Algae Green

Ascophyllum nodosum and its ecophysiology

Ascophyllum nodosum commonly named “the knotted wrack” in Ireland (“An Fheamainn Bhuí” in Irish) is the main source of OGT’s AlgaeGreen range of products. The seaweed is attached to the rocks using a clump (holdfast) and at high tide, floats vertically in the water column due to the presence of vesicles or air bladders (pneumatocysts); at middle tide, the vesicles also allow a wide repartition of the top of the seaweed at the surface of the water and guaranties maximum light exposure for photosynthesis. This floating apparatus is therefore perfectly designed for the seaweed species of natural sheltered habitat.

From the holdfast, a main shoot is growing at an average rate of 13cm per year (from 8cm to 21cm) and to each year of growth corresponds one vesicle. It is therefore quite easy to age the seaweed shoot by counting the number of vesicles on the main shoot. Lateral shoots are also growing from the main shoot as well as  basal shoots which also grow from the holdfast which lead to a “bush-like” morphology. Marine biologists have established that by leaving about 25cm over the holdfast on the main shoot, it allows the plant to regenerate in 2 to 5 years, depending on the growing area. Even though there is a sexual reproduction involving gametes, it has been observed that the fastest biomass reproduction means remains to be the re-growth of cut or shredded (storms) primary shoots.

The species are traditionally hand harvested by local cutters in Ireland. OGT’s raw material harvesters are following a careful rotation and selection of cutting areas in relation to the natural growth and physiological parameters mentioned above. The primary concern of these local harvesters and OGT is to ensure the sustainability of this valuable resource in respect to its natural environment and ecosystem.