Aquatic Organisms and Petroleum Hydrocarbon Degrading Bacteria Associated with Their Digestive System
Laboratory investigation was carried out on the abundance and composition of bacteria in the digestive system of a total of 35 specimens, including bivalve molluscs, i.e. swan mussel Anodonta cygnea (Linnaeus, 1758) from Lake Spėra (Širvintos district) and swollen river mussel Unio tumidus (Philipson, 1788) from the Curonian Lagoon near Juodkrantė, zebra mussel (Dreissena polymorpha) from the Curonian Lagoon near Juodkrantė and an anostracan – Chirocephalus josephinae (Grube, 1853) from a pond in Ilčiukai village, Utena district, and in the water of related water bodies. Studies on bivalve molluscs (swan mussel and swollen river mussel), zebra mussel and an anostracan – Chirocephalus josephinae, as well as microbiological investigation of water demonstrated that the number of microorganisms in the digestive system of mollusc and anostracan species fluctuated and varied between different species and water bodies. The greatest percentage of HDB among total heterotrophic bacteria was found in the digestive system of swollen river mussels (21.53%) and in zebra mussels (19.99%) caught in the Curonian Lagoon and in the water of the lagoon (24%). A considerably smaller percentage of HDB was detected in the digestive system of swan mussels from Lake Spėra (17.6%) and in the water of the lake (16.66%). The smallest percentage of HDB was found in the digestive system of Chirocephalus josephinae (6.63%) and in the water of the Ilčiukai pond (2.72%). According to the values of abundance of petroleum hydrocarbon-degrading bacteria (HDB) and total coliform bacteria (TCFB) in the digestive system of aquatic organisms we can state that the water ecosystem of Ilčiukai pond was the least contaminated with petroleum, its products and sewage water, and the Curonian Lagoon water ecosystem was the most contaminated. Abundance of petroleum hydrocarbons degrading bacteria could be used as a bioindicator reflecting the level of ecosystem pollution petroleum and its products.