Development of versicolored microbial mats: Succession of microbial communities

Abstract

Today, microbial mats are confined to a restricted range of habitats including hypersaline and coastal marine environments, hot springs and alkaline lakes. In the last few years, these systems have been considered a major subject of study and many articles (Cohen et al. 1984; Cohen and Rosenberg 1989) have been published, which extensively revise the structure, physiology, genetics and evolution of microbial mats. A preliminary investigation of these microbial ecosystems distributed along the west Mediterranean coast, from Almería (SE corner of the Iberian Peninsula) to the Ebro Delta has been done (Esteve et al. 1992b). More exhaustive investigations have been done about microbial mats of La Banya spit, the southern peninsula of the Ebro Delta (Mir et al. 1991), which thrive in several areas that may be flooded during the occasional rises in the sea level due to tides, waves and storms. Here we describe the structure and the development of communities in different microbial mats in la Banya spit, the ultrastructure of individual cells, as well as the spatial and temporal variations of these communities. Distribution and typology of the Ebro deltamicrobial mats The studied microbial mats are located at the Ebro Delta (40°35' N, 0°40' E), 50 km south from Tarragona. They occur all along the coast in the narrow ephemeral ponds of the backshore, on the flanks of the storm inlets and, most commonly, on the sand flats and channels of La Banya spit. In the last few years, we have studied ten sites along La Punta de la Banya, which were selected in order to study spatial variations. All of them lay 1 to 7 cm below the water surface during the flooded periods. The temperature of water covering these microbial mats ranged from 12 to 30°C; conductivity from 59 to 105 mS.cm -l ; salinity from 40 to 75 ‰, and pH from 7.5 to 9.0.