Grazer-diatom size relationships in an epiphytic community

Tall, Laure, Louise Cloutier, Antonella Cattaneo

Limnol. Oceanogr., 51(2), 2006, 1211-1216 | DOI: 10.4319/lo.2006.51.2.1211

ABSTRACT: We investigated the animal-food size relationships of an invertebrate grazer community that feeds on the epiphytic diatoms of mosses in a Que┬┤bec stream. The relationship between invertebrate head width and maximum size of ingested diatoms was significant (r2 = 0.57, n = 82, p <0.00001). This relationship did not differ significantly among widely different taxa of insects, crustaceans, and worms. The comparison of our results with relationships developed in the laboratory for zooplankton and benthos indicated that artificial particles or simplified algal assemblages underestimate the size range of algae ingested by grazers. The examination of the size distribution of the ingested diatoms and of those available in the environment showed that grazers fed preferentially on different diatom size classes in accordance with their head width. Concepts of resource partitioning, optimal foraging, and size efficiency proposed for other habitat types are relevant to stream invertebrate communities. This recognition should facilitate the study of algal-grazer interactions in streams.

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