STUDENT ABSTRACTS - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 279

ECOTOX - a biomonitoring system for UV-effects and toxic substances
C. STREB, P. RICHTER, D.-P. HÄDER
Friedrich-Alexander-Universität, Institut für Botanik und Pharmazeutische Biologie,
Erlangen, Germany
In view of increasing water pollution and UV radiation, the importance of
biomonitoring is growing. These bioassays determine the responses of living organisms
to stressors. The biological test system ECOTOX can be used in ecotoxicology as a
fully automatically early warning system to analyze the water quality, but also in
toxicology to study direct influences of chemical substances or radiation.
Euglena gracilis is a unicellular photoautotrophic freshwater flagellate. In its
natural environment the organism reaches the optimal position for its photosynthetic
apparatus in the water column by photo- and gravitaxis. At low irradiances the organism
swims towards the light, at high irradiances it shows negative phototaxis, until this
effect is balanced by negative gravitaxis. In darkness, like in the cuvette of the
ECOTOX-system, cells show a precise negative gravitaxis 1 .
The movement behaviour such as swimming velocity, direction of movement,
precision of gravitactic orientation, percentage of motile cells and the cell shape can be
determined by the ECOTOX-system. The optical apparatus includes the observation
cuvette, an infrared diode, a miniaturized microscope, and a CCD camera coupled to a
framegrabber card in the computer. With the real-time image analysis software the
picture can be optimized, a threshold to distinguish between background and objects can
be adjusted. Cell culture and sample water are pumped in automatically, the organisms
are tracked, and significant parameters are displayed. The results are stored in ASCII
files and can be examined in a spreadsheet program, where dose-effect relationships can
easily be calculated. Euglena gracilis was found to be highly sensitive to external
influences in the used parameters and therefore is an ideal bioassay. Toxic effects of
pollution in aqueous habitats, waste water and freshwater with heavy metal ions or
organic solvents and effects of UV radiation can be determined 2 .
References
1. Tahedl H, Häder D-P (1999) Fast examination of water quality using the automatic biotest ECOTOX based
on the movement behavior of a freshwater flagellate, Wat Res 33: 426-432.
2. Tahedl H, Häder D-P (2000) The use of image analysis in ecotoxicology, in D-P Häder (ed.) Image
analysis methods and applications , CRC Press, Boca Raton, pp 447-458.