Clearance, Ingestion and Release of N and P by Daphnia Obtusa Feeding on Scenedesmus Acutus of Varying Quality
Physiologically-uniform groups of Daphnia oblusa were fed various qualities of a constant quantity of Scenedesmus acutus food in short term (8 h), mass balance measurements of nutrient flux. Rates of clearance (mls⋅MGDW–l⋅h–1) as well as N and P ingestion (μmol⋅MGDW–1⋅h–1); and N and P release (μmol⋅MGDW–l⋅h–1) depended on the quality of food. When offered low-growth-rate Scenedesmus, which are poor in nutritional quality, Daphnia exhibited lower rates of clearance, ingestion and release than when feeding on higher-growth-rate Scenedesmus, which are high in nutritional quality. The large amount of variation in the rates of elemental flux in Daphnia indicates a strong physiological component to mass flux in ecosystems. Adjustments observed in feeding rate are qualitatively consistent with optimization models based on gut absorption. Gross production efficiency in terms of phosphorus, but not nitrogen, was a function of the ingestion rate of that element.
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Document Type: Research Article
Publication date: 1993-07-01
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