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.
Seasonal and intra-thallus variations of energy content and chemical composition were assessed in an intertidal population of Macrocystis in southern Chile. Phylloid protein and lipid from cultured material were compared with seasonal variation in native Macrocystis. Furthermore, populations in northern and southern Chile and Falkland Islands were compared with various intra-/ inter-cultivar genotypes of Chilean Macrocystis. Energetic values did not show seasonal or intra-thallus variations, with the exception of pneumatocysts, which had high levels of ash (49.9% DW) and low values of total energy (8.3% DW). Seasonal patterns were detected in protein and carbohydrate composition, with opposite trends. Likewise, holdfasts contained high amounts of protein (21.0% DW), and phylloids were high in soluble carbohydrates (4.5% DW). Lipids instead showed two peaks per year in an intertidal population and reached up to 0.4% DW. Alginic acid was the major organic compound in intertidal Macrocystis (46.8% DW), with differences on seasonal and intra-thallus levels. Mannitol content, in contrast, was erratic and lower than in other Laminariales (<5% DW). In general, protein and lipid content in our cultivars were 20% higher than in natural populations. Our experimental results indicate the possibility to manipulate the chemical composition of Macrocystis thalli through inter-/intra-specific crosses. This will be a basis, upon which selected genotypes can open new perspectives to Macrocystis mariculture industries in 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≈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 (≈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 laboratorygrown seedlings are unavailable, mature sporophylls from nearby Macrocystis beds can be used to establish new recruits on rocky substrata.
In Bahia Chasco, Atacama, the integrifolia morph of Macrocystis forms one of the most important kelp forests in northern Chile. In order to determine effects of local harvesting policies, we evaluated the population dynamics of this resource in intact, frequently disturbed, and permanently and completely harvested areas. Recruitment, frond length, reproductive phenology and standing crop were assessed monthly. In intact areas, frond length and ratio of reproductive individuals were higher, but recruitment was poorly stimulated. On the other hand, complete harvest had an important effect on Macrocystis population dynamics. Whereas recruitment and growth were much higher after harvest events, reproductive phenology was lower. The harvest techniques with different frequencies practiced by Bahia Chasco fishermen were less harmful than complete harvest, and we conclude that current exploitation techniques applied in this location are not deleterious for the giant kelp beds. They even have favorable effects by renewing the population through stimulation of sexual reproduction, recruitment and growth of young individuals.
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