Aquatic Sciences Meeting, Albuquerque 2001

PC01 Harmful Algal Blooms

Date: Tuesday, February 13, 2001

Location: Southwest Hall

Gudex, L, I, Arizona State University, Tempe, USA, gudex@asu.edu

Urabe, J, , Kyoto University, Otsu, Japan, urabe@ecology.kyoto-u.ac.jp

Elser, J, J, Arizona State University, Tempe, USA, j.elser@asu.edu

DAPHNIA GROWTH ON DIFFERENT SIZE FRACTIONS OF AMBIENT AND AGED SESTON: EFFECTS OF PARTICLE SIZE AND ELEMENTAL AND BIOCHEMICAL COMPOSITION

Ingestible size and nutritional aspects of food quality of late summer colonial phytoplankton (Volvox aureus and Microcystis aeruginosa) for herbivorous zooplankton, Daphnia galeata, were examined using near-shore seston from Lake Biwa, Japan. Seston was provided in two size fractions: <200 um to remove ambient zooplankton and <30 um to provide edible seston alone. In addition, a portion of the <200 um seston fraction was mechanically broken by mixing and sonication to reduce particle size. Seston was also incubated with aeration in the dark for 12-15 days and fed to Daphnia as aged seston to examine the effects of microbially degraded seston. Mechanically reducing seston particle size improved Daphnia growth compared to the same food quantity provided as whole seston. When provided aged seston, Daphnia growth was reduced by more than one third as compared to corresponding fresh seston treatments. Analyses of species composition and biomass, elemental, and fatty acid composition of the seston provided during the growth experiments allow evaluation of the underlying basis for differences in the nutritional value of seston for Daphnia.

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Aquatic Sciences Meeting, Albuquerque 2001

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