Feeding preferences for juvenile and adult algae depend on algal stage and herbivore species

Abstract

Juvenile marine organisms are physically and chemically different from adults. Consequently, the ecology of juveniles, particularly their interactions with other organisms, may change as they age. Yet, they are often considered to function as 'miniature adults'. To explore how ecological interactions change as juvenile seaweeds mature, we investigated among-species food preferences of 4 species of grazers for 8 species of common intertidal and subtidal macroalgae in laboratory multiple-choice feeding-preference experiments. Grazers were offered either juvenile tissues or adult tissues of 8 species of macroalgae. Food preferences of grazers among both juvenile and adult brown algae differed among herbivore species. Within herbivore species, the relative grazing rates on juveniles of a given species were not significantly correlated with grazing rates on adult tissues of that species. Thus, food preferences of herbivores among species of macroalgae are dependent upon the age of the algal tissue and the species of herbivore being considered. Stage-specific differences in preferences between juveniles and adults are likely a result of chemical and morphological changes occurring during algal development. Further work is needed to characterize these changes and further determine their impacts on the ecological characteristics of juvenile marine macroalgae.