RESUMO
Biovolume calculation of micro algae is commonly used for the assessment in relative abundance (as biomass or carbon) of coexistent algae that vary in shape and/or size. Periphyton samples were obtained within a more general program, in fishery tanks and streams situated in the upper basin region of Tibagi River, nearby Londrina, Paraná state, south of Brazil. The present work proposes new algorithms for the determination of algal species volume. Results showed that Gyrosigma scalproides (Rabenhorst) Cleve 1894 and Tetraedron gracile (Reinsch) Hansgirg 1889 were exceptions inside their genus and the present new formula for biovolume and area gives more adequate results. In addition, new formulas applied for Phacus longicauda (Ehrenberg) Dujardin 1841 and Kirchneriella lunaris (Kirchner) Möbius 1894 also showed much more accurate results than in the previous works. The difference in the calculations of biovolume between the present method and others was not small and could not be neglected.