Albert O. Amosu, Gavin W. Maneveldt & Deborah V. Robertson-Andersson
Department of Biodiversity & Conservation Biology
University of the Western Cape
Photo: Gavin W. Maneveldt
A
bout 9% (900 species) of all the world’s seaweeds are found around the South African
coastline, making the region the richest in
Africa and one of the richest marine floras
in the world. Seaweeds are among the healthiest foods
on the planet with high calorific values, vitamins, minerals (over 90) and antioxidants. Medical research has
shown that coastal inhabitants living off a diet of seaweeds live longer, and have lower incidences of hypertension, arteriosclerosis and cancer than inland inhabitants whose diets generally do not comprise of seaweeds.
known as U. lactuca) is far more widely grown. Ulva
species are currently South Africa’s largest aquaculture
products by volume with estimated annual figures of
about 2884 t wet weight. The use of on-land Integrated Multitrophic Aquaculture (IMTA) units, incorporating paddle-wheel raceways, is now widely viewed by
the aquaculture industry as the preferred method for
growing seaweeds such as Ulva.
Ulva aquaculture
Aquaculture production of the green seaweed Ulva has
developed in South Africa since the early 1990s, mainly
as a feed supplement for the abalone Haliotis midae.
Three species of Ulva are currently cultivated in South
Africa, but the free-floating U. armoricana (previously
Seaweeds in Integrated Multitrophic Aquaculture
IMTA is an ecosystem-based approach that effectively
mitigates the over-abundance of nutrients introduced
by fish farming. Seaweeds are excellent biological filters, readily absorbing excess nutrients, making them
the ideal candidates for IMTA culture systems on marine animal production farms. Recent research has
shown that abalone farms incorporating an IMTA seaweed-abalone system, not only mitigate the excess animal nutrients, but also significantly reduce their green-
In South Africa most abalone farmers use fresh kelp
as feed.
The kelp Ecklonia maxima is harvested for both
abalone feed and for its plant growth stimulants.
Photo: Gavin W. Maneveldt
Photo: Gavin W. Maneveldt