Water Science & Technology Vol 42 No 7-8 pp 291–296 © IWA Publishing 2000
Effects of inoculum's mean cell volume on algal toxicity tests
M-R Chao* and C-Y Chen**
*
Department of Environmental Engineering, National Cheng Kung University,
Tainan 70101, Taiwan
**
Institute of Environmental Engineering, National Chiao Tung University 75,
Po-Ai Street, Hsinchu, Taiwan 300
ABSTRACT
The aim of the present study is to compare the effects of the mean cell
volume (MCV) of algal inoculum to the sensitivity and reproducibility of the
toxicity test. Two sets of experiments were conducted using inoculums with
the MCV equal to 60  m3/cell and 40 m3/cell,
respectively. The initial cell densities, however, were kept the same at
10,000 cells/mL. The results show that larger MCV of the inoculum results
in greater EC50 values. Similar observations and conclusions were
obtained from comparisons based on NOEC values. Thus, MCV of the
inoculum significantly influences the observed toxic response in
terms of EC50 and NOEC values. It is also evident that, there is a
significant increase in the test variability if the MCV is not
controlled properly. This study reports that standardizing the
initial mean cell volume of algal culture can improve inter-laboratory
and intra-laboratory precision. Furthermore, replacing the EC50 values
by the calculated exposure values (EE50) can reduce the variability in
data due to differences in the MCV of the inoculum.
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