Red-shifted chlorophylls in the seston of water bodies of Middle Volga basin

Pigment analysis of >350 seston samples from aerobic and microaerobic layers of lakes and reservoirs in the basin of the Middle Volga and Kama had been performed. The resulting data explicitly indicate the presence of lipophilic pigments causing abnormally high absorption in the wavelength range 690-700 nm in significant fraction of studied samples. In some samples this anomalous absorption may be explained by degradation products of plant pigments (e.g. of purpurine derivates). However in some samples from upper microaerobic part of the chemocline of stratified lakes, it is most likely caused by the presence of “red-shifted chlorophylls” - chlorophylls d and f. Taking into account the environmental characteristics of these layers and widespread distribution of chlorophyll-d containing cyanobacteria in the oceans, the development of phototrophic organisms (presumably, cyanobacteria) obligately or facultatively synthesizing these chlorophylls is one of the possible explanation for this phenomenon.