Total and Potentially Active Bacterial Communities Entrapped in a Late Glacial Through Holocene Ice Core From Scarisoara Ice Cave, Romania.

Our understanding of the icy-habitat microbiome is likely limited by a lack of reliable data on microorganisms inhabiting underground ice that has accumulated inside caves. To characterize how environmental variation impacts cave ice microbial community structure, we determined the composition of total and potentially active bacterial communities along a 13,000-year-old ice core from Scarisoara cave (Romania) through 16S rRNA gene Illumina sequencing. An average of 2,546 prokaryotic gDNA operational taxonomic units (OTUs) and 585 cDNA OTUs were identified across the perennial cave ice block and analyzed in relation to the geochemical composition of ice layers. The total microbial community and the putative active fraction displayed dissimilar taxa profiles. The ice-contained microbiome was dominated by Actinobacteria with a variable representation of Proteobacteria, while the putative active microbial community was equally shared between Proteobacteria and Firmicutes. Accordingly, a major presence of Cryobacterium, Lysinomonas, Pedobacter, and Aeromicrobium phylotypes homologous to psychrotrophic and psychrophilic bacteria from various cold environments were noted in the total community, while the prevalent putative active bacteria belonged to Clostridium, Pseudomonas, Janthinobacterium, Stenotrophomonas, and Massilia genera. Variation in the microbial cell density of ice strata with the dissolved organic carbon (DOC) content and the strong correlation of DOC and silicon concentrations revealed a major impact of depositional processes on microbial abundance throughout the ice block. Post-depositional processes appeared to occur mostly during the 4,000-7,000 years BP interval. A major bacterial composition shift was observed in 4,500-5,000-year-old ice, leading to a high representation of Beta- and Deltaproteobacteria in the potentially active community in response to the increased concentrations of DOC and major chemical elements. Estimated metabolic rates suggested the presence of a viable microbial community within the cave ice block, characterized by a maintenance metabolism in most strata and growth capacity in those ice deposits with high microbial abundance and DOC content. This first survey of microbial distribution in perennial cave ice formed since the Last Glacial period revealed a complex potentially active community, highlighting major shifts in community composition associated with geochemical changes that took place during climatic events that occurred about 5,000 years ago, with putative formation of photosynthetic biofilms.

Plants accumulating heavy metals in the Danube River wetlands.

BACKGROUND: We present herein our results regarding the accumulation of four heavy metals (copper, cadmium, lead, and zinc) in four aquatic species plants (Ceratophyllum demersum, Potamogeton pectinatus, Potamogeton lucens, Potamogeton perfoliatus) collected from the Danube River, South-Western part of Romania and their possible use as indicators of aquatic ecosystems pollution with heavy metals. METHODS: Elements concentration from the vegetal material was determined through Inductively Coupled Plasma - Mass Spectrometry. RESULTS: The species were chosen based on their previous use as bioindicators in aquatic ecosystems and due to the fact they are one of the most frequent aquatic plant species of the Danube River ecosystems within the Iron Gates Natural Park. Highest amounts are recorded for Ceratophyllum demersum (3.52 µg/g for Cd; 22.71 µg/g for Cu; 20.06 µg/g for Pb; 104.23 µg/g for Zn). Among the Potamogeton species, the highest amounts of heavy metals are recorded in Potamogeton perfoliatus (1.88 µg/g for Cd; 13.14 µg/g for Cu; 13.32 µg/g for Pb; 57.96 µg/g for Zn). The sequence for the bioconcentration factors (BCFs) calculated in order to describe the accumulation of the four metals is Cd >> Zn > Pb > Cu. Increase of the zinc concentration determines an increase of the cadmium concentration (Spearman rho=0.40, p=0.02). CONCLUSIONS: Despite the low ambiental levels of heavy metals, the four aquatic plants have the ability to accumulate significant amounts, which make them useful as biological indicators. BCF value for Ceratophyllum demersum indicated this species as a cadmium hyperaccumulator.

Determination of arsenic content of some Romanian natural mineral groundwaters.

Romania is one of the countries that have natural arsenic groundwater problems. This paper presents the results of a study of arsenic concentration monitoring in natural mineral waters collected from 23 sampling sites located in the northern, central, and western regions of Romania. The sampling sites are both natural springs and drilled wells. The graphite furnace atomic absorption spectrometry was used for arsenic content determination. The Piper's classification principle was applied in order to find out the hydrochemical type of the analyzed waters. Depending on the concentration of arsenic, the water analyzed can be classified into three main categories: (1) mineral natural waters containing less than 10 µg/L arsenic, (2) mineral natural waters containing arsenic at concentrations several times higher than the limit of 10 µg/L but less than 100 µg/L, and (3) mineral natural waters containing arsenic at concentrations of ten to a hundred times higher than the allowed limit of 10 µg/L. The last-mentioned waters are of bicarbonatate sodium type and were sampled from seven sources only, being prohibited for human and animal use.

Barium concentrations and speciation in mineral natural waters of central Romania.

This paper reports the results obtained for the determination of Ba concentrations in mineral groundwater samples collected from drilled outlets located in the counties of Covasna and Harghita (34 sampling points), in five expeditions (spring, summer, and autumn), during 3 years: 2005, 2006, and 2007. The experimental data show that there are some sampling sites in which the barium concentration exceeds 1 mg/L, which is the maximum concentration admitted for barium. These mineral natural waters could be used only for therapeutic purposes. All other analyzed natural mineral waters are proper as both drinking and therapeutic water. By means of a principal component analysis a statistical approach was performed, using the data obtained during those analyzing processes. The distribution of the water saturation indexes with respect to a series of mineral species (alstonite, barite, barytocalcite, nitrobarite, sanbornite, and witherite) suggests that barium tends to remain in solution as ionic species in different concentrations and to be further carried away as such.