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-(Ceramium nitens (Ceramiaceae, Rhodophyta), an uncommon species from Brazil). Morphological studies on Ceramium nitens (C. Agardh) J. Agardh, a completely corticated species, were carried out based on specimens rediscovered in Brazil fifty years after its first record. Its occurrence in Brazil was considered doubtful since it had been collected only once since 1945. Ceramium nitens can be recognized by having axial cells entirely covered by cortical cells, except for the cells near the apex, obscuring the nodal and internodal banding thalli, characteristic of most Ceramium species. In this paper the occurrence of Ceramium nitens in Brazil is confirmed and its vegetative and tetrasporangial structures are described in detail and their implications for the taxonomy of the genera Ceramium, Centroceras and Corallophila are discussed. Brief comments on the geographic distribution of C. nitens are also included.RESUMO -(Ceramium nitens (Ceramiaceae, Rhodophyta), uma espécie incomum no Brasil). Estudos morfológicos em Ceramium nitens (C. Agardh) J. Agardh, uma espécie inteiramente corticada, foram desenvolvidos baseados nos espécimes redescobertos no Brasil após 50 anos. Ceramium nitens tinha sido coletada apenas uma vez, em 1945. Sua ocorrência em águas brasileiras tinha sido considerada duvidosa. C. nitens pode ser reconhecida pela presença de células axiais inteiramente cobertas pelas corticais, exceto nas células próximas ao ápice, obscurecendo o talo com nós corticados e entrenós sem corticação, característico da maioria das espécies de Ceramium. A ocorrência de Ceramium nitens no Brasil é confirmada e o desenvolvimento das estruturas vegetativas e tetrasporangiais da espécie é apresentada, fornecendo subsídios para discussão da implicação dessas características na taxonomia dos gêneros Ceramium, Centroceras e Corallophila. Uma breve discussão sobre a distribuição geográfica de Ceramium nitens foi incluída.

In this study, we analyzed the antioxidant activity and total phenolic content of the intertidal seaweed Palisada perforata collected from different reef microhabitats (sheltered site, tide pool, plateau, and exposed site) along the coast of Pernambuco (Brazil). Both parameters were compared with the same parameters of this species grown in the laboratory under two experiments simulating temperature, salinity, and desiccation conditions found in the reef. After both experiments (temperature x salinity and desiccation), the algal photosynthetic performance was measured through chlorophyll fluorescence parameters using a pulse–amplitude modulation fluorometer to test their stress response. Palisada perforata likely underwent stress by desiccation due to tidal fluctuations rather than to temperature or salinity changes. This conclusion agrees with our observations of the plateau site´s specimens, which were exposed to both air and UV radiation during low tides and exhibited higher antioxidant activity to avoid oxidative damage. However, despite the environmental stress, the antioxidant activity remained low, suggesting that photoinhibition is a crucial protection mechanism against oxidative damage.