Ulva (the sea lettuce) is ubiquitous in shallow seas around the world and has been grown in land-based systems for many decades. The aquaculture of Ulva is increasing rapidly, globally, with much potential for new products and processes (Bolton et al., 2016). Foliose Ulva species are generally the seaweed of choice for integrated land-based systems, grown in the effluent from marine animal aquaculture. In the past, selecting an Ulva has generally been done by trial and error. This contribution will discuss the choice of an Ulva species for cultivation.
Since 2003 Ulva has included both foliose (bladed) and tubular (formerly ‘Enteromorpha’) forms. Currently over 100 species of Ulva are recognised, although many of these are little-known. A major upheaval is taking place in Ulva diversity/taxonomy and it is currently very difficult to put an accurate name on Ulva without molecular barcoding studies, given their morphological similarities. Material in land-based systems is still mostly recorded as Ulva lactuca, usually erroneously, but commercial species recently barcoded include Ulva lacinulata (in South Africa and Europe) and Ulva ohnoi (in Australia).
There are numerous reasons for cultivating Ulva, and thus critical decisions are needed in choosing an Ulva species for land-based cultivation. Important characteristics include: high growth rate, ability to grow vegetatively for long periods, chemical composition (depending on product), and palatability, attractiveness and sensory quality if grown for feed/food.
There is currently an explosion of research on Ulva cultivation around the world and examples of ‘reinventing the wheel’, including the spreading of some unfortunate myths. It is critical that the taxonomy of this genus reaches consensus soon, and then that those working to establish Ulva in land-based systems try different species/strains and choose their material on carefully selected criteria. A good rule of thumb is to experiment initially with material growing unattached in sheltered bays or lagoons, similar habitats to the environment in land-based aquaculture systems. Alternatively, the more biotechnological approach (being carried out in Europe) is to take large numbers of species/strains and test them for various parameters in the laboratory. It is to be hoped that material which shows promise can be barcoded to give an accurate comparative picture of the best species/strains for specific purposes. Relevant countries/regions should set up a barcoding laboratory for aquaculture organisms and, as the industry develops, seriously consider funding a seaweed biobank.
Reference:
Bolton JJ, Cyrus MD, Brand MJ, Joubert M, Macey BM (2016). Why grow Ulva? Its potential in the future of seaweed aquaculture. Perspectives in Phycology 3: 113-120.
This study received funding from the EU Horizon 2020 Research & Innovation Programme ASTRAL Project under Grant Agreement No. 863034