Journal of Plankton Research, Vol 21, 957-970, Copyright © 1999 by Oxford University Press
D Dobberfuhl and J Elser
Zooplankton growth and nutrient recycling are key processes in the
operation of pelagic food webs. Most studies investigating these processes
rely on complex methods and often require extensive laboratory facilities.
Here we introduce a technique for preserving algae by rapid drying for
later use in laboratory- or field-based growth and nutrient recycling
experiments. Chemostat-grown Scenedesmus acutus was
rapidly dried for later experiments evaluating its nutritional composition,
suitability for animal growth and potential for use in nutrient release
experiments. Reconstituted dried algae had slightly lower nitrogen (N),
Phosphorus (P) and protein content (% dry weight) than fresh algae, but
lipid content did not differ and elemental ratios were in the range
considered to indicate favorable food quality. These elemental and
biochemical differences did not appear functionally important, as
Daphnia magna grew identically on fresh and dried
food. Freeze-dried S.acutus did not work as an
alternative to oven drying as it resulted in 100% mortality. NH4 and PO4
concentrations did not change over 24 h when dried algae were resuspended
in normal media or boiled lake water. However, concentrations of PO4
decreased over 24 h, suggesting chemical adsorption of PO4 to the dried
algae and reinforcing the need for animal-free controls in nutrient release
experiments using this approach. N and P release rates for
D.magna and natural zooplankton communities were
estimated using dried algae, and values were comparable to published ones.
Thus, dried algae may be a useful, simple technique for studying food
quality and nutrient release in environments where maintaining active algal
cultures may not be practical and a constant supply of consistent quality
food is needed.
ORIGINAL ARTICLES
Use of dried algae as a food source for zooplankton growth and nutrient release experiments
Department of Biology, Arizona State University, Tempe, AZ 85287-1501, USA
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