title: Size structure of the metazoan community in a Piedmont stream.
abstract: We characterized the size structure of virtually the entire metazoan community in a fourth order, sandybottomed Piedmont stream during late summer. Our study, the first to sample across all habitat types and sizes of metazoans in an aquatic ecosystem, indicates that at the community level, stream size spectra may be bimodal for the benthos or trimodal when fish are included. Animals spanning 10 orders of magnitude in dry mass (from gastrotrichs to fish) were quantitatively collected from nine habitat types. The bimodal benthic size spectrum was characterized by a meiofaunal component (mostly oligochaetes and micro-crustacea) and a macrobenthic component (mostly the introduced asiatic clam, Corbicula fluminea). Insects contributed little to overall standing crop. Size-specific contribution to whole-community metabolism was assessed using allometric equations for respiration, and we found a distinctly bimodal distribution across the entire metazoan size range, with peaks in the meiofaunal and benthic macrofaunal size ranges. Our bimodal benthic size spectrum is similar to that observed for marine benthos but not to other freshwater benthic systems, possibly because the entire range of habitat types and/or animal sizes were not sampled in the latter. Numerous factors may influence size spectra in stream ecosystems, including local geomorphic (habitat) conditions, water level fluctuations, species introductions, and predation processes.
authors.affiliation: Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
authors.forename: N LeRoy
authors.initials: NL
authors.lastname: Poff
authors.affiliation: U.S. Fish & Wildlife Service, Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, 24061-0321, Blacksburg, VA, USA.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Palmer
authors.affiliation: U.S. Fish & Wildlife Service, Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, 24061-0321, Blacksburg, VA, USA.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Angermeier
authors.affiliation: Department of Fisheries & Wildlife Sciences, Virginia Polytechnic Institute and State University, 24061-0321, Blacksburg, VA, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Vadas
authors.affiliation: Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
authors.forename: Christine C
authors.initials: CC
authors.lastname: Hakenkamp
authors.affiliation: Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
authors.forename: Alexa
authors.initials: A
authors.lastname: Bely
authors.affiliation: Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Arensburger
authors.affiliation: Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Martin
keywords: Aquatic ecology; Body size; Community structure; Energy flow; Size spectrum