For the first time, transplants with moss-bags and mussels together were applied to study the water quality in standing water bodies. The tested species: Fontinalis antipyretica Hedw. and Sinanodonta woodiana (Lea, 1834) were collected from unpolluted sites and analyzed to obtain background levels. Then, the moss and mussels were left in cages for a period of 30 days in three reservoirs where both are not present naturally. Two of the reservoirs suffer from old industrial contamination and one is affected by untreated wastes. Twenty-four compounds were studied, among them trace elements Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn and organic priority substances: six polybrominated diphenyl ethers (PBDEs) congeners and short-chain chlorinated paraffins (SCCPs). The trace element accumulation was significant after the exposition period in all studied stations. PBDEs and SCCPs were also accumulated up to two times more in the moss tissues. PBDEs in the mussels exceeded the environmental quality standard (EQS). The applied combined transplants, and especially the moss-bags, revealed severe contamination with heavy metals not detected by the water samples. The moss and the mussel followed a different model of trace element and PBDEs accumulation. The SCCPs levels were alarmingly high in all plant samples. The study confirmed PBDEs and SCCPs as bioaccumulative compounds and suggested that an EQS for SCCPs in biota needs to be established.

Body condition is increasingly used to assess the status of populations and as a proxy for individual fitness. A common, quick and non-invasive approach is to estimate condition from the relation between body length and mass. Among the methods developed for this purpose, the Scaled Mass Index (SMI) appears best suited for comparisons among populations. We assembled data from 17 populations of European green toads (Bufotes viridis) with the aim of devising a standard formula applicable for monitoring this species. The mean value of the exponents describing length–mass allometry in these samples was 3.0047. Hence, we propose using 3 as a scaling coefficient for calculating the SMI in green toads. From the contrast of SMI values for both sexes within populations, estimated with either the population-specific or the standard coefficient, we conclude that applying the standard formula not only facilitates comparisons among populations but may also help to avoid misinterpretation of variation within populations.

Moss-bags were applied to study the effect of contamination in three standing water bodies in Bulgaria (Kardzhali, Studen Kladenets and Zhrebchevo Reservoirs), the first two with old industrial contamination and the last polluted with short-chain chlorinated paraffins (SCCPs). Fontinalis antipyretica Hedw. collected from background (unpolluted) site was placed in cages for a period of 30 days. The present study examined whether inorganic and organic pollution detected with moss-bags resulted in corresponding differences in molecular, chemical and micromorphological markers. Suppressed large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) expression was assessed in moss-bags from two of the reservoirs, contaminated with heavy metals. There was a decrease of the total phenolic content (TPC) in the moss-bags, which provides a basis for further studies of the chemical content of aquatic mosses. Fontinalis antipyretica also showed a response through leaf micromorphological characteristics. In the all three reservoirs, an increase of the twig leaf cell number was recorded (p ≤ 0.01 for Kardzhali and p ≤ 0.001 for Studen Kladenets and Zhrebchevo reservoirs), as well as of the stem leaf cell number in Zhrebchevo Reservoir (p ≤ 0.001). On the contrary, the width of the cells decreased in the studied anthropogenically impacted reservoirs. All three studied groups of biomarkers (molecular, chemical and micromorphological) appeared to be sensitive to freshwater pollution. The results achieved indicated that rbcL gene expression, TPC, cell number and size are promising biomonitoring tools.

Background and purpose: In the current study we aimed to investigate the lysosomal membrane stability in haemocytes of the invasive mollusk zebra mussel (Dreissena polymorpha) by applying the neutral red retention assay (NRRA), as well as changes in the respiration rate and survival under acute heavy metal exposure. Materials and methods: The mussels were treated with different concentrations of Ni and Pb in laboratory conditions for a total acute period of 72 hours. These metals are considered as priority substances in surface waters according to Directive 2008/105/EO of the European parliament and the Council. The metal concentrations were prepared as 75, 50 and 25 % of the maximum permissible levels (100%) set by national and EU law.Results and conclusions: We found that after the first 24 h the lysosomes retained the dye between 60 and 90 min. in the mussels exposed to the higher Ni and Pb concentrations (100, 75 and 50 %). We also registered a negative, statistically significant correlation between the metal concentrations and the average time the lysosomes retained the dye after the 24th and 72nd h. Moreover, we found that the lysosomes could not retain the dye more than 60 min. after the 72nd h of exposure compared to the control (100 min.). The respiration rate increased in a dose-dependent manner after the 24th and 72nd h. We can conclude that the acute metal exposure, including all metal concentrations below the allowable concentrations, lead to destabilization of the lysosomal membrane stability and changes in the respiratory rate of zebra mussel, thus altered physiological functions. Overall, we consider that such experiments can be successfully applied in risk assessment and monitoring programs on metal-contaminated aquatic systems, and the obtained results in the field of water policy, respectively.

The current paper reviews the available literary data as well as original unpublished data on the distribution and the species' richness of the vertebrate fauna (Pisces, Amphibia, Reptilia and Mammalia) in the city of Plovdiv (South Bulgaria) and its relations to the level of urbanization. The species richness of each vertebrate group was presented, along a spatial gradient denoted by three points, representing low, moderate, and high levels of urbanization. We recorded no visible total general pattern of decrease of the total species richness in all studied vertebrate groups from the rural zones to the city center. Some differences in species richness along the urban—rural gradient apparently exist among the taxa. The only vertebrate group that showed a degrease pattern in the species richness from the rural to urban zones were the amphibians. Similar pattern was recorded in the reptiles, except for the urban zone, where a slight increase in the species richness was observed. The fishes and mammals showed very peculiar distribution pattern along the urban-rural gradient with highest species richness in the suburban zone. Possible explanations of these patterns are discussed.