Agri Kultuur March/ Maart 2016 - Page 76

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