The stability of an ecosystem strongly depends on the biodiversity of its microorganisms population. The network of interactions between microorganisms provides a flexible response to various changes of the coenotic equilibrium. This equilibrium changes drastically if such a network is damaged by oil spills or any other kind of pollution, representing a danger to the existence of a whole ecosystem. Bioremediation is a method employing microorganisms to remove pollutants and to restore the ecology of populations. Understandably due to its nature, this approach is considered to be the most gentle and safe one what makes it very attractive. Our focus was to improve the efficiency of the treatment of oil pollution in the Baltic Sea. As a part of “BioBind” project, we aimed to create artificial associations of alkanotrophic bacteria and phototrophic partners (algae or cyanobacteria) and to use them as an effective tool for the removal of oil spills. In summer and winter 2011–2012, we isolated 157 strains of both algae and cyanobacteria and 199 bacteria. The samples were taken from four different places of the Baltic Sea in the areas of Rostock, St. Petersburg, Kiel and Sassnitz. After the screening, we have selected 19 strains of alkanotrophyc bacteria and 23 strains of green algae and cyanobacteria showing resistance to the pollutants. The screening was performed in media containing an oil, phenol and phenanthrene at low temperatures (4°C and 10°C) and different salt concentrations. All selected species of bacteria belonged to the genus Rhodococcus. Further selection was aimed at finding combinations of bacterial strains which show an increased degrading capacity and exceeding the one of the originally isolated microorganisms. As a result, we have selected associations with the degradation of crude oil (at the concentration of 2 g/L) with a degradation rate from 25% up to 35%. Furthermore, we have discovered that the presence of the phototrophic microorganisms in these associations resulted to a positive modest effect with regard to the efficiency of the system by several percent. Our result proves clearly the concept that bioremediation represents an effective mean to clean up oil spills. This is remarkable that the system also shows plasticity and can be improved by creating different variations of the microorganisms constituting it. Thus bioremedation provides scope for further development. The selected artificial associations can be recommended for the purification of oil pollution in the Baltic Sea.
