Effects of lateral connectivity on zooplankton community structure in floodplain lakes

Anna Goździejewska,Sylwia Lew,Magdalena Grabowska,Roman Kujawa,Krystian Obolewski,Mirosław Grzybowski,Katarzyna Glińska-Lewczuk

doi:10.1007/s10750-016-2724-8

Abstract

Hydrological conditions are responsible for the changes in lateral connectivity between the main river channel and the floodplain lakes, a factor controlling zooplankton abundance and diversity. We tested the hypothesis that the degree of connectivity between the aquatic habitats and the river channel governs the zooplankton densities and community structure. Abundances, community composition and species diversity of zooplankton were analysed against the gradient of lakes’ connectivity and the water quality parameters under a natural flood pulse in the Biebrza River (North-Eastern Poland). Our findings revealed that the water level fluctuations directly affect the availability of nutrients, aeration, what in turn controls the densities and biovolumes of zooplankton communities. Along with the increase in the lake isolation, the taxonomic diversity of zooplankton decreased, while the eudomination of taxa indicative of advanced trophy (Rotifera) was observed. Qualitative parameters, as number of species, diversity and richness, were significantly higher at mean water levels, which supports the intermediate disturbance hypothesis. The sensitivity of the zooplankton community to variable hydrological conditions and lateral connectivity gradient demonstrates its potential as an unexploited indicator of any habitat changes in the aquatic ecosystems.

Highlights

Floodplain lakes play numerous roles among mosaics of the riverine ecosystems; their function as biodiversity hotspots has gained some degree of attention due to significant and global loss of natural river-floodplain systems
According to Amoros & Roux (1988), they represent the following types which differed by the water residence time: eupotamic—the main river channel; parapotamic— lotic side-channels with flowing water lotic habitats; plesiopotamic—semi-lotic abandoned meanders, permanently connected to the river by a downstream arm, as well as paleopotamic—paleopotamic side-channels and depressions filled with stagnant water and isolated from the river, except in cases of flooding
Floodplain lakes were generally abundant in organic matter, whose average content was estimated at 12.59 ± 4.64 mg of Total organic carbon (TOC) per l-1 with a significant share of dissolved organic carbon (DOC) (10.50 ± 3.18 mg l-1)

Summary

Introduction

Floodplain lakes play numerous roles among mosaics of the riverine ecosystems; their function as biodiversity hotspots has gained some degree of attention due to significant and global loss of natural river-floodplain systems. Many rivers have been strongly transformed as a result of an intensive engineering (Buijse et al, 2002), and their potential for biodiversity development has been seriously impoverished (Dembowska, 2015). The floodplain of the Biebrza River is internationally recognised as a reference area for the restoration of deteriorated wetlands (Wassen et al, 2002). The river has a natural, untransformed floodplain and an undisturbed hydrological regime, allowing for the development of mosaics of aquatic habitats, which differed from the parent river by a degree of lateral connectivity. According to Amoros & Roux (1988), they represent the following types which differed by the water residence time (water age): eupotamic—the main river channel; parapotamic— lotic side-channels (bypasses) with flowing water lotic habitats; plesiopotamic—semi-lotic abandoned meanders, permanently connected to the river by a downstream arm, as well as paleopotamic—paleopotamic side-channels and depressions filled with stagnant water and isolated from the river, except in cases of flooding (lentic habitats)

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