Coscinodiscophyceae and Fragilariophyceae (Diatomeae) in the Iguaçu River, Paraná, Brazil
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Acta Botanica Brasilica 28(1): 127-140. 2014. Coscinodiscophyceae and Fragilariophyceae (Diatomeae) in the Iguaçu River, Paraná, Brazil Margaret Seghetto Nardelli1,4, Norma Catarina Bueno1, Thelma Alvim Veiga Ludwig2, Priscila Izabel Tremarin2 and Elaine Cristina Rodrigues Bartozek3 Received: 20 October, 2012. Accepted: 28 November, 2013 ABSTRACT A taxonomic survey was carried out on Coscinodiscophyceae and Fragilariophyceae found in the Iguaçu River ca- tchment area within Iguaçu National Park, in the state of Paraná, Brazil. Between September 2007 and August 2008, we collected 24 samples from two stations on the Iguaçu River, upstream and downstream of the falls. We identified 37 taxa, including 22 specific and infraspecific taxa of Coscinodiscophyceae, together with 15 specific and infraspe- cific taxa of Fragilariophyceae. Melosira ruttneri Hustedt and Fragilaria alpestris Krasske ex Hustedt represent new records for Brazil. Key words: diatoms, lotic systems, southern Brazil, taxonomy Introduction Caxias hydroelectric power plant, both identifying centric diatoms. Similar studies were conducted by Tremarin et al. Diatoms are algae with siliceous cell walls that are fairly (2009a), in the Maurício River, and by Santos et al. (2011), well-represented in aquatic systems, in terms of richness as in the Salto Amazonas River and in an artificial lake in the well as abundance (Hoek et al. 1995). The identification of municipality of General Carneiro. Other studies of diatoms these organisms is complex (Stoermer & Smol 1999) be- in the Iguaçu River were performed by Brassac & Ludwig cause of variations in the form and frustule ornamentation. (2003; 2005; 2006), Ludwig et al. (2008) and by Bartozek In water quality studies, diatoms are excellent bioindicators et al. (2013). At Iguaçu Falls, Metzeltin & Lange-Bertalot (Round 1991; Descy & Ector 1999), mainly because of their (1998; 2007) identified 45 taxa, of which only six were short life cycle and their selective sensitivity to certain centric and none were araphid. limnological conditions, making them respond promptly The aim of this study was to inventory the species and to environmental changes (Lobo et al. 2002; Stevenson & taxonomic varieties of the classes Coscinodiscophyceae and Smol 2003). Fragilariophyceae in the Iguaçu River, within the catchment Taxonomic studies are of extreme importance for ex- area of Iguaçu National Park, thereby expanding the knowl- panding knowledge on the biodiversity of diatoms (Lobo edge on the flora of the diatoms of the state of Paraná and et al. 2002). They enable the proposal of indices that providing support for future studies on this community of might express the ecological significance of the complex rheophilic species in freshwater environments. relationships among species in the environments studied (Senna & Magrin 1999; Dinnerstein et al. 1995).Floristic surveys of diatoms in the watershed of the Iguaçu River Material and methods started with Moreira-Filho et al. (1973), Contin (1990) and Lozovei & Shirata (1990), in a stretch of the river near Iguaçu National Park, which comprises approximately the municipality of Curitiba. Subsequently, other studies of 169765.00 ha, is the largest protected area within the Atlan- diatoms were conducted along the watershed. Ludwig & tic Forest biome of Brazil. The area has a humid temperate Flôres (1995; 1997) conducted studies in rivers within the climate (Ibama 1999); the average annual rainfall in the catchment area of the Segredo hydroelectric power plant, Iguaçu River watershed is approximately 1500 mm/year; and Brassac et al. (1999) studied the area around the Salto and the rainfall distribution is fairly irregular in time and 1 Universidade Estadual do Oeste do Paraná, Programa de Pós-Graduação em Conservação e Manejo de Recursos Naturais, Cascavel, PR, Brazil 2 Universidade Federal do Paraná, Setor de Ciências Biológicas, Centro Politécnico, Curitiba, PR, Brazil 3 Universidade Estadual do Oeste do Paraná, Programa de Pós-Graduação em Recursos Pesqueiros e Engenharia de Pesca, Toledo, PR, Brazil 4 Author for correspondence: [email protected] Margaret Seghetto Nardelli, Norma Catarina Bueno, Th elma Alvim Veiga Ludwig, Priscila Izabel Tremarin and Elaine Cristina Rodrigues Bartozek space, without a well-defined wet period (Lactec 2005). The were prepared using Naphrax® as mountant (refractive index mean annual temperature is 26 °C, monthly averages rang- = 1.73; Brunel Microscopes Ltd., Chippenham, UK). The ing from 3 °C to 40 °C (Salamuni et al. 2002). analysis of the permanent slides was performed with an The Iguaçu River watershed, located at the southern Olympus BX60 optical microscope coupled to an Olympus portion of the state of Paraná, is the largest drainage basin in DP71 microscope digital camera (Olympus, Tokyo, Japan). the state and extends into the state of Santa Catarina as well The systematic classification and the terminology followed as into some areas of Argentina (Maack 2002). The river is Round et al. (1990) and Houk & Klee (2004). 2 1275 km in length, and its drainage area covers 70800 km For all of the taxa identified, we quantified morphometric and flowing in an east-west direction from the source at the and meristic characters — apical axis (AA); transapical axis Serra do Mar mountain range to the mouth in the Paraná (TA); pervalvar axis (PA); mantle height (MH); diameter River (Paraná 2010). (D); striae (S); areolae (A) and fultoportulae (F) — providing Two sampling stations were selected, in the backwater, descriptions and including comments when relevant. on the right bank of the Iguaçu River, in the municipality Frequencies of the taxa were based on the observation of Foz do Iguaçu (Fig. 1): of samples in permanent slides and calculated with the -Station 1 (25°35’72”S, 54°23’63”W), located upstream following equation: of Iguaçu Falls, with a width of 869.89-1200.00 m, a flow rate of 0.424 m.s-1 and a depth ranging from 0.90 m to 4.62 m, depending on the season (Paraná 2010). F = (p × 100)/P -Station 2 (25°38’55”S, 54°27’27.5”W), located down- stream of Iguaçu Falls, with a width of 69.89 m, a flow rate where F is the frequency, p is the number of samples con- of 6.8 m s-1 and a depth ranging from 4.62 m to 27.00 m, taining the species and P is the total number of samples depending on the season (Paraná 2010). analyzed. The diatom taxa identified in the 24 samples A total of 24 samples were monthly collected between were classified into the following categories (Dajoz 2005): September 2007 and August 2008 from subsurface water at constant (F ≥ 70% in the samples), frequent (30% ≥ F ≤ both stations (Tab. 1). The samples were fixed with Tran- 69%), sporadic (10% ≥ F ≤ 29%) and occasional (F ≤ 9%). seau’s solution (Bicudo & Menezes 2006) and oxidized by The material was deposited in the Herbarium of the the technique proposed by Simonsen (1974) modified by Universidade Estadual do Oeste do Paraná (UNOP, Western Moreira-Filho & Valente-Moreira (1981). Microscope slides Paraná State University), Cascavel campus. Figure 1. Location of sampling stations 1 and 2, upstream and downstream of Iguaçu Falls, respectively. Iguaçu National Park, state of Paraná, Brazil. Source: Iguaçu National Park Geoprocessing Sector/Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio, Chico Mendes Institute for the Conservation of Biodiversity), 2011. 128 Acta bot. bras. 28(1): 127-140. 2014. Coscinodiscophyceae and Fragilariophyceae (Diatomeae) in the Iguaçu River, Paraná, Brazil Table 1. Collection dates, UNOP Herbarium accession number of the herbarium samples from stations 1 and 2, upstream and downstream of Iguaçu Falls, res- pectively and samples collectors. Iguaçu National Park, state of Paraná, Brazil. UNOP Herbarium accession number Collection date Collector(s) Station 1 Station 2 September 2007 2702 2703 F.A. Gurski s.n. October 2007 2704 2705 M.X. Silva s.n. November 2007 2706 2707 M.X. Silva s.n. December 2007 2708 2709 M.X. Silva s.n. January 2008 2710 2711 M.X. Silva s.n. February 2008 2712 2713 F.A. Gurski s.n., M.X. Silva s.n. March 2008 2714 2715 F.A. Gurski s.n., M.X. Silva s.n. April 2008 2716 2717 F.A. Gurski s.n., M.X. Silva s.n. May 2008 2726 2727 F.A. Gurski s.n., M.X. Silva s.n. June 2008 2728 2729 F.A. Gurski s.n., M.X. Silva s.n. July 2008 2730 2731 F.A. Gurski s.n., M.X. Silva s.n. August 2008 2799 2800 F.A. Gurski s.n. UNOP – Universidade Estadual do Oeste do Paraná (Western Paraná State University). Results and discussion Valves circular, with concentric central area surrounded by radial striae in the shape of a rosette and marginal striae In the taxonomic evaluation, 37 taxa were identified. of equal length. D: 9.3-23.8 μm; S: 11-16 in 10 μm. Constant Of those, 22 belonged to the class Coscinodiscophyceae, taxon, occurring in 70.7% of the samples. within seven families and nine genera, with one taxon The population studied coincided with those described identified down to the genus level, 17 identified down to and illustrated by Contin (1990), Krammer & Lange-Ber- the species level, four identified down to the level of variety talot (1991), Brassac et al. (1999) and Guerrero & Echenique and two identified as non-typical taxonomic forms. In the (2006). The smaller dimensions shown by Contin (1990, D: class Fragilariophyceae, we identified 15 taxa, within one 8.60-12.35 μm) and Bertolli et al. (2010, D: 7.11-13.43 μm) family and four genera, with one taxon identified down to were not observed in the specimens of this study. the genus level, 13 taxa identified down to the species level Occurrence in samples: UNOP 2702, 2703, 2704, 2705, and two taxa identified as non-typical taxonomic forms.