Nowlin W H, Drenner R W
Texas Christian University, Department of Biology, Fort Worth, TX 76129, USA e-mail:
Oecologia. 2000 Feb;122(3):421-426. doi: 10.1007/s004420050048.
Most knowledge of direct and indirect effects of zooplanktivorous fish has come from studies in which a treatment with a zooplanktivore is compared to a fishless control. However, effects of a zooplanktivore may be different in the presence of other fish species because the other fish have direct and indirect effects that may alter the effects of the zooplanktivore in question. To test this hypothesis, we conducted a tank mesocosm experiment of 2×2 factorial design in which the presence and absence of bluegill (Lepomis macrochirus) were cross-classified with the presence and absence of a fish assemblage composed of western mosquitofish (Gambusia affinis) and common carp (Cyprinus carpio). The presence of bluegill decreased Daphnia, Ceriodaphnia, cyclopoid copepodids, calanoid copepodids, copepod nauplii, amphipods, gastropods, and notonectids. Daphnia, Ceriodaphnia, cyclopoid copepodids, copepod nauplii, gastropods, notonectids, Najas, and Chara were decreased and herbivorous rotifers, turbidity, chlorophyll a, total nitrogen and total phosphorus were increased in the presence of the fish assemblage. Significant bluegill×fish assemblage interaction effects were detected for Daphnia, Ceriodaphnia, cyclopoid copepodids, copepod nauplii, gastropods, and notonectids. Analysis of simple effects for these response variables revealed that all significant bluegill effects in the absence of the fish assemblage were not significant in the presence of the fish assemblage. Our results indicate that the effects of bluegill may be context dependent, or dependent upon the presence of other trophically similar fish species.
大多数关于食浮游动物鱼类直接和间接影响的知识来自于这样的研究，即将有食浮游动物鱼类的处理组与无鱼对照组进行比较。然而，在有其他鱼类物种存在的情况下，食浮游动物鱼类的影响可能会有所不同，因为其他鱼类具有直接和间接影响，可能会改变所讨论的食浮游动物鱼类的影响。为了验证这一假设，我们进行了一项2×2析因设计的水箱中宇宙实验，其中蓝鳃太阳鱼（Lepomis macrochirus）的有无与由西部食蚊鱼（Gambusia affinis）和鲤鱼（Cyprinus carpio）组成的鱼类组合的有无进行交叉分类。蓝鳃太阳鱼的存在减少了水蚤、角突网纹溞、剑水蚤幼体、哲水蚤幼体、桡足类无节幼体、端足类、腹足类和仰泳蝽。在有鱼类组合存在的情况下，水蚤、角突网纹溞、剑水蚤幼体、桡足类无节幼体、腹足类、仰泳蝽、茨藻属植物和轮藻属植物减少，而草食性轮虫、浊度、叶绿素a、总氮和总磷增加。对于水蚤、角突网纹溞、剑水蚤幼体、桡足类无节幼体、腹足类和仰泳蝽，检测到显著的蓝鳃太阳鱼×鱼类组合交互作用效应。对这些响应变量的简单效应分析表明，在无鱼类组合时所有显著的蓝鳃太阳鱼效应在有鱼类组合时均不显著。我们的结果表明，蓝鳃太阳鱼的影响可能取决于环境，或取决于其他营养级相似的鱼类物种的存在。
