Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tdia20 Diatom Research ISSN: 0269-249X (Print) 2159-8347 (Online) Journal homepage: https://www.tandfonline.com/loi/tdia20 Ecology and distribution of Aulacoseira species (Bacillariophyta) in tropical reservoirs from Brazil Denise C. Bicudo, Priscila I. Tremarin, Pryscilla D. Almeida, Stéfano Zorzal- Almeida, Simone Wengrat, Samantha B. Faustino, Lívia F. Costa, Elaine C.R. Bartozek, Angélica C.R. Rocha, Carlos E.M. Bicudo & Eduardo A. Morales To cite this article: Denise C. Bicudo, Priscila I. Tremarin, Pryscilla D. Almeida, Stéfano Zorzal- Almeida, Simone Wengrat, Samantha B. Faustino, Lívia F. Costa, Elaine C.R. Bartozek, Angélica C.R. Rocha, Carlos E.M. Bicudo & Eduardo A. Morales (2016) Ecology and distribution of Aulacoseira species (Bacillariophyta) in tropical reservoirs from Brazil, Diatom Research, 31:3, 199-215, DOI: 10.1080/0269249X.2016.1227376 To link to this article: https://doi.org/10.1080/0269249X.2016.1227376 Published online: 16 Sep 2016. Submit your article to this journal Article views: 330 View Crossmark data Citing articles: 19 View citing articles https://www.tandfonline.com/action/journalInformation?journalCode=tdia20 https://www.tandfonline.com/loi/tdia20 https://www.tandfonline.com/action/showCitFormats?doi=10.1080/0269249X.2016.1227376 https://doi.org/10.1080/0269249X.2016.1227376 https://www.tandfonline.com/action/authorSubmission?journalCode=tdia20&show=instructions https://www.tandfonline.com/action/authorSubmission?journalCode=tdia20&show=instructions http://crossmark.crossref.org/dialog/?doi=10.1080/0269249X.2016.1227376&domain=pdf&date_stamp=2016-09-16 http://crossmark.crossref.org/dialog/?doi=10.1080/0269249X.2016.1227376&domain=pdf&date_stamp=2016-09-16 https://www.tandfonline.com/doi/citedby/10.1080/0269249X.2016.1227376#tabModule https://www.tandfonline.com/doi/citedby/10.1080/0269249X.2016.1227376#tabModule Diatom Research, 2016 Vol. 31, No. 3, 199–215, http://dx.doi.org/10.1080/0269249X.2016.1227376 Ecology and distribution of Aulacoseira species (Bacillariophyta) in tropical reservoirs from Brazil DENISE C. BICUDO1∗, PRISCILA I. TREMARIN2, PRYSCILLA D. ALMEIDA1, STÉFANO ZORZAL- ALMEIDA1, SIMONE WENGRAT1, SAMANTHA B. FAUSTINO1, LÍVIA F. COSTA1, ELAINE C.R. BARTOZEK1,3, ANGÉLICA C.R. ROCHA1, CARLOS E.M. BICUDO1 & EDUARDO A. MORALES4 1Department of Ecology, Instituto de Botânica de São Paulo, Av. Miguel Stefano 3687, 04301-902 São Paulo, SP, Brazil 2Department of Botany, Universidade Federal do Paraná, Caixa Postal 19031, 81531-990 Curitiba, Paraná, Brazil 3Universidade Estadual Paulista – UNESP, Campus de Rio Claro, SP. Av. 24A, 1515, 13506-900 Rio Claro, SP, Brazil 4Herbario Criptogámico, Universidad Católica Boliviana San Pablo, Calle M. Márquez esq. Plaza Jorge Trigo s/n, P.O. Box 5381, Cochabamba, Bolivia Ecological preferences and distribution of Aulacoseira species in southeastern Brazilian reservoirs with varying trophic states were studied. One hundred and fourteen plankton samples (winter and summer) from 57 sites located in 16 reservoirs were analysed. Ten water quality parameters were measured. Ten Aulacoseira species were identified using light, scanning and transmission electron microscopy, and new information on their ecological preferences is provided here. Our results indicate that trophic gradient is the main driver of species distribution. Principal components analysis and calculation of weighted average nutrient optima revealed three indicator taxa, Aulacoseira tenella characteristic for oligotrophic waters and two varieties of Aulacoseira granulata (nominate and var. angustissima) typical for eutrophic reservoirs. This is the first ecological study of Aulacoseira in Brazil, adding information on the distribution of this genus in the tropics, and highlighting the need for species-level identification and regional studies to improve the use of diatoms in water quality assessment. Keywords: autecology, bioindication, centric diatoms, South America, taxonomy, weighted average Introduction Aulacoseira Thwaites is a widespread genus inhabiting lacustrine and lotic freshwaters, where it is an impor- tant component of the phytoplankton developing in var- ious trophic conditions (Denys et al. 2003). Based on a review of the literature, Edgar & Theriot (2004) reported approximately 60 species. Although Aulacoseira species have been widely stud- ied, mainly in temperate regions (e.g., Krammer & Lange- Bertalot 1991, Siver & Kling 1997, Houk 2003, Houk & Klee 2007, Potapova et al. 2008, Tuji 2010), the genus remains poorly known in South America. Only Oliveira & Steinitz-Kannan (1992), Sala et al. (1999, 2002, 2008), Metzeltin & Lange-Bertalot (2007), Tremarin et al. (2011, 2012, 2013a, b, 2014a, b), Dunck et al. (2012), Wet- zel et al. (2014) and Morales et al. (2015) include some considerations of selected species occurring in tropical South America. In Brazil, 25 species have been reported (Tremarin et al. 2014a, b), 8 of which were originally described from Brazilian material (Hustedt 1965, Tremarin *Corresponding author. E-mail: denisecbicudo@gmail.com (Received 28 January 2016; accepted 26 June 2016) et al. 2012, 2013a, 2014a, b). Most taxa were recorded in floristic studies based on light microscopy (LM), with- out a more detailed analysis of the frustule (e.g., Silva et al. 2010, Nardelli et al. 2014, Faustino et al. 2016). In ecological studies, frequently reported taxa correspond to widely distributed ones, such as those in the Aulacoseira granulata (Ehrenberg) Simonsen species complex and A. ambigua (Grunow) Simonsen (e.g., Nogueira 2000, Raupp et al. 2009, Costa-Böddeker et al. 2012). Autecological information for Aulacoseira is frag- mented and very scarce worldwide, particularly for tropical and subtropical regions. In Brazil, a few ecological aspects of Aulacoseira italica (Ehrenberg) Simonsen were investi- gated by Nakamoto et al. (1976), Lima et al. (1979, 1983) and Marins (1978), and the tolerance of A. granulata to copper sulphate, an algicide used to control cyanobac- terial blooms, was demonstrated in an ecotoxicological study (Viana & Rocha 2005). Nevertheless, the study of ecological preferences and distributions, based on sound taxonomy, is critical for the successful use of diatoms in © 2016 The International Society for Diatom Research Published online 16 Sep 2016 mailto:denisecbicudo@gmail.com 200 Bicudo et al. water quality bioassessment (Ponader et al. 2007). This is particularly relevant in the context of the growing threats to freshwater ecosystems by human impact (Dundgeon et al. 2006, Smith et al. 2006). This study uses a large tropical reservoir dataset cov- ering a wide range of trophic states to calculate optima for Aulacoseira taxa. The goal is to describe the diver- sity of species of Aulacoseira in southeastern Brazil and to improve understanding of their ecology and distribution patterns. Material and methods The study includes three drainage basins in the State of São Paulo, southeastern Brazil (Fig. 1), and is part of a larger research effort, the AcquaSed Project. This project aims to establish baseline conditions and to reconstruct the anthropogenic impact history in the Guarapiranga Reser- voir, focusing on the ecological quality of the water supply reservoirs of the Alto Tietê and surrounding basins, and to enhance the use of diatoms as bioindicators in tropical reservoirs. The climate is tropical, dry in winter and rainy during summer, the average temperature for the hottest month is above 22°C, and for the coldest month is below 18°C (CEPAGRI 2015). The drainage basins include pro- tected and highly urbanized reservoirs encompassing a large gradient of trophic states (from oligo- to hyper- eutrophic conditions). This study was conducted on 16 reservoirs with different uses (recreational, electricity gen- eration, navigation and public water supply), ranging from shallow to deep (maximum depth from 2 up to 33 m) and from small to large (surface area from 0.2 to 241.3 km²). One to eight sampling sites per reservoir were chosen, con- sidering maximum depth, size and main water inputs (main streams). The sampling sites are located between 22.5°–24.3°S and 45.7°–48.5°W. In total, 57 sites were sampled dur- ing austral winter and summer, from 2009 to 2014 (114 samples). Integrated plankton samples were collected with a van Dorn sampler along vertical profiles (subsurface, mid-depth, and 1 m above the sediments). Temperature, pH and conductivity were measured in the field using standard electrodes (Horiba U50). Water chemistry mea- surements were conducted following American Public Health Association protocols (APHA 2005). Water sam- ples filtered through Whatman GF/F membrane filters were used for measuring, ammonium (N–NH4), nitrate (N−NO− 3 ), nitrite (N−NO− 2 ), soluble reactive phosphorus Fig. 1. Map of the study area with the locations of the 16 sampled reservoirs. Aulacoseira species from tropical reservoirs 201 Table 1. Summary of water quality data for the 57 studied sites (water column mean). Summer Winter Mean Maximum Minimum Mean Maximum Minimum Temperature (°C) 24.8 28.9 19.8 17.9 21.8 12.5 pH 6.7 8.5 5.3 6.8 8.7 5.1 Conductivity (μS cm−1) 93.6 383.0 10.4 137.5 487.7 10.4 Alkalinity (mEq L−1) 0.482 1.546 0.051 0.527 1.861 0.051 TN (μg L−1) 1415.7 10652.1 88.5 1373.2 9767.0 178.1 DIN (μg L−1) 654.2 5386.2 13.0 840.6 7728.1 23.0 TP (μg L−1) 58.2 381.3 4.0 55.9 502.9 4.0 SRP (μg L−1) 18.9 163.6 2.6 26.4 446.0 4.0 SRS (mg L−1) 2.8 6.5 1.1 2.7 6.2 0.6 Chlorophyll a (μg L−1) 20.6 149.9 0.5 22.1 175.9 0.5 Note: TN: total nitrogen, TP: total phosphorus, DIN: dissolved inorganic nitrogen, SRP: soluble reactive phosphorus, SRS: soluble reactive silica. (P–PO4), and soluble reactive silica (SRS). Dissolved inorganic nitrogen (DIN) was calculated as the sum of ammonium, nitrate and nitrite. Unfiltered samples were used for alkalinity, total nitrogen (TN) and total phos- phorus (TP) determinations. Chlorophyll a, corrected for phaeophytin, was measured using 90% ethanol extrac- tion (Sartory & Grobbelaar 1984). A summary of data for the selected water quality variables is shown in Table 1. For diatom analyses, samples were digested accord- ing to standard procedures (Battarbee et al. 2001) using 35% by volume H2O2 and 37% HCl. Slides were mounted with NAPHRAX, and LM observations, measurements and micrographs were obtained using a Zeiss Axioskop 2 plus, equipped with a DC500 high-resolution digital camera, under 1000 × magnification. Subsamples were cleaned using the method of Hasle & Fryxell (1970), dried on aluminium stubs and coated with gold at 1 kV for 5 min in a Balzers SCD030 sputter coater. Scanning elec- tron microscope (SEM) observations were performed with a JEOL JSM 6360LV operated at 15 kV and 8 mm work- ing distance. Subsamples were also dried on grids (300 mesh) for TEM observations with a JEOL JEM 1200EX- II operated at 80 kV. At least 400 valves were counted per slide at 1000 × magnification. Samples were deposited at the ‘Herbário Científico do Estado Maria Eneyda P. Kauffmann Fidalgo’, São Paulo, Brazil. Species abundances were expressed as a percentage of the total diatom counts in each sample. Optima for temperature, pH, conductivity, alkalinity, soluble reactive phosphorus, DIN, TP and TN were calculated as weighted average values (ter Braak & van Dam 1989) based on species relative abundances. We analysed the distribution of Aulacoseira species with principal components analysis (PCA) followed by environmental factor fitting, which projects passive envi- ronmental variables (chlorophyll a, conductivity, pH, TN, TP and water temperature) onto the PCA diagram with- out any constraints, allowing post hoc interpretation of ordination axes (Bocard et al. 2011). The environmental variables (except pH) were log-transformed (log x + 1) and species abundances were Hellinger-transformed in order to approximate more closely the linear relation- ship assumed by PCA (Legendre & Gallagher 2001). For this analysis, we considered species with relative abun- dance equal to or greater than 5%. Diatom names were coded according to the OMNIDIA software (Lecointe et al. 1993). All analyses were performed using R version 3.1.3 (R Core Team 2015) and the ‘vegan’ package (Oksanen et al. 2013). Results and discussion Morphometric data for the studied Aulacoseira species are presented in Table 2. Figure 2 shows the relative abun- dances of the Aulacoseira species (described below) in relation to water temperature, pH, conductivity and alkalin- ity ranges. Figure 3 shows relative abundances of the taxa in relation to soluble reactive phosphorus (P–PO4), DIN, TP and TN concentrations. Weighted average optima are shown for each taxon and each environmental variable. Aulacoseira ambigua (Grunow) Simonsen (Figs 4–11) Morphology: Aulacoseira ambigua differs from other Aulacoseira species by the presence of a hollow and nar- row ringleist in the valve mantle. Besides this character- istic, the species is characterized by forming long chains (observed in non-oxidized material) in which frustules are linked by many small spines, obliquely curved striae on the mantle and a narrow ringleist (Tremarin et al. 2013a). Ecology and distribution: This is a cosmopolitan species, commonly found in lotic and lentic environments from different regions of Brazil (Tremarin et al. 2013a) and the world (Guiry & Guiry 2014). It is found in oligotrophic to eutrophic waters (van Dam et al. 1994, Stenger-Kovacs et al. 2007), but prefers nutrient-rich waters (Houk 2003, Taylor et al. 2007). This species is also reported during 202 Bicudo et al. Table 2. Frequency of occurrence, abundance (%) and morphometric data for studied Aulacoseira species. Taxa Occurrence (%) Maximum abundance Mean abundance D (μm) MH (μm) Ratio (MH/D) Striae (in 10 μm) Areolae (in 10 μm) A. ambigua 77.2 67.7 7.0 3.7–11.1 5.6–13.1 0.6–2.7 14–20 14–18 A. brasiliensis 16.7 12.9 0.8 14.0–16.0 4.0–5.0 0.2–0.3 13–16 16–20 A. calypsi 7.9 16.4 0.6 8.4–12.0 3.1–6.1 0.3–0.6 14–26 16–18 A. granulata var. angustissima 45.6 61.1 3.4 2.1–5.1 6.0–18.5 1.5–7.3 12–16 10–15 A. granulata var. australiensis 41.2 11.9 1.3 4.3–19.3 8.5–23.1 0.6–2.7 8–18 7–13 A. granulata var. granulata 93.0 79.2 13.1 5.0–18.1 7.8–22.5 0.6–4.2 8–14 7–13 A. herzogii 15.8 23.3 0.8 5.0–12.0 6.0–30.0 0.9–5.8 24–27 Inconsp. A. laevissimaa – – – 3.5–8.9 2.0–3.7 0.3–0.9 24–28 Inconsp. A. pusillaa – – – 4.0–6.9 1.8–2.7 0.7–4.0 20–24 Inconsp. A. tenella 81.6 80.5 11.8 4.6–6.6 1.1–2.2 0.2–0.4 20–28 2–3 Note: D: valve diameter, MH: mantle height. aVery scarce taxa, observed in qualitative analysis. water mixing and low light conditions (Houk 2003, Taylor et al. 2007). In our data set, it was the third most frequent species, achieving high maximum abundances (Table 2). It was more abundant in colder (winter), slightly acid (Fig. 2) and, contrary to reports in the literature (Houk 2003, Taylor et al. 2007), in mesotrophic waters (Fig. 3). This species usually co-occurred at lower abundances with the nominate variety of A. granulata var. granulata, which had a preference for eutrophic waters (Fig. 3). Aulacoseira brasiliensis Tremarin, Torgan et Ludwig (Figs 12–21) Morphology: The population of A. brasiliensis resem- bles type material of the species (Tremarin et al. 2012). The obovate marginal spines and the double row of ses- sile rimoportulae in the mantle differentiate A. brasiliensis from other morphologically similar taxa, such as Aula- coseira muzzanensis (Meister) Krammer and Aulacoseira agassizii (Ostenfeld) Simonsen (Tremarin et al. 2012). This diatom forms short chains with frustules linked by several ovate-attenuate spines, and has a shallow man- tle, undeveloped ringleist, and completely areolated valve face and mantle with straight rows of conspicuous areo- lae. Connection valves have not been described for this taxon. Ecology and distribution: Thus far, this species has only been reported from tropical and subtropical regions of Brazil (Tremarin et al. 2012). Tremarin et al. (2012) reported it from warm (21.3–29.9°C), slightly acidic to neutral pH, and low conductivity (6.3–26 µS cm−1) waters. Aulacoseira brasiliensis in our mate- rial was rare and always at relatively low abundance (Table 2). Sometimes it co-occurred with Aulacoseira tenella (Nygaard) Simonsen, but always at lower abun- dances. Aulacoseira brasiliensis was mainly found in colder, oligotrophic, low conductivity and slightly acidic waters (Figs 2–3), corroborating literature reports for this species. Aulacoseira calypsi Tremarin, Torgan et Ludwig (Figs 22–33) Morphology: This taxon resembles A. brasiliensis in its mantle striation pattern, but differs in spine morphology, distribution of areolae on the valve face and position of the rimoportulae (Tremarin et al. 2013b). It is character- ized by long filaments, spathulate linking spines, obovate to conic separation spines, a variably ornamented valve face, straight striae on the mantle and a narrow ringleist (Tremarin et al. 2013b). The sessile rimoportulae, arranged in an irregular ring near the ringleist are diagnostic for this species. Ecology and distribution: This species was described from a meso-eutrophic lake with high water temperature (30.8°C) and neutral pH in the State of Pará, north- ern Brazil (Tremarin et al. 2013b); this is the second report of the taxon. In our study, it was the least abun- dant and frequent species (Table 2), occurring in oligo to mesotrophic waters, rarely in hypereutrophic conditions, and at relatively low water temperatures (Figs 2–3). It prefers mesotrophic, slightly acidic and low conductivity waters. This taxon co-occurred with Aulacoseira herzogii (Lemmermann) Simonsen, which has similar ecological preferences. Aulacoseira granulata (Ehrenberg) Simonsen var. granulata (Figs 34–37) Morphology: This taxon differs from other species in the genus by the presence of one or two long separation spines, a coarsely ornamented mantle with rounded to square areolae, and a narrow ringleist. Ecology and distribution: This taxon has a worldwide distribution (Guiry & Guiry 2014) and occurs in a wide range of trophic conditions, but is mostly associated with eutrophic waters (Taylor et al. 2007, Zalat & Vildary 2007, Kiss et al. 2012). It is also associated with water column mixing (Zalat & Vildary 2007), high flood conditions and erosion events, regardless of trophic state (Costa-Böddeker Aulacoseira species from tropical reservoirs 203 Fig. 2. Relative abundances of eight Aulacoseira species in relation to water temperature, pH, conductivity and alkalinity. Dashed lines indicate weighted average optima. et al. 2012). In addition, an ecotoxicological study demon- strated its tolerance to copper sulphate (Viana & Rocha 2005), an algicide used to control growths of cyanobac- terial blooms in some Brazilian reservoirs. In our material, this variety was the most widespread, present in 93% of all samples and in high abundances particularly during winter (Table 2), when water mixing is more frequent. It co- occurred with A. granulata var. angustissima and presented the second highest TP and TN optima (Fig. 3), confirming its preference for enriched waters. 204 Bicudo et al. Fig. 3. Relative abundances of eight Aulacoseira species in relation to soluble reactive phosphorus (P–PO4), DIN, TP and TN concentrations. Dashed lines indicate weighted average optima. Aulacoseira granulata var. angustissima (O. Müller) Simonsen (Figs 38–40) Morphology: This variety differs from the nominate by the presence of a single and elongated separation spine and a narrower valve diameter (3–5 μm) (Hustedt 1930, Krammer & Lange-Bertalot 1991). The nominate variety has commonly two long separation spines and a valve diameter of 5–35 μm (Krammer & Lange-Bertalot 1991). Ecology and distribution: This is a cosmopolitan taxon (Guiry & Guiry 2014), which is found mainly in eutrophic rivers and lakes (Krammer & Lange-Bertalot 1991, Taylor Aulacoseira species from tropical reservoirs 205 Figs 4–11. Aulacoseira ambigua. Figs 4–9. Frustules in girdle view, LM. Fig. 10. Areolae occlusions, TEM. Fig. 11. Linking valves in girdle view, the arrow shows an external opening of rimoportula, SEM. Scale bars = 10 μm (Figs 4–9), 500 nm (Fig. 10), 2 μm (Fig. 11). et al. 2007). In our data set, this variety was recorded in approximately half of all sites, achieving high abundances in eutrophic reservoirs (Table 2). Compared to other taxa it has the highest ecological optimum for all measured environmental variables, particularly for phosphorus and nitrogen (Figs 2–3). Aulacoseira granulata var. australiensis (Grunow) Moro (Figs 41–42) Morphology: The variety australiensis is characterized by the presence of 1–4 separation spines and conspicuous rimoportulae, visible in LM (Frenguelli 1923, Moro 1991). On the other hand, the nominate variety has one or two long separation spines and the rimoportulae are not visible in LM. Ecology and distribution: This taxon has been recorded in different parts of the world including South Amer- ica (e.g., Van Heurck 1880–1885, Tempère & Peragallo 1907–1915, Frenguelli 1923, Moro 1991). No ecological information was found in the literature. In our study, this taxon was found in low abundances in 41% of all sites (Table 2). It was mostly found in reservoirs with low nutri- ent content in the oligo-mesotrophic range (Fig. 3), low conductivity, slightly acidic waters and at relatively low temperature (Fig. 2). Our data indicate distinct ecological preferences for A. granulata var. australiensis compared to the nominate variety and A. granulata var. angustissima. 206 Bicudo et al. Figs 12–21. Aulacoseira brasiliensis. Figs 12–14. Valve face, LM. Figs 15–18. Valves in girdle view, LM. Fig. 19. Areolae occlusion, external and internal openings of a rimoportula (white and black arrow, respectively), TEM. Fig. 20. External view of valve face, SEM. Fig. 21. Internal openings of rimoportulae on the mantle (arrows). Scale bars 10 μm (12–18), 0.5 μm (19), 5 μm (20, 21). Aulacoseira herzogii (Lemmermann) Simonsen (Figs 43–48) Morphology: In LM, this taxon is easily distinguishable by two to four long spines on opposite sides of the valves and very small mantle areolae. Aulacoseira herzogii occurs as single cells or in short chains. Ecology and distribution: According to Hustedt (1952), A. herzogii occurs in tropical and subtropical regions of South America. Further studies report a worldwide dis- tribution (Hickel & Håkansson 1991, Jewson et al. 1993, Guiry & Guiry 2014), including different regions of Brazil (Hickel & Håkansson 1991, Torgan et al. 1999, Tremarin et al. 2009, Silva et al. 2011, Cavalcante et al. 2013). It was found developing in littoral zones in mesotrophic to eutrophic lakes (Houk & Klee 2007). In our mate- rials, it was found in 15.8% of all sites, and usu- ally in low abundances (Table 2); occurring in oligo to hypereutrophic, but mostly in mesotrophic reservoirs (Fig. 3). As mentioned above, this species has similar eco- logical preferences to, (Figs 2–3) and co-occurred with, A. calypsi. Aulacoseira laevissima (Grunow) Krammer (Figs 49–62) Morphology: Under LM, this species is distinguishable by its delicate areolae arranged in straight rows on the man- tle, valve face completely covered by areolae, and several small linking spines, which in SEM have the shape of an anchor (Krammer & Lange-Bertalot 1991, Krammer 1991b). Ecology and distribution: Aulacoseira laevissima has been reported from different parts of the world (Krammer 1991b, Houk & Klee 2007, Guiry & Guiry 2014), includ- ing Brazil, but only in the state of São Paulo (Morandi Aulacoseira species from tropical reservoirs 207 Figs 22–33. Aulacoseira calypsi. Figs 22–27. Frustules in girdle view, LM. Figs 28–29. Separation (Fig. 28) and linking (Fig. 29) valves in valve view, LM. Fig. 30. External view of separation valve, SEM. Fig. 31. Frustule with separation and linking valves in girdle view, SEM. Fig. 32. Valve in girdle view showing separation spines, areolae on the mantle and external opening of a rimoportula (arrow), SEM. Fig. 33. Internal opening of a rimoportula (arrow), SEM. Scale bars 10 μm (22–29), 2 μm (30, 32), 5 μm (31), 1 μm (33). 208 Bicudo et al. Figs 34–48. Aulacoseira species. Figs 34–37. Aulacoseira granulata var. granulata, LM; Figs 38–40. Aulacoseira granulata var. angustissima, LM. Figs 41–42. Aulacoseira granulata var. australiensis, LM. Figs 43–48. Aulacoseira herzogii. Valves in girdle view, LM (Figs 43–47). Valve in girdle view with a separation spine, SEM (Fig. 48). Scale bars 10 μm (34–47), 2 μm (48). et al. 2006). This is a rare species with little ecological information (Houk & Klee 2007). In our study, it was found with relative abundances lower than 0.5% in two oligo-mesotrophic reservoirs. Aulacoseira pusilla (Meister) Tuji et A. Houki (Figs 63–74) Morphology: This diatom has a similar mantle striation pattern and frustule dimensions to Aulacoseira alpigena Aulacoseira species from tropical reservoirs 209 Figs 49–62. Aulacoseira laevissima. Frustules in girdle view, LM (Figs 49–55). Valve views, LM (Figs 56–59). External view of a valve, SEM (Fig. 60). Detail of a valve showing spines mantle areolae, SEM (Fig. 61). Chain of two frustules in girdle view, SEM (Fig. 62). Scale bars 10 μm (49–59), 2 μm (60), 1 μm (61), 5 μm (62). (Grunow) Krammer, but its valve face is covered by are- olae, and it differs in the number of striae and areolae in the mantle, spine shape, rimoportula morphology and ringleist thickness (Krammer 1991a, Krammer & Lange- Bertalot 1991, Tuji 2002). Aulacoseira pusilla differs from other species with shallow mantles by having curved (dex- trorse) mantle striae, delicate areolae and a wide ringleist (Potapova 2010). Ecology and distribution: Aulacoseira pusilla has been found in eutrophic environments (Houk & Klee 2007, Tay- lor et al. 2007, Tuji & Williams 2007). In Brazil, it has commonly been confused with A. alpigena (ex. Ludwig & Valente-Moreira 1990, Bicudo et al. 1993, 1995, Lud- wig & Flôres 1995, Brassac et al. 1999, Ludwig et al. 2005, Dunck et al. 2012), Aulacoseira distans (Ehrenberg) Simonsen (ex. Ludwig et al. 2004, Raupp et al. 2006) or 210 Bicudo et al. Figs 63–87. Aulacoseira species. Figs 63–74. A. pusilla. Frustules in girdle view, LM (Figs 63–68). Valve views focused on ringleists, LM (Figs 69–73). External view of a valve face, SEM (Fig. 74). Figs 75–87. Aulacoseira tenella. Frustules in girdle view, LM (Figs 75–79). Valve views, LM (Figs 80–84). Frustule in girdle view, SEM (Fig 85). External view of a valve face, SEM (Fig 86). Internal view of valve showing rimoportulae (arrows), SEM (Fig 87). Scale bars 10 μm (63–73, 75–84), 2 μm (85, 87), 1 μm (86). Aulacoseira species from tropical reservoirs 211 Fig. 88. PCA biplot showing position of samples and species in the ordination space of the first and second PCA axes and a posteriori projection of environmental variables. Black circles are oligotrophic sites, open circles are mesotrophic and grey circles are eu-hypereu- trophic sites. Species codes: A. ambigua (AAMB), A. brasiliensis (AUBR), A. calypsi (ACLY), A. granulata var. angustissima (AUGA), A. granulata var. australiensis (AUAU), A. granulata var. granulata (AUGR), A. herzogii (AUHE), A. tenella (AUTL). Environmental variables codes: Chlorophyll a (Chl a), conductivity (cond), total nitrogen (TN), total phosphorus (TP), water temperature (Temp). A. muzzanensis (ex. Morandi et al. 2006). In our data set, A. pusilla was very rare and found at low abundances in two reservoirs of contrasting trophic status, namely olig- otrophic and eutrophic, expanding its distribution to clean waters. Aulacoseira tenella (Nygaard) Simonsen (Figs 75–87) Morphology: This species is characterized by having its valve face completely covered by areolae, small marginal spines, striae composed of few areolae, shallow mantle and very shallow ringleist (Florin 1981). Ecology and distribution: The species has been reported from different parts of Europe and USA (Eloranta 1986, Camburn & Kingston 1986, Siver & Kling 1997, Potapova et al. 2008). In Brazil, A. tenella was mistak- enly recorded as A. distans by Tavares & Valente-Moreira (2000), and as A. alpigena by Landucci & Ludwig (2005). Subsequent records as A. tenella were made by Raupp et al. (2006), Silva et al. (2010), Laux & Torgan (2011) and Cavalcante et al. (2013). Aulacoseira tenella has been reported from oligotrophic to oligo-mesotrophic and slightly acidic to neutral waters (Siver & Kling 1997). In this study, it was the second most frequent and abun- dant species (Table 2), usually present in abundances above 40% in oligotrophic sites. It was well represented in both winter and summer. Compared to other taxa, it has the lowest ecological optimum for TP, conductivity and 212 Bicudo et al. prefers temperatures around 21°C (Figs 2–3). Although our records expand its distribution in a wide range of nutrient status waters, A. tenella was typically associated with olig- otrophic and oligo-mesotrophic reservoirs, corroborating the limited ecological information for it. Principal components analysis The first PCA axis extracted 45% of the variation, and the analysis indicates the trophic status gradient as the main driver of species distribution. Conductivity had the strongest correlation with the ordination axes, followed by TP (Fig. 88). Oligotrophic sites were placed on the left side of the diagram, and eu- and hypereutrophic sites were mainly on the right side. Aulacoseira tenella was the only species associated with clean waters, while A. gran- ulata var. granulata and A. granulata var. angustissima were associated with enriched sites, which is in agreement with their ecological optima, particularly for phospho- rus and nitrogen (Fig. 3). Other species were associated with mesotrophic and meso-eutrophic sites (A. ambigua, A. brasiliensis, A. calypsi, A. granulata var. australiensis and A. herzogii). Our results highlight three potential indi- cator taxa, reinforcing the scarce ecological information for A. tenella (Siver & Kling 1997), and corroborating previ- ous findings for the varieties of A. granulata (Taylor et al. 2007, Zalat & Vildary 2007, Kiss et al. 2012). In conclusion, our findings report ten Aulacoseira taxa from tropical reservoirs in southeastern Brazil, and provide new information on their ecological preferences, adding species optima for several water quality variables. Fur- thermore, our results expand the ecological information for five species (A. brasiliensis, A. calypsi, A. herzogii, A. laevissima and A. pusilla) and provide new information for A. granulata var. australiensis. This study reinforces the need to identify taxa to species level during water quality assessments (Ponader & Potapova 2007), given that different Aulacoseira species showed different eco- logical preferences. Finally, we highlight the need for further regional studies combining floristic and ecological approaches. Such information would improve the accuracy of diatoms as indicators, enhancing their value in water quality assessments and paleoenvironmental reconstruc- tions. Acknowledgements We deeply appreciate the valuable assistance of personnel from the agency in charge of the public water supply in São Paulo – SABESP/RHMS (Companhia de Saneamento do Estado de São Paulo, Divisão de Recursos Hídricos Metropolitanos Sudoeste) and Votorantin Energia for their valuable logistical support dur- ing the fieldwork. We are also grateful to Prof. William de Queiróz (Universidade de Guarulhos, Laboratório de Geoproces- samento) for providing the illustration of the study area. We thank all the students and technicians from the Department of Ecology, Institute of Botany, involved in field and laboratory work. We acknowledge Dr Václav Houk, Dr Marina Potapova and Dr Luis Maurício Bini for providing helpful comments that improved the quality of our manuscript. Funding This study was carried out within the framework of the AcquaSed project supported by funds from FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo, AcquaSed Project) [num- ber 2009/53898-9]. DCB and CEMB thanks CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for Research Fellowships [number 310940/2013-3] and [number 309474/2010-8]. References APHA – AMERICAN PUBLIC HEALTH ASSOCIATION. 2005. Standard methods for the examination of water and wastew- ater. 21st edition. APHA, Washington, DC. 1368 pp. BATTARBEE R.W., JONES V., FLOWER R.J., CAMERON N., BENNION H., CARVALHO L. & JUGGINS S. 2001. Diatoms. In: Tracking environmental change using lake sed- iments (Ed. by J.P. SMOL, H.J.B. BIRKS & W.M. LAST), pp. 155–203, Kluwer Academic Publishers, London. BICUDO D.C., BICUDO C.E.M., CATSRO A.A.J. & PICELLI- VICENTIM M.M. 1993. Diatomáceas (Bacillariophyceae) do trecho a represar do rio Paranapanema (usina hidrelétrica de Rosana), Estado de São Paulo, Brasil. Hoehnea 20: 47–68. BICUDO D.C., DE-LAMONICA-FREIRE E., FIGUEIREDO D.M. & LIMA D. 1995. Ficoflórula do Pantanal de Poconé, estado de Mato Grosso, Brasil: Centrales e Eunotiaceae (Bacillar- iophyceae). Hoehnea 22: 165–182. BORCARD D., GILLET F. & LEGENDRE P. 2011. Numerical ecology with R. Springer, New York. 306 pp. BRASSAC N.M., ATAB D.R., LANDUCCI M., VISINONI N.D. & LUDWIG T.V. 1999. Diatomáceas cêntricas de rios da região de abrangência da usina hidrelétrica de Salto Caxias, PR (Bacia do rio Iguaçu). Acta Botanica Brasilica 13(3): 277–289. CAMBURN K.E. & KINGSTON J.C. 1986. The genus Melosira from soft-water lakes with special reference to northern Michigan, Wisconsin and Minnesota. In: Diatoms and lake acidity (Ed. by J.P. SMOL, R.W. BATTARBEE, R.B. DAVIS & J. MERILAINEN), pp. 17–34. W. Junk, Dordrecht. CAVALCANTE K.P., TREMARIN P.I. & LUDWIG T.A.V. 2013. Taxonomic studies of centric diatoms (Diatomeae): unusual nanoplanktonic forms and new records for Brazil. Acta Botanica Brasilica 27(2): 237–251. CEPAGRI – CENTRO DE PESQUISAS METEOROLÓGICAS E CLIMÁTICAS APLICADAS A AGRICULTURA. 2015. A clas- sificação climática de Koeppen para o Estado de São Paulo [online]. Available from: http://www.cpa.unicamp.br/outras- informacoes/clima-dos-municipios-paulistas.html [Accessed 24 September 2015]. COSTA-BÖDDEKER S., BENNION H., JESUS T.A., ALBU- QUERQUE A.L.S., FIGUEIRA R.C.L. & BICUDO D.C. 2012. Paleolimnologically inferred eutrophication of a shal- low tropical urban reservoir, Southeast Brazil. Journal of Paleolimnology 48(4): 751–766. http://www.cpa.unicamp.br/outras-informacoes/clima-dos-municipios-paulistas.html http://www.cpa.unicamp.br/outras-informacoes/clima-dos-municipios-paulistas.html Aulacoseira species from tropical reservoirs 213 DENYS L., MUYLAERT K., KRAMMER K., JOOSTEN T., REID M. & RIOUAL P. 2003. Aulacoseira subborealis stat. nov. (Bacillariophyceae): a common but neglected plankton diatom. Nova Hedwigia 77(3/4): 407–427. DUDGEON D., ARTHINGTON A.H., GESSNER M.O., KAWA- BATA Z., KNOWLER D., LÉVÊQUE C., NAIMAN R.J., PRIEUR R.A.H., SOTO D. & STIASSNY M.L.J. 2006. Freshwater biodiversity: importance, threats, status and con- servation challenges. Biological Review. 81(2):163–182. DUNCK B., NOGUEIRA I.S. & MACHADO M.G. 2012. Plank- tonic diatoms in lotic and lentic environments in the Lago dos Tigres hydrologic system (Britânia, Goiás, Brazil): Cos- cinodiscophyceae and Fragilariophyceae. Brazilian Journal of Botany 35(2): 181–193. EDGAR S.M. & THERIOT E.C. 2004. Phylogeny of Aulaco- seira (Bacillariophyta) based on molecules and morphology. Journal of Phycology 40: 772–788. ELORANTA, P. 1986. Melosira distans var. tenella and Euno- tia zasuminensis, two poorly know planktonic diatoms in Finnish Lakes. Nordic Journal of Bototany 6(1): 99–103. FAUSTINO S.B., FONTANA L., BARTOZEK E.C.R., BICUDO C.E.M. & BICUDO D.C. 2016. Composition and distribu- tion of diatom assemblages from core and surface sediments of a water supply reservoir in Southeastern Brazil. Biota Neotropica 16(2): e20150129. FLORIN, M.B. 1981. The taxonomy of some Melosira species: a comparative morphological study. II. In: Proceedings of the 6th symposium on recent and fossil diatoms, Budapest, 1980 (Ed. by R. ROSS), pp. 43–73. Koeltz, Koenigstein. FRENGUELLI J. 1923. Diatomeas del rio Primero. Boletin de la Academia Nacional de Ciencias en Córdoba 27: 13–119. GUIRY M.D. & GUIRY G.M. 2014. AlgaeBase [on line]. Worldwide electronic publication, National University of Ireland, Galway. Available from: http://www.algaebase.org [Accessed 8 December 2014]. HASLE G.R. & FRYXELL G.A. 1970. Diatoms: cleaning and mounting for light and electron microscopy. Transactions of the American Microscopical Society 89: 469–474. HICKEL B. & HÅKANSSON H. 1991. The freshwater diatom Aulacoseira herzogii. Diatom Research 6(2): 299–305. HOUK V. 2003. Atlas of freshwater centric diatoms with a brief key and descriptions. Part I. Melosiraceae, Orthoseiraceae, Paraliaceae and Aulacoseiraceae. Czech Phycology Sup- plement, Olomouc. 114 pp. HOUK V. & KLEE R. 2007. Atlas of freshwater centric diatoms with a brief key and descriptions Part II. Melosiraceae and Aulacoseiraceae (supplement to part I). Fottea 7(2): 85–255. HUSTEDT F. 1930. Bacillariophyta (Diatomeae). In: Die Süsswasser-Flora Mitteleuropas, Heft 10a (Ed. by A. PASCHER). G. Fischer, Jena. 466 pp. HUSTEDT F. 1952. Neue und wenig bekannte Diatomeen. IV. Botaniska Notiser 4: 365–409. HUSTEDT F. 1965. Neue und wenig bekannte Diatomee IX. Süßwasserdiatomeen aus Brasilien insbesondere des Ama- zonasgebietes. Internationale Revue der gesamten Hydrobi- ologie und Hydrogeographie 50(3): 391–410. JEWSON D.H., KHONDKER M., RAHMAN M.H. & LOWRY S. 1993. Auxosporulation of the freshwater diatom Aulacoseira herzogii in Lake Banani, Bangladesh. Diatom Research 8: 403–418. KISS K.T., KLEE R., ECTOR L. & ÁCS É. 2012. Centric diatoms of large rivers and tributaries in Hungary: morphol- ogy and biogeographic distribution. Acta Botanica Croatica 71(2): 311–363. KRAMMER K. 1991a. Morphology and taxonomy in some taxa of the genus Aulacoseira Thwaites (Bacillariophyceae). I. Aulacoseira distans and similar taxa. Nova Hedwigia 52(1– 2): 89–112. KRAMMER K. 1991b. Morphology and taxonomy in some taxa of the genus Aulacoseira Thwaites (Bacillariophyceae). II. Taxa in the A. granulata-, italica- and lirata-groups. Nova Hedwigia 53(3–4): 477–496. KRAMMER K. & LANGE-BERTALOT H. 1991. Bacillario- phyceae, Teil. 3: Centrales, Fragilariaceae, Eunotiaceae. Süsswasserflora Mitteleuropa 2/3. Gustav Fischer Verlag, Stuttgart. 576 pp. LANDUCCI, M. & LUDWIG, T.A.V. 2005. Diatomáceas de rios da bacia hidrográfica Litorânea, PR, Brasil: Coscinodisco- phyceae e Fragilariophyceae. Acta Botanica Brasilica 19(2): 345–357. LAUX M. & TORGAN L.C. 2011. Diatomáceas com plastídios no plâncton da foz dos rios do Delta do Jacuí, sul do Brasil: um complemento à taxonomia tradicional. Iheringia, Série Botânica 66(1): 109–132. LECOINTE C., COSTE M. & PRYGIEL J. 1993. ‘‘Omnidia’’: software for taxonomy, calculation of diatom indices and inventories management. Hydrobiologia 209(270): 509– 513. LEGENDRE P. & GALLAGHER E.D. 2001. Ecologically mean- ingful transformations for ordination of species data. Oecologia 129(2): 271-280. LIMA W.C., TUNDISI J.C. & MARINS M.A. 1979. A systemic approach to the sensitivity of Melosira italica (Ehr) Kutz. Revista Brasileira de Biologia 39: 559–563. LIMA W.C., MARINS M.A. & TUNDISI J.G. 1983. Influence of wind on the standing stock of Melosira italica (Ehr.) Kütz. Revista Brasileira de Biologia 43: 317–320. LUDWIG T.A.V. & VALENTE-MOREIRA I.M. 1990. Con- tribuição ao conhecimento da diatomoflórula do parque regional do Iguaçu, Curitiba, Paraná, Brasil: II. Cêntri- cas (Bacillariophyceae). Arquivos de Biologia e Tecnologia 33(4): 843–852. LUDWIG T.A.V. & FLÔRES T.L. 1995. Diatomoflórula dos rios da região a ser inundada para a construção da usina hidrelétrica de Segredo, PR. I. Coscinodisco- phyceae, Bacillariophyceae (Achnanthales e Eunotiales) e Fragilariophyceae (Meridion e Asterionella). Arquivos de Biologia e Tecnologia 38(2): 631–650. LUDWIG T.A.V., FLÔRES T.L., MOREIRA-FILHO H. & VEIGA L.A.S. 2004. Inventário florístico das diatomáceas (Ochro- phyta) de lagoas do Sistema Hidrológico do Taim, Rio Grande do Sul, Brasil. Iheringia, Série Botânica 59(1): 97–106. LUDWIG T.A.V., BIGUNAS P.I.T., NEIVA T.F., COQUEMALA V. & PICCININI C. 2005. Diatomáceas (Ochrophyta) dos lagos do Jardim Botânico. Revista do Museu Nacional do Rio de Janeiro, série livros, 10: 301–323. http://www.algaebase.org 214 Bicudo et al. MARINS M.A. 1978. Ecologia, distribuição e densidade da alga Melosira italica (Bacillariophyceae: Centricae) na Represa do Lobo (Broa), Estado de São Paulo, Brasil. Revista de Biologia Tropical 26(1): 19–35. METZELTIN D. & LANGE-BERTALOT H. 2007. Tropical diatoms of South America II. Special remarks on bio- geographic disjunction. Iconographia Diatomologica 18: 1–877. MORALES E.A., RIVERA S.F., RUBIN S.D.C., VIS M.L. & HOUK V. 2015. Aulacoseira kruegeriana (Diatomeae, Ciscinodiscophyceae): a new centric diatom from high- elevation Andean rivers and streams in Bolivia. Diatom Research 30: 269–277. MORANDI L.L., RITTER L.M.O., MORO R.S. & BICUDO C.E.M. 2006. Criptógamos do Parque Estadual das Fontes do Ipiranga, São Paulo, SP. Algas, 20: Coscinodiscophyceae. Hoehnea 33(1): 115–122. MORO R.S. 1991. Morphology of Aulacoseira granulata (Ehren- berg) var. australiensis (Grunow) nov. comb. under light microscopy. Arquivos de Biologia e Tecnologia 34(2): 353– 359. NAKAMOTO N., MARINS M.A. & TUNDISI J.G. 1976. Syn- chronous growth of a freshwater diatom Melosira italica under a natural environment. Oecologie 23: 179–184. NARDELLI M.S., BUENO N.C., LUDWIG T.A.V., TREMARIN P.I. & BARTOZEK E.C.R. 2014. Coscinodiscophyceae and Fragilariophyceae (Diatomeae) in the Iguaçu River, Paraná, Brazil. Acta Botanica Brasilica 28(1): 127–140. NOGUEIRA M.G. 2000. Phytoplankton composition, dominance and abundance as indicators of environmental compartmen- talization in Jurumirim Reservoir (Paranapanema River), São Paulo, Brazil. Hydrobiologia 431: 115–128. OKSANEN J., BLANCHET F.G., KINDT R., LEGENDRE P., MINCHIN P.R., O’HARA R.B., SIMPSON G.L., SOLYMOS P., STEVENS M.H.H. & WAGNER H. 2013. Vegan: Com- munity Ecology Package [online]. R package version 2.0-9. Available from: http://CRAN.Rproject.org/package = vegan [Accessed 20 September 2015]. OLIVEIRA P.E. & STEINITZ-KANNAN M. 1992. The diatom flora (Bacillariophyceae) of the Cuyabeno Faunistic Reserve, Ecuadorian Amazonia. Nova Hedwigia 54: 515– 552. PONADER K.C. & POTAPOVA M.G. 2007. Diatoms from the genus Achnanthidium in flowing waters of the Appalachian Mountains (North America): ecology, distribution and taxo- nomical notes. Limnologica 37: 227–241. PONADER K.C., CHARLES D.F. & BELTON T.J. 2007. Diatom-based TP and TN inference models and indices for monitoring nutrient enrichment of New Jersey streams. Ecological Indicators 7: 79–93. POTAPOVA M. 2010. Aulacoseira tenella [online]. Diatoms of the United States. Available from: http://westerndiatoms. colorado.edu/taxa/species/aulacoseira_tenella [Accessed 5 January 2012]. POTAPOVA M.G., BIXBY R.J., CHARLES D.F., EDLUND M.B., ENACHE M.E., FUREY P., HAMILTON P.B., LOWE R.L., MANOYLOV K.M., OGNJANOVA-RUMENOVA N., PONADER K.C., REN L., SIVER P.A., SPAULDING S.A. & ZALACK J. 2008. Eighteenth NAWQA workshop on harmonization of algal taxonomy – representatives of the genus Aulacoseira Thwaites in NAWQA samples. Report n. 08-07. PCER, ANSP, Philadelphia, PA. 56 pp. R CORE TEAM. 2015. R: a language and environment for sta- tistical computing. R Foundation for Statistical Computing, Vienna. RAUPP S.V., TORGAN L.C. & BAPTISTA L.R.M. 2006. Com- posição e variação temporal de diatomáceas (Bacillario- phyta) no plâncton da represa de Canastra, sul do Brasil. Iheringia, Série Botânica, 61(1–2): 105–134. RAUPP S.V., TORGAN L.C. & MELO S. 2009. Planktonic diatom composition and abundance in the Amazonian flood- plain Cutiuaú Lake are driven by the flood pulse. Acta Limnologica Brasiliensia 21(2): 227–234. SALA S.E., DUQUE S., NUÑÉZ M. & LAMARO A. 1999. Nuevos registros de diatomeas (Bacillariophyceae) de la Amazonia Colombiana. Caldasia 21: 26–37. SALA S.E., DUQUE S., NÚÑEZ M. & LAMARO A. 2002. Diatoms from the Colombian Amazonia. Cryptogamie Algo- logie 23: 75–99. SALA S.E., RAMÍREZ J.J. & PLATA Y. 2008. Diatoms from lentic and lotic systems in Antioquia, Chocó and Santander Departments in Colombia. Revista de Biologia Tropical 56(3): 1159–1178. SARTORY D.P. & GROBBELAAR J.U. 1984. Extraction of chlorophyll a from freshwater phytoplankton for spec- trophotometric analysis. Hydrobiologia 114: 177–187. SILVA A.M., LUDWIG T.A.V., TREMARIN P.I. & VER- CELLINO I.S. 2010. Diatomáceas perifíticas em um sistema eutrófico brasileiro (reservatório do Iraí, estado do Paraná). Acta Botanica Brasilica 24(4): 997–1016. SILVA W.J., NOGUEIRA I.S. & SOUZA M.G.M. 2011. Catálogo de diatomáceas da região Centro-Oeste brasileira. Iheringia, Série Botânica 66(1): 1–32. SIVER P.A. & KLING H. 1997. Morphological observations of Aulacoseira using scanning electron microscopy. Canadian Journal of Botany 75: 1807–1835. SMITH V.H., JOYE S.B. & HOWARTH R.W. 2006. Eutrophica- tion of freshwater and marine ecosystems. Limnology and Oceanography 51: 351–355. STENGER-KOVACS C., BUCZKÓ K., HAJNAL E. & PADISÁK J. 2007. Epiphytic, littoral diatoms as bioindicators of shallow lake trophic status: Trophic Diatom Index for Lakes (TDIL) developed in Hungary. Hydrobiologia 589: 141–154. TAVARES B. & VALENTE-MOREIRA I.M. 2000. Diatomoflórula do lago de Cascavel, município de Cascavel, estado do Paraná, Brasil. Hoehnea 27(1): 1–24. TAYLOR J.C., HARDING W.R. & ARCHIBALD G.M. 2007. An illustrated guide to some common diatom species from South Africa. WRC report TT 282/07. 224 pp. TEMPÈRE J. & PERAGALLO H. 1907–1915. Diatomees du Monde Entier collection Tempére et Peragallo. Arcachon. 68 pp. TER BRAAK C.J.F. & VAN DAM H. 1989. Inferring pH from diatoms – a comparison of old and new methods. Hydrobi- ologia 178: 209–223. TORGAN L.C., BECKER V. & PRATES M. 1999. Checklist das diatomáceas (Bacillariophyta) de ambientes de águas http://CRAN.Rproject.org/package=vegan http://westerndiatoms.colorado.edu/taxa/species/aulacoseira_tenella http://westerndiatoms.colorado.edu/taxa/species/aulacoseira_tenella Aulacoseira species from tropical reservoirs 215 continentais e costeiros do estado do Rio Grande do Sul, Brasil. Iheringia, Série Botânica 52: 89–144. TREMARIN P.I., FREIRE E.G., BERTOLLI L.M. & LUDWIG T.A.V. 2009. Catálogo das diatomáceas (Ochrophyta – Diatomeae) continentais do estado do Paraná. Iheringia, Série Botânica 64(2): 79–107. TREMARIN P.I., LOVERDE-OLIVEIRA S., LUDWIG T.A.V. & TORGAN L.C. 2011. Ultrastructure and distribution of Aulacoseira gessneri. Diatom Research 26: 189–197. TREMARIN P.I., LUDWIG T.A.V. & TORGAN L.C. 2012. Ultra- structure of Aulacoseira brasiliensis sp. nov. (Coscinodisco- phyceae) and comparison with related species. Fottea 12: 171–188. TREMARIN P.I., PAIVA R.S., LUDWIG T.A.V. & TORGAN L.C. 2013a. Aulacoseira calypsi sp. nov. (Coscinodisco- phyceae) from an Amazonian lake, northern Brazil. Phyco- logical Research 61: 292–298. TREMARIN P.I., LUDWIG T.A.V. & TORGAN L.C. 2013b. Morphological variation and distribution of the freshwater diatom Aulacoseira ambigua (Grunow) Simonsen in Brazil- ian continental environments. Iheringia, Série Botânica 68(1): 139–157. TREMARIN P.I., LUDWIG T.A.V. & TORGAN L.C. 2014a. Four new Aulacoseira species (Coscinodiscophyceae) from Matogrossense Pantanal, Brazil. Diatom Research 29(2): 183–199. TREMARIN P.I., LUDWIG T.A.V. & TORGAN L.C. 2014b. Aulacoseira veraluciae sp. nov. (Coscinodiscophyceae, Aulacoseiraceae): a common freshwater diatom from Brazil. Phytotaxa 184: 208–222. TUJI A. 2002. Observations on Aulacoseira nipponica from lake Biwa, Japan, and Aulacoseira solida from North America (Bacillariophyceae). Phycological Research 50: 313–316. TUJI A. 2010. Examination of type material of Melosira nivalis W. Sm. (Bacillariophyceae) and its synonymy with Aulaco- seira pfaffiana (Reinsch) Krammer. Bulletin of the National Science Museum, Series B 36: 161–164. TUJI J. & WILLIAMS D.M. 2007. Type examination of Japanese diatoms described by Friedrich Meister (1913) from Lake Suwa. Bulletin of the National Science Museum, Series B 33(2): 69–79. VAN DAM H., MERTENS A. & SINKELDAM J. 1994. A coded checklist and ecological indicator values of freshwa- ter diatoms from the Netherlands. Netherlands Journal of Aquatic Ecology 28: 117–133. VAN HEURCK H. 1880-1885. Synopsis des diatomées de Bel- gique, 2 vols. Atlas, Anvers. 120 pp. VIANA S. & ROCHA O. 2005. The toxicity of copper sul- phate and atrazine to the diatom Aulacoseira granulata (Ehrenberg) Simmons. Acta Limnologica Brasiliensia 17: 291–300. WETZEL C.E., ECTOR L. & BICUDO D.C. 2014. Type anal- ysis of Aulacoseira gessneri (Hustedt) Simonsen (Bacil- lariophyceae) from South America. Nova Hedwigia 143: 381–390. ZALAT A.A. & VILDARY S.S. 2007. Environmental change in Northern Egyptian Delta lakes during the late Holocene, based on diatom analysis. Journal of Paleolimnology 37: 273–299. Introduction Material and methods Results and discussion Aulacoseira ambigua (Grunow) Simonsen (Figs 4–11) Aulacoseira brasiliensis Tremarin, Torgan et Ludwig (Figs 12–21) Aulacoseira calypsi Tremarin, Torgan et Ludwig (Figs 22–33) Aulacoseira granulata (Ehrenberg) Simonsen var. granulata (Figs 34–37) Aulacoseira granulata var. angustissima (O. Müller) Simonsen (Figs 38–40) Aulacoseira granulata var. australiensis (Grunow) Moro (Figs 41–42) Aulacoseira herzogii (Lemmermann) Simonsen (Figs 43–48) Aulacoseira laevissima (Grunow) Krammer (Figs 49–62) Aulacoseira pusilla (Meister) Tuji et A. Houki (Figs 63–74) Aulacoseira tenella (Nygaard) Simonsen (Figs 75–87) Principal components analysis Acknowledgements Funding References