A glasshouse study concerning the halophyte Spartina densiflora was carried out to determine its tolerance and capacity to accumulate As. S. densiflora presented a high tolerance to As-induced stress, since all plants were able to survive at concentrations higher than 6.7 mmol l(-1) As. However, As increment caused a reduction in S. densiflora growth, owing to a decrease in net photosynthetic rate. This reduction was prompted by the adverse effect on the photochemical apparatus and the reduction in the absorption of essential nutrients, which was linked with the reduction in G(s), caused by the alteration of the K/Ca ratio, and with the reduction of photosynthetic pigment and Rubisco carboxilation. Arsenic tolerance was associated with the capacity to accumulate As in its roots (with values up to 2 mg g(-1)) and largely avoid its transport to the leaves, this fact indicating that this species could be useful for arsenic phytostabilization purposes. (C) 2011 Elsevier Ltd. All rights reserved.