The overarching goal of this in situ study was to investigate the integrated impact(s) that metal/metalloid contamination might have on the overall health and performance of the ecologically important aquatic macrophyte, Vallisneria neotropicalis. Morphological (i.e., shoot growth-based endpoints) and photo-physiological (i.e., photosynthetic activity measured as chlorophyll a fluorescence and oxygen exchange) variables, along with aboveground tissue metal/metalloid concentrations, were measured in natural populations of V. neotropicalis that differed with respect to their anthropogenic pressure. With the exception of an overall negative effect on growth, our results suggest that there were no detrimental effects of low/moderate contamination of V. neotropicalis by trace elements (i.e., arsenic As and mercury Hg; 1.04-2.77 mu g g(-1) dry wt. and 3.76-15.18 ng g(-1) dry wt., respectively) on the photosynthetic physiological performance of this species. V. neotropicalis appears to tolerate low/moderate levels of trace element contamination with little impact on plant health and performance. (C) 2011 Elsevier B.V. All rights reserved.