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Various studies report contrasting results on the substrate-type effect on diatom community composition, but the particularly important question is whether or not it affects diatom-based assessments of water quality. We investigated whether the substrate type is a significant predictor of the diatom community composition and if it affects lake water quality assessment based on diatom indices. This study took place in Sava Lake (Serbia). We used glass, ceramic, willow and yew tree tiles as artificial substrates for periphyton development, and pebbles from the lake littoral as natural substrate. Results revealed differences in both the diatom community composition and diatom indices values related to the substrates. A distinction was recognized between natural, artificial wooden, and artificial inert substrates. However, the final lake quality assessment based on diatom indices was more or less similar in all substrate types in our study, and depended on value ranges associated with water quality classification and on diatom index choices. Artificial substrates in our study did show potential as an alternative for natural substrate, but further studies are required, particularly in various types of lentic ecosystems to confirm our findings and support artificial substrate employment in lake water quality assessment., Diverses études rapportent des résultats contrastés sur l'effet du type de substrat sur la composition de la communauté de diatomées, mais la question particulièrement importante est de savoir si cela affecte ou non les évaluations de la qualité de l'eau basées sur les diatomées. Nous avons cherché à savoir si le type de substrat est un prédicteur significatif de la composition de la communauté de diatomées et s'il affecte l'évaluation de la qualité de l'eau des lacs basée sur les indices de diatomées. Cette étude a eu lieu dans le lac Sava (Serbie). Nous avons utilisé des carreaux de verre, de céramique, de saule et d'if comme substrats artificiels pour le développement du périphyton, et des galets du littoral du lac comme substrat naturel. Les résultats ont révélé des différences dans la composition de la communauté de diatomées et dans les valeurs des indices de diatomées liées aux substrats. Une distinction a été reconnue entre les substrats naturels, artificiels en bois et artificiels inertes. Cependant, l'évaluation finale de la qualité du lac basée sur les indices de diatomées était plus ou moins similaire dans tous les types de substrats de notre étude, et dépendait des plages de valeurs associées à la classification de la qualité de l'eau et des choix d'indices de diatomées. Les substrats artificiels dans notre étude ont montré un potentiel comme alternative au substrat naturel, mais des études supplémentaires sont nécessaires, en particulier dans divers types d'écosystèmes lentiques pour confirmer nos résultats et soutenir l'utilisation de substrats artificiels dans l'évaluation de la qualité de l'eau des lacs.

The main aim of this study was to investigate the application of benthic diatoms and the efficiency of diatom indices in water ecological assessment of rivers in Serbia, as well as the influence of trout farms on rivers water quality. Research was conducted in one year period along the Crnica and Radovanska rivers (Eastern Serbia), in 11 sampling sites (taking into account the position of trout fish farms that are built on both rivers). Results showed that fish farms affect the physical and chemical parameters, as well as diversity of the epilithic diatom assemblage along the rivers. Canonical correspondence analysis (CCA) indicated that among tested physical and chemical parameters, conductivity “EC”, water hardness “WH”, sulfates “SO42-”, ionized ammonia fraction “NH4+”, nitrates “NO3–“, “pH”, mud, stone and depth were the most important variables affecting the distribution of diatom species. A total of 206 epilithic diatom taxa were recorded in the Radovanska and 170 in the Crnica River. Based on diatom indices, trout fish farms have no significant negative impact on the water quality of the investigated rivers (indices are not enough sensitive). Redundancy analysis (RDA) showed a high degree of correlation between the majority of indices which mostly indicated to good water quality of studied rivers. TID and TDI were the only two indices indicating moderate and poor water quality of both rivers. Water quality based on the TIDRS, the first proposed diatom index for Serbia was differ in two classes in most sites compairing with TID.

Aerophytic phototrophs, colonizers of different substrates exposed to air, among which are rock substrates in cave habitats, are in general not sufficiently investigated and studied. From the ecological point of view, seasonal/temporal variations and parameters that influence aerophytic phototrophic communities through seasons still remain largely unknown. Seasonal analysis of phototrophic microorganisms from biofilms developed at entrances of Samar and Jezava caves in Eastern Serbia was performed four times a year. All identified phototrophic representatives were assigned to a certain division or group. The relationship between documented groups and different measured, determined and observed ecological parameters was illustrated using principal component analysis (PCA). A high diversity of cyanobacteria and algae was observed as a result of seasonal sampling: 141 taxa in Samar and 61 taxa in Jezava Cave. Cyanobacteria were dominant in both caves (coccoid forms prevailing) and were followed by Bacillariophyta. Bacillariophyta were positively correlated with light intensity and sites where seeping water was present, and cyanobacteria with water content in biofilm, Chl a and relative air humidity. Higher diversity of phototrophs was documented in December and March, and lower in May and August in both caves with Chl a values having the same trend as the diversity of phototrophic microorganisms. This was especially the case with biofilms in which diversity was more prone to seasonal changes and where Cyanobacteria dominated. Only 24 taxa were documented during all four seasons in Samar Cave (Cyanobacteria, Bacillariophyta and Chlorophyta representatives) and three in Jezava Cave (Cyanobacteria only).

A total of 15 Navicula taxa were recorded in epilithic communities occurring in seven rivers of Serbia, all of which are new to the diatom flora of Serbia. The most interesting of them are N. splendicula and N. moskalii. When observing N. splendicula specimens under SEM, we noticed a characteristic silicate tongue in the center of raphe ends, which had not been previously reported in the available literature. The insufficiently researched distribution of N. moskalii and scarce autecological information on the taxon prompted us to provide new details about the species in this study. These findings clearly indicate the need for further comprehensive research that would provide new information on rare taxa.

Analizom zajednice silikatnih algi moņe se dobiti slika opńteg stanja, ekolońkog integriteta i kvaliteta vode odreĊenog vodenog ekosistema. U cilju implementacije Okvirne direktive o vodama, u Srbiji je doneta zakonska regulativa na osnovu koje je obavezna procena ekolońkog statusa povrńinskih voda na osnovu bentosne zajednice silikatnih algi. Predmet ove doktorske disertacije je floristiĉka studija epilitskih zajednica silikatnih algi, njihova sezonska dinamika i primena dijatomnih indeksa kao relevantnih parametara u proceni ekolońkog statusa odabranih reka istoĉne i jugoistoĉne Srbije. Algolońki i fiziĉko-hemijski uzorci su sakupljeni ńest puta u periodu od dvanaest meseci sa ńest lokaliteta duņ toka reke Vrle i reke Crnice, odnosno sa pet lokaliteta duņ toka reke Mlave i Radovanske reke. Pri izboru lokaliteta vodilo se raĉuna o poloņaju pastrmskog ribnjaka i njegovom uticaju kao potencijalnom izvoru zagaĊenja ovih reka. Tokom istraņivanog perioda identifikovano je ukupno 375 taksona epilitskih silikatnih algi u Vrli, Mlavi, Crnici i Radovanskoj reci. Pored ugroņenih taksona, identifikovani su i taksoni koji se smatraju retkim. Od ukupnog broja identifikovanih, 50 taksona je prvi put zabeleņeno u flori algi Srbije. Rod Decussata predstavlja novi rod za floru algi Srbije. CCA analiza uticaja ekolońkih parametara na distribuciju taksona epilitske zajednice silikatnih algi iz 4 istraņivane reke je pokazala da ribnjaci utiĉu na fiziĉko-hemijske osobine vode, a samim tim na sastav epilitske zajednice. Kao znaĉajni fiziĉko-hemijski faktori izdvojili su se NH4+, NH3 i EP. Na osnovu većine dijatomnih indeksa voda sve ĉetiri istraņivane reke je dobrog ekolońkog statusa (II klasa kvaliteta). Prema zakonskoj regulativi Srbije, na osnovu biolońkih (fitobentos) i fiziĉko-hemijskih elemenata, ekolońki status vode istraņivanog dela reke Vrle je dobar (II klasa), a reke Mlave umeren (III klasa). Konaĉan ekolońki status Crnice i Radovanske reke je procenjen kao slab (IV klasa)..., By analyzing the benthic diatom community, a picture of the general condition, ecological integrity and water quality of a particular aquatic ecosystem can be obtained. In order to implement the Water Framework Directive, a legislation has been adopted in the Republic of Serbia that requires an assessment of the ecological status of surface waters based on the benthic diatoms. The aim of this PhD thesis was the floristic analysis of the epilithic diatom communities, their seasonal dynamics and the application of diatom indices as relevant parameters in the ecological status assessment of the selected rivers from the Eastern and Southeastern Serbia. Algological and physico-chemical samples were collected six times over a period of twelve months from six sites along the Vrla and Crnica rivers, and from five sites along the Mlava and Radovanska rivers. In selecting the sites taken into account the position of a trout ponds and its impact as a potential sources of pollution of the rivers. A total of 375 epilithic diatom taxa in Vrla, Mlavi, Crnica and Radovanova rivers were identified during the investigated period. Some endangered and rare taxa were identified. Of the total number of identified taxa, 50 taxa were new records for the Serbian algal flora. The genus Decussata, with the rare species D. hexagona, was recorded for the first time in Serbia. The CCA analysis of the impact of ecological parameters on the distribution of the diatom taxa from the investigated rivers has shown that the fish ponds affect the water physico-chemical properties and, consequently, the composition of the epilithic diatom communities. NH4+, NH3 and EP have been identified as important physical-chemical factors...

Diatoms are a widespread group of organisms with well-known ecological preferences. Knowledge of their diversity is of great importance for assessing the environmental status of different aquatic ecosystems. The present study was based on 55 different localities that included rivers, streams, channels, accumulations and salt marshes throughout Serbia. The results of this study expanded the diatom checklist by 80 taxa, including two new recorded genera (Fistulifera and Microfissurata) for Serbia. The data were obtained by combining light microscopy (LM) and scanning electron microscopy (SEM) that provided reliable identification, which is very important in diatom diversity studies.

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.

The main objective of this study was to assess the ecological status of the Mlava River based on epilithic diatoms and to test the use of diatom indices as a tool for estimating the quality of fl owing waters in Serbia. Quantitative analysis showed that in April Achnanthidium minutissimum was dominant at each site, except at the fi fth site, where Amphora pediculus was dominant. In July and September, Achnanthidium minutissimum, Achnanthidium pyrenaicum, Amphora pediculus, Denticula tenuis, Diatoma vulgaris, Gomphonema elegantissimum, Cocconeis pseudolineata and Cocconeis placentula var. lineata dominated. Detrended correspondence analysis (DCA) was used to detect the major patterns of variation in species composition. The fi rst DCA axis summarizes the distribution of the diatom community, mainly through temperature, conductivity, oxygen and water hardness gradient. The second DCA axis was weakly correlated with few variables. Based on the average values of the pollution sensitivity index (IPS), commission for economical community metric (CEE) and biological diatom index (IBD), the water of the Mlava River belonged to water class I during all three seasons. Values of the diatom-based eutrophication/pollution index (EPI-D) indicated class II water quality. According to calculated trophic diatom index (TDI) values, water of the Mlava River was characterized by intermediate nutrient concentrations during three seasons. Principal components analysis was used to represent the correlation between diatom indices, and the highest correlation among the selected diatom indices is seen between EPI-D, IPS and IBD.

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.