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The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary
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Abstract: This work presents the results of the studies on the benthic diatom communities from the Ţiganilor Rivulet (“Alexandru Borza” Botanical Garden, Cluj - Napoca, Romania) in 2008. Comparing our data with that from two similar studies, one carried out in 1999 by Morari (Morari, 2000), the other one in 2001 by Neag et al., (2005), we set the following objectives: to establish the qualitative composition of the benthic diatom communities, to conduct quantitative evaluations, to observe the seasonal and multiannual dynamics and to evaluate the water quality based on the indicator diatom species. From the fourteen samples collected during 2008, we identified only diatom species (Bacillariophyta). We found 63 taxa, belonging to 18 genera, the best represented being Navicula and Nitzschia. From the qualitative structure point of view, the number of diatom species varied according to the season: 28 species in spring, 29 species in summer and 48 species in autumn. Quantitatively, in the samples collected in spring, the species Navicula gregaria prevailed, followed by Nitzschia palea. In summer, the most common species was Diadesmis contenta, followed by Navicula gregaria, Nitzschia palea, N. constricta and N. intermedia. In autumn, the predominant species was Navicula gregaria, followed by Nitzschia palea, N. intermedia and Navicula mutica. The analysis of the diatom community structure showed a seasonal dynamics, with a peak of development in autumn. The floristic similarity had relatively low values. In addition, the Canonical Correspondence Analysis (CCA), the equitability and the Shannon’s diversity suggested, once again, the seasonal dynamics. Considering the saprobity, apart from the indifferent species, more than half (57%) of the diatoms identified indicated a critical saprobic level. Many of the species were also indicators of eutrophic waters, according to the salinity and conductivity values. The comparative study was based on the qualitative composition of the diatom communities from 1999, 2001 and 2008. The values of floristic similarity were low, suggesting a multiannual dynamics. Strong human impacts, like accidental sewage evacuations, could be the cause of this particular situation.
Keywords: diatom, seasonal dynamics, trophicity, saprobity, indicator species. |
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