3.2.1 Kappaphycus – Carrageenan Industry
Carrageenans are polysaccharides extracted from certain kinds of algae whose gelling and emulsifying properties make them a widely used and valuable food additive. Kappaphycus alvarezii (see Figure 11) is one of the main carrageenan producing algae harvested in an industrial scale. It is a global industry with large scale Kappaphycus farms in the Philippines, Zanzibar, India, Fiji and Brazil. However, after a few years of favourable farming, producers encountered a number of diseases and epiphyte related issues.
Any changes in light intensity, ocean temperature and salinity cause stress to Kappaphycus, when stressed they produce organic compounds that attracts several types of bacteria, including those in the Vibrio-Aeromonas and Cytophaga-Flavobacteria complexes. Under those conditions, bacterial attacks will promote a characteristic softening, ‘bleaching’ or ‘whitening’ of the seaweed’s tissue called Ice-ice disease (Figure 12). Ice-ice disease can wipe out whole production sites. Outbreaks have occurred in almost every location where Kappaphycus production was introduced, with high ecological and societal impacts.
Epiphyte outbreaks also occur regularly in major carrageenophyte farms. They are mainly caused by red filamentous ceramiales (Vairappan, 2006 [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ; Vairappan et al., 2008). First signs of early epiphyte infection are observed with the appearance of black spots on Kappaphycus cuticle. Those spots are caused by embedded ceramiale sporelings that will emerge and mature in a matter of weeks. The multiple epiphyte infection sites will evolve further in a characteristic ‘goose-bump’-like symptom.
Epiphytic colonisation will promote productivity and quality decrease, bacterial secondary infections, and lead to farm collapse in the case of severe outbreaks.
3.2 Red algae: Carrageenan and Agar