Effects of phosphorus-deficient diets on the carbon and phosphorus balance of Daphnia magna
Limnol. Oceanogr., 43(6), 1998, 1147-1161 | DOI: 10.4319/lo.19126.96.36.1997
ABSTRACT: We used laboratory growth and feeding experiments to study the balance of carbon (C) and phosphorus (P) in Daphnia magna. Daphnia were fed high-concentration mixtures of P-sufficient and P-deficient green algae (Scenedesmus acutus; molar C : P 80 and 900, respectively) or mixtures of P-deficient Scenedesmus and a P-rich cyanobacterium (Synechococcus elongatus; C : P = 60). P-deficient diets resulted in, rapid declines in the growth rates of Daphnia and unexpected declines in Daphnias P-to-dry-weight ratio. P-deficient Scenedesmus and P-rich Synechococcus supported poor growth as sole foods but improved growth in mixtures. A 2-d experiment with a dietary C : P gradient from 120 to 900 revealed a linear relation between Daphnias final P-to-dry-weight ratio and its growth rate (r2 = 0.92). Growth in mass (mean ± SE) ranged from 0.54 ± 0.01 to 0.17 ± 0.02 d-1 whereas final specific P content ranged from 1.47 ± 0.01% to 1.08 ± 0.02%.