engleski

Major forces shaping periphyton in tufa-depositing karstic freshwaters

Tufa, a secondary calcium-carbonate deposit in freshwaters, creates a myriad of microhabitats for periphyton within hydrologically heterogeneous barrage-lake ecosystems. The aim of this study was to determine major forces shaping periphyton at a number of microhabitats spread within the two tufa-depositing systems (NP Plitvice Lakes an NP Krka, Croatia), using artificial substrata (AS) in a series of colonization experiments. In situ experiments included time series as well as one-month exposure of AS on tufa barriers through the year. Tufa deposition and chlorophyll a were measured, and protozoa and micro-metazoa determined upon retrieval. Tufa deposition was highest during summer in both systems. In NP Krka, the summer values on AS were up to fivefold higher in comparison to other seasons. In Plitvice Lakes, this was even more pronounced, with three orders of magnitude higher tufa deposition during summer vs. winter. It was likely due to lower winter temperatures in this system, when compared to Mediterranean NP Krka. Chlorophyll a showed clear seasonal differences in both systems. Ciliates dominated among periphytic protozoa, with around 80 morphospecies in each system. Periphyton community composition was mostly influenced by the position of microhabitats within the lake system. Communities on tufa barriers located closely below lakes were dominated by peritrichs and suctorians, using plankton-rich overflowing water as a food source. On microscale, flow velocity was the dominant factor structuring periphyton, evidenced by clear relationship between ciliate biomass and frequency of taxa within certain velocity range.

colonization, artificial substrates, protozoa, chlorophyll a

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