abstracts der vorträge und poster - Technisches Büro für Ökologie

Mathieu, Francine, WasserKluster Lunz und Universität Wien, francine.mathieu@univie.ac.at
Kainz, Martin, WasserKluster Lunz, martin.kainz@donau-uni.ac.at
DOES PLANKTON SIZE MATTER? – THE ROLE OF PLANKTON SIZE FOR PREDICTING
TROPHIC LEVEL AND THEIR ESSENTIAL NUTRIENTS OF ARTIFICIAL LAKES
We study food web dynamics of selected artificial lake systems (i.e., gravel pit lakes) and hypothesize
that trophic transfer of essential nutrients, as measured by essential fatty acids (EFA), follows that of
food webs in natural lakes. This hypothesis is based on the assumption that phagotrophic organisms
such as zooplankton will regulate their dietary nutrient retention according to their somatic
requirements, which are, in large, not predicted by dietary supply. Our artificial lake systems receive
their water and most of their nutrients from ground water and are most often eutrophic in their trophic
status and poor in EFA supply. Preliminary results indicate that the planktonic food web differs
among the examined systems and is predominantely composed of cyanobacteria and zooplankton
(mostly cladocerans), as macroplankton (>500 um). Ongoing analysis of trophic level and EFA
composition of organisms evaluates the transfer of essential nutrients at the aquatic plant-animal
interface of these aquatic food webs. Results will be discussed with respect to trophic transfer
concepts of planktonic food webs of natural lakes.
Melcher Andi, IHG - Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU, Wien,
andreas.melcher@boku.ac.a
Schmutz Stefan, IHG - Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU, Wien,
stefan.schmutz@boku.ac.at
CLIMATE CHANGE IMPACTS ON FISH IN AUSTRIAN RIVERS
Water temperature is amongst other factors a driver of fish community composition in rivers. Climate
change and local human impacts can warm water bodies and cause changes of its fish fauna.
In this paper the methodological strategy is (1) to use observed water temperature data from 1976 to
2005 to develop multiple linear regression models and to predict water temperature from abiotic
parameters. Three variables, altitude, mean monthly flow rate, and distance from the source, described
up to 80% of the variance of mean water temperatures during summer.
Furthermore (2), we evaluate the impact on fish communities using ecological models driven by water
temperature. The models were significantly correlated with fish assemblages and typical temperature
ranges could be assigned to the river regions. Analyses of water temperature timelines showed a
warming trend over the last 30 years. Our results should improve the understanding of how climate
change may alter the structure and functioning of freshwater ecosystems in Austrian rivers.
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