Introduction of Chemostat System into Ecological Studies on Zooplankters

1.由于褶皱臂尾轮虫对饵料和生长速度的敏感性，过去通过分批培养实验获得的生态学参数的可靠性较低。因此，用那些“经典”的数字来证实我们在恒化器系统中的结果是没有意义的。稳定同位素（^<15>N）的引入使代谢的评估变得非常精细，以重新确认去年的实验。在提供食物的条件下，消化率、毛生长率和净生长率分别为22.8%、17.4%和77.5%。这表明轮虫将80%的氮素作为饲料排出，20%的氮素被同化。同化氮中20%用于生长和繁殖，80%用于排泄。这些结果与恒化器系统的结果一致。将两个恒化器系统串联连接，以便在去除超过40 μ m的颗粒后，将从前恒化器抽取的介质引入后恒化器。在后部恒化器中观察到任何抑制的生长，尽管两倍负荷的DON和NH_4。这表明，在大量饲养池中，由于相对于生长密度投喂较多，导致PON较高，从而抑制了生长.对于轮虫的大量培养，防止突然大量死亡或抑制生长的最有效方法是通过吸附去除构成大部分有机负荷的PON或在有机负荷达到最大之前更新培养物本身。

1. Last-year experiments made clear that those ecological numerals formerly obtained through batch-culture experiments had less reliability because of the delicacy of Brachionus plicatilis in the response on both feedind and growth rates afterencountered with food deficiency. Accordingly, it is nonsence to substantiate ourresults from a chemostat system with those "classic" numerals.The stable isotope (^<15>N) which enables very fine evaluation of metabolism was introduced for reconfirmation of last-year experiments. Digestivity, gross growth rate and net growth rate were 22.8,17.4 and 77.5%, respectively, when food was provided sufficient-ly. Those values mean that the rotifer extruded nearly 80% of grazed nitrogen as feaces, and 20% was assimilated. And more, as to the assimilated nitrogen, 20% was utilized for both growth and reproduction immediately, and 80% was excreted. These coincide with results from a chemostat system.2. Two chemostat systems were serially connected in order that the medium drawn from the front chemostat was introduced into the rear one after particles over 40mum was removed. Any suppressed growth was observed in the rear chemostat, in spite of two fold load of DON and NH_4. This suggests that the suppressed growth in a mass-rearing pond iscaused by high PON deriving from the more feeding relative to growing density.3. Concerning mass culture of the rotifer, the most effective way to prevent sudden mass mortality or suppressed growth is to remove PON which consists large part of organic load through adsorption or to renew the culture itself before the organic load reaches maximum.