Seasonal patterns of Potamoplankton in a Large Lowland River of Temperate zone (Upper Ob as a case study, Russia)

Abstract

The paper presents the results of seasonal potamoplankton dynamics in a Siberian lowland river<br />and its relationships with environmental variables. The sampling was carried out every 10-15 days from April to<br />September 2001 at the left and right banks including the midstream of the Upper Ob River close to the big<br />industrial center,Barnaul city(53º21'24"N, 83º47'14"E). Thepresence of 145 species (158 taxa) with predominance<br />of diatoms (45.6% of total number of species) and green algae (35.8%) was noted. Remarkable seasonal<br />potamoplankton variations were revealed using measures of inclusions and amultigraph. The correlation analysis<br />indicated that physical factors (e.g. hydrological variables) and major nutrients (e.g. nitrates) were of equal<br />importance for controlling the variation in structure and abundance of the large lowland Upper Ob River<br />potamoplankton. Based on the regional trophic classification, the Upper Ob River can be currently characterized<br />as oligo-mesotrophic since the total abundance and biomass of algae were less than 1260×103 cells/L and 780<br />mg/m³ throughout the sampling seasons. The results of the saprobiologic analysis showed that the greatest<br />number of bioindicators belong to β-mesosaprobionts that is indicative of the β-mesosaprobic environment.<br />Water qualitywas ranked among I-III classes.Our studypresents a baseline formonitoring theplanktonic component<br />in the river ecosystem as a main factor of its stability. In spite of the regional aspect of the study, the investigation<br />of potamoplankton in the environments of the south ofWest Siberiawill be useful for understanding of phytoplankton<br />development in large unregulated lowland rivers.