will briefly summarize our labors by saying that the aforesaid Quicklime did grievously smite the spiny enemies of Your glorious empire in such a fashion that most of them perished as they so richly deserved.”—Brock Bernstein Letter of Transmittal to Queen Elizabeth II, 30 October 1981, cover letter of Bernstein and Welsford (1982). Kelp forests provide numerous regulatory, provisionary, and cultural services with large economic value, including carbon sequestration and nutrient remediation, coastal protection, enhanced fisheries and tourism, and harvestable food and materials for sustenance and trade (Bennett et al, 2016; Wernberg et al, 2019) When these macroalgal forests are lost, less productive and structurally simple states such as urchin barrens or algal turfs are frequently left in their wake, with ecological and socio-economic ramifications (Graham, 2004; Filbee-Dexter and Wernberg, 2018). Urchin populations must be reduced to very low levels
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.