Kelp Harvesting and Farming in South Africa

Kelp refers to large brown seaweeds found along South Africa’s west and south coasts, with two main species: Sea Bamboo (Ecklonia maxima) and Split Fan (Laminaria pallida). These underwater forests support diverse marine life and provide valuable bioproducts for industry, e.g. Biofuel, alginates, fertilizers, Bioplastics, Pharmaceuticals etc. Let’s explore how kelp is harvested and the plans for farming it in South Africa.

The life history of kelp

Before we discuss the harvesting and farming of kelp plant, we need to understand how these plants grow. The big plants we see in the water are actually just one part of a greater life history. The figure below, taken from this kelp havesting guide, shows the different stages of kelp growth.

The large kelp plant we commonly see is known as the sporophyte, or the stage that produces spores. This is the stage that releases microscopic spores from fertile areas on the fronds (leaf-looking bit). These areas are visible as lighter-coloured patches on the frond. The spores swim in the water and soon land on the rock where they attach and germinate. These spores are either male or female and will grow into separate male or female plants called gametophytes (egg and sperm-producing plants). These gametophytes are like tiny tufts of filaments, and they become
fertile and produce either eggs or sperm. The male plants release sperm, and they will find their way to the female plants to fertilize the egg. The fertilized egg grows into a tiny sporophyte, which start as small flat blades. Over time they develop secondary blades or fronds, and later a long stipe that becomes hollow at the top. After about 2 years, the plants will be able to reach the top of the water if it started at about 12–15 meters underwater.

Harvesting Kelp

In South Africa, harvesters either collect the entire kelp plant, known as ‘whole plant harvesting,’ or they cut only the fronds, known as `frond-only harvesting`. Both methods have advantages and disadvantages.

Whole-plant harvesting

Whole-plant harvesting occurs when harvesting kills the entire plant. This could happen by either cutting the stipe near the base (usually done by divers), or cutting the whole kelp head (from a boat, or divers). If the head of a kelp plant is damaged or destroyed, the entire organism will perish. However, it will be replaced by younger plants sprouting from its base, typically within a two-year period. This is why it is important for harvesters not to damage young plants at the base. This method gets more material out, but is the most destructive.

Frond-only harvesting

Frond-only harvesting occurs when cutting the kelp plant’s fronds allows it to survive and regrow its fronds. The main growth region is near the base of each frond, and older fronds are continually eroding at their tips. Therefore, by cutting the fronds at least 25 cm from their base, you can obtain most of the frond material without killing the plant. You will not kill the kelp plant if you do not damage the growing zone at the base of the frond, or the primary blade, bulb or stipe. The fronds will grow back in 4–6 months. This method initially collects less material, but over time, it allows for harvesting much more product from the same area.

Kelp farming in South Africa

There are currently no Kelp farms in South Africa, however there are plans on creating them in the future. The South African Kelp Farming Project has already completed the phase 1 feasibility study. In the study they have recommended that trails begin on the three kelp species, Ecklonia maxima, Laminaria pallida and macrocystis pyrifera. The study updated the value of the South African kelp industry, estimating it at R357 million. They will begin trails in Saldana Bay, since this area already has mussel and oyster aquaculture infrastructure in place. It will also support the local agriculture industry by supporting job creation and livelihoods in the area.

Since there are already mussel and oyster farms in the area, there is potential for a kelp farming system to work well with the other two. A seaweed farm can retake, recirculate, and recycle the waste material from animal farms. Professor John Bolton from UCT explains this concept in a YouTube video.

Currently, the project is in Phase 2, which is testing the methodologies in a pilot farm. This phase will demonstrate proof-of-concept and evaluate seasonal variations, among other factors as alluded to in the feasibility report.

References

Amosu, A.O., Robertson-Andersson, D., Maneveldt, G., Anderson, R.J. and Bolton, J.J., 2013. South African seaweed aquaculture: a sustainable development example for other African coastal countries.

Anderson, R., Rothman, M., 2024. The Guide to Kelp Harvesting in South Africa. Department of Forestry, Fisheries and the Environment.

Kelp Value Chain Analysis, Market Assessment, and Roadmap for Development of Kelp Farming in South Africa. Department of Forestry, Fisheries and the Environment.

Taurus Cape Kelp | Kelp Suppliers | South Africa, 2024. Available at: https://www.tcck.co.za/ (Accessed: 3 December 2024.