Effect of Type and Concentration of Algal Food (Chlorella Vulgaris and Scenedesmus Acutus) on the Population Dynamics of Daphnia Ambigua Scourfield, 1947 (Cladocera, Daphniidae)

Abstract

We quantified changes in the population abundance of Daphnia ambigua, separately cultured on Chlorella vulgaris or Scenedesmus acutus, respectively, at three different algal concentrations (dry weight, 1.45, 4.35, and 13.05 μg ml −1 ). These population growth experiments were carried out for 30 days under laboratory conditions, with the medium and the algal food (at the initial density) renewed daily. Our study showed that a population of D. ambigua grew well on either Chlorella vulgaris or Scenedesmus acutus, when offered as an exclusive diet. Regardless of the algal type, increased algal density generally resulted in an increased population abundance of D. ambigua. The peak population abundance of D. ambigua was approximately 6 ind.ml −1 on Chlorella, at a concentration of 4.35 μg ml −1 . The rate of population increase of D. ambigua varied from 0.123 ± 0.012 to 0.224 ± 0.006 per day, depending on the algal species and its concentration. Daily population growth rates of D. ambigua when plotted as a function of population density, yielded an inverse relationship. These results are interpreted in terms of population growth characteristics of various species of Daphnia from the literature. RESUMENSe cuantificaron los cambios en la densidad poblacional de Daphnia ambigua, cultivadas por separado con las algas Chlorella vulgaris y Scenedesmus acutus en 3 diferentes concentraciones (peso seco, 1,45, 4,35 y 13,05 μg ml −1 ). Los experimentos de crecimiento poblacional se llevaron a cabo durante 30 días bajo condiciones del laboratorio, con el medio y la densidad de alga diariamente renovada. El estudio mostró que la población de D. ambigua creció de manera similar con ambos tipos de alga, cuando se ofrece como una dieta exclusiva cualquiera de ellas. En