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.

Brejo do Pau Fincado is a natural aquatic body located at the Araruama's Lagoon Complex, presenting a great variability in salinity with range from hipersaline to brackish. Intending to add information to the distribuition and ecology of cyanobacterial taxons, this study shows a survey of the subsurface cyanobacteria in brejo do Pau Fincado. Within this objective, samples were collected monthly from december 2008 to october 2009, the period of ebb and flood tide. The taxonomic analysis processing involved the preparation of permanent and fresh slides, through optic microscope measurement, that allowed to observe its classic morphological characteristics. Based on optical microscopy analysis identified 19 species of cyanobacteria subsurface were conducted monthly collections of superficial water and the analysis were based in optical microscopy, and revealed 19 psammic cyanobacterial species. The genus Aphanothece is the most representative qualitatively with a frequency of 31,58%. The species Aphanothece stagnina, A. halophytica and Spirulina subsalsa were the most expressive visually, being well adapted to a high salinity gradient and they are also the species more halotolerants and eurihaline of this community.

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