engleski

The effect of current velocity on ditaom colonization on the glass slides in unpolluted headwater creek

The intention was to determinate the effect of current velocity on diatom colonisation rate during the first 30 days of exposure of artificial substrates (glass slides). Artificial substrates were submerged in a not polluted small mountain stream near Zagreb, Croatia. The glass slides were oriented parallel to the different current velocity values (<30 cms-1, 30-60 cms-1 and >80 cms-1), protected from debris, 10 cm beneath the surface of the water. Investigation took place from the autumn to the summer, and samples were collected seasonally. A total of 71 diatom species were found on the glass slides. To define the diatom colonisation in a non-linear regressive analysis of empirical data the model of BERTALANFFY (1938) was used. The results suggests that current velocity have a decisive effect on the dynamics of colonisation like as on composition of diatom community in flowing water streams. Time needed for reaching the equilibrium progressively increases together with the current velocity (F= 16.7 ; P< 0.01). In the summer and autumn periods the longest time was necessary for the stabilisation of the diatom community and the opposite situation was in the spring and winter periods. The species Cocconeis placentula EHR. and Navicula gracilis EHR. were independent to the current velocity. Surirella ovata KÜTZ. was abundant at the slowest (&#61603; 30 cms-1) and Gomphonema olivaceum KÜTZ. at highest (&#61603; 60 cms-1) current velocity values.

current velocity; periphyton; diatoms; non-linear regressive analysis

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