Spatial Distribution and Interannual Dynamics of Sedimentary Pigments as Productivity Indicators of the Volgograd Reservoir

For the first time, long-term data (2011–2021) on the content of plant pigments in bottom sediments of the large floodplain-valley Volgograd Reservoir (Lower Volga, Russia) are summarized. It is shown that the distribution of pigments over the bottom area depends on the activity of hydrodynamic processes that form the structure of the ground complex. Low values of the total concentration of chlorophyll a and pheopigments in the upper (5 cm) layer of bottom sediments (<1 μg/g dry sediments) are confined to the zones of transit and transsedimentation of suspended matter; high values (100–240 μg/g dry sediments) are noted in places with weak hydrodynamics (mouth zones of tributaries, bays, dam area). The average pigment concentration increases from the river to the lake segments from 9.1 ± 6.3 to 54.5 ± 10.7 μg/g dry sediments. The interannual dynamics of pigment concentration in the upper layer of bottom sediments is characterized by stochasticity without a pronounced trend. In the cores of gray clayey silt, pigment concentrations increased from the lower layers to the upper ones. The trophic state of the benthal of the Volgograd Reservoir, estimated by the concentrations of chlorophyll a with derivates in bottom sediments, is mesotrophic. The results of the work can be used to assess the productivity of bottom biotopes of reservoirs.