Seaweeds are algal organisms of which there are about 4000 species worldwide, diverse in form, biology and chemistry. Seaweeds fall into three distinct groups and are simply identified as brown, red and green seaweed. Brown seaweeds range in size from the giant kelp, which is often 20 metres long, to thick, leather-like seaweeds 2–4 m long, to small species, 30–60 cm long. Red seaweeds range from a few centimetres to about one metre in length; and in colour from red, to brownish red, to purple. Green seaweeds are similar sized to the red seaweeds. In their natural habitat, seaweeds are the natural diet of many marine grazing organisms.
Seaweed is widely used as a food source throughout Asia particularly in Japan, China and Korea. Traditional food species include Porphyra sp. (nori) and Undaria sp. (wakame). In coastal regions of the world, seaweed has a long history of use as fertiliser and in industrial processes. Seaweeds also provide a source of compounds and chemicals that are used in food, cosmetic and health food manufacturing, such as agar.
In Australia, as at 2014, the seaweed industry is based on the harvest of stormcast kelp for the production of alginate and fertiliser; or wild-harvest of the introduced species of Undaria for extraction of bioactive compounds. Future opportunities are anticipated with the cultivation of seaweed for high value end uses, through identifying the functional properties of different seaweed species, and supplying compounds for the nutraceutical and pharmaceutical markets. Opportunities also exist for the selection and growing of species that command high value as fresh and dried food in the restaurant and specialty food markets.
Seaweed has particular potential for cultivation, when it is used in an Integrated Multi Trophic Aquaculture system, or adaptations of the system. The role of seaweed in the system is dual purpose. First, to provide a food source for fish, crustaceans and mollusc species grown in the system, and second to use the organic waste generated by the farmed species. The system is well established in Asia, growing in popularity in Canada and internationally recognised as promising for future sustainable aquaculture.
The principles of Integrated Multi Trophic Aquaculture systems are attractive in Australia because they can be applied to existing land-based aquaculture (e.g. finfish, abalone or prawns) or sea-based aquaculture (e.g. blue-fin tuna or salmon production). The system also has potential where manufacturers or land managers are looking for options to use wastewater and reduce run-off, particularly to avoid eutrophication of coastal waters. In Australia, there has been little validation of Integrated Multi Trophic Aquaculture in a commercial context.
Production of cultivated seaweed could also have great potential for industrial or rural blocks of land adjacent to resources capable of feeding seaweed such as saline water basins.
The development and establishment of a commercial seaweed enterprise in Australia is not for the faint-hearted—technically or financially. However, aquaculture farmers will have many of the skills required. There is much to be learnt about the biology and cultivation of Australian seaweed species and prospective seaweed farmers are advised to consult and potentially establish cooperative research relationships with seaweed scientists in their state, to determine the best species for their situation.
As at 2014, there was no industry body for seaweed producers in Australia. The University of Wollongong hostsSeaweeds Australia, a networking forum for research, development, marketing and commercialisation of seaweed in Australia.
Facts and figures
- Of the 1000s species of seaweed found in southern Australian waters, over 60% do not occur anywhere else in the world
- Seaweeds are not plants, in botanical terms, they are macroalgae
- Chocolate milk, yoghurt, health drinks and some beers contain hydrocolloids (agars, carrageenans or alginates) derived from seaweeds
- Australian seaweed production is very small by world standards, and as at 2014, the commercial focus is mainly on collection of stormcast kelp for alginate and fertiliser production
- Seaweeds are the fastest growing ‘plants’ on earth
- Future Australian opportunities are anticipated for the cultivation of seaweed for high value end uses
The seaweed industry in Australia is generally characterised by vertically integrated businesses that source or grow seaweed to produce specific products. A 2010 publication about industry development reported that the main commercial seaweed businesses in Australia were based on:
- collection of stormcast bull kelp (Durvillea pototorum) for the production of alginate, fertiliser and animal feed
- wild harvest of the introduced brown seaweed (Undaria pinnatifida) to extract fucoidan compounds to make nutraceutical, skin care and pharmaceutical products. Australian sourced material is augmented with seaweed imported from Canada, Patagonia and some South Pacific islands
- cultivation of micro-algae (Dunaliella salina) in land-based saline ponds, for the extraction of beta-carotenoids, which are used for food colouring and other food products, and as vitamin supplements.
Australian statistical data is only available for production from one kelp drying operation, of which 1900 tonnes of dried product was produced in 2009–10. Dried kelp comprises 30–50% alginate, which is extracted and used in dehydrated foods, and as gelling and thickening agents. Australian exports of alginate generally have been less than 10 tonnes per year, throughout the 2000s, however there are exceptions; in 2009–10 for example, 77.5 tonnes of alginate was exported.