Abundance of Related Species, Kellicottia bostoniensis (Rousselet, 1908) and K. longispina (Kellicott, 1879) (Rotifera: Brachionidae), in the Zooplankton Communities of the Pustynskaya Lake-River System (Nizhny Novgorod Region)

The article describes the features of the spatial distribution of zooplankton communities in the waters of the Pustynskaya lake-river system. The abundance of two related species of genus Kellicottia , the alien Kellicottia bostoniensis (Rousselet, 1908) and the indigenous K. longispina (Kellicott, 1879), was analyzed in some communities in 2013–2017. The greatest abundance of the alien species was noted in zooplanktic communities of mesotrophic water bodies (Seryozha River and Lake Svyato). It was found that, after the period of mass development of K. bostoniensis in 2013–2014, which could have been due to the initial stage of establishment of the alien species, its abundance sharply decreased. In 2013–2014, the abundance of the indigenous species K. longispina (Kellicott, 1879) was significantly lower than that of the alien species. Rotifer K. longispina dominated in the Protoka and Lake Svyato in 2017. The highest density of both species was found in the metalimnion of the mesotrophic Lake Svyato. A statistically significant positive correlation was found between the abundance of K. bostoniensis and the water temperature, transparency, and pH, as well as the abundance of predatory zooplankton species. The abundance of the native species K. longispina correlated negatively only with the value of water pH.