Impact of Pesticide Contamination on Aquatic Microorganism Populations in the Littoral Zone

The effect of pesticide contamination of the littoral zone on the population of bacteria and fungi was analyzed using the example of a eutrophic water reservoir exposed for >30 years to the influence of expired crop-protection chemicals, mainly DDT. For three consecutive years, quantity analyses of bacteria and fungi were conducted and the composition of the microorganism population analyzed against seasonal dynamics. Mold and yeast-like fungi were also isolated and identified. Within the Bacteria domain, in addition to the large groups of microorganisms (Alphaprotobacteria, Betaprobacteria, and Gammaproteobacteria, Actinobacteria, and Cytophaga-Flavobacterium), the analysis also involved the presence of bacteria predisposed to degraded pesticides in natural environments: Pseudomonas spp. and Alcaligenes spp. The quantity dynamics of aquatic microorganisms indicated that bacteria and fungi under the influence of long-term exposure to DDT can adapt to the presence of this pesticide in water. No modifying effect of DDT was observed on the quantity of microorganisms or the pattern of seasonal relationships in the eutrophic lake. Changes were shown in the percentage share of large groups of bacteria in the community of microorganisms as was an effect of contamination on the species diversity of fungi. The data show the effectiveness of aquatic microorganism–community analyses as a tool for indicating changes in the water environment caused by pesticide contamination.