NITROGEN FLOW IN A CHEMOSTAT CULTURE OF THE ROTIFER BRACHIONUS-PLICATILIS

Nitrogen flow in a chemostat culture of the rotifer Brachionus plicati lis was measured. It was found that a chemostat could keep the rotifer in a stable condition and were suitable for studying the effect of al gal density. The rotifer egested 70-80% of the ingested nitrogen as pa rticulate organic nitrogen (PON) and about 80% of the remaining assimi lated nitrogen was utilized for reproduction. Low net growth efficienc y (K-2) at high algal densities proved ''superfluous feeding''. 20% of PON egested was incorporated in the rotifer again by bacteriovory, an d 13% of that was remineralized to NH4+ by bacteria. The PON was accum ulated as a suspended or attached form in the culture vessel, which mi ght cause an unstable environment. For a safety culture of the rotifer , removal of PON is an effective counter plan.