Variability of Trophic State of Bottom Biotopes of the Gorky Reservoir by Sedimentary Pigments

Abstract

New data on the contents of plant pigments and organic matter in bottom sediments of channel, floodplain and estuarine biotopes of the Gorky Reservoir (upstream Volga, Russia) are presented. Patterns of the distribution of sedimentary chlorophyll a and the products of its degradation, pheopigments, depending on the water current velocity, depth and type of the bottom sediments were revealed. Taking into account the zoning of the reservoir by abiotic factors, the trophic conditions in bottom sediments were estimated by the total content of chlorophyll a and pheopigments. Average concentration of sedimentary pigments, calculated considering the areas of bottom sediments of different types, in 2009–2010 (25.3 ± 1.5 μg/g dry sediments) is less than in the years of previous observations, 1996–1998 and 2001 (59.1 and 31.9 ± 3.7 μg/g, respectively). The trophic state of the reservoir’s benthal remains mesotrophic.