Algal and cyanobacterial saline biofilms of the Grande Coastal Lagoon, Lima, Peru

Tropical coastal wetland ecosystems are widely distributed in arid regions. The Grande coastal lagoon in Peru’s central plain is shallow, eutrophic and alkaline, exposed to the annual hydrological regime with flooding and desiccation periods, when a salt crust is formed. The brackish to hypersaline habitats showed salinity gradients from 2-90 ppt (NaCl) to saturation, pH values from 7.0 to 10.5, temperatures from 18 to 31°C, phosphate concentrations from 0.5 to 50 mg l and nitrate up to 0.88 mg l. Dominance of halophilic biofilms of benthic cyanobacteria followed by diatoms and the submerged macrophytes Chara hornemannii and Ruppia maritima during the clear water state supported the alternative stable states for this lagoon. A cohesive slimy layer formed mainly of the cyanobacteria Chroococcus dispersus, C. turgidus, Aphanothece stagnina, Oscillatoria tenuis, Lyngbya martensiana, L. diguetti, Phormidium valderianum associated with C. hornemannii, Rhizoclonium hieroglyphicum resting cells, Aphanizomenon flos-aquae akinetes, and Tetraselmis contracta cysts. Cyanobacterial biofilms flourished on the dried lagoon bed below the dicotyledonous halophytes Salicornia fruticosa, Sesuvium portulacastrum and Baccopa monnieri. The adaptive strategies included a biomass allocation (extracellular matrix formation) and complex reproductive processes for successful colonization.