Herbivore biocontrol and manual removal successfully reduce invasive macroalgae on coral reefs
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Abstract
Invasive macroalgae pose a serious threat to coral reef biodiversity by monopolizing reef habitats, competing with native species, and directly overgrowing, and smothering reef corals. Several invasive macroalgae (Eucheuma clade E, Kappaphycus clade A and B, Gracilaria salicornia, and Acanthophora spicifera) are established within Kāne‘ohe Bay (O‘ahu, Hawai‘i, USA), and reducing invasive macroalgae cover is a coral reef conservation and management priority. However, invasive macroalgae control techniques are limited and few successful large-scale applications exist. Therefore, a two-tiered invasive macroalgae control approach was designed, where first, divers manually remove invasive macroalgae (Eucheuma and Kappaphycus) aided by an underwater vacuum system (“The Super Sucker”). Second, hatchery-raised juvenile sea urchins (Tripneustes gratilla), were outplanted to graze and control invasive macroalgae regrowth. To test the effectiveness of this approach in a natural reef ecosystem, four discrete patch reefs with high invasive macroalgae cover (15 – 26 %) were selected, and macroalgae removal plus urchin biocontrol (treatment reefs, n = 2), or no treatment (control reefs, n = 2), was applied at the patch reef-scale. In applying the invasive macroalgae treatment, the control effort manually removed ~ 19,000 kg of invasive macroalgae and ~ 99,000 juvenile sea urchins were outplanted across to two patch-reefs, totaling ~ 24,000 m2 of reef area. Changes in benthic cover were monitored over two years (five sampling periods) before-and-after the treatment was applied. Over the study period, removal and biocontrol reduced invasive macroalgae cover by 85 % at treatment reefs. Our results show that manual removal in combination with hatchery raised urchin biocontrol is an effective management approach for controlling invasive macroalgae at reef-wide spatial scales and temporal scales of months to years.
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2018. Herbivore biocontrol and manual removal successfully reduce invasive macroalgae on coral reefs. PeerJ Preprints 6:e26796v1 https://doi.org/10.7287/peerj.preprints.26796v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Brian J Neilson conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft, wrote manuscript, analyzed data, performed and collected the data.
Christopher B Wall analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft, wrote the manuscript and performed the analysis.
Frank T Mancini conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft, developed the study design, oversaw data collection and management, edited manuscript.
Catherine A Gewecke conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft, developed study design, edited the manuscript and collected data.
Data Deposition
The following information was supplied regarding data availability:
Zenodo (tbd)
Funding
This work was made possible by funding provided by The State of Hawai‘i, Department of Land and Natural Resources, a Hawai‘i Invasive Species Council grant, a NOAA Estuary Restoration Grant, and a USFWS Sport Fish Restoration Grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.