Stressed, but not defenceless: no obvious influence of irradiation levels on antifeeding and antifouling defences of tropical macroalgae

Abstract

The production of defence metabolites is assumed to be costly in metabolic terms. If this holds true, low-light stress should reduce the ability of seaweeds to defend themselves chemically against herbivory and fouling. We investigated the eVect of energy limitation on the defensive status of seaweeds by assessing their attractiveness to mesograzers and their activity against a bivalve macrofouler in comparison with non-stressed conspeciWcs. The macroalgae Codium decorticatum (Woodw.) M. Howe, Osmundaria obtusiloba (C. Agardh) R. E. Norris, Pterocladiella capillacea (S. G. Gmel.) Santel. and Hommer., Sargassum vulgare C. Agardh and Stypopodium zonale (Lamour.) Papenf. collected at the southeastern Brazilian coast were exposed to six levels of irradiation (between 1 and 180 mol photons m ¡2 s ¡1 ) for 10-14 days. After this period, algae from all treatment levels were: (a) processed as artiWcial food and oVered to an amphipod community dominated by Elasmopus brasiliensis Dana and (b) extracted to test for diVerences in settlement rates of the fouling mussel Perna perna L. on Wlter paper loaded with the crude extracts. Generally, photosynthesis rates and growth were reduced under low light conditions. Attractiveness to herbivores and macrofoulers, however, was insensitive to energy limitation. We discuss possible explanations for the observed absence of a relationship between light availability and algal defence including the change in nutritional value of the algal tissue, the allocation of resources towards defence instead of growth and the absence of costs for defence.

Effects of limitation stress and of disruptive stress on induced antigrazing defense in the bladder wrack Fucus vesiculosus

“…While numerous studies demonstrated defense induction against herbivores in marine macroalgae in recent years (reviewed in Toth & Pavia 2007), so far none have rigorously demonstrate incurring costs (e.g. Pansch et al 2009, Appelhans et al 2010; but see Dworjanyn et al 2006 for costs of constitutive defense against fouling).…”

A non-native macroalga is less attractive for herbivores but more susceptible to light limitation and grazing stress than a comparable native species

“…Pansch, Cerda [35] found no effect of light limitation on chemically mediated defences against grazers and foulers in four brown algae from the coast of Chile and Appelhans, Lenz [34] reported the same for five seaweed species from the coast of Brazil (one green, two red, two brown including S. zonale). In contrast to this, Kubicek, Bessho [64] observed that grazing rates of the snail Lacuna smithii on the red alga Chondrus yendoi increased with decreasing light availability.…”

Ecologia Química Marinha: Origem, Evolução E Perspectivas No Brasil

“…Macroalgas marinhas alvos de estudos de ecologia química marinha no Brasil. Soares et al 2003Pereira et al 2004Weidner et al 2004Appelhans et al 2010 As macroalgas pardas (Phaeophyceae) comumente produzem terpenóides, polifenóis, substâncias de origem biossintética mista, terpenoaromático, e hidrocarbonetos voláteis como seus metabólitos secundários mais comuns (Blunt et al 2011 e revisões prévias deste autor). Um estudo pioneiro da Ecologia Química Marinha brasileira foi realizado com a macroalga parda Sargassum furcatum, e compreendeu a avaliação da atuação de polifenóis como defesa química contra a herbivoria (Pereira 1989).…”

“…Dentre fatores ambientais, a irradiância, embora cause alterações nas taxas de fotossíntese e crescimento das macroalgas Codium decorticatum, Osmundaria obtusiloba, Pterocladiella capillacea, Sargassum vulgare e Stypopodium zonale, não afeta a produção de defesa química (Appelhans et al 2010). No entanto, fatores ambientais extremos caracterizando qualquer estresse são capazes de tornar macroalgas suscetíveis ao consumo por redução de suas defesas químicas (ex.…”