-(Phytoplankton flora of two rivers in Southeast Brazil-Paraibuna and Pomba Rivers, Minas Gerais). This work is a survey of the phytoplankton communities of the Paraibuna and Pomba Rivers. It aims is to contribute to the existing albeit scarce knowledge of the phytoplankton of Minas Gerais and of lotic phytoplankton in general. The results are based on 32 samples collected from Paraibuna and Pomba Rivers, in Minas Gerais State, during the dry (July and August, 2001) and rainy seasons (February 2002). Forty-eight taxa were identified, 20 from Paraibuna River and 28 from Pomba River, thirty-eight of which are new records for Minas Gerais State. The phytoplankton community of Paraibuna River was strongly influenced by a reservoir close to its source, thus the occurrence of lentic species of cyanobacteria and desmids. However, the phytoplankton community of Pomba River was typical of lotic environments, with great number of diatoms and desmids. Key words-potamoplankton, taxonomy, tropical rivers RESUMO-(Flora fitoplanctônica de dois rios no Sudeste do Brasil-Rios Paraibuna e Pomba, Minas Gerais). É apresentada a composição fitoplanctônica dos Rios Paraibuna e Pomba, contribuindo para o escasso conhecimento do fitoplâncton de ambientes lóticos e também do Estado de Minas Gerais. Os resultados são baseados em 32 amostras coletadas nos Rios Paraibuna e Pomba, em Minas Gerais, durante a estação seca (agosto, julho/2001) e chuvosa (fevereiro/2002). Foram identificados 48 táxons, sendo 20 no Rio Paraibuna e 28 no Rio Pomba. Destes, 38 são primeira citação para o Estado de Minas Gerais. O fitoplâncton do Rio Paraibuna foi influenciado pela presença de um reservatório, favorecendo a ocorrência de cianobactérias de ambientes lênticos juntamente com desmídias. A composição do Rio Pomba foi tipicamente de ambientes lóticos, com maior número de diatomáceas e desmídias. Palavras-chave-potamoplâncton, rios tropicais, taxonomia
Foi realizado um inventário das espécies dos gêneros Euastrum Ehrenberg ex Ralfs e Micrasterias C.Agardh de dois ambientes de águas pretas do município de Manaus, um lago de inundação (lago Tupé), e o rio Negro. As coletas foram realizadas com rede de plâncton em quatro estações no lago e uma no rio Negro, situada próxima ao lago. Um total de 93 amostras foi analisado, coletadas em escala mensal no período de março de 2002 a outubro de 2003. As espécies foram descritas e ilustradas com base na sua morfologia e morfometria. Um total de 12 espécies foi identificado, sendo cinco do gênero Euastrum (E. evolutum var. perornatum; E. gemmatum var. monocyclum; E. ornans; E. sinuosum e E. spinulosum), e sete do gênero Micrasterias (M. borgei; M. radiata var. brasiliensis; M. torreyi; M. laticeps var. acuminata; M. mahabuleshwarensis var. amazonensis; M. rotata var. rotata; M. siolii). Todas as espécies, exceto M. radiata Hassal var. brasiliensis Grönblad, foram registradas no rio Negro, enquanto no lago Tupé foi registrado, no geral, apenas sete espécies, três de Euastrum e quatro de Micrasterias.
Although desmids (Zygnematophyceae) are widely distributed, their diversity in subaerial environments remains little known and explored. Subaerial algae live above the soil in a thin water film, directly exposed to the air. Desmids possess specific strategies to face environmental stress, such as mucilaginous sheaths that enable them to adhere to the substrate and protect the cells against desiccation. Also, zygospore production may be a strategy to survive. We conducted a taxonomic survey of the subaerial desmids in the Atlantic Forest biome (Rio de Janeiro city and other municipalities in the state of Rio de Janeiro). Briefly, we analyzed their strategies to resist sudden environmental changes, especially desiccation, a common condition in this environment. From 2006 through 2008, 100 samples were taken from natural and artificial vertical wet surfaces and tree bark. The material collected was identified based on morphological and metric characteristics of the vegetative and reproductive phases of the life cycle. We identified 57 species, varieties, and taxonomic formae, distributed in 12 genera, 2 orders, and 4 families. The study revealed that most subaerial algae were previously reported for Europe and North and South America. From the total taxa, 12% are reported for the first time for Brazil and 14% for South America. Even though subaerial environments are subject to stressful conditions, only three of the 57 taxa showed adaptive structures such as thick mucilage envelopes, spores, or zygospores.
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