MEPS 380:33-41 (2009)  -  doi:10.3354/meps07937

Consumer diversity indirectly changes prey nutrient content

Helmut Hillebrand1,4,*, Lars Gamfeldt1,2, Per R. Jonsson2, Birte Matthiessen3

1Botanical Institute, University of Cologne, Gyrhofstrasse 15, 50931 Köln, Germany
2Department of Marine Ecology, Tjärnö, University of Gothenburg, 45296 Strömstad, Sweden
3Leibniz-Institute for Marine Science, IfM-GEOMAR, Düsternbrooker Weg 20, 24105 Kiel, Germany
4Present address: Institut für Chemie und Biologie des Meeres, Carl-von Ossietzky Universität Oldenburg, Schleusenstrasse 1, 26382 Wilhelmshaven, Germany

ABSTRACT: Ecological stoichiometry can be a powerful tool to understand food web consequences of altered biogeochemical cycles as well as consequences of biodiversity loss on biogeochemistry and has proved to be a suitable framework to predict effects of consumers on the nutrient content of their prey. However, predictions from ecological stoichiometry have mainly been tested using single consumer species, whereas in most natural ecosystems several consumer species coexist. We conducted 2 outdoor mesocosm experiments with marine rock pool communities to test whether species richness and species combination of benthic invertebrates affected the nutrient content of periphyton. We independently manipulated 12 different consumer combinations ranging from 0 to 6 (2004) or 0 to 4 (2005) grazer species and measured the biomass and nutrient content of the algae. Grazers included 3 gastropods and 3 crustaceans. In 2005, we additionally analyzed animal nutrient content and N excretion rate. Algal biomass and C:N ratios decreased in the presence of grazers in both years, indicating that the remaining algae had higher internal N content. Also, both biomass (2004 and 2005) and C:N ratios (only 2004) decreased even further when grazer richness increased. In 2004, significant net diversity effects of grazer richness on periphyton C:N ratios indicated that periphyton N content under multispecies grazing could not be predicted from the effect of single species. In 2005, significant net diversity effects on C:N ratios were rare, but periphyton C:N ratios consistently decreased with increasing grazer excretion rate, indicating that higher nitrogen regeneration by grazers led to higher N incorporation by algae. The effects of species richness were mainly affected by the presence of one efficient grazer, the gastropod Littorina littorea. Our experiments indicate that non-additive intraguild interactions may qualitatively alter the stoichiometric effects of multispecies consumer assemblages.

KEY WORDS: Biodiversity · Ecological stoichiometry · Ecosystem function · Algae · Grazer · Trophic interaction

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Cite this article as: Hillebrand H, Gamfeldt L, Jonsson PR, Matthiessen B (2009) Consumer diversity indirectly changes prey nutrient content. Mar Ecol Prog Ser 380:33-41

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