Fig. 1. Location of the Guadiana river estuary (southwest Iberian Peninsula), including designated bathing areas inside the estuary and in the adjacent coastal zone. Inside the estuary, some undesignated areas are also used for bathing. The beaches with the Blue Flag Award (BFA) are represented by stars and the ones without it by squares. Data on BFA concerns 2011 season. The BFA is an eco-label that guarantees environmental quality of the beaches awarded. The major urban centers are represented by red dots. The blue dot highlights Pulo do Lobo sampling station.