Sandra S. Brake

Influence of water chemistry on the distribution of an acidophilic protozoan in an acid mine drainage system at the abandoned Green Valley coal mine, Indiana, USA

Abstract Euglena mutabilis , a benthic photosynthetic protozoan that intracellularly sequesters Fe, is variably abundant in the main effluent channel that contains acid mine drainage (AMD) discharging from the Green Valley coal mine site in western Indiana. Samples of effluent (pH 3.0–4.6) taken from the main channel and samples of contaminated stream water (pH 3.3 to 8.0) collected from an adjacent stream were analyzed to evaluate the influence of water chemistry on E. mutabilis distribution. E. mutabilis communities were restricted to areas containing unmixed effluent with the thickest (up to 3 mm) benthic communities residing in effluent containing high concentrations of total Fe (up to 12110 mg/l), SO 4 (up to 2940 mg/l), Al (up to 1846 mg/l), and Cl (up to 629 mg/l). Communities were also present, but much less abundant, in areas with effluent containing lower concentrations of these same constituents. In effluent where SO 4 was most highly concentrated, E. mutabilis was largely absent, suggesting that extremely high concentrations of SO 4 may have an adverse effect on this potentially beneficial Fe-mediating, acidophilic protozoan.

Eukaryotic stromatolite builders in acid mine drainage: Implications for Precambrian iron formations and oxygenation of the atmosphere?

Biological activity of Euglena mutabilis , an acidophilic, photosynthetic protozoan, contributes to the formation of Fe-rich stromatolites in acid mine drainage systems. E. mutabilis is the dominant microbe in bright green benthic mats (biofilm), coating drainage channels at abandoned coal mine sites in Indiana. It builds biolaminates through phototactic and aerotactic behavior, similar to prokaryotes, by moving through precipitates that periodically cover the mats. E. mutabilis also contributes to formation of Fe-rich stromatolites by (1) intracellularly storing Fe compounds released after death, contributing to the solid material of stromatolites and acting as nucleation sites for precipitation of authigenic Fe minerals, and (2) generating O2 via photosynthesis that further facilitates precipitation of reduced Fe, any excess O2 not consumed by Fe precipitation being released to the atmosphere. Recognition of E. mutabilis –dominated biofilm in acidic systems raises a provocative hypothesis relating processes involved in formation of Fe-rich stromatolites by E. mutabilis to those responsible for development of Precambrian stromatolitic Fe formations and oxygenation of the early atmosphere.

Diatoms in Acid Mine Drainage and Their Role in the Formation of Iron-Rich Stromatolites

Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatomdominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola. Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished. Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system.

Eukaryote-Dominated Biofilms and Their Significance in Acidic Environments

Biodiversity of benthic eukaryotic microorganisms in highly acidic (pH ≤ 3.5) aquatic environments is limited to species that have developed strategies to tolerate elevated concentrations of H+ and dissolved metals and low nutrients levels that commonly characterize these environments. To survive adverse conditions, some algae, protozoa, and fungi have developed mechanisms to make their cell membranes impermeable to protons and maintain cytosolic pH at near neutral levels; others have developed a cell boundary mechanism that blocks H+ ions from entering the cell. High concentrations of heavy metals are also toxic, adversely impacting growth by disrupting physiological, biochemical, or metabolic processes. Some algae, fungi, and protozoans are able to tolerate high metal concentrations via metal complexation outside the cell, extracellular binding and precipitation of metals, reduced metal uptake, increased metal efflux, and detoxification or compartmentalization of metals within the cell. In acidic environments, benthic eukaryotic microorganisms form biofilm communities in which they are the dominant members numerically and ecologically. Eukaryote-dominated benthic communities produce heterogeneous microenvironments that vary spatially and temporally in their physicochemical character. The eukaryotes in these biofilms can be considered ecosystem engineers as they directly or indirectly modulate the availability of resources to other species within the biofilm. These eukaryote-dominated communities may play a significant role in mediating their environment by actively and passively contributing to metal attenuation through various processes of biosorption and via formation of laminated organosedimentary structures, which may be used as analogs for similar structures in the rock record.

Eukaryote-Dominated Biofilms in Extreme Environments: Overlooked Sources of Information in the Geologic Record

Our quest to find the earliest forms of microbial life and understand their role in the mediation of surficial processes has focused primarily on bacteria, since they represent the most primitive forms of life and possess the ability to contribute to the precipitation and dissolution of minerals (e.g., Fortin et al., 1997; Little et al., 1997; Nealson and Stahl, 1997) and the formation of biolaminated structures such as stromatolites (e.g., Awramik et al., 1976; Golubic, 1976). Stromatolites are the mineralized counterparts of microbial mats and represent some of the most tangible sources of morphological, biological, and chemical evidence for life on early Earth (e.g., Grotzinger and Knoll, 1999; Hofmann, 2000; Schopf et al., 2007). Stromatolite microstructures preserve paleobiological and paleoenvironmental information that can provide insight on the early evolution of the biosphere, atmosphere, and geosphere. Today, as in the distant past, bacteria are found in a range of environments from oxic to anoxic, thermal to arctic, and acid to alkaline, and they are important in biofilms and in rare, modern stromatolites (Cavicchioli, 2002; Gupta et al., 2004; Edwards et al., 2005). Our understanding of bacteria is, therefore, important in our search for similar life forms in extraterrestrial locations. Our focus on the role of bacteria, however, has created a gap in our understanding of the importance of eukaryotic microorganisms in some of these same environments. Eukaryotes are often overlooked in the study of early Earth since their body fossils are rarely preserved in the geologic record (Knoll, 1985; Schopf, 1999). The origin of eukaryotic cells, however, is considered to be one of the most important evolutionary steps in the history of life (Schopf, 1999), as it led to the evolution of multicellular life (Awramik, 1981). Fossil evidence indicates that eukaryotic microorganisms evolved …

Trace element uptake in plants grown on fly ash amended soils

Four crop plants were grown in a greenhouse in soils amended with 0, 5, 10, and 20% by weight of coal combustion fly ash to evaluate potential trace element uptake by the vegetation. The leaves and stems from each plant were harvested and analyzed for As, Cd, Co, Cu, Mn, Mo, Pb, Se, Tl, and Zn content during early, middle, and late growth. The trace element data were statistically analyzed using Analysis of Variance (ANOVA) to determine whether the trace element uptake in the four crop plants differed significantly between the soil treatments, and to identify significant differences in trace element uptake through time. The results show that the amount of amended fly ash does not significantly influence the concentration of most trace elements in plant tissue, and that some concentrations actually decrease with time. Although this study did not find a significant increase in trace element uptake, care must be taken in a natural environment where plants may behave differently.

IMPLICATION OF SPHALERITE COMPOSITION AT A CENTRAL TENNESSEE MISSISSIPPI VALLEY TYPE DEPOSIT

mineralization. The origin of the CTZD deposits remains ambiguous due to the complexities of ore fluid genesis, movement, evolution, and interaction with country rock. The CTZD is hosted within Lower Ordovician, nearly horizontal platform carbonates located along the paleo-structural highs of the Nashville Dome and Cincinnati Arch. Samples of sphalerite were collected from the Cumberland Mine in the CTZD where sphalerite ore occurs with barite, calcite, fluorite, and pyrite gangue. Sphalerite mineralization is present in two forms: open space filling in dolomite collapse breccia and replacement ore hosted in limestone. This study uses inductively coupled plasma optical emission spectrometry to investigate element compositional heterogeneity between nine breccia ore samples and six replacement ore samples. Analysis detected Zn up to 99 wt%, Fe up to 0.3 wt%, Mg up to 1,600 ppm, Mn up to 560 ppm, Mo up to 14 ppm, Cu up to 1,500 ppm, Pb up to 190 ppm, Cd up to 4,400 ppm, Co up to 22 ppm, and Ti up to 14 ppm. Arsenic, Sr, Ba, Cr, Sn, and Ag were below detection limit. Concentrations of Fe, Cd, and Co in sphalerite are similar to other MVT deposits in the U.S. Copper concentrations commonly exceed concentrations reported in MVT districts globally. Data show that sphalerite in replacement ores is depleted in Cu, Cd, and Pb, but enriched in Mg relative to the breccia-hosted ore counterpart. A weak correlation exists between Fe and commonly substituting Mg and Mn, and a strong positive correlation (R=0.97) exists between Cd and Pb. The data indicate that the ores either precipitated from different compositional fluids or precipitated during different mineralizing events from a single evolved fluid. These results have important implications in understanding the nature of MVT mineralization and act as a reference for pathfinder elements when searching for such deposits.