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Microbial mats are organo-sedimentary ecosystems formed by autotrophic and heterotrophic bacterias. Cyanobacteria contribute to the formation of these structures from the entrapment and engulfment of sediments contributing to the formation of carbonate rocks found in the geological record from the Precambrian to the Recent. In this research we identified the living cyanobacteria mats type 1 (gelatinous) and type 2 (cohesives) present in Brejo do Espinho and Araruama saline, east Fluminense, Rio de Janeiro state. The microbial mats type 1, were found in compartiment A and B of Brejo do Espinho and the Araruama saline in the tank with a depth of 10 cm. The mats type 2 were only found in compartiment A and in tank with 15 cm depth. In the microbial mats of compartiments A and B predominated the spherical forms of genres Chroococcus Nägeli 1948 and Aphanothece Nägeli 1948. In the tanks predominated filamentous forms of the Leptolyngbya Anagnostidis and Komárek 1988 genre. In mats type 1, the diversity indices (H') were 1.95 and 2.24 and in type 2 of 2.16 and 2.14 for the Brejo do Espinho and Araruama saline, respectively. The highest values of diversity indices found in saline tanks occurred by stable salinity conditions.

Chroococcales in blister microbial mats at brejo do Pau Fincado, Rio de Janeiro, Brazil. Brejo do Pau Fincado (22º55' 56,75" S e 42º16' 54,7" W) is a natural natural coastal aquatical body. It is located at the Lagoa de Araruama complex, formed at least 7000 years ago. The local climate is characterized by low precipitation rates and high evaporation rates; due to this, the lagoons tend to become hypersalyne. Microbial mats are organic-sedimentary structures composed mainly of cyanobacteria. Whilst the photosynthesis process cyanobacteria induct an environmental change, which leads to calcium carbonate precipitation. The aim of this study was to typify and identify the cyanobacteria at the blister microbial mat. Samples were processed and analyzed using an optical microscope. The blister mat is composed of twelve species of cyanobacteria disposed in a fragile and amorphous mass. In this structure, both quantitative and qualitative domains belong to Chroococcales Westtein 1924. Measurement has shown that the place is very selective, and cyanobacteria presented great resistance and adaptability, because they are forms which had got success surviving to big changes occurred on Earth since the beginning of life and the evolutionary history.

Julieta saline receives water from lagoa de Araruama, which is located in the state of Rio de Janeiro, to the East of the city of Araruama and to the west of the city of Cabo Frio, between 22º49' and 22º57' S latitude and 42º00' and 42º23' W longitude. It is composed by a series of soil tanks obtained by natural excavation, where water gradually concentrates through natural evaporation until salt precipitation. The reservoirs can be divided in three types, according to their activity: cargo, evaporator and crystallizer tanks. The process of making such reservoirs waterproof is enabled by a fine layer of algae which is formed naturally with the passing of time. This study is based on monthly collects within the period ranging from May, 2004 to October, 2004, along three collection stations set up in different saline reservoirs. To identify the microbic composition, fresh, semi-permanent and permanent laminae were obtained and their analysis were performed by means of optical microscopy. The analysis revealed a total of twenty cyanobacterial types. In all layers, a predominant amount of oval spherical forms was observed. The predominance of cyanobacteria is justified by the fact that they are carriers of high morphological adaptations which enables them to survive in various types of environments and be predominant in hypersaline sites.

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