Effects of water acidity and metal concentration on accumulation and within-plant distribution of metals in the aquatic bryophyte fontinalis antipyretica

With the aim of investigating the effects of water acidity and metal concen trations on the accumulation of heavy metals by aquatic bryophytes, batches of Fontinalis antipyretica Hedw. were transplanted from a clean site to on e of four sites with characteristics ranging from clean to severely contami nated (high acidity and high heavy metal concentrations). After 1-35 days, metal levels were determined in the extracellular and intracellular compart ments of the transplanted material. The results show that heavy metal uptak e is clearly lower in acid waters than in near-neutral waters, possibly due to competitive displacement of metal cations from extracellular binding si tes and membrane transport proteins by protons. The reduced accumulation is particularly marked in the extracellular compartment; the intracellular co mpartment shows rapid accumulation of large amounts of metal, followed by e qually rapid release. The effects of heavy metals and acidity on physiology were also investigated, on the basis of levels of the essential cations po tassium (K), magnesium (Mg) and calcium (Ca) in the extracellular and intra cellular compartments. Bryophytes transplanted to the severely contaminated sites showed loss of intracellular K (indicating altered membrane permeabi lity), loss of extracellular Mg, and loss of both extra- and intracellular Ca (implying damage to the cell wall).