Seaweed cultivation: potential and challenges of crop domestication at an unprecedented pace

The world-wide macroalgae industry has increased exponentially over the last 50 years (Fig. 1a,b). Between 2003 and 2012, its average annual growth was 8.13% in quantity and 6.84% in monetary value (Food & Agriculture Organization of the United Nations (FAO), 2014). Over 23 million tons of macroalgae (dry weight) were produced in 2012 from aquaculture, which were worth over six billion US$ (FAO, 2014). Approximately 83% of this biomass is produced for human consumption while the remainder is used as fertilizers, animal feed additives and, increasingly, for medical and biotechnological applications (McHugh, 2003). Seaweeds have a recognized, though barely tapped, potential for biotechnology and sustainable biofuel production (Mazarrasa et al., 2014). A more immediate expansion driver is, however, the prospect that seaweed farming can improve the sustainability of fish and shellfish aquaculture in integrated cultivation initiatives. With an annual growth of nearly 10%, fish farming is the world's most rapidly expanding food-producing sector and represents a major stake toward meeting soaring global demand for dietary proteins over the forthcoming decades (Duarte et al., 2009). Encouraged by these demands and efforts to reduce the over-exploitation of natural resources, seaweed farming has been expanding rapidly across several continents from south-eastern Asia down to South America and East Africa (Rebours et al., 2014).