Role of bottom sediments in ecological assessment of oil-polluted waterbodies

Abstract

Bottom sediments are one of the most objective indicators of the ecological state of water body as a whole. Of particular importance is the assessment of bottom sediments quality in the regions subject to intensive anthropogenic load. In the Middle Ob basin, an intensive long-lasting oil production resulting in oil-pollution of bottom sediments takes place. One of the major water bodies used for oil production is Lake Samotlor. In September 2007, the macroinvertebrates were sampled from the Samotlor sediments, which differed in granulometric composition. It is shown that benthos communities of different sediments (sand, silt, mixed sediments) differed significantly in taxonomic composition, abundance and structure of dominant macroinvertebrates. To choose a method for assessing the ecological state of the water body, the correlation of biotic indices with oil concentration in the bottom sediments was determined. It is noted that the Goodnight-Whitley index significantly correlated with oil concentration in all types of bottom sediments except for sands. Indices of diversity correlated with oil only on mixed sediments, the Woodiwiss biotic index - only on sands and silts with detritus. The level of pollution of bottom sediments corresponded to the 3rd class, i.e. "moderately polluted". The decrease in environmental quality (class 4-5) was observed only in the western part of the lake, as well as in some parts of the central sectors. Recommendations on the choice of indices for environmental monitoring of water bodies in the region are given.