58 DECEMBER 2013 • WORLD AQUACULTURE • WWW.WAS.ORG Today, macroalgae with elevated protein content and production rates are receiving increasing attention as novel feed ingredients with potential nutritional benefits (Buschmann et al. 2001, Rupérez and Saura-Calixto 2001) and as a possible ingredient in fish diets (Appler 1985, Davies et al. 1997, Wahbeh 1997). Nitrogen-enriched conditions, such as effluents of fish farms, can increase the protein content of macroalgae used as a biofilter (Lahaye et al. 1995). Apart from potential nutritional value as protein substitutes, macroalgae may also provide an important contribution to fish diets as lipid sources and binding or coloring agents. (Nakagawa et al. 1987, Hashim and Mat Saat 1992). Macroalgae as dietary additives contribute to increased growth and feed utilization of cultured fish due to efficacious assimilation of dietary protein, improvement in physiological activity, stress response, starvation tolerance, disease resistance and carcass quality. In fish fed macroalgae-supplemented diets, accumulation of lipid reserves was generally well controlled and reserve lipids were mobilized to energy prior to muscle protein degradation. Feeding trials to evaluate macroalgae as fish feed have used fresh macroalgae as a whole diet and dried macroalgal meal as a partial or complete replacement of fishmeal protein in pelleted diets. Dietary inclusion levels variy from 5-100 percent. The performances of fish fed diets containing 10-20 percent macroalgae meal are similar to those fed fishmeal based standard control diet and responses are similar for most fish species tested. These inclusion levels effectively supply only about 3-5 percent protein of control diets, which contain about 26-47 percent crude protein. Only about 10-15 percent of the dietary protein requirement can be met by macroalgae without compromising growth and feed utilization efficiency. There is a progressive decrease in fish performance when dietary incorporation of algal meal rose above 15-20 percent. The addition of Porphyra spheroplasts to a semipurified red seabream diet improves growth (Kalla et al. 2008). Replacing 5 or 10 percent of a fish protein hydrolysate diet with dried Gracilaria busra-pastonis improves growth of European seabass (Valente et al. 2006). However, test diets were not isonitrogenous and had a lower protein level than the control diet. Using diets supplemented with two seaweeds (Undaria pinnatifida and Ascophyllum nodosum), the best growth and feed efficiency of sea bream occurred with a diet containing 5 percent U. pinnatifida followed by a diet containing 5 percent A. nodosum (Yone et al. 1986a,b). Effects on growth and feed utilization of red sea bream were more pronounced by feeding a diet containing Spirulina compared to one containing Ascophyllum (Mustafa et al. 1994b). Mustafa et al. (1995) studied the comparative efficacy of three macroalgae (Ascophyllum nodosum, Porphyra yezoensis and Ulva pertusa) for red sea bream. Feeding Porphyra had the most pronounced effects on growth and energy accumulation, followed by Ascophyllum and Ulva. More recently a commercial salmon seaweed-based diet (Oceanfeed) was formulated by Ocean Harvest Technology, Ltd. The diet contains mixture of Ulva, Ascophyllum nodosum, Sargassum, Gracilaria, Laminaria, Palmaria, Maerl, Polysiphonia, Falkenbergia, Delleseria, Osmundia pinnatifida, Plocamium cartilagineum. The diet resulted in improved weight gain, feed conversion, growth index, gutted weight and less mortality, better natural pigmentation and reduced lice recruitment and re-population (Kraan and Mair 2010, Kraan et al. 2010). Macroalgae for Biofuels Over the last thirty years, macroalgae has been investigated as a source of biofuel (Brehany 1983, Hanisak and Ryther 1986, Bird and Benson 1987, Flowers and Bird 1987, Morand et al. 1991, Gao and McKinley 1994, Kelly and Dworjanyn 2008, Bruton et al. 2009). First-generation biofuels, such as biodiesel and bioethanol derived from biomass, have environmental benefits related to carbon-neutral energy. However, increasing biofuel production from land crops strains the global food supply. Second-generation biofuels from biomass generate carbon-neutral energy without competing with food production. These can be produced from the residual non-food parts of current crops, as well as energy crops such as macroalgae. As the need for renewable energy continous to grow, macroalgae farming has the potential to help meet future energy needs. Oceans cover over 70 percent of the Earth’s surface. Just 1 percent of that area along the ocean margins could supply about 3.5 billion dry tons of macroalgal biomass annually, assuming production rates (~116 t dry macroalgae y-1 km-1) already achieved in coastal macroalgae farms in China (Turan and Neori 2010). This is three times the maximum terrestrial biomass that can be collected annually in countries such as the USA. Such systems would not compete for the availabile freshwater, land and nutrients needed to sustain terrestrial agriculture. Large-scale open-ocean macroalgae cultivation for biofuel production is the key for sustainable bioenergy production. The culture of macroalgae has unique characteristics that make it different and in many ways attractive in comparison with other biofuel sources. Several macroalgae species are perhaps the most attractive of all CO2 removal and biofuel aquatic crops because of very high yields and low costs of production. Therefore, efficient production of biodiesel and bioethanol from macroalgae has been considered (Hanisak and Ryther 1986, Bird and Benson 1987, Flowers and Bird 1987, Morand et al. 1991, Gao and McKinley 1994, Kelly and Dworjanyn 2008). Macroalgae are more photosynthetically efficient than terrestrial plants and are highly effective CO2 fixers. Many species of macroalgae are rich in oil or sugars that can be converted into biofuels. As a consequence, the biofuel productivity of macroalgae per unit area is much greater compared with conventional farm crops, such as wheat and maize. Producing one ton of dry algal biomass requires approximately 360 kg carbon, 63 kg nitrogen and 8.6 kg phosphorus (Sinha et al. 2001). Utilization of anthropogenic CO2 as an industrial byproduct for macroalgae production holds great promise as a carbon sink and a source of food, fodder, fuel and pharmaceuticals. The three most commonly mentioned fuels that can be derived from macroalgae are methane, ethanol and butanol. The interest in macroalgae for biofuels was re-initiated recently, mainly in Japan, Korea and Europe. In Japan, Tokyo Gas studied the production of biogas from seaweed biomass collected from natural deposits on beaches after storms and high tides (Huesemann et al. 2010). However, the small amounts and sporadic nature of such harvests, the sand and dirt collected with biomass and transportation costs
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