PARENT SESSION
Symposium #33: The ecology and evolution of coupled energy and material flows: integration of multiple scales and multiple biota.

Organized by: JD Schade, T Markow, and S Hobbie
Friday, August 9. 9:00 AM to 12:00 PM. Crystal Ballroom, TCC.

How much or, rather, how yummy?: towards an understanding of heterotrophic consumption in ecosystems.

Cebrian, Just^*,1,2, Lartigue, Julien^3,1, ¹ MESC/Dauphin Island Sea Lab, Dauphin Island, AL, jcebrian@disl.org² University of South Alabama, Mobile, AL³ Department of Marine Sciences, AL

ABSTRACT- Elucidating the extent and controls of herbivory and decomposition in ecosystems is important to understand the levels of secondary production maintained and the impact of consumers on elemental cycling and storage. Previous research has identified producer nutritional quality (i.e. internal nutrient contents) as a major control of heterotrophic consumption in a number of specific communites, with more nutritional communities supporting higher consumption. The strength of this relationship, however, seems to depend on the range of communities compared because, when aquatic and terrestrial communities are examined together, heterotrophic consumption proves independent of producer quality and it is instead associated with primary production. Here, I use an extensive literature compilation to examine the dependence of heterotrophic consumption on primary production and producer quality within aquatic and terrestrial communities. Within both types of community, primary production and producer quality are completely unrelated. Aquatic and terrestrial communities composed of more nutritional producers have a higher percentage of production consumed by herbivores. Absolute herbivory also increases with higher producer quality within terrestrial communities. Across aquatic communities, however, the variability in absolute primary production exceeds that in the percentage consumed and, as a consequence, absolute herbivory remains closely associated with primary production and independent of producer quality. The percentage of detritus decomposed also increases with higher producer quality within aquatic and terrestrial communities. Within each community type, however, absolute decomposition is strongly associated with primary production and independent of producer quality because the percentage of detritus decomposed varies little in comparison with the absolute magnitude of detrital production. The effects of these patterns on total consumption by heterotrophs, total secondary production, and role of heterotrophs on carbon and nutrient recycling within each community type are also explored.

KEY WORDS: primary production, producer nutritional quality, herbivory, decomposition