Algal Chemical Ecology

pp 245-271

Oxidative Burst and Related Responses in Biotic Interactions of Algae

  • Philippe PotinAffiliated withStation Biologique, Marine Plants and Biomolecules, Centre National de la Recherche Scientifique-Université Pierre et Marie Curie

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Herbivores and pathogens can have strong effects on algal fitness, regulate population dynamics, and cause considerable damage in marine ecosystems. This was exemplified in kelp forests by dramatic changes associated with the reduction or extinction of local populations of some key predators controlling macroalgal grazers (Estes and Duggins 1995), or in coral reef ecosystems, where coralline lethal orange disease (CLOD), a disease affecting various coralline algae, has led to the destruction of thousands of kilometers of reefs (Littler and Littler 1995). Such diseases or predation may also be highly destructive in managed ecosystems, as reported for Laminaria japonica (Ishikawa and Saga 1989), Porphyra yezoensis (Fujita et al. 1972), and Eucheuma/Kappaphycus (Ask and Azanza 2002; Hurtado et al. 2006) aquaculture fields. In the context of global change, including human impacts and introduction of alien species, the frequency of pathogens and epidemics has increased in recent decades and sessile invertebrate and algal populations will have to adapt their defense strategies to cope with new challenges (Harvell et al. 1999, 2002; Mydlarz et al. 2006). Marine algae have evolved a variety of defensive mechanisms against grazers and pathogens (Pohnert 2004). They strongly depend on their chemical repertoire to influence interactions with other organisms and with the environment. A portion of these chemicals may provide constitutive barriers against grazers or parasites. Constitutive production of secondary metabolites provides antimicrobial compounds (see Chap. 11; de Nys and Steinberg 2002; Kubanek et al. 2003) and grazer deterrents (see Chaps. 2–6, 9; Paul and Puglisi 2004; Paul et al. 2006c). Considering the fundamental question of the investment of physiological resources in defense structures or metabolites (see Chap. 7; Amsler and Fairhead 2006; Ianora et al. 2006), however, it is obvious that marine algae have also developed activated and induced defense mechanisms. Nonetheless, in striking contrast with the knowledge on host-pest interactions in terrestrial crop or wild plants (e.g., Nürnberger et al. 2004), very little is known about signaling or defense induction and regulation in marine algae (Bouarab et al. 2001a; Potin et al. 2002).