Ingestion and assimilation rates of Oocystis sp. by Daphnia magna in treated wastewaters

• Published in: Environmental pollution. Series A. Ecological and biological 1983, Vol.31 (2), p.77-95
• Main Authors: Myrand, Bruno, de la Noüe, Joël
• Format: Article
• Language: English
• ISSN: 0143-1471
• DOI: 10.1016/0143-1471(83)90001-6

This study was aimed at examining the possibility of using Daphnia magna to recover the phytoplankton produced in high concentration during the biological treatment of wastewaters. Ingestion rate, assimilation rate and assimilation efficiency were measured for Daphnia grown under controlled experimental conditions in secondarily treated wastewaters. The rate of ingestion was higher at 15°C than at 20°C and depended on the high concentrations of algae ( Oocystis sp.) used: 10 and 50 mg C litre −1. The rate of assimilation was constant at about 1·8 μg C per Daphnia per hour. It is proposed that the incipient limiting level of ingestion corresponds to the concentration where the assimilation rate is maximum. At food concentrations higher than this level of ingestion, Daphnia control mechanisms normally maintain a constant ingestion rate and prevent superfluous feeding. Our results revealed the inefficiency of these mechanisms at high food concentrations, leading Daphnia to superfluous feeding. Nevertheless, Daphnia reveals itself as a good candidate for the filtration of Oocystis produced in wastewaters.