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Additional information on the distribution and ecology of the recently described diatom species Geissleria gereckei

Vidakovic D., Cantonati M., Mogna M., Jakovljević O., Šovran S., Lazović V., Stojanović K., Đorđević J., Krizmanić J.

Oceanological and Hydrobiological Studies

2017

Vol. 46, No. 1

18--23

The main objective of this paper is to report new information about the distribution and ecology of a recently described diatom species, Geissleria gereckei. The opportunity for updating the information on the distribution and ecology of the species was provided by the finding of well-developed G. gereckei populations on the lithic material and bryophytes in the Raška and Mlava rivers (Serbia). For several years after the first description, G. gereckei has been known only from the type locality and from another spring in the Dolomiti Bellunesi National Park (the south-eastern Alps). After accurate LM and SEM observations, we provide evidence for the occurrence of the species also in the two above-mentioned rivers in Serbia, as well as in the south-western and south-eastern Alps. After an extensive literature search, it appears that the species is known with certainty only from these sites. Our observations and details from the literature suggest that the species is able to occupy a much broader ecological niche than the very-specific one observed at the time of discovery. The two main determinants for the species’ occurrence appear to be the carbonate nature of the catchments or aquifers, and the ability of the species to be competitive in habitats or microhabitats exposed to seasonal desiccation.

Benthic diatoms of the Vrla River (Serbia) and their application in the water ecological status assessment

Jakovljević O., Popović S., Živić I., Stojanović K., Krizmanić J.

Oceanological and Hydrobiological Studies

2016

Vol. 45, No. 3

304--315

Epilithic diatoms from the Vrla River (Serbia) have been used to assess the ecological status of water. A total of 227 diatom taxa belonging to 50 genera were identified in the Vrla River during six research seasons with 13 dominant species recorded. Gomphonema (30 species), Navicula (28) and Nitzschia (26) were the most species-rich genera, followed by Pinnularia (12) and Encyonema (11). One taxa was recorded as new to Serbia – Geissleria acceptata. CCA grouped the diatom taxa into three main groups. The first group included taxa found at most of the sampling sites, the second group involved diatom taxa significantly positively correlated with the oxygen, while the third group showed positive correlation with temperature. RDA showed that some diatom taxa, including: Cocconeis placentula var. placentula, C. placentula var. lineata, C. pseudolineata and Mayamaea atomus var. permitis, are significantly positively correlated with temperature, while others, for example Achnanthidium minutissimum, Hannaea arcus, Nitzschia pura are mostly correlated with total phosphorus, alkalinity and water hardness. The ecological status of the Vrla River ranged from moderate, good to high. It was shown that according to the diatom indices, the ecological status of water downstream and upstream of a trout fish pond was slightly different.

Organic geochemical study of the Lower Miocene Kremna Basin, Serbia

Perunović T., Stojanović K., Simić V., Kašanin-Grubin M., Šajnović A., Erić V., Schwarzbauer J., Vasić N., Jovančićević B., Brčeski I.

Annales Societatis Geologorum Poloniae

2014

Vol. 84, No. 3

185--212

The Kremna Basin is located in southwest Serbia, in the Zlatibor area, which is part of the Internal Dinarides. This basin is noteworthy because of the type of bedrock drainage, which it represents. It was formed on ultrabasic rocks and volcanic materials that influenced the occurrence of organic matter (OM) in the basin fill. The objective of the study was to determine the organic geochemical characteristics of sediments from the central part of the Kremna Basin. The sediments studied belong to an intrabasinal facies, in which two sequences were distinguished. The lower sequence occurs at depths of 216–343 m, while the upper sequence is found from 13.5–216 m. At the start of basin development (265–343 m) sedimentation took place in shallow alkaline water, rich in Mg ions. Through time, a slight deepening of the basin occurred. This was followed by chemical deposition of carbonates (216–265 m). The most important change in the sedimentary environment occurred with the formation of sediments marking the transition between the sequences (at about 200 m). Sediments from the lower sequence are characterized by the dominance of dolomite and magnesite. There are indications of volcanic activity, i.e. tuff layers and the presence of searlesite. The upper sequence is characterized by the prevalence of calcite and dolomite. The amounts of MgO, Na2O and B are higher in the lower sequence, whereas the CaO content is higher in the upper sequence. The sediments contain different amounts of immature OM (late diagenesis). Biomarker analysis shows diverse precursors of the sedimentary OM: methanogenic archaea, photosynthetic green sulfur bacteria (Chlorobiaceae), bacterivorous ciliates, various bacteria, both photosynthetic and non-photosynthetic, the green unicellular microalga, Botryococcus braunii race A (exclusively in the upper sequence) and terrestrial plants. The lower sequence contains lower amount OM, composed primarily of kerogen II/III and III types, indicating a higher contribution of the allochtonous biomass of land plants from the lake catchment, particularly in the lower part. The sediments of the upper sequence are enriched in autochthonous aquatic OM, which comprises mostly kerogen I, I/II and II types. The transition from the lower sequence to the upper one is associated with a decrease in pristane to phytane ratio, gammacerane index and content of C28 steroids, absence or significantly lower amount of squalane, absence of C24 and C25 regular isoprenoids, 8-methyl-2-methyl-2-(4,8,12-trimethyltridecyl) chroman and C30 hop-17(21)-ene. Pyrolytic experiments showed that the sediments of the upper sequence, rich in aquatic OM, at a catagenetic stage could be a source of liquid hydrocarbons. The values of hopane, sterane and phenanthrene maturation parameters indicate that through pyrolysis at 400°C the samples investigated reached a value of vitrinite reflectance equivalent of approximately 0.70%. It was estimated that the sediments should be found at depths of 2300–2900 m in order to become active source rocks. The calculated minimum temperature, necessary for catagenetic hydrocarbon generation, is between 103 and 107°C.