Division of Biology, Faculty of Science, University of Zagreb
Abstract
The small karstic Zrmanja River (69 km long) discharges into the central-eastern Adriatic Sea. High oxygen saturation and water transparency, as well as low nutrient concentrations, indicated the oligotrophic character of the river.We present the taxonomic composition and vertical distribution of diatoms attached on an artificial substrate (Plexiglass) in the lower reach of the Zrmanja River, in July 2000. Thirty attached diatoms were determined
on Plexiglass throughout the 2.5 m deep water column, and Achnanthes sp. and Fragilaria sp.were found to be the most frequent (> 89%) and abundant (> 105 cells cm–2) diatoms. The highest abundance of attached diatoms (1.2 x 106 and 7.5 x 105 cells cm–2)
was found at the depth of 0.5 m. The maximum number of diatom taxa was also found below the surface
