Long-Term Changes of Species Composition and Functional Traits of Epiphytic Diatoms in the Szigetköz Region (Hungary) of the Danube River

Éva Ács,Tibor Bíró,Krisztina Buczkó,András Hidas,Zsuzsa Trábert,István Grigorszky,Mónika Duleba,János L Korponai,Edit Vadkerti,Angéla Földi,Judit Knisz,Csaba Berta

doi:10.3390/w12030776

Abstract

Here we report the results of our decades-long study on epiphytic communities from two tributary systems of the Szigetköz section of the Danube River. The main goal of the investigation was to detect changes in the epiphytic communities at structural (core species, changes in the relative abundance of common species) and functional (trait changes) levels as a result of the most important anthropogenic effects on Szigetköz, i.e., hydro-morphological modifications. We also examined the impact of rehabilitation on the tributary systems in terms of ecological potential. We discovered that mainly motile diatom species characterized the epiphyton due to reduced water volume were introduced into the tributary system after the diversion of the Danube. The ecosystem stabilized in the rehabilitated section, while the non-rehabilitated section showed a worsening tendency, mainly in the parapotamic branches. Our long-term data sets may provide a good basis for comparisons of different aquatic ecosystems, to define changes in the abundance of core species and in the structure of community in response to different anthropogenic pressures. It is fundamental to determine adaptive traits in assessing the impact of global warming stressors on biodiversity.

Highlights

Riverine ecosystems are among the most vulnerable to anthropogenic effects [1]
We examined the temporal variation of the mean relative abundance of Top1 species, cumulative core species, cumulative common species and evenness in the case of epiphytic diatom communities formed on deployed reeds and natural reeds in the eupotamic branches of both the Cikola tributary system (c5 and c6) and the Ásvány tributary system (a4 and a6)
Our results revealed greater spatial differences in the relative abundance of core species than in time due to spatial differences in environmental condition

Summary

Introduction

Riverine ecosystems are among the most vulnerable to anthropogenic effects [1]. While eutrophication is still the most common water quality problem on Earth, the reversal of eutrophication is becoming a global issue [2]. A wastewater treatment program implemented in the early 2000s resulted in re-oligotrophization of the Hungarian section of the Danube, while the effects of global warming (rise in water temperature, altered water flow) contributed to detectable changes in the riverine ecosystem [7]. These changes may lead to processes that can fundamentally shape the composition and diversity of actual communities. The minimum amount of water needed to maintain good ecological status/potential of waters should be determined considering ecological, engineering, and economic aspects

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Conclusion