Dr Andy Foggo1, Mr Kieran Richmond1
1University Of Plymouth, Plymouth, United Kingdom
A significant body of research exists describing the role of constitutive and induced polyphenolic defence against mesopredator attack across many species of brown macroalgae. Kelps are amongst the best-studied and understood macroalgae in this respect, being important in the ecosystem context as ecological engineers and providing habitat and potential food resources for a variety of mesoherbivores. The Optimal Defense Hypothesis (ODH) explains relative defendedness of different parts of the algal thallus in terms of their importance to lifetime inclusive fitness. Research into other brown macroalgae supports the proposition that kelp stipes should be heavily defended relative to frond tissues as the stipe provides attachment and, if broken due to mesopredator attack, the whole thallus enters the detrital cycle effectively signalling the death of the individual. The kelp frond meanwhilst is naturally constantly eroding distally and a broken frond can be replaced relatively quickly provided meristematic integrity and the right conditions. The relative importance of stipe and frond in fitness terms might also be expected to change through sporophyte development if the ODH applies. Here we present data describing natural rates of frond and stipe damage and laboratory rates of feeding of grazers upon reconstituted algal media in stipes and fronds of three Laminaria species across a size range from earliest identifiable sporophyte through to mature kelp. We relate these to polyphenolic content (both constitutive and after induction by artificial damage) and carbon : nitrogen ratios of the kelp tissues and interpret the results in the context of the ODH.
Presentation Slides – Andy Foggo
