Essential fatty acid content
and the phosphorus to carbon ratio in cultured algae as indicators of food
quality for Daphnia
S. Park, M.T. Brett, D.C. Muller-Navarra, C.R.
Goldman-2002
Freshwater Biology, 47(8): 1377-1390
(from Current Contents)
Abstract :
1. A series of experiments examined growth of Daphnia
magna on three algal diets (Rhodomonas minuta, Scenedesmus acutus and
Synechococcus sp.) at varying physiological states [nitrogen and phosphorus
(P) limitations] to test whether variation in algal fatty acid and/or
elemental composition can predict Daphnia growth.
2. These algae differed widely in their essential fatty acid (EFA)
composition while phosphorus (P) or nitrogen limitation had only a small
influence on their omega3-polyunsaturated fatty acid (PUFA) content.
3. Individually, algal omega3-PUFA content explained 69% of the variation in
the normalised growth of D. magna, while algal phosphorus content explained
11% of the variation. Quantitative models for D. magna growth used both
algal omega3-PUFA content and algal C : P ratio as food quality indices.
Together, algal omega3-PUFA content and C : P ratio explained 70% of the
variation in the normalised growth rate of D. magna.
4. Our results indicate that EFA influenced algal food quality much more
strongly than P. The EFA and mineral P impacts appear to be independent.
(Univ Calif Davis; Dept Environ Sci & Policy; 1
Shields Ave; Davis; CA 95616; USA: skpark@ucdavis.edu)