Seaweed aquaculture in Tasmania is an emerging industry. It provides the potential to develop a range of products including animal feed, nutraceuticals, pharmaceuticals, fertiliser, bioplastics, and food products for human consumption. Seaweed aquaculture also allows opportunities to rehabilitate coastal ecosystems, mitigate carbon emissions, provide employment in regional coastal communities, and manufacture products for domestic and export markets.
Commercial cultivation of seaweeds is separate to Tasmania’s Marine Plant Fishery which focuses on the collection of native seaweed 'cast' onshore and largely occurs in the north-west of the state. The taking of native seaweed species directly from the ocean in Tasmania is not allowed as per the Fisheries (Marine Plant) Rules 2017. On the east coast of Tasmania, a small amount of the non-native species Undaria Pinnatifida (Wakame) is harvested from the wild for its fucoidan (long chain polysaccharides) properties.
A diverse range of seaweed species grow naturally in Tasmania. Conditions also allow for a wide range of suitable areas to farm seaweed. Key species being investigated, by proponents and through research projects, for cultivation are:
Ecklonia radiata (Golden Kelp)
Durvillaea spp. (Bull Kelp)
Macrocystis pyrifera (Giant Kelp)
Lessonia corrugata (Tasmanian Kombu)
Ulva spp. (Sea Lettuce)
Caulerpa spp., Chaetomorpha spp., Codium spp. (edible green seaweeds)
Undaria pinnatifida (Wakame) – Non-native
Seaweed growing research trials at Sea Forest in Tasmania
A range of methods are used to grow seaweeds around the world on land and in the marine environment.
Land-based cultivation occurs in closed (contained) systems, where juvenile seedlings are placed into tank or pond facilities, greenhouses and raceway systems. An advantage of this method is the ability to control environmental factors including light, temperature and nutrient content or availability. Seaweed is grown in (circular or rectangular) tanks/ponds or raceways where it is kept in motion by bottom aeration or mechanical systems. Seaweed is grown to the desired size then harvested from the system. While there are many benefits to land-based cultivation, this approach can be space intensive with high capital, energy and ongoing costs.
Land-based facilities can also play a part in completing the life cycle for culture in sea-based methods, by attaching the hatchery reared seedlings/spores onto ropes for their transfer to sea to complete their grow-out phase.
Long-line aquaculture is one of the more common methods for cultivation of seaweed. Seaweed can be grown on ropes (grow-out ropes) along the seafloor or suspended in the water column. Depending on the species, grow-out ropes can be hung in the water column either vertically or horizontally and at varying depths to make use of natural light and nutrients. The ropes seaweed is grown on can be ‘seeded’ with seaweed spores in a land-based facility (hatchery) prior to being deployed at sea. Another method to attach seaweed is by securing seedlings directly onto the grow-out ropes.
Some small to medium-sized species of seaweed (Porphyra/Pyropia) can be cultured using nets. The nets, like ropes, are initially 'seeded' with seaweed spores in a hatchery and then deployed at sea. When nets are deployed, they can be secured in shallow waters at either a fixed height, semi or free floating. This method suits estuarine or near-shore locations.
IMTA (Integrated Multi-trophic Aquaculture)
IMTA is the farming of species from different trophic (food chain) levels that have complementary ecosystem functions. Growing different species near one another allows one species to recapture nutrients or by-products of the other. Seaweed and shellfish can be integrated into established finfish farms for instance to mitigate environmental impacts such as eutrophication, by making use of the excess nutrients.
Management of seaweed aquaculture in Tasmania
The Department of Natural Resources and Environment Tasmania works with aquaculture industries, the community, other agencies, and research organisations to support sustainable development and operation of marine farms in Tasmania. The Aquaculture Branch supports the aquaculture industry with services including:
- Planning and management
- Permitting, leasing and licensing
- Extension activities and compliance monitoring
- Environmental management of non-finfish species
The MFPA provides for the development of Marine Farming Development Plans (MFDPs) which establish zones where marine farming leases may be granted. The MFDP also specifies the species of ‘fish’ (the LMRMA defines ‘fish’ and includes finfish, shellfish, seaweed or other species) that may be farmed in a zone. Existing MFDPs can be viewed here.
In addition, permits can be issued under the LMRMA to allow for short-term research or development of marine farming. Permits specify conditions as set by the Aquaculture Branch and other relevant areas of the Department, for example, Biosecurity Tasmania and the Wildlife Health & Marine section.