Repopulation techniques for Macrocystis integrifolia (Phaeophyceae: Laminariales) in Atacama, Chile

The giant kelp Macrocystis (integrifolia) has been intensely harvested in northern Chile for several years. In order to prevent a future disaster, we developed two different techniques for restoration of damaged Macrocystis integrifolia beds in the Atacama region of Chile. (1) Explantation: Laboratory-grown juvenile sporophytes were fixed to different substrata (plastic grids, ceramic plates, or boulders) by elastic bands or fast-drying glue (cyanoacrylate). Explants reached 150-200 cm in length within 5 months (relative growth rate a parts per thousand aEuro parts per thousand 1.3-1.7 % day(-1)), and reproductive maturity in 5-7 months. (2) Seeding of spores: Mature sporophylls were placed at 8 m depth on the sea bottom, supported by cotton gauze sleeves attached to boulders of different origin. Sixty percent of clean boulders collected on the beach produced up to seven recruits per boulder. In contrast, 20 % of the boulders from the sea bottom, colonized by epibionts, showed up to two recruits. Relative growth rates, however, were similar (a parts per thousand 2.4-2.6 % day(-1)). Practical applications of our findings are: laboratory-produced juvenile sporophytes fixed to various substrata by elastic bands or cyanoacrylate glue can be used to colonize rocks or artificial reefs. In cases, where laboratory-grown seedlings are unavailable, mature sporophylls from nearby Macrocystis beds can be used to establish new recruits on rocky substrata.