engleski

Structure of periphytic community on artificial substrata: influence of depth, slide orientation and colonization time in karstic Lake Visovačko jezero, Croatia

The aim of this study was to determine the potential of periphyton growth on artificial surfaces. Plexiglas slides were exposed for 30, 60, and 90 days on a vertical profile (1, 9 and 18 m depth) in lower, lentic area of River Krka during the summer period of 1995. Orientation of the slides, horizontal versus vertical as well as differences between upper and lower side of horizontal slides were also researched. During the investigated period, 88 taxa were identified. Most abundant group was Bacillariophyceae with 57 taxa. Species Cyclotella comta (Ehrenb.) Kutz., Achnanthidium affine (Grunow) Czarn., Cocconeis placentula Ehr. and Eolimna minima (Grun) L-B were present in all samples. Highest growth potential was observed after 60 days of exposition on upper side of horizontally placed surface in 1 m depth. During the same exposition time, the lowest growth potential was noted on the vertical slide at 18 m depth. Results show significant differences in abundance, number and composition of algae between growth surfaces and depths. There were statistically significant differences between numbers of species considering all three factors (days of colonization, depth and side ; p=0.025841, p=0.000055 and p=0.003122, respectively) and between total number of cells per square centimeter for days and depth (p=0.0166 and p=0.019653, respectively) while sides did not show any statistically significant differences (p>0.05). Cluster analysis and NMDS showed grouping mostly according to depth. Physical and chemical parameters and their relations to algal periphyton assemblages were also observed.

periphytic community; artificial substrate; slide orientation; colonization time; depth; karst

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