Tuesday, May 27, 2008
196

Epilithic diatoms of the Itajaí Mirim river in southern Brazil: A contribution to the development of bioassessment protocols in Neotropical lotic systems

Ana Luiza Burliga1, Antonio Carlos Beaumord1, Eleonora Appel Nobrega1, Carolina Sutil1, Lezilda Carvalho Torgan2, and Roselane Laudares Silva3. (1) Laboratório de Estudos de Impactos Ambientais, Universidade do Vale do Itajaí, Itajaí, SC, 88302-202, Brazil, (2) Museu de Ciências Naturais, Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre, RS, 90690-000, Brazil, (3) Departamento de Botânica, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040-900, Brazil

The Itajaí Mirim River has been used as natural laboratory for the development of protocols to assess the environmental integrity of coastal rivers in Neotropical regions. This watershed has been thoroughly studied regarding land uses, vegetation cover, water quality, flow regime, and biological communities. Surveys were conducted from May 2004 to May 2006 at six sampling sites encompassing pristine, both moderate and relatively disturbed by agriculture and urbanized areas. The sampling procedure for epilithic diatoms entailed collecting twelve stones about the same size in approximately 0.5 m depth. The upper surface of each stone was brushed yielding composite samples for each site. The cleaned diatoms were mounted in Naphrax. Approximately 400 valves per sample were identified and counted, using phase contrast light microscope (1000x). Eighty-five species were identified from forty-eight samples. The most abundant species at disturbed sites were Hydrosera whampoensis, Luticola goeppertiana Pinnularia mesolepta, Gomphonema truncatum, Gyrosigma acuminatum, Mayamea atomus and the most abundant species at pristine sites were Pleurosira laevis, Encyonema mesianum, Gomphonema subclavatum, Encyonema silesiacum, Encyonema perpusillum, Encyonema minutum, Planothidium lanceolatum, Cymbella tumida, Diadesmis contenta. This study revealed consistent correlations between the biological indices and environmental conditions.


Web Page: Periphyton, Diatoms, Coastal Rivers

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