Aim . As a result of fluctuations in water level, waves, circulation, rise and fall of the water levels there are constant partial erosion and leaching of soil banks in water bodies, with intensive ongoing pollution of the waters of the Caspian Sea, which we have seen in recent decades, and in the long run may dangerously affect the transparency of the water and reduction of biomass of the benthic community in the western part of the South Caspian Sea. The paper presents the results of the last 60 years of monitoring studies to determine the nature of transparency, depth of the euphotic layer, the primary production of phytoplankton photosynthesis, phytoand zoobentos biomass and destruction of organic matter in the coastal western shelf of the South Caspian. Methods. In the course of research, modern methods of quantitative and qualitative analysis were used, regulated by normative documents, duly approved for environmental monitoring of water bodies. Results. Studies have shown that since the second half of the 90’s, the mainland coast strip is strongly deformed, starting from the village of Shihva to Kura area, further from the south of the village of Narimanabada to Astara. Dozens of artificial coves, bays, islands were created with clay-soil mounds. Conclusions. A huge mass of clay and soil goes to the coastal waters of the western shelf as a result of the destruction of the structure of the coasts due to waves and wind, resulting in clastic particles in the water increased by 2.5 3 times, the transparency of the water in the area of 5-10 m depth contours is reduced by more than 2 fold, increasing the degradation 1.6 times. During this period, because of the intensity of sedimentation and the overall pollution in the study area, phytobenthos has almost disappeared and flowering has been reduced by 7580%. Zoobenthos has been badly damaged and biomass of bento detritivorous organisms has also been reduced.