Özet:

In this study, plexiglas substrates were used for biofilm formation to observe short-term variations in heavy metals in Izmit Gulf. The substrates were inserted and collected in a two-week period as three times in the autumn season. The averaged accumulation values of metals were decreased in the order of Fe>Mn>Zn>Cu>Pb>Cr>Ni>Cd. The same trend was observed in the first and third samples of the autumn without any exception in the sequence. The order for the second sample was as Fe>Mn>Zn>Pb>Cr>Cu>Ni>Cd. Among the 37 species found, 22 belonged to Bacillariophyceae, 2 species to Cyanophyceae and 13 species to Dinophyceae taxa. While Bacillariophyceae consisted of about 55 % of total colony, 38 %  and 7 % comsosed of species of Dinophyceae and Cyanophyceae taxa, respectively. Total biodensity values are 22362, 23513 and 21348 cell/ml. For various incubation days (15, 30 and 45), it was seen that increasing incubation time would not always result in the increase in densities of all species and total density of biofilms. Metal levels did not show big variations. Low correlations were observed in relative abundances of first three dominant species occupying around 85 % of total algal community with some metals, though the variations are not much significant. 

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