Cyr Hélène, Curtis Janelle M
Department of Zoology, University of Toronto, Toronto, Ontario, M5S 3G5, Canada e-mail:
Oecologia. 1999 Mar;118(3):306-315. doi: 10.1007/s004420050731.
The body size of an individual zooplankton is well related to its grazing rate and to the range of particle sizes it can ingest, and since cladocerans and copepods feed differently, they follow different relationships. Based on these general patterns in individual organisms, we tested whether the size structure and taxonomic composition of more complex natural zooplankton communities are related to their in situ grazing rate and to the range of algal sizes they graze. We compared community grazing rates on individual algal taxa in two communities dominated by small cladocerans, three communities dominated by large cladocerans and three copepod-dominated communities. Small algae were usually grazed most intensively, but grazing rates were poorly related to algal size alone. The range in size of grazed algae increased with increasing mean zooplankton body size, but differed systematically with their taxonomic composition. Communities dominated by Ceriodaphnia or Holopedium grazed a narrower size range of algae [maximum greatest axial length dimension (GALD)=16-36 μm)] than communities with large biomasses of Bosmina or Daphnia (maximum GALD=28-78 μm). Copepod-dominated communities followed the same general relationship as cladocerans. Daphnia-dominated communities grazed the broadest range of algal sizes, and their total grazing rates were up to 2.4 times their grazing rates on small (<35 μm) "highly edible" algae, a difference of similar magnitude to those found in successful trophic cascade biomanipulations.
个体浮游动物的体型与它的摄食率以及它能够摄取的颗粒大小范围密切相关，而且由于枝角类动物和桡足类动物的摄食方式不同，它们遵循不同的关系。基于个体生物的这些一般模式，我们测试了更复杂的自然浮游动物群落的大小结构和分类组成是否与它们的原位摄食率以及它们所摄食的藻类大小范围相关。我们比较了以小型枝角类动物为主的两个群落、以大型枝角类动物为主的三个群落和以桡足类动物为主的三个群落对单个藻类类群的群落摄食率。小型藻类通常被摄食得最为密集，但摄食率仅与藻类大小的关系不大。随着浮游动物平均体型的增加，所摄食藻类的大小范围也增加，但随其分类组成而系统地不同。以角突网纹溞或透明薄皮溞为主的群落摄食的藻类大小范围较窄[最大轴向长度尺寸（GALD）=16 - 36μm]，而以大型溞或水蚤生物量较大的群落（最大GALD = 28 - 78μm）则不同。以桡足类动物为主的群落遵循与枝角类动物相同的一般关系。以水蚤为主的群落摄食的藻类大小范围最广，它们的总摄食率高达其对小型（<35μm）“极易食用”藻类摄食率的2.4倍，这一差异与成功的营养级联生物操纵中发现的差异幅度相似。
