Sustainable Harvesting of the Ecosystem Engineer Corallina officinalis for Biomaterials

Caroline L Magill,Mark P Johnson,Christine A Maggs,Nessa O’Connor

doi:10.3389/fmars.2019.00285

Abstract

Macroalgae are of increasing interest for high-value biotechnological applications, but some seaweeds, such as coralline red algae, cannot be grown in cultivation cost-effectively. Wild harvesting of seaweeds, particularly of those that are ecosystem engineers, must be demonstrably sustainable: here we address the topic of resource sustainability in the context of harvesting Corallina officinalis in Ireland for bioceramics. C. officinalis provides habitat for a diverse macrofaunal community and the effects of harvesting C. officinalis on the associated fauna must be included in any assessment of harvesting sustainability. Corallina intertidal turfs subject to experimental harvesting were confirmed, using DNA barcoding with cox1, to comprise only C. officinalis and not the pseudocryptic species C. caespitosa, despite the wide range of morphologies, and they had high genetic diversity. Harvesting of C. officinalis was carried out at experimental sites by two techniques (hand cutting and pulling) to test the recovery of the primary resource and the associated macroinvertebrate assemblage. Harvesting the alga by both methods encouraged regrowth: cut and pulled plots had a much higher growth rate than unharvested turfs, regaining their original length within 4-6 months of harvesting, suggesting that turfs of this species may grow to a predetermined length. The structure, richness and evenness of the invertebrate assemblage were not significantly affected by harvesting C. officinalis by cutting or pulling, though some organisms within the community showed a response to harvesting. The pattern of recovery of the sediment, an important component of the C. officinalis habitat, was consistent with the shorter (harvested) turf trapping more sediment than longer natural turfs. As many of the organisms associated with the habitat use the sediment for food or building materials, this may have ameliorated the effects of harvesting on the community. A period of a year between harvests is recommended to allow the C. officinalis biomass to return to baseline levels and unharvested fallow areas should be included in a harvesting plan to allow macroinvertebrates to re-colonise the harvested turf.

Highlights

Algae are increasingly important as a potentially sustainable resource for biotechnological applications (Kim and Chojnacka, 2015; Rocha et al, 2018)
Whilst microalgae are suitable for culture in bioreactors and some macroalgae, or seaweeds, are grown on frames and ropes in the open water (FAO, 2003–2015; Chung et al, 2017), other seaweeds are more efficiently harvested from the wild (McLaughlin et al, 2006; Mac Monagail et al, 2017)
Analysis of the cox1 sequences, in an alignment with multiple GenBank sequences of Corallina spp., indicated that the five Fanad samples were all conspecific. They were identifiable as C. officinalis because some sequences were identical to the C. officinalis epitype cox1 GenBank accession no

Summary

Introduction

Algae are increasingly important as a potentially sustainable resource for biotechnological applications (Kim and Chojnacka, 2015; Rocha et al, 2018). Wild algae can be commercially harvested either by hand or mechanically. Intertidal species with long thalli which float on the surface, such as Ascophyllum nodosum, can likewise be harvested mechanically at high tide by shallow-draft paddlewheel or water jet-driven cutters (Meland and Rebours, 2012). Species with short or delicate thalli are not suitable for mechanical harvesting and must be harvested by hand. Manual (artisanal) harvesting of wild seaweeds has a long history in coastal communities, where they have been collected for food, medicine and as a soil improver (Reed, 1907; Morrissey et al, 2001; Mac Monagail et al, 2017; Yang et al, 2017). Manual harvesting is informed by traditional practices and hand harvesting of seaweeds is largely regarded as sustainable (McLaughlin et al, 2006; O’Toole and Hynes, 2014). Unregulated wild harvest can lead to depletion of a species in an area, increasing market value and intensifying harvest efforts on the remaining resources (e.g., Chondracanthus chamissoi in Peru: Rebours et al, 2014)

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