Fungi play important geoactive roles in the biosphere, particularly element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. Fungi can apply various mechanisms to effect changes in metal speciation, toxicity and mobility, mineral formation and/or mineral dissolution. This research has examined fungal roles in bioweathering and bioleaching of zinc sulfide ore, together with an investigation of the role of fungal phosphatases in the bioprecipitation of uranium and lead when utilising an organic phosphorus-containing substrate as the sole phosphorus source. The results obtained revealed that test fungal species showed bioweathering effects on zinc sulfide ore, and clear evidence of biotransformation and bioleaching of zinc sulfide was obtained after growth of A. niger. The formation of zinc oxalate dihydrate resulted from oxalic acid excretion. The formation of uranium- and lead-containing biominerals after growth of yeasts and filamentous fungi with organic phosphorus sources have also been demonstrated and characterized. Test fungi were capable of precipitating uranium phosphate and pyromorphite, and also produced mycogenic lead oxalate during this process. This work is the first demonstration that filamentous fungi are capable of precipitating a variety of uranium- and lead-containing phosphate biominerals when grown with an organic phosphorus source. The role of fungal processes in the bioweathing and bioleaching of mineral ores, and the significance of phosphatases in the formation of uranium and lead secondary minerals has thrown further light on potential fungal roles in metal and mineral biogeochemistry as well as the possible significance of these mechanisms for element biorecovery or bioremediation.

Saxicolous lichens on exposed bedrock are subjected to desiccation stress and intense light levels. Members of the genera Xanthoparmelia and Arctoparmelia are common foliose lichens on the Precambrian Shield, produce abundant sexual structures, and form part of the bedrock communities. The general goal of this thesis was to better understand the influence of community and underlying geology on three saxicolous lichens: Arctoparmelia centrifuga, Xanthoparmelia viriduloumbrina and X. cumberlandia. More specific goals were further examined in five chapters to investigate: 1) life history strategies of the three species, 2) a trade-off between fecundity and fungal secondary metabolite production; 3) an effect of substratum element composition on previously defined communities and lichen biology, 4) substratum preferences of Xanthoparmelia species, and 5) the photobiont guild hypothesis of the three species in a preliminary study. Field collections of lichens and environmental data were made in four locations on the Precambrian Shield in Manitoba and Ontario. Secondary metabolites were determined by digitally enhanced thin-layer chromatography. Fecundity was measured by number of apothecia, ascospores, and percent germination. Elements in rock samples were quantified by aqua-regia digest and inductively coupled plasma optical emission spectroscopy analysis and light microscopy was used to observe and quantify fungal germination and growth. The results showed eighty-one lichen species comprising three lichen communities; mossy rock, grassy rock, and treed rock communities. Lichen communities and fecundity were used to characterize life history strategies as competitive for Arctoparmelia centrifuga, stress tolerant for Xanthoparmelia viriduloumbrina, and ruderal generalist for Xanthoparmelia cumberlandia. A potential trade-off was reported for X. cumberlandia between sexual fecundity and a secondary metabolite. Substratum preferences were found at the genus level and element differences at the species level. Experimental evidence further supported geological preferences for the three species. Finally, the photobiont guild hypothesis could not be supported by this preliminary work. This research provides a broad overview of ecological and biological patterns found in Arctoparmelia and Xanthoparmelia species. The research forms a foundation for further studies in substratum preference and life history characterization in lichens. It can be further applied to habitat suitability modelling which may be valuable for phylogenetic context or in conservation biology of lichens. / October 2015