The disturbance-driven changes of periphytic algal communities in a Danubian floodplain lake

Abstract

Key-words:periphyton, algae, artificial substrata, disturbance, floodplain Disturbance event-driven changes in periphytic algal communities were studied in a Danubian floodplain using artificial substrata (glass slides). The hydrological regime of the river-floodplain system strongly influenced the physical and chemical environment of the investigated lake. Directional changes in the algal communities, demonstrated by the results of non-metric multidimensional scaling, indicated three distinct phases in periphyton development. Strong seasonal influences in the initial accrual phase favored diatom dominance in spring and rapid development of a community composed of filamentous and stalk-forming chlorophytes towards "climax" in summer. Macrophyte and metaphyton stands spreading represented a physical constraint for periphytic algal development. Irrespective of periphyton age and structure, the onset of disturbances resulted in an immediate decrease in periphytic biomass. Disturbances deeply transformed algal communities, whereas the morpho-functional properties of algal species were found to be decisive in community adaptations to altered environmental conditions. Tightly attached and stalk forming diatoms were shown to have an ability to resist and quickly recover from physical disturbance. Our results highlight the necessity for further development of the morpho-functional classification of periphytic algae, which will contribute to more precise evaluations of disturbancedriven events in freshwater ecosystems. RÉSUMÉLes changements des communautés d'algues périphytiques induits par les perturbations dans un lac de la plaine inondable du Danube Mots-clés :périphyton, algues, substrats artificiels, perturbation, plaine inondable Des modifications provoquées par les événements perturbants dans les communautés d'algues périphytiques ont été étudiés dans une plaine inondable du Danube en utilisant des substrats artificiels (lames de verre). Le régime hydrologique du système rivière-plaine inondable influence fortement l'environnement physique et chimique du lac étudié. Les changements de trajectoire dans les communautés d'algues, démontrés par les résultats d'analyse multidimensionnelle non mé-trique, ont indiqué trois phases distinctes dans le développement du périphyton. De fortes influences saisonnières dans la phase initiale d'implantation favorisent la domination de diatomées au printemps et le développement rapide d'une communauté composée de filamenteuses et de chlorophytes à tige vers un "climax" en été. Le développement des macrophytes et des métaphytes représente une contrainte physique pour le développement d'algues périphytiques. Indépendam-ment de l'âge du périphyton et de sa structure, l'apparition de perturbations a entraîné une diminution immédiate de la biomasse périphytique. Les perturbations ont transformé profondément les communautés d'algues, alors que les proprié-tés morpho-fonctionnelles des espèces d'algues sont décisives dans les adaptations de la communauté aux conditions environnem...

The first record of Hydrurus foetidus (Villars) Trevisan (Ochrophyta: Chrysophyceae) in Croatia with ecological notes

“…Benthic algae or phytobenthos are rarely in the focus of interest, although it is investigated in the Pannonian ecoregion, more specifically in the Danubian floodplain (Žuna Pfeiffer et al, 2015). Benthic algae have also been investigated in experiments on tufa barriers and artificial substrates in karstic lakes (Kralj et al, 2006;Plenković-Moraj et al, 2002), but never in small mountainous rivers.…”

The role of abiotic and biotic environmental factors in shaping epiphyton on common reed in shallow, hydrologically transformed, temperate lakes

“…Rodríguez et al (2011) showed that in humic shallow lakes in Argentina, the structure of the epiphytion assemblages on the emergent rush Schoenoplectus californicus changed in relation to WLFs, showing a major proportion of planktonic, metaphytic, and ticoplanktonic components during high water phases. Diatoms may be good indicators of some disturbance processes, including WLFs (Barbour et al, 1999;Pfeiffer et al, 2015). For example, the small pennate A. minutissimum is often the first species colonizing the substratum, and its relative abundance, lower than 25% of the total diatom abundance, is characteristic for undisturbed water bodies (Barbour et al, 1999).…”

“…In general, the reports on the role of zooplankton and fish in shaping epiphyton communities are scarce and mostly experimental (Tall et al, 2006;Abe et al, 2007;Blanco et al, 2008;Guariento et al, 2010). Some anthropogenic disturbances, like man-made water level fluctuations (WLFs), eutrophication or water pollution are also important factors that influence epiphyton (Barbour et al, 1999;Kernan et al, 2010;Pfeiffer et al, 2015). Hydromorphological modifications of lakes, which allow manipulation of water level, may strongly affect epiphyton on emergent macrophytes.…”

Main predictors of periphyton species richness depend on adherence strategy and cell size

“…Recent studies have also shown that habitat heterogeneity and regional microalgae species richness have a strong influence on richness of periphyton algae communities [ 9 – 11 ]. Finally, hydrological factors may be as important as nutrient levels in determining periphyton growth [ 12 , 13 ].…”