N. Bowers et al., COMPARATIVE-EVALUATION OF SOIL TOXICITY USING LETTUCE SEEDS AND SOIL CILIATES, Environmental toxicology and chemistry, 16(2), 1997, pp. 207-213
The toxicity of elutriates from 25 putatively contaminated soils was e
valuated using the standard seed (Lactuca sativa) germination test and
a recently developed soil ciliate (Colpoda inflata) growth test. Corr
espondence in the identification of presence or absence of toxicity in
the 25 soil elutriates between the two tests was 60% and concordance
in ranking of toxicity between the two tests was significant (p < 0.05
) using Spearman's rank correlation test (r(s) = 0.3831). Stepwise mul
tiple regression analysis of toxicity results against soil elutriate c
hemistry indicated that pH explained the greatest amount of variation
in response in both tests, despite high concentrations of several meta
ls in the elutriates. For the germination test, a multiple regression
model that included pH and cadmium explained 58.5% of response variati
on, whereas over 83% of response variation in the ciliate growth test
could be explained by pH, copper, and cadmium. Differences in the resp
onse of the plant and protozoan models appeared to be due primarily to
differences in their sensitivity to elutriate pH. In addition to bett
er correspondence between elutriate chemistry and ciliate response com
pared to the seed germination test, lower response variability associa
ted with the measure of ciliate growth compared with seed germination
provided greater statistical sensitivity for detecting toxic effects.