Os gêneros Staurastrum, Staurodesmus e Xanthidium (Desmidiaceae, Zygnemaphyceae) da Lagoa do Caçó, Estado do Maranhão, Nordeste do Brasil

Abstract

-(The genera Staurastrum, Staurodesmus and Xanthidium (Desmidiaceae, Zygnemaphyceae) from Caçó Pond, Maranhão State, Norhteastern Brazil). This work is a contribution to the knowledge of Desmidiaceae biodiversity of Brazilian Northeastern region, poorly known in relation to its phycological flora. Collections were performed at eight sampling stations, following a transect on the longest lake axis during the rainy (April 1999) and dry (November 1999) seasons. The samples were concentrated in a 20 µm mesh net and preserved on 4% formalin solution. Analysis revealed that Desmidiaceae was the dominant group qualitatively. A total of 29 taxa were identified among the three genera, 18 belonging to Staurastrum, eight to Staurodesmus and three to Xanthidium. IntroduçãoAs desmídias constituem um grupo de algas muito importante quando considerada a riqueza e diversidade de espécies em inúmeros ambientes e habitats, bem como pela variedade de formas geométricas e padrões de decoração de parede (Brook

Is it possible to evaluate the ecological status of a reservoir using the phytoplankton community?

“…For the phytoplankton sampling, mesh net with 20 µm was used in horizontal trawls at the water surface (one point per zone), and fixed with formaldehyde (4%); and by direct collection in the photic zone, fixed with 1% acetic lugol, the material was subsequently identified according to current works (Sant'anna et al, 2006;Biolo et al, 2008;Dellamano-Oliveira et al, 2008;Menezes et al, 2011;Nogueira et al, 2011;Ramos et al, 2012;Rosini et al, 2013;Aquino et al, 2014;Souza & Felisberto, 2014;Alves-da-Silva & Klein, 2015), and counted according to Utermöhl (1958) methodology, in sedimentation chambers (Lund et al, 1958) and inverted microscope Zeiss (Axiovert 40C). The density of the phytoplankton community (cel.L -1 ) was obtained from the count of the organisms in relation to the area of the used sample container (INAG, I.P., 2009), following the Equation 1.…”