Plants, specifically bryophytes, have been used to study the impacts of trace level contamination of heavy metals in aquatic ecosystems. Bryophytes placed in mine drainages have been shown to accumulate zinc, cadmium, and lead. In North America, the bryophyte Hygrohypnum ochraceum has been widely used to study heavy metals in aquatic environments. In a previous study on Fountain Creek water quality, H. ochraceum was shown to uptake selenium from Se-rich water found in the Fountain Creek watershed. Data analyses suggested that selenium uptake is correlated with Se and Fe concentrations in the water, which led to the hypothesis that Se transport into bryophytes requires soluble Fe. Subsequent investigations tested this hypothesis by mimicking watershed conditions in the laboratory with the highly characterized bryophyte Physcomitrella patens as a model organism. The first set of experiments examined the effect of dissolved Fe on Se uptake by P. patens and used two sets of flasks---one with Fe (12.5 ppm) and one without. Both sets contained Se levels of 0, 4, 8,16, and 32 ppb while maintaining pH constant (7.0). A second set of experiments was used to determine the effect of pH on Se uptake, while maintaining media pH at 6.5, 7.0, 7.5, 8.0, or 8.5 with Se (32 ppb) and Fe (12.5 ppm) constant. Fe solubility decreased in the media above pH 7.5 and more markedly above pH 8.0. All cultures were maintained for 10 days, harvested, dried, and digested according to EPA Method 3052. ICPMS was used to determine metals, Se and Fe in digest solutions. P. patens showed a statistically significant, log linear uptake of Se in the presence of dissolved Fe (R2=0.915, p=0.011). Se uptake was undetectable in the absence of dissolved Fe, which supports the hypothesis that soluble iron is required for Se uptake by P. patens.

Bioaccumulation of selenium in the model bryophyte Physcomitrella patens

251st National Meeting (2016)

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