HR: 10:45h
AN: NB32E-02    [Abstracts]
TI: Top-Down Control of Stream Food Webs: How to Detect a Predator's Impact on Physiological Fitness of Macroinvertebrates
AU: * Ortmann, C
EM: ortmann@bafg.de
AF: Federal Institute of Hydrology, Am Mainzer Tor 1, Koblenz, 56068 Germany
AU: Hellmann, C
EM: claudia.hellmann@Mailbox.tu-dresden.de
AF: Dresden University of Technology; Institute of Hydrobiology, Zellescher Weg 40, Dresden, 01217 Germany
AU: Benndorf, J
EM: bennd@rcs.urz.tu-dresden.de
AF: Dresden University of Technology; Institute of Hydrobiology, Zellescher Weg 40, Dresden, 01217 Germany
AU: Koop, J H
EM: koop@bafg.de
AF: Federal Institute of Hydrology, Am Mainzer Tor 1, Koblenz, 56068 Germany
AB: Before prey is extinguished by its predator physiological stress increases. This is true for a single individual as well as on a population level. We prove this assumption for the first time in a field experiment. It is designed as a paired ecosystem study of two streams with benthivorous fish as predators. So far, top-down manipulation is well established in lentic habitats in order to improve water quality. However, there is hardly any physiological approach to be found within former projects. Behavioral changes to avoid predator encounters are well known concepts, nevertheless every organism is obliged to obtain food and energy for growth and reproduction, they cannot totally avoid their predators. Increased stress during fight or flight reactions will change the energy charge inside the cells (nucleotide composition). Certain metabolites like phosphagens will decrease while others like lactate may accumulate. On a long time scale increased stress will result in lower energy storage, mainly detectable as lower glycogen and triglyceride content compared to individuals without high predation risks. Together with the determination of species biomasses and abundances it should be possible to develop a comprehensive impression of sub lethal effects within the invertebrate community. (supported by German Research Foundation)
DE: 1845 Limnology
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly