Assessment of multifaceted toxicity induced by heavy metal contamination in the Gelevera stream using the Allium test

Determining the effects of pollution in a water source on life is critical for the balance of nature. The aim of this study was to determine heavy metal pollution in Gelevera Stream and its effect on Allium cepa, an agricultural organism. Germination percentage, root elongation and weight gain were used as physiological parameters, mitotic index (MI), micronucleus (MN), chromosomal abnormalities (CAs) were used as cytogenetic parameters, malondialdehyde (MDA), proline, superoxide dismutase (SOD), catalase (CAT) were used as biochemical parameters and meristematic cell damage was used as anatomical parameters. The amount of DNA damage was assessed using the comet test. Four stations, namely A1, A2, A3 and A4, were identified in Gelevera stream to determine heavy metal pollution in water. ICP-MS was used to measure the heavy metals in water samples that were taken from each station. In the water samples taken from each station, bulbs were germinated for 72 h and the collected root samples were used in the analysis. As a result, the highest heavy metal pollution was measured in water samples collected from stations A4 > A3 > A2 > A1. Concentrations of elements such as Al, Hg, Ba, Ti, Ti, RB Cd, Mn, Sr, U and Co measured in water samples collected from station A4 were found to be above the reference values set by the Turkish Standards Institution (TSI), European Union (EU) and World Health Organization (WHO). The germination parameters of bulbs exposed to Gelevera stream water decreased. In Group V germinated with river water sample, in which the most pollution was detected, germination decreased by 45%, root length decreased by about 3.0 times and weight decreased by about 4.8 times. In Group III, Group IV and Group V, which were germinated with water samples collected from stations A2, A3 and A4 where heavy metal pollution was high, statistically significant (p < 0.05) decreases in MI and DNA percentages were found. Compared to Group I (control), MI decreased by 0.54% in Group II, 1.25% in Group III and 1.77% in Group V. In addition, statistically significant changes (p < 0.05) were found in MN and CAs frequency, MDA levels, proline levels and SOD and CAT enzyme activities of these groups. Different kinds of CAs and anatomical damage in root meristem cells were encouraged by heavy metal ions in Gelevera stream water. As heavy metal pollution increased, comet test findings indicated a decrease in the amount of head DNA and an increase in the percentage of tail DNA. As a result, it was determined that there is heavy metal pollution in Gelevera stream originating from different sources and far above the reference values, which promotes multifaceted toxicity in A. cepa, a non-target eukaryotic organism.