Knisely Karin, Geller Walter
Limnologisches Institut, Universität, D-7750, Konstanz, Germany.
Oecologia. 1986 Apr;69(1):86-94. doi: 10.1007/BF00399042.
Grazing experiments evaluated by microscopical counting were conducted with different size classes of Daphnia hyalina, D. galeata, Eudiaptomus gracilis, and Cyclops sp., all from Lake Constance, using natural lake phytoplankton as food. Species-specific grazing selectivity coefficients were calculated for the dominant phytoplankton species from weekly experiments. Specific selectivities were found to be largely invariant through the growing season. All zooplankters grazed more efficiently on phytoflagellates such as Rhodomonas and Cryptomonas than on coccales such as Chlorella and Scenedesmus, regardless of their relative abundance in the phytoplankton assemblage. Filtering rates did not decrease in the presence of filamentous algae. Certain filamentous species were grazed efficiently, but only by D. hyalina: Anabaena planktonica, Oscillatoria amphigranulata, and Stephanodiscus binderanus. Large diatom colonies like Asterionella formosa and Fragilaria crotonensis were grazed well only by Cyclops sp. Some algal species were consistently selected against: Mougeotia thylespora and Dinobryon sp. The species-specific selectivity coefficients can be used as weighting factors to assess the 'effective food concentration' relative to Rhodomonas minuta, a reference species for optimal food.
利用来自康斯坦茨湖的不同大小类别的透明溞、盔形溞、纤细真镖水蚤和剑水蚤属，以天然湖泊浮游植物为食物，通过显微镜计数进行了放牧实验。通过每周的实验，计算了优势浮游植物物种的物种特异性放牧选择系数。发现特定选择性在整个生长季节基本不变。所有浮游动物对诸如红胞藻属和隐藻属等植鞭毛虫的放牧效率高于对诸如小球藻属和栅藻属等球菌藻的放牧效率，无论它们在浮游植物群落中的相对丰度如何。丝状藻类存在时，过滤率并未降低。某些丝状物种被有效放牧，但仅被透明溞放牧：浮游鱼腥藻、双颗粒颤藻和宾德小环藻。大型硅藻群落如美丽星杆藻和克罗顿脆杆藻仅被剑水蚤属良好放牧。一些藻类物种一直被排斥：蒂莱斯波拉转板藻和锥囊藻属。物种特异性选择系数可作为加权因子，以评估相对于微小红胞藻（一种最佳食物的参考物种）的“有效食物浓度”。
