Revista Brasil. Bot., V.30, n.3, p.433-450, jul.-set. 2007 Phytoplankton flora of two rivers in Southeast Brazil – Paraibuna and Pomba Rivers, Minas Gerais MARIA CAROLINA S. SOARES1,2, MARIA DA GRAÇA SOPHIA1 and VERA L. DE M. HUSZAR1 (received: May 5, 2005; accepted: July 19, 2007) ABSTRACT – (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 Introduction 1964, 1969, Scott et al. 1965, Thomasson 1971). Most of the taxonomic studies of river phytoplankton in Brazil River phytoplankton has never received the same are concentrated in the southern states. The diatom flora attention from phycologists or ecologists as phytoplankton from rivers in Rio Grande do Sul State was described from lakes (Reynolds & Descy 1996). According to by Corte-Real & Aguiar (1972), Martau et al. (1977), Reynolds et al. (1994), the occurrence of phytoplankton Torgan & Aguiar (1978), Buselato & Aguiar (1979), in rivers is highly influenced by turbulence and low light Laudares-Silva (1987), Lobo & Torgan (1988), Callegaro intensity, which produces high richness of diatoms and et al. (1993) and Lobo et al. (1996). In Santa Catarina green algae in rivers worldwide. In tropical rivers, where State by Rodrigues (1982, 1992) and Rodrigues & Moreira the variability of species is greater than in temperate rivers, Filho (1990). In Paraná State Bittencourt-Oliveira (2002) desmids is another important group of phytoplankton described the phytoplankton community of River Tibagi. (Rojo et al. 1994). In the same state Contin (1990), Ludwig & Flôres (1995, Potamoplankton also attracts scarce attention in Brazil. 1997), Brassac et al. (1999), Brassac & Ludwig (2003), Despite the extensive Brazilian hydrographic system, Brassac & Ludwig (2005) and Landucci & Ludwig (2005) the number of studies on phytoplankton community carried out a survey of diatoms of various rivers. In the structure in lotic systems is much smaller than in lentic Southeast, Bicudo et al. (1992) and Bicudo et al. (1993) ones. In Brazil, pioneer studies were carried out in the studied phytoplankton and diatoms, respectively, in Amazonian region rivers, such as Negro River, Tapajós Paranapanema River in a region to be dammed by Rosana River and Madeira River (Dickie 1881, Förster 1963, Hydroelectric Power Plant. Necchi Júnior & Pascolato (1993), Necchi Júnior et al. (1994), Necchi Júnior & Moreira (1995), Branco & Necchi Júnior (1996, 1998), Branco 1. Universidade Federal do Rio de Janeiro, Museu Nacional, Horto et al. (1999) and Necchi Júnior et al. (2000) provided Botânico, Laboratório de Ficologia, Quinta da Boa Vista, São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brasil. information of macroalgae distribution and composition 2. Corresponding author: [email protected] in São Paulo State. The taxonomic studies in Minas Gerais 434 M. C. S. Soares et al.: Phytoplankton of two Brazilian rivers State are scarce, even for lakes and reservoirs. Nordstedt average precipitation from 1,200 to 1,600 mm and annual (1870, 1877, 1878), Warming (1892), Wille (1884), Bicudo average temperature between 17.4 °C and 24.7 °C. The & Ventrice (1968), Bicudo (1969), Sormus (1991, 1993, Paraibuna River is 176 km in length, with a 6,859 km2 basin 1996) and Oliveira (2001) described desmids from different and flows into Paraíba do Sul River. Thirty-three kilometers environments, while Eterovick & Giani (1997) and Giani away from the source, the river is dammed, to form the Chapéu D’Uvas Reservoir, with a surface area of 12 km2, volume of 146 et al. (1999) surveyed the phytoplankton of the Pampulha million cubic meters and maximum depth of 41 m. According Reservoir. Other taxonomic works include a study of the to historical average values, the Paraibuna River flow is green algae from a pool located at the “Universidade greatest in its lower stretches, where the gradient is steepest. Federal de Viçosa” (Lovo 1997), a work on diatoms from The greatest flow rates occur during the months of January “Universidade Federal de Juiz de Fora” lake (Costa & and February. The Pomba River runs for 265 km and flows Torgan 1991) and another survey on diatoms from Salto into the Paraíba do Sul River. Its catchments area is 8,735 km2 River, in “Parque Nacional do Ibitipoca” (Canani 2005). and the historical average flow rate is 130 m3 s-1 (Torres 1992). The objective of this work is to improve the scarce The study of phytoplankton community was based on knowledge of lotic phytoplankton, especially for Minas 32 samples collected at nine and seven stations in Paraibuna Gerais State, describing the flora of the Paraibuna and and Pomba Rivers, respectively, during dry (July, August, 2001) and rainy seasons (February, 2002) (table 1). Samples Pomba Rivers. were collected by filling bottles directly in the water and fixed in acetic Lugol´s solution in 0.05% or with a 25 µm mesh net Material and methods and fixed with Transeau’s solution. For diatoms study, slides were prepared according to Van Stoch (1970) using Naphrax. The Paraibuna and Pomba Rivers are the main tributaries Samples were deposited at the Herbarium of the “Departamento of Paraíba do Sul River in Minas Gerais (figure 1). The climate de Botânica”, “Museu Nacional”, “Universidade Federal do is moderate wet subtropical (Cwa, Köppen), with annual Rio de Janeiro” (R). N Minas Gerais Espírito Pomba River Santo Paraibuna Minas Gerais River Paraíba do Sul River Espírito Rio de Santo Janeiro 0 100 km Pomba River Paraibuna River Paraíba do Sul River Rio de N Janeiro 0 100 km Figure 1. Map of Pomba and Paraibuna Rivers catchments showing the sample sites. Revista Brasil. Bot., V.30, n.3, p.433-450, jul.-set. 2007 435 Table 1. Geographic coordinates (GC) of sampling sites (SS) in Paraibuna and Pomba Rivers and its herbarium number (R). PARAIBUNA RIVER POMBA RIVER GC SS Date/R GC SS Date/R 21°30’14” S 1. Dores do Paraibuna 2-VII-01/205584 21°16’05,9” S 1. Santa Bárbara 16-VIII-01/205567 43°38’27” W 23-II-02/205593 43°38’04,3” W do Tugúrio I 24-II-02/205574 21°35’16,9” S 2. Chapéu D’Uvas 2-VII-01/205585 21°14’58,2” S 2. Santa Bárbara 16-VIII-01/205568 43°33’20,9” W Reservoir, Juiz de Fora 23-II-02/205594 43°34’03,9” W do Tugúrio II 24-II-02/205575 21°35’26,8” S 3. Chapéu D’Uvas, 2-VII-01/205586 2°14’04,1” S 3. Mercês 16-VIII-01/205569 43°30’36,4” W Juiz de Fora 23-II-02/205595 43°19’06,2” W 24-II-02/205576 21°38’44,3” S 4. Barreira, Juiz de Fora 2-VII-01/205587 21°16’51,4” S 4. Rio Pomba 16-VIII-01/205570 43°26’14,6” W 23-II-02/205596 43°10’33,4” W 24-II-02/205577 21°41’27,8” S 5. Distrito Industrial, 2-VII-01/205588 21°18’54,4” S 5. Astolfo Dutra 16-VIII-01/205571 43°25’38,4” W Juiz de Fora 23-II-02/205597 42°51’41,8” W 24-II-02/205578 21°43’54,2” S 6. Milho Branco, 2-VII-01/205589 21°23’32,1” S 6. Cataguases 16-VIII-01/205572 43°23’19,7” W Juiz de Fora 23-II-02/205598 42°41’35,7” W 24-II-02/205579 21°45’32,9” S 7. Halfeld, Juiz de Fora 2-VII-01/205590 21°23’35,3” S 7. Laranjal 16-VIII-01/205573 43°20’31,1” W 23-II-02/205599 42°29’25,0” W 24-II-02/205580 21°47’15,1” S 8. Marmelos I, 2-VII-01/205591 21°27’27,2” S 43°18’14,4” W Juiz de Fora 23-II-02/205600 42°21’01,0” W 21°54’53,3” S 9. Cotegipe 2-VII-01/205592 43°20’41,6” W 23-II-02/205601 The taxonomic classification for division and classes desmids were the main groups in Pomba River (figure 2).