BACTERIAL ABUNDANCE AND ACTIVITY IN OIL POLLUTED AND RESTORED ARTIFICIAL WETLANDS
SILVENA BOTEVA1*, EMILIA BANKOVA2, ANELIA KENAROVA1, SAVA TISKOV3, IVAN TRAYKOV1
1 – Department of Ecology and Nature Protection, Faculty of Biology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
2 – Medical University - Pleven, Faculty of Public Health
3 – Department of Microbiology, Faculty of Biology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
*Corresponding author: silvenab@abv.bg
Keywords: oil pollution, wetland, heterotrophic and oil-degrading bacteria
Abstract: The oil industry has a great environmental risk throughout ship accidents and the impact of waste generated during the oil refining or production of petrochemicals and their derivatives. The waste waters of petrochemical industry commonly contain gross amounts of oil and suspended solids. After the purification processes, in some cases the wastewaters are discharged into artificial wetlands for sedimentation and biodegradation of refractory petrochemicals and organic matter.
This paper studied the dynamics of heterotrophic and oil-degrading bacteria in a polluted and a restored artificial wetland of petrochemical plant concerning the local specificity of wetlands and the seasonal changes. The oil polluted wetland was characterized both with higher water and lower sediment abundances of heterotrophs comparing to that of restored wetland. The number of oil-degrading bacteria was relatively similar in the two environments, except that in the sediments of restored wetland, which exceeded up to several times the number of oil-degrading bacteria elsewhere. The share of oil-degrading bacteria in the community of heterotrophs was higher (0.63% vs. 0.04%) in the water column and in the sediments (3.01% vs. 0.009%) of the restored wetland compared to the polluted one. The total activity of water and sediment heterotrophic bacteria was not significantly different between the wetlands with average value ranging from 4.5±2.0 μg O2 l-1 to 5.3±1.3 μg O2 l-1. In a contrast, the relative bacterial activity, calculated per cell of heterotrophs, differed significantly between the water of polluted vs. restored wetland (81.8±182 x 10-4 μg O2 l-1 vs. 30.3±34.4 x 10-4 μg O2 l-1), and between their sediments (0.07±0.1 x 10-4 μg O2 l-1 vs. 0.04±0.05 x 10-4 μg O2 l-1). The ANOVA analysis indicated a significant contribution of water temperature in the variance of heterotrophs abundance and activity, and water temperature and wetland local conditions, both contributing in the variance of oil-degrading bacteria abundance.