Small Organisms in a Large River: What Provides the High Diversity of Scaled Chrysophytes in the Ob River?

Abstract

Currents are one of the main factors favoring the dispersal of microscopic planktic organisms over inland lakes and rivers. Large rivers of the northern hemisphere, flowing from south to north, can increase the diversity of northern latitudes with boreal species, while high water levels and floods expand the range of ecotopes and the biodiversity of rivers. We studied the distribution of the taxonomic structure and species richness of scaled chrysophytes downstream of the Ob river—a large river in West Siberia—at the end of the high-water period (June). Methods of scanning and transmission microscopy allowed the determination of a high taxonomic richness of these organisms, 67 species in total. The species were unevenly distributed by stations, with the maximum number of species (54) occurring in a shallow still bay without current and with minimum turbidity and a small number of diatoms. The species diversity in the main current was represented mainly by ubiquitous and cosmopolitan species.Water level fall usually coincides with the end of the vegetation of many scaled chrysophytes and the formation of stomatocysts. The stomatocysts of different species may drift downstream and then germinate when they find suitable conditions at theappropriatetime. Large rivers that are subject to significant changes in water level during their hydrologicalperiodsare able to host ahigh diversity of microscopic planktic organisms. Studying this capacity may reinforce the hypothesis of an omnipresence, i.e., that “everything is everywhere”.

Diversity of Silica-Scaled Chrysophytes in the Steppe Zone of the Southern Urals with a Description of a New Species from the Genus Mallomonas

“…It has been registered in North and South America, Great Britain, Europe, Asia, and Australia [4]. In the territory of Russia, it was found in water bodies of St. Petersburg and Leningradskaya Oblast [15], Nizhegorodskaya Oblast [28,49], Neneczkii Autonomous Okrug [20], Yamalo-Neneczkii Autonomous Okrug [19], the Republic of Komi [20,35], Krasnoyarskii Krai [17], and the Republic of Buryatia [32].…”

“…Mallomonas annulata (Figure 2D,E) is a widespread species recorded in North and South America, Great Britain, Europe, Asia, and Australia [4]. In the territory of Russia, the species was recorded in the water bodies of St. Petersburg and Leningradskaya Oblast [11,15,27], Yamalo-Neneczkii Autonomous Okrug [19], and the Republic of Sakha (Yakutia) [34].…”

“…Mallomonas eoa (Figure 2N,O) is a widespread species known in North and South America, Great Britain, Europe, Asia, and Australia [4]. In the territory of Russia, M. eoa was previously found in the water bodies of the Republic of Karelia [11], St. Petersburg and Leningradskaya Oblast [15], Yaroslavskaya Oblast, Nizhegorodskaya Oblast [12,13], the Republics of Buryatia [32] and Sakha (Yakutia) [18,34], Bolshezemelskaya tundra [20], Yamalo-Neneczkii Autonomous Okrug [19], and reservoirs of the Volga basin [13].…”

“…Mallomonas insignis (Figure 3P-T) is a widespread species, recorded in North America, Great Britain, Europe, Asia, and Australia [4]. On the territory of Russia, M. insignis was found in water bodies of the Yamalo-Neneczkii Autonomous Okrug [19], Yaroslavskaya Oblast [13], Nizhegorodskaya Oblast [28], Permskiy Krai [13], Krasnoyarskii Krai [17], and the Republic of Buryatia [31,32].…”

“…A number of interesting works have been published on the study of rivers, reservoirs, lakes, and swamps in Eastern Siberia, most of which have been carried out in the last decade [30][31][32][33][34]40]. The Ural region and Western Siberia have been studied to a much lesser extent [19,27,[35][36][37]39]. However, studies of silica-scaled chrysophytes of the Polar Urals revealed a high diversity and abundant flora, including taxa new to science and to the flora of Russia [27,35,36].…”