engleski

Ecological determinants of rotifer vertical distribution in a coastal karst lake (Vrana Lake, Island Cres, Croatia)

Vrana Lake is a karst coastal lake situated on Cres Island within the eastern Adriatic coast. It is classified as an oligotrophic lake and serves as a natural water supply reservoir (average depth 74.5 m ; surface area 5.5 km2 ; water volume 220, 000 km3). It appears to have formed as a cryptodepression on karstified carbonate rocks, filled with fresh water. The aim of this study was to assess the influence of seasonally and spatially varying ecological conditions (i.e., thermal stratification, chlorophyll a, dissolved oxygen, orthophosphate concentrations) on the vertical distribution of the non-predatory rotifer plankton community within the lake. The rotifer community was observed at one- or two-month sampling intervals over a one year period. During the study period, a total of 28 rotifer taxa was identified. The predominant taxa were Ascomorpha spp., Filinia longiseta, Keratella cochlearis, Synchaeta spp. and Polyarthra vulgaris, representing more than 90% of the total rotifer abundance. Observed seasonal and spatial patterns of non-predatory rotifer population densities along a vertical profile of Vrana Lake were considerably affected by the thermal and chemical stratification of the lake. Additionally, our findings suggest that rotifer community dynamics were affected by food availability and trophic preferences of the observed taxa.

coastal lakes; karst lake; thermal stratification; non-predatory rotifers; macro-filter-feeders; microfilter-feeders

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