Structural Organization of Zooplankton Communities in Different Types of River Mouth Areas

Abstract

The gradients of hydrological, hydrophysical, and hydrochemical conditions form the transition zones in river mouth areas. These areas are considered ecotones in the presence of the edge effect. Our research aimed to identify the main patterns in the structural organization of zooplankton communities in different types of river mouth areas in lowland reservoir tributaries within the Middle Volga basin. A cluster analysis was performed to structure and determine the zooplankton communities. The identified zooplankton communities were characterized by the noticeable heterogeneity in the species structure. We analyzed the spatial distribution of the structural indicators of zooplankton communities and, on the basis of RDA, determined the factors that significantly affect the organization of the ecotone community. An ecotone was found in all types of river mouth areas where the highest density, biomass, diversity, species, and functional richness of zooplankton were noted, as compared to bordering zooplankton communities. As the morphological structure of the mouth areas became more complex, the values of the main structural parameters of zooplankton communities increased. It was demonstrated that conditions in the ecotones are favorable to the development of zooplankton alien species. The major factors determining the species structure of the ecotone zooplankton community were water electrical conductivity (R2 = 21.07%, p-value = 0.001), dissolved oxygen content (R2 = 10.33%, p-value = 0.003), and water transparency (R2 = 9.77 %, p-value = 0.001).

Biodiversity of zooplankton (Rotifera, Cladocera and Copepoda) in the tributaries of Cheboksary Reservoir (Middle Volga, Russia)

“…Rivers are the most widespread type of water body in the world. They have rich faunistic diversity and their estuaries act as refuges for zooplankton ( Krylov et al 2010 , Mukhortova et al 2015 , Zhikharev et al 2023a , Zhikharev et al 2023b ). River ecotones formed in estuaries maintain high biodiversity, bioproduction and nutrient transformation ( Ward and Wiens 2001 , Ward et al 2002 ).…”

“…By invading ecosystems, invasive species can displace native species and reduce local biodiversity ( Havel et al 1995 , Swaffar and O'Brien 1996 , Zanata et al 2003 , Mergeay et al 2004 , Strecker and Arnott 2008 , Wittmann et al 2013 , Walsh et al 2016 ). Often rivers act as transit corridors for the distribution of zooplanktonic invasive species ( Lazareva and Zhdanova 2014 , Lazareva 2019 , Lazareva et al 2022 ) and their estuaries could be acclimatisation habitats ( Zhikharev et al 2023a ). Knowledge about the findings of alien species in new habitats is necessary for monitoring the process of their dispersal.…”