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Significant differences (ANOVA) in three out of six meristic characters and in 16 out of 18 morphometric characters were found among Syngnathus abaster caught in the River Danube at sites 900 km upwards from the mouth of the Black Sea, the fresh waters of Ukraine, the Black Sea and the Azov Sea. The Danube populations showed significantly greater values for antedorsal (aD) and anteanal (aA) distances, but considerably smaller values for postdorsal (pD) distance and head length (L H ) than other populations analysed (Tukey-Kramer's test). The relation of total length (L T ) to standard length (L S ) for the Danube populations was L S =0·97 . L T , the length-mass relationship was M=4·122 . L 3·63 T and the mean .. of Fulton condition factor was 0·34 0·08.

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In urban and industrial areas, higher plants are used as biomonitors of exposure. The objective of this study was to assess metals accumulation in leaves of dendroflora for the city of Novi Sad, Serbia, in May and September. The investigation was conducted at three sites in the urban area of Novi Sad. Determination of metals concentration for Al, As, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the sample was performed by inductively coupled plasma-optical emission spectrometry (ICP/OES). In the leaves of the examined tree species the highest concentrations were obtained for: Al, Fe, Mn, and Zn. The highest mean concentrations of metals were present in leaves of Aesculus hippocastanum in September. Trees from Liman and the Danube Park contained higher mean concentrations of metals in the leaves. In A. hippocastanum and Platanus hybrida an increase of al., As, Cr, Fe, and Pb concentrations occurred from May to September, with higher concentrations of Al and Fe noted in May. However, in Celtis australis, Juglans regia, and Tilia platypyllos there was a reduction in Al, Mn, Fe, and Zn from May to September. The basis for these findings requires further investigation, but diverse washing procedures may account partially for these observations.

Given the role of algae as primary producers and the possibility of reduction in their numbers by some fish species, as well as possible food competition between some autochthonous and allochthonous fishes which are consumers of algae, feeding of two autochthonous species (carp and roach) and two allochthonous species (crucian carp and bighead carp) was investigated. Investigations were carried out in the following aquatic ecosystems: Stari Begej, Palicko Jezero and Bukinski Rit which are parts of the legally protected areas (nature reserves). All investigated aquatic ecosystems are eutrophic ones, characterized by high density of phytoplankton communities in which Bacillariohyta and Chlorophyta are the dominant algal groups. Feeding spectra preliminary investigation showed that algae take an important place in feeding of investigated fish species. Analyses of the algal component showed that participation of the different algal groups varied, but, generally, Bacillariophyta and Chlorophyta were dominant, which correspond to their domination in the waters. Detailed analyses of the algal component showed that, concerning the contribution of algal groups, there were no significant differences between the investigated fish species. It suggests likely possibility for food competition, as well as that some autochthonous species, such as the carp and roach, can decrease the density of algae as successful as the allochthonous ones, such as the crucian carp and bighead carp. Given that all of the investigated water bodies are the parts of protected areas characterized by a high diversity of autochthonous species, and that the allochthonous species can be a real threat to them, it is necessary to carry out measures directed to reducing the numbers or eliminating the allochthonous species from the protected water bodies.