Biochemical Study of Brackish-Water Marine Ecosystems

The concentrations and the elemental and biochemical composition of dissolved and particulate organic matter (OM) characteristic of southern and Arctic seas are presented. The rate of OM transformation in the production–decomposition cycle and that of the phosphate cycle are estimated from the activity of the redox enzymes of the electron-transport system and that of phosphatase. Carbohydrates and protein are shown to be the main biochemical components in the water of all the seas under study in dissolved and particulate OM, respectively. The contribution of carbohydrates to particulate OM under the conditions of intense primary production is demonstrated to be comparable to that of protein. High concentrations of lipids are shown to be characteristic of the coastal ecosystems in the middle Caspian Sea and northwestern shelf of the Black Sea because of severe pollution in these areas. It is noted that at higher trophic levels, the ecosystem of the Caspian Sea intensely assimilates allochthonous OM, and that the Black Sea ecosystem transfers considerable amounts of OM to the hydrogen sulfide zone.