Ivan Traykov

Community level physiological profiles of bacterial communities inhabiting uranium mining impacted sites.

Bacterial activity and physiological diversity were characterized in mining and milling impacted soils collected from three abandoned uranium mine sites, Senokos, Buhovo and Sliven, using bacterial dehydrogenase activity and Biolog (EcoPlate) tests. The elemental composition of soils revealed high levels of uranium and heavy metals (sum of technogenic coefficients of contamination; TCC(sum) pollution as follows: Sliven (uranium - 374 mg/kg; TCC(sum) - 23.40) >Buhovo (uranium - 139.20mg/kg; TCC(sum) - 3.93) >Senokos (uranium - 23.01 mg/kg; TCC(sum) - 0.86). The physiological profiles of the bacterial community level were site specific, and indicated intensive utilization of polyols, carbohydrates and carboxylic acids in low and medium polluted environments, and i-erithrytol and 2-hydroxy-benzoic acid in the highly polluted environment of Sliven waste pile. Enzymes which take part in the biodegradation of recalcitrant substances were more resistant to pollution than these from the pathways of the easily degradable carbon sources. The Shannon index indicated that the physiological diversity of bacteria was site specific but not in line with the levels of pollution. A general tendency of increasing the importance of the number of utilizable substrates to bacterial physiological diversity was observed at less polluted sites, whereas in highly polluted sites the evenness of substrate utilization rate was more significant. Dehydrogenase activity was highest in Senokos upper soil layer and positively correlated (p<0.01) with the soil organic matter content. The bacterial activity (EcoPlate) and physiological diversity (Shannon index) correlated significantly and negatively with As, Cu, Zn, Pb and U, and Co, Cr, Ni and Mn, respectively. We concluded that the observed site specific shifts in bacterial communities were complex due to both the environmental peculiarities and the bacterial tolerance to the relevant level of pollution, rather than a strong indication of uranium and heavy metals toxicity.

Effects of long-term radionuclide and heavy metal contamination on the activity of microbial communities, inhabiting uranium mining impacted soils

Ore mining and processing have greatly altered ecosystems, often limiting their capacity to provide ecosystem services critical to our survival. The soil environments of two abandoned uranium mines were chosen to analyze the effects of long-term uranium and heavy metal contamination on soil microbial communities using dehydrogenase and phosphatase activities as indicators of metal stress. The levels of soil contamination were low, ranging from ‘precaution’ to ‘moderate’, calculated as Nemerow index. Multivariate analyses of enzyme activities revealed the following: (i) spatial pattern of microbial endpoints where the more contaminated soils had higher dehydrogenase and phosphatase activities, (ii) biological grouping of soils depended on both the level of soil contamination and management practice, (iii) significant correlations between both dehydrogenase and alkaline phosphatase activities and soil organic matter and metals (Cd, Co, Cr, and Zn, but not U), and (iv) multiple relationships between the alkaline than the acid phosphatase and the environmental factors. The results showed an evidence of microbial tolerance and adaptation to the soil contamination established during the long-term metal exposure and the key role of soil organic matter in maintaining high microbial enzyme activities and mitigating the metal toxicity. Additionally, the results suggested that the soil microbial communities are able to reduce the metal stress by intensive phosphatase synthesis, benefiting a passive environmental remediation and provision of vital ecosystem services.

Toxicological Effects of Fastac Insecticide (Alpha—Cypermethrin) to Daphnia Magna and Gammarus Pulex

ABSTRACT Fastac is a widely used in field pest control insecticide, belonging to the group of synthetic pyrethroids. These insecticides are highly toxic to many aquatic and terrestrial organisms. The purpose of the study was to evaluate the acute toxicity of Fastac on Daphnia magna Straus and Gammarus pulex (L.). The 48h—EC50 for Daphnia magna was estimated to be 0.8 μg/l and 24h—LC50 for Gammarus pulex—0.3 μg/l. The low solubility of the Fastac resulted in higher toxicity toward Gammarus pulex probably due to its adsorption into the sediments.

Natural Communities of Uranium Mining Impacted Area in the Vicinity of the Senokos Village

ABSTRACT Uranium containing wastes accumulated during mine activities have resulted in a multitude of contaminated sites in Bulgaria. The lack of biomonitoring programs limits the environmental impact assessment of uranium impacted areas. The aim of the study was to investigate the health of natural terrestrial (vegetation, soil bacteria and millipedes) and freshwater (macrozoobenthos) communities in the impacted area of former uranium mine Senokos. The mine is one of the forty-nine former uranium mines in Bulgaria, reclaimed in the beginning of the 90s, but the reclamation was compromised due to surface erosion of the protective layers. The vegetation is typical for the region and uranium pollution has not caused any significant adverse affects on it. Adverse affects on soil bacterial communities are recorded only to their activity, but not to the abundance. Soil millipedes are in low density dominated by Pachyiulus cattarensis (Latzel 1884). The benthic community of Luda River is influenced by both uranium loaded sediments and infiltrate water from the mine.

NEW CHOROLOGICAL DATA OF SOME SUBMERGED MACROPHYTES IN BULGARIA

ABSTRACT The data on the distribution of some submerged macrophytes from different types of limnetic water bodies from the ecoregions of Bulgaria were summarized. New chorological data for 11 species were found: Ceratophyllum demersum, Ceratophyllum submersum, Elodea canadensis, Hydrocharis morsus-ranae, Myriophyllum spicatum, Najas marina, Nymphaea alba, Potamogeton gramineus, Potamogeton pectinatus, Potamogeton pusillus, Trapa natans. The distribution of Potamogeton berchtoldii Fieb. has been confirmed for the territory of Bulgaria.

Vertical Distribution of Bacterioplankton in Dolnoto Lake—Seven Rila Lakes

ABSTRACT Temporal and vertical distribution of bacterial abundance (BA) was studied in the high mountain Dolnoto Lake (max depth 11.0 m), the lake at lowest elevation (2 095 m a.s.l.) from the system of the Seven Rila Lakes. The research was performed in July and September, both in 2006 and 2007. Bacteriological analysis was completed with measurements of selected physicochemical parameters such as temperature, oxygen, pH, and inorganic nitrogen and phosphorous concentrations. BA was higher in 2007 (on average 93.92 x 105 cell ml−1), especially in Julq (121.56 x 105 cell ml−1) than in 2006 (on average 17.48 x 105 cell ml−1). The vertical distribution of bacteria depended on temperature, pH and PO4-P, and the most abundant was the subsurface layer of water column in most of the sampling occasions. Bacterial communities from the different vertical layers had different metabolic profiles (EcoPlates Biolog). The lowest physiological diversity was recoded for the subsurface bacterial community.

Comparison of ecological state/potential assessment of 19 Bulgarian water bodies based on macrophytes and phytoplankton (2011 2012)

Nowadays, one of the most striking challenges for Bulgarian limnologists comes from the attempts to implement the requirements of Water Framework Directive (WFD) for assessment of the ecological status of the water bodies. This work represents results from the monitoring of the reservoirs Aleksandur Stamboliyski, Antimovo, Batak, Burzina, Gorni Dubnik, Zhrebchevo, Iovkovtsi, Krapets, Mandra, Ognyanovo, Rabisha, Suedinenie, Tsonevo and the lakes Alepu, Atanasovsko Ezero, Dourankoulak, Pomoriysko Ezero, Shabla and Sreburna. The studies were conducted simultaneously in the summer months of 2011 and 2012 on the following parameters: algal taxonomic composition and abundance, presence/absence of algal blooms and blooms of potential toxic species, algal group index, reference index for macrophytes, water temperature, transparency, pH, conductivity, chlorophyll a, total phosphorus, total nitrogen, phosphate phosphorus, ammonium nitrogen, nitrate nitrogen and chemical oxygen demand. The ecological status was registered in the five WFD categories. The set of data, based on the detected species composition of 236 algal taxa and 33 species of macrophytes, allowed us to compare statistically the values of the used parameters and the water bodies according to their biodiversity and abiotic features. The obtained results are important for clarifying the official classification of the surface water bodies of Bulgaria according to State Order N4/14.09.2012 and for making proposals for its improvement. Comparisons of the finally attributed ecological status/potential, based on macrophytes and phytoplankton, showed some significant differences and were used as a basis for discussion of the parameters and their weighted values, used up-to-now for the assessment of Bulgarian water bodies.

Shifts from Clear to Turbid State in a Small Semi-Artificial Headwater Wetland Following Macrophyte Removal

ABSTRACT Wetlands in Bulgaria have been altered, degraded or lost due to a wide range of human activities. The main objective of the study was to restore a densely overgrown semi artificial headwater wetland through macrophyte removal. Since the mid 80s rapid macrophyte invasion has taken place in the lake and by the end of the 90s it has been completely overgrown by pondweed. In 2005, 70% of the pondweed was removed and the effects of the restoration activities were monitored. The reduced amount of organic matter and increased circulation of the water led to increased oxygen content, reduced amounts of phosphates and chlorophyll-a and increased amounts of dissolved inorganic nitrogen. The small size and the shelter from the trees, as well as the incorporation of nutrients in newly developing macrophytes biomass, have helped to maintain the clear water state of the lake throughout the first year after the restoration activities. Subsequently, a shift to phytoplankton dominated state was established after introduction of grass-carp.

Role of the Planktonic Communities in the Regulation and Indication of Eutrofication Processes in Shallow Mountain Wetlands

Protection and restoration of wetlands requires correct evaluation of their ecological and trophic state, i.e. detection and verification of appropriate indicators. The aim of the study is to clarify the role of planktonic communities (phytoplankton and bacterioplankton) in eutrophication processes in shallow landslide-dammed lakes and to apply routine indicators of eutrophication processes for a case study of Dragichevo lake. From May 2001 through September 2002 a bathometric map and map of macrophyte distributions was constructed, changes in the main hydrochemical parameters, phyto- and bacterioplankton were tracked, and the Carsons trophic state index determined. The results suggested that re-suspension processes and active interaction between sediments and water significantly influence both the plankton communities and chemical parameters of these wetlands.