Lessonia Nigrescens 

 

Description 

The genus Lessonia is made up of several species that have often been confused in literature and in common usage, due mainly to the fact that the characteristics that are most often used to distinguish species (blade/stipe length, shape of blade base, formation of mucilage canals and hollow stipes) have been found to be fairly dependent on environmental conditions and plant age. Lessonia nigrescens is one of the major species found around the southern coasts of South America. It is distinguished from other Lessonia species in the area by the presence of numerous stipes arising from a single holdfast.  Lessonia nigrescens is able to grow up to 4 meters tall (though some have described it as tall as 6 meters) with up to 20 terete stipes arising from a large conical holdfast composed of tightly fused haptera. These stipes are dichotomously branched, up to 4 centimeters in diameter, and terminating in narrow, linear blades up to 3 centimeters wide with entire margins. Blades on a single plant may be quite variable in width and can vary depending on environmental conditions.  Lessonia nigrescens is found more shallowly than other species such as Lessonia flavicans, often seen at the low water line of rocky, exposed shores. Some stands have been reported to be completely emergent at low tide, though this is not the norm. The massive holdfast of Lessonia nigrescens is what allows it to withstand the rough waters and high wave exposure common on these coasts, making it the dominant species in the low intertidal.

 

 

Names 

aracanto negra, aracanto negro, chascón, huiro negro, mop weed

 

Phylum Classification 

Ochrophyta

 

Geographic Distribution 

Lessonia nigrescens is limited in distribution to the Southern Hemisphere from central Peru to Cape Horn, between 14° and 40° S.

 

Uses 

Lessonia nigrescens is one of the kelp species that is harvested in Chile for extraction of alginate, a gelling agent with many applications in medical, textile, and food industries, often as a thickening agent in drinks, ice cream, and cosmetics. Lessonia nigrescens is an ingredient in body wraps and body polish from companies in Chile, Canada, and the United States.  Lessonia nigrescens is also used as a food source for aquaculture invertebrates, such as abalone.

 

Harvesting 

Lessonia nigrescens is only known to be harvested in northern and central Chile in September through December.

 

Harvesting Techniques 

Harvesting of Lessonia nigrescens is done by hand at low tide. Standard practice is to take the entire plant but to remove no more than 2/3 of the population. This leaves large openings between the plants and allows for regeneration of the population by the remnant population of Lessonia nigrescens.

 

Ecosystem 

Lessonia nigrescens is an important component of its ecosystem, forming the basis of a complex food web.  Many species use Lessonia nigrescens for food and shelter. The canopy formed by this species also form a protected area for less tolerant algal species to thrive, increasing the complexity and biodiversity of the ecosystem.  Lessonia nigrescens is also especially important because of the massive holdfast of these plants is often teeming with a wide variety of life. Invertebrate species such as crustaceans, snails, and worms create complex networks of holes and tunnels within these holdfasts which are then able to serve as valuable refuge space for juveniles of many species.  Lessonia nigrescens is threatened by over-harvesting and by natural disasters such as El Niño events, which have been known to destroy almost the entire population of Lessonia nigrescens.  Good management of kelp communities including sustainable harvest is critical to the health of these ecosystems.