Lessonia nigrescens

Lessonia nigrescens, the grey weed or giant grey weed, is a South American kelp species in the genus Lessonia.

Lessonia nigrescens
Lessonia nigrescens at El Quisco beach, Chile
Scientific classification
Domain:	Eukaryota
Clade:	Sar
Clade:	Stramenopiles
Phylum:	Ochrophyta
Class:	Phaeophyceae
Order:	Laminariales
Family:	Lessoniaceae
Genus:	Lessonia
Species:	L. nigrescens
Binomial name
Lessonia nigrescens Bory de Saint-Vincent, 1826

There is at least two populations of the seaweed, marked by the difference in phenolic content. There is a subtidal population with higher phenol content and an intertidal population with a lighter phenol content. The difference in the phenolic content can be explained by the herbivory selection pressure due to the sea snail Tegula tridentata.^[1]

UV treatment induces the production of phlorotannins that accumulate in physodes.^[2]

This weed contains the phytosterol saringosterol that shows an inhibitory effect on Mycobacterium tuberculosis growth.^[3]

Illustration from "Nordisk familjebok".