Poff N LeRoy, Palmer Margaret A, Angermeier Paul L, Vadas Robert L, Hakenkamp Christine C, Bely Alexa, Arensburger Peter, Martin Andrew P
Department of Zoology, University of Maryland, 20742-4415, College Park, MD, USA.
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.
Oecologia. 1993 Aug;95(2):202-209. doi: 10.1007/BF00323491.
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.
我们对夏末一条位于皮埃蒙特的四级沙质底河流中几乎整个后生动物群落的大小结构进行了表征。我们的研究是首次对水生生态系统中所有后生动物栖息地类型和大小进行采样，结果表明，在群落水平上，底栖生物的河流大小谱可能是双峰的，若将鱼类纳入则为三峰。从9种栖息地类型中定量收集了干重跨越10个数量级（从腹毛动物到鱼类）的动物。双峰底栖生物大小谱的特征是小型底栖生物成分（主要是寡毛类和小型甲壳类）和大型底栖生物成分（主要是引入的亚洲蛤蜊，河蚬）。昆虫对总现存量的贡献很小。使用呼吸的异速生长方程评估了对整个群落代谢的大小特异性贡献，我们发现在整个后生动物大小范围内有明显的双峰分布，在小型底栖生物和大型底栖动物大小范围内出现峰值。我们的双峰底栖生物大小谱与海洋底栖生物的类似，但与其他淡水底栖生物系统不同，这可能是因为后者没有对所有栖息地类型和/或动物大小范围进行采样。许多因素可能影响河流生态系统中的大小谱，包括当地地貌（栖息地）条件、水位波动、物种引入和捕食过程。
