This lagoon is usually the one that maintains the accumulation of water for the longest period of time, and on occasions the flocks of flamingos that gather there number around half a thousand. This is where, due to the salinity, they find the highest concentration of artemia, a tiny crustacean that gives them the characteristic colouring of their plumage.
The eggs of this crustacean survive in unfavourable conditions of drought, but they need the microplankton of saline algae, which is particularly vulnerable in times of drought. This is why, even when dry, the slightest deterioration of the bottom of the lagoons has serious consequences. Let us not forget that the lagoon, even if it loses its water layer, is still an important ecosystem in which life remains dormant until the arrival of the first autumn waters.
This lagoon is the deepest and largest (approximately 30 hectares) of the endorheic complex and is also seasonal, although on occasion it has been able to maintain a sheet of water all year round. The salinity of its waters allows the proliferation of algae and aquatic plants that are very suitable for the birds that gather and nest there. The large concentrations of ducks in autumn in this lagoon are due to the fact that this flora is their source of food. For this reason, access to the three lagoons of the complex is prohibited.
Tamarisks, brooms, bulrushes, rushes, reeds and salicornias (also called sea asparagus or glasswort) are distributed in different areas around the perimeter of the lagoon depending on the characteristics of the soil, depth and orientation. This makes it a lagoon with diverse biotopes that give added value to its already high ecological value.
This diversity of the surroundings extends to the aquatic birds it shelters, some of which are in danger of extinction, including the flamingo, the white-headed duck, the horned coot, the marbled teal, the red-crested pochard, the spoon-billed duck, the stilt, the pintail and the lapwing, as well as the cattle egrets that use the large tamarins in the lagoon as roosts.