Weithoff Guntram
Department of Ecology and Ecosystem Modelling, Institute for Biochemistry and Biology, University of Potsdam, Maulbeerallee 2, 14469 Potsdam, Germany.
Oecologia. 2004 May;139(4):594-603. doi: 10.1007/s00442-004-1545-z. Epub 2004 Mar 31.
Herbivore populations are commonly restricted by resource limitation, by predation or a combination of the two. Food supplement experiments are suitable for investigating the extent of food limitation at any given time. The main part of this study was performed in an extremely acidic lake (pH 2.7) where the food web consists of only a few components and potential food sources for herbivores are restricted to two flagellates. Life table experiments proved that Chlamydomonas was a suitable food source whereas Ochromonas was an unsuitable food source. The two flagellates and the two rotifers exhibit a pronounced vertical distribution pattern. In this study, a series of food supplement experiments were performed in order to: (1) quantify and compare potential resource limitation of two primary consumers (Cephalodella hoodiand Elosa worallii, Rotatoria) over time, (2) compare their response at different temperatures, (3) evaluate the effect of having an unsuitable food source alongside a valuable one, (4) estimate the effect of predation on rotifers by Heliozoa, and (5) compare the results with those from other acidic lakes. Additionally, the spatio-temporal population dynamics of both species were observed. The field data confirmed a vertical separation of the two species with E. worallii dominating in the upper water layers, and C. hoodi in the deeper, cooler water layers. The results from the food supplement experiments in which Chlamydomonas served as the supplemented suitable food source showed that the two rotifers were food limited in the epilimnion throughout the season to different extents, with Cephalodella being more severely food limited than Elosa. The experiments at different temperatures provided evidence that Elosa had a higher optimum temperature for growth than Cephalodella. When the unsuitable food algae Ochromonas was added alongside the suitable food source Chlamydomonas, C. hoodi was unaffected but E. worallii was negatively affected. Predation of Heliozoa on rotifers was observed but the total effect on the rotifer dynamics is probably low. The comparison with other lakes showed that resource limitation also occurred in one other lake, although to a lesser extent. Overall, the vertical separation of the two rotifers could be explained by both their differential extent of resource limitation and differential response to temperature.
食草动物种群通常受到资源限制、捕食或两者共同作用的制约。食物补充实验适用于研究在任何给定时间食物限制的程度。本研究的主要部分是在一个极端酸性的湖泊（pH 2.7）中进行的，该湖泊的食物网仅由少数几个部分组成，食草动物的潜在食物来源仅限于两种鞭毛虫。生命表实验证明衣藻是合适的食物来源，而赭球虫是不合适的食物来源。这两种鞭毛虫和两种轮虫呈现出明显的垂直分布模式。在本研究中，进行了一系列食物补充实验，目的是：（1）量化并比较两种初级消费者（胡氏头冠轮虫和沃氏艾氏轮虫，轮虫纲）随时间的潜在资源限制，（2）比较它们在不同温度下的反应，（3）评估在有价值的食物来源旁边存在不合适食物来源的影响，（4）估计太阳虫对轮虫的捕食影响，（5）将结果与其他酸性湖泊的结果进行比较。此外，还观察了这两个物种的时空种群动态。实地数据证实了这两个物种的垂直分离，沃氏艾氏轮虫在上层水体中占主导地位，而胡氏头冠轮虫在较深、较冷的水层中占主导地位。以衣藻作为补充的合适食物来源的食物补充实验结果表明，这两种轮虫在整个季节的上层水体中都受到不同程度的食物限制，头冠轮虫比艾氏轮虫受到的食物限制更严重。不同温度下的实验证明，艾氏轮虫的生长最适温度高于头冠轮虫。当在合适的食物来源衣藻旁边添加不合适的食物藻类赭球虫时，胡氏头冠轮虫未受影响，但沃氏艾氏轮虫受到负面影响。观察到太阳虫对轮虫的捕食，但对轮虫动态的总体影响可能较小。与其他湖泊的比较表明，另一个湖泊也存在资源限制，尽管程度较小。总体而言，这两种轮虫的垂直分离可以通过它们不同程度的资源限制和对温度的不同反应来解释。
