Chlorophyll a Content in Bottom Sediments of the Shallow Busse Lagoon, Sakhalin Island

The present study provides the first results of measurements of chlorophyll a and chlorophyll degradation products in bottom sediments of the Busse Lagoon, Sakhalin Island, that were carried out at nearshore and central sites of different types in this body of water. The relationship between the sedimentary pigment content and the physicochemical characteristics of bottom sediments has been identified. As determined by the sedimentary phytopigment content the trophic level of the lagoon varies from oligo- to eutrophic in its different parts. The nearshore waters with an average content of chlorophyll a and pheopigments can be assigned to the oligotrophic category; the waters of the central part belong to the mesotrophic category. The concentration of chlorophyll with derivatives in sediments decreased from 21.4 ± 5.6 μg/g dry weight (d.w.) in the summer to 6.1 ± 1.9 μg/g d.w. in the autumn; for the entire lagoon, it averaged 16.3 ± 4.4 μg/g. The seasonal dynamics of sedimentary pigments does not correlate with that of phytoplankton and can depend to a greater extent on the hydrodynamic activity. With a relatively low sedimentary pigment content, the lagoon ecosystem shows signs of the terminal phase of the oligotrophic–eutrophic succession, that is, periodic mortality of aquatic organisms and silt accumulation.