Holdfast fragmentation of Macrocystis pyrifera (integrifolia morph) and Lessonia berteroana in Atacama (Chile): a novel approach for kelp bed restoration

Abstract

The kelps Macrocystis pyrifera (integrifolia morph) and Lessonia berteroana (northern lineage of Lessonia nigrescens) are intensely harvested in Atacama, northern Chile, for abalone forage and alginate production. Local situations call for simple restoration techniques for over-exploited kelp beds. We excised holdfast portions from parental specimens, including parts of stipes and phylloids. Untreated adult thalli and unmanipulated specimens served as controls. Fragments of both species were attached to boulders or rock platforms with elastic bands or cyanoacrylate glue. Transplanted fragments quickly formed new haptera, colonized new substrata, and reached reproductive maturity. Macrocystis regenerates increased in total length and holdfast diameter in one or both directions of the rhizome, forming a pair of stipes, followed by rhizome and haptera development. In Lessonia, tissue of non-injured zones took over new holdfast growth. Success of this propagation method varied with season and substrata. Both species proceeded to complete regeneration of holdfasts. However, holdfasts of older Macrocystis thalli partly decomposed, resulting in two apparently identical individuals. Advantages of these propagation methods are discussed in ecological and restoration contexts.

Giant kelp vegetative propagation: Adventitious holdfast elements rejuvenate senescent individuals of the Macrocystis pyrifera “integrifolia” ecomorph

“…, Westermeier et al. ). These observations raise questions as to what extent this potential occurs in natural populations, and how it is affected by intense harvesting.…”

“…Westermeier et al. (, ) pointed out that these stoloniferous holdfasts may contribute to propagation in “ integrifolia ” populations. Holdfast fragments are able to re‐attach to suitable substrata, to grow in two directions when excised, and even to produce more stipes and fronds.…”

“…(d) Cultivation system in boulders after Westermeier et al. (), trying to immobilize the hapteron‐like structure using elastic bands (arrow). (e) Development of early secondary holdfasts from a stipe, after the first month in culture.…”

“…Thirty clones were selected and attached to boulders, using elastic bands as described by Westermeier et al. () (Fig. d), and placed within the Macrocystis bed at Bahia Chasco at 6–8 m depth.…”

“…), as well as in repopulation experiments by holdfast fragmentation, recruits and outplants produced in the laboratory (Westermeier et al. ). Adventitious holdfasts grew especially well within the first 2 months (Friedman's χ 2 4 = 24.730, P < 0.05), reaching 8 cm from 1 cm initial size (Fig.…”