Spartina densiflora has demonstrated a high tolerance to
heavy metal contamination and a high capacity for accumulating
metal in its tissues. In the Gulf of Cadiz this species has colonized habitats with different degrees of
metal pollution. The aim of this study is to analyse the responses of populations of Spartina densiflora to this pollution. Germination, growth, photosynthesis and
metal uptake of two populations of Spartina densiflora collected from contaminated sites (Odiel and Tinto marshes) and of one population from a clean site (
Piedras marshes) were examined through two reciprocal experiments, in which seeds and adult plants were exposed to
metal-contaminated and uncontaminated soil under greenhouse conditions. The seeds of Spartina densiflora were able to germinate in all sediments with little differences between populations, even in more contaminated
soils. However, these conditions decreased the growth and survival of the seedlings to a similar degree for all populations. Likewise, no differences were recorded in relation to physiological and
metal uptake. Contrarily, in the adult experiment, we found that the Odiel population differed from the other populations in growth and
metal uptake, with overall greater values. These differences in growth were strongly supported by lower photosynthetic rates and stomatal conductance in the
Piedras and Tinto populations. The reduction in photosynthetic performance was largely due to the reduction in photosynthetic pigment concentration in both populations. Despite these differences, there was insufficient evidence to support that Spartina has evolved to heavy-tolerant ecotypes, since all Spartina densiflora populations proved to have a great capacity for accumulating
heavy metals in its roots. Nonetheless, this finding suggests that the Odiel population could have a greater phytoremediation potential.