Published: May 13, 2011 r2011 American Chemical Society 5332 dx.doi.org/10.1021/es200720u | Environ. Sci. Technol. 2011, 45, 5332–5338 ARTICLE pubs.acs.org/est Cd Tolerance and Accumulation in the Aquatic Macrophyte, Chara australis: Potential Use for Charophytes in Phytoremediation Bernadette L. Clabeaux, † Divina A. G. Navarro, ‡ Diana S. Aga, ‡ and Mary A. Bisson †, * † Department of Biological SciencesUniversity at Buffalo, State University of New York at Buffalo, 109 Cooke Hall Buffalo, New York 14260, United States ‡ Chemistry Department, University at Buffalo, State University of New York at Buffalo, 611 Natural Sciences Complex Buffalo, NY 14260, Unites States b S Supporting Information ABSTRACT: We investigated the potential use of the alga Chara australis (R. Br.) forphytore mediation of Cd-contaminated sediments in aquatic systems. Chara tolerated up to 20 mg added Cd (kg soil) 1 in laboratory culture. Chlorophyll a and b levels were not affected even at Cd concentrations that suppressed growth. Levels of glutathione were suppressed at 235 mg added Cd (kg soil) 1 to 200350 nmol GSH (g DW) 1 , while control levels were 660 nmol GSH (g DW) 1 ). Histochemical studies showed Cd occurred throughout cell walls and cytoplasm in plants grown in 520 mg Cd (kg soil) 1 . Quantification using ICP-MS showed the maximum concentration in shoots was 72 mg Cd (kg DW) 1 at 35 mg added Cd (kg soil) 1 , while the maximum in rhizoids was 116 mg Cd (kg DW) 1 at 25 mg added Cd (kg soil) 1 . The bioconcentration factor (BCF, concentration in plant/concentration in soil) exceeded 1.0, the critical value for hyperaccumulators, for shoots exposed to 35 mg Cd (kg soil) 1 and rhizoids exposed to g25 mg Cd (kg soil) 1 . Translocation factors (TF, shoot concentration/rhizoid concentration) did not exceed 1.0 for any treatment. While Chara cannot be considered a hyperaccumulator, it shows promise for use in phytoremediation efforts. ’ INTRODUCTION Cadmium (Cd) contamination is a worldwide environmental concern, since it is a toxic heavy metal with no known biological function. Typically, noncontaminated soils contain less than 1 mg Cd/kg soil. 1 However, this level may be increased by industrial, agricultural, and municipal activities, along with the weathering of parent materials containing high concentrations of Cd. 2 Reme- diation of sites is recommended when Cd is g1 mg Cd/kg soil. 3 Phytoextraction is the removal of contaminants from soil by rhizoids or roots, followed by the translocation of the contami- nants to harvestable shoot tissues. It has been shown to be a cost- effective approach to soil remediation. 4 Much research exists on the role of land plants in the phytoextraction of metals from soil and there are some investigations of aquatic macrophytes for the phytoremediation of metals from aqueous solution. 5 However, less is known about the use of macrophytes for the phytoreme- diation of contaminated sediments in aquatic systems. We explore here the possibility of using the macrophytic algae Chara australis (R. Br.) to remediate contaminated sediments in aquatic systems. This alga and its relatives in Order Charales, Division Charophyta, appear to be good candidate phytoextractors because they can grow in dense meadows in shallow or deep waters (up to 65 m). 6 Imbedded in the sediment are rhizoids, fine filamentous struc- tures that, like roots, anchor the plant and have some role in the uptake of nutrients. 7,8 The aboveground structures, shoots, can import nutrients from the rhizoids or accumulate them directly from the water column. Rhizoids can also regenerate shoots, facilitating continuous, sustainable harvest. To be a successful phytoextractor, a plant must tolerate contami- nants, accumulate them to a signi ficant extent, and translocate them to an easily harvestable tissue. Some plants are designated hyper- accumulators for their high potential for phytoextraction. For Cd, concentrations above 100 mg Cd (kg DW) 1 (0.01% or 100 ppm) in plant tissues is one defining criterion for hyperaccumulator status. 9 Other hyperaccumulator criteria include a bioconcentra- tion factor (BCF, or ratio of metal concentration in the plant to that in the soil), and a translocation factor (TF, or ratio of metal concentration in roots to that in shoots) each greater than 1.0. 10,11 A high BCF implies that the plant is efficient at concentrating metals in its tissues, while a high TF implies that the plant is efficient at translocating metals from root to shoot tissues, both of which are important characteristics for a plant’s potential use for phytoremediation. Our research evaluates whether Chara australis meets these hyperaccumulator criteria. In addition, in exploring possible mechanisms for Cd resis- tance, we measure glutathione (GSH), a tripeptide found in many organisms that has been implicated in a variety of stresses, including oxidative and heavy metal stress. 1214 Received: August 11, 2010 Accepted: April 25, 2011