Aquatic Sciences Meeting, Albuquerque 2001

SS19 Revisiting Redfield: C:N:P Stoichiometry in Aquatic Ecosystems (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 3:00:00 PM

Location: Acoma/Zuni/Tesuque

Pape, B, J, Indiana-Purdue University, Fort Wayne, USA, joelle1978@hotmail.com

DeMott, W, R, Indiana-Purdue University, Fort Wayne, USA, demott@ipfw.edu

EFFECTS OF PHOSPHORUS-DEFICIENT DIETS ON THE PHOSPHORUS BALANCE OF LABORATORY AND FIELD POPULATIONS OF DAPHNIA.

We studied the growth and P-balance of nine species of Daphnia cultured in the laboratory and made comparisons of P balance with field populations. In lab experiments, animals were cultured for 4-d on P-rich (molar C:P ratio 80) or P-deficient (C:P ratio 1,000) diets of the green alga Ankistrodesmus falcatus (1 mgC/L). P-rich diets resulted in P-contents of 1.3 to 1.6% body mass, whereas P-deficient diets caused declines to 0.9 to 1.2% mass. Although P-deficient diets caused declines in the P balance and growth of each species, we found interspecific variation in P balance with the P-rich diet and in responses to the P-deficient diets. We collected data on the seston C:P ratio and P-balance for six of the Daphnia species from local lakes and from large enclosures within lakes. In contrast to previous studies, our results show that the P-content of Daphnia from lakes declines as the C:P ratio of food resources increases.

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Aquatic Sciences Meeting, Albuquerque 2001

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