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Contrasting ‘Top-Down’ Effects of Crustacean Zooplankton Grazing on Bacteria and Phytoflagellates

Contrasting ‘Top-Down’ Effects of Crustacean Zooplankton Grazing on Bacteria and Phytoflagellates The combined effects of grazing and nutrient regeneration by Daphnia and Eudiaptomus on the growth of Rhodomonas and heterotrophic bacteria was assessed experimentally. The responses of Rhodomonas and bacteria to the grazers were measured as net specific growth rate over the entire experimental periods, as well as production and specific production at the end of the experiments. Both zooplankton species had a negative effect on Rhodomonas net specific growth rate due to grazing and a positive effect on specific primary production due to nutrient regeneration. Daphnia had no effect on bacterial net specific growth rate, bacterial production or specific bacterial production in one of two experiments. In the other experiment, however, both bacterial growth rate and production decreased as a result of grazing. Furthermore, Daphnia had a negative effect on specific bacterial production, but Eudiaptomus had a positive effect on all bacterial parameters due to nutrient regeneration, probably of phosphorus. Positive effects of copepods on bacterial growth has previously been attributed to trophic cascades via protozoa. However, the present experiments show that regeneration of nutrients, especially phosphorus, may account for a large part of the stimulation of bacterial growth. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aquatic Ecology Springer Journals

Contrasting ‘Top-Down’ Effects of Crustacean Zooplankton Grazing on Bacteria and Phytoflagellates

Aquatic Ecology , Volume 39 (3) – Jan 27, 2005

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References (58)

Publisher
Springer Journals
Copyright
Copyright © 2005 by Springer
Subject
Life Sciences; Freshwater & Marine Ecology; Ecosystems
ISSN
1386-2588
eISSN
1573-5125
DOI
10.1007/s10452-005-1326-8
Publisher site
See Article on Publisher Site

Abstract

The combined effects of grazing and nutrient regeneration by Daphnia and Eudiaptomus on the growth of Rhodomonas and heterotrophic bacteria was assessed experimentally. The responses of Rhodomonas and bacteria to the grazers were measured as net specific growth rate over the entire experimental periods, as well as production and specific production at the end of the experiments. Both zooplankton species had a negative effect on Rhodomonas net specific growth rate due to grazing and a positive effect on specific primary production due to nutrient regeneration. Daphnia had no effect on bacterial net specific growth rate, bacterial production or specific bacterial production in one of two experiments. In the other experiment, however, both bacterial growth rate and production decreased as a result of grazing. Furthermore, Daphnia had a negative effect on specific bacterial production, but Eudiaptomus had a positive effect on all bacterial parameters due to nutrient regeneration, probably of phosphorus. Positive effects of copepods on bacterial growth has previously been attributed to trophic cascades via protozoa. However, the present experiments show that regeneration of nutrients, especially phosphorus, may account for a large part of the stimulation of bacterial growth.

Journal

Aquatic EcologySpringer Journals

Published: Jan 27, 2005

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