Author(s): Elisabeth Bondar-Kunze; Veronica Kasper; Thomas Hein
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Keywords: No Keywords
Abstract: Hydrology and natural flow regime are known as master variables for river networks [1], [2]. The alteration of those has been identified as a leading cause for changes in the physical, chemical and biological condition and function of these systems [3]. Along a river continuum (from low order to high order running waters) the magnitude and characteristics of hydrological alterations can vary. In low-order streams hydromorphological alterations and flow regulations (e. g. storage-type power plants) change the discharge and therefore the water table and flow velocity on a daily basis [4]. A literature review [5] about flow alterations and ecological responses showed that the majority of studies deal with macroinvertebrates, fish and riparian vegetation. Aquatic primary producers (e. g. periphyton) were not included in the quantitative analysis, because of poor data availability. However to asses and understand hydrological alterations especially with short-term impacts from a minute to daily level, periphytic algae are useful indicators. They have a rapid reproduction rate and very short life cycles and can therefore be expected to reflect short-term impacts and disturbances in the environment. Periphytic algae are also the trophic base for riverine food webs [6] and the basal dietary sources for consumers [7]. Their nutritional quality – expressed in fatty acid composition – is controlled beside of light, temperature and nutrient availability, by hydrology [8]. This makes periphytic algae an essential part to understand the whole riverine ecosystem and the induced alterations [9]. In this study we focused on thermopeaking (TP), which combines stress of sudden flow velocity increase and abrupt water temperature alteration. The aim of this study was to answer the question how TP alters structural (composition, biomass) and functional (rETRmax, phosphatase activity) characteristics of periphyton. In this context, do the effect of time (duration of TP 10 days or 52 days) and the combined effect of time and habitat (riffle/pool) influence the outcomes? An experiment was conducted for 52 days in Lunz am See (Austria) in an experimental flume setting. The major investigated algal parameters were biomass, algal pigment distribution (proxy for algal compositions), phosphatase activity and relative electron transport rate (photosynthesis). Periphyton was exposed to two treatments (cold TP and warm TP, ± appr. 10°C) and no treatment (control), whereas TP was performed daily for one hour. Additionally, flumes were subdivided into pool and riffle sections and habitat specific effects were investigated.
Year: 2018