Diatoms of the Peatbog Sediments from Shemya Island (Aleutian Islands, United States)

Resumo

Results of a study of diatoms from Holocene peatbog sediments from Shemya Island (Aleutian Islands, United States) are presented. The column of peat sediments (385 cm depth) was investigated (formation of peat sediments began more than 9500 years ago). Sixty-seven taxa of 31 genera, 17 families, eight orders, and three classes were identified. According to results of taxonomical and eco-geographical analyses, most taxa belong to the order Naviculales and family Pinnulariaceae and are benthic organisms with cosmopolitan distribution. Forms with different quality of frustule preservation were revealed. Centric diatoms demonstrate the best preservation in sediment. Of special interest is the dissolution of frustules in a water body with presumably low pH value. Dynamics of the pattern of species relative abundance was studied. Several zones with characteristic diatom complexes are distinguished. Analysis of distribution of diatoms in the column showed that, apparently, this locality was a shallow oligotrophic reservoir with a relatively low pH in the past. Water level changed occasionally, but trophic level did not change over the period of the reservoir’s existence.