engleski

Periphyton in different microhabitats on tufa barrier in National Park Plitvice Lakes (Croatia)

Tufa, freshwater carbonate deposit, develops under specific physico-chemical conditions. In Plitvice Lakes tufa creates barriers between succeeding lakes, resulting with a barrage system. On microscale, tufa formation increases the habitat complexity, supporting heterogenous periphytic communities. With the aim to test the differences in community composition of periphyton in different microhabitats, we performed in situ experiment using artificial substrates (glass slides) between May and November 2010. Four microhabitats on the barrier between last two lakes in the hydro-system (15th and 16th) differed with respect to current velocity and vertical position (Gs – upside in slow current ; Gm – upside in medium current, Ds – underside in slow current, Dm – underside in medium current). Tufa deposition was more intense on upside microhabitats compared to underside. Gs microhabitat supported the highest chlorophyll a concentration, the highest taxa number and abundance of protozoa and micro-metazoa. Ciliates dominated among heterotrophs with the share in abundance between 64% and 76%, followed by Rotatoria and Gymnoamoebae. Among 133 determined species, 73 were ciliates. Endemic species of heterotrichids Lagotia dinaridica was determined on the underside community in medium water current velocity (Dm). Periphyton on the underside had on the average 16 times lower abundance and 8 times lower taxa number, compared to the upside communities on the same current velocity, probably due to deprived food resources. Microhabitat conditions structured ciliate communities, for instance Peritrichia and Hypotrichia were significantly more abundant in slow current. Our results highlight the heterogeneity of periphyton on microscale with tufa deposition possibly even increasing habitat complexity. Sampling designs for periphyton in such habitats should consider possible high within-habitat variability.

microhabitats; ciliates; current velocity; artificial substrate

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