Influence of Trophic Relations in the Shelf Communities on Benthos: Trophic Structure and the Effects of Grazing Pressure

Abstract

Influence of the plankton and nekton on the benthos, which form total shelf community is considered. Trophic structure of benthos of different parts of the World Ocean shelves has been reviewed and made its classification. Three types of trophic structure are oligotrophic, eutrophic and hypertrophic; a brief description of each of the three types is given. In oligotrophic and eutrophic structures distribution of food formed trophic zonation and was caused by the interaction of three factors – geomorphological structure of the shelves, speed of bottom currents and intensity of organic matter sedimentation from the pelagic zone. Hypertrophic structures occur at very high organic matter sedimentation causes kills and, as a result, the trophic structure of benthos is determined by the oxygen regime. In Caspian, grazing of benthivorous fish, sturgeon, became a very strong factor which even takes place in speciation, and adaptive responses of benthic organisms and the entire benthic community to this effect are defined. Because of intensive grazing pressure, benthos organisms become smaller, their life cycle is shorter, that is typical for r-strategists; however, all other properties belong to K-strategists. Beside that, intensive grazing causes drastic reduction in the role of carnivores, whose functions are taken over by the sturgeons

Keywords

• benthos
• shelf community
• trophic relations
• oligotrophic structure
• eutrophic structure
• hypertrophic structure
• influence of grazing pressure on benthos