Intracellular crystals of aragonite have been identified by selected area electron diffraction (SAED) in a species of the freshwater filamentous alga Spirogyra from the Thames River, Ontario, Canada. The crystals are 2 to 24 μm in diameter, and characterized by a unique cross‐shaped morphology, in which needle‐like, or prismatic outgrowths develop from a common axis. Crystals may be dispersed throughout filaments, but tend to cluster as aggregates towards the centre.

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Monocultures of the freshwater green algae Ankistrodesmus sp. grown at pH 8.1–8.2 and 13–16 °C, in solutions containing 2 ppm U chelated with EDTA, acquired 1000 – 10 000 ppm uranium by dry weight. In some algae, a uranium mineral of cubic habit was detected. At Elliot Lake, Ontario, Euglena sp. thriving in tailings discharge contain on average 184 ppm U. Tailings waters contain high concentrations of dissolved uranium, on average 273 ppb. In natural drainage waters, above and below tailings, dissolved U averages 0.23 ppb. Thames River algae average 28 ppm U, whereas waters have an average dissolved U of 1.46 ppb, representing about twice the global mean riverine value of 0.6 ppb U.

Multielement analysis of fresh water algae, including unicellular Euglena sp. and some filamentous Cladophora sp. species, revealed extremely high concentrations of various chemical elements such as A1 -28,000 ppm (mg/L), Sr -150, Ba -40, Zn -150, Pb -1600, Cu -200, and Be -180 ppm. These concentrations are highly variable, and depend on both the algal species and the host environments. Samples were colleded from the Elliot Lake (U), Timmins (Au), and Sudbury (Cu, Ni, Pt) mining camps of northern Ontario. These results endorse the premise that microorganisms mediate the transfer of many solutes between hydrosphere and sedimentary regime, and by sequestering toxic metals released from the mine tailings, they are useful in the retardation of metal dispersion into the environment and as a possible mechanism to enhance secondary recovery of precious metals where solute levels are too low for conventional technology.

Acidic effluent containing enhanced concentrations of toxic heavy metals discharges from a cumulative total of lo4 ha of mine-tailings waste in Canada. Communities of acidophilic microorganisms, specifically the unicellular alga Euglena sp. and bacteria, thrive in many of the hostile, low-pH effluent environments, which are otherwise devoid of life. The microorganisms concentrate aqueous dissolved metals onto cell walls and at intracellular sites, during the life cycle, and strongly bind metals during early diagenesis. A sequence is observed in which amorphous Fe and Ti concentrated at cell walls are progressively transformed to microcrystalline aggregates of goethite, ferrihydrite, maghemite, magnetite, haematite, lepidocrocite, and ilmenite. The bioprecipitated Ti-and Fe-oxides and oxyhydroxides act as scavengers for heavy metals such as Cu, Pb, Zn, Ni, Cd, and Th. Acidophilic microorganisms play a central role in the toxic-metal budget of mine-tailings waste by efficiently sequestering aqueous metals and by promoting nucleation of oxide minerals whose inorganic formation is kinetically inhibited, thereby retarding toxic-metal dispersion into the natural environment.