Naviculadicta sp. 1

Ruwer, Daiane Trevisan & Rodrigues, Liliana, 2021, Sediment diatoms from Upper Paraná River floodplAiN lAKeS: New recordS, Iheringia, Série Botânica (e 2021012) 76, pp. 1-16 : 12-14

Naviculadicta sp. 1

( Figs. 140-152)

Valves elliptical or linear-lanceolate with rounded ends. Axial area narrow and linear. Central area rectangular limited by a shortened striae, asymmetrical, wider in larger individuals. Raphe filiform. Striae parallel to slightly radiate toward the central area. Length: 8-16 μm; width: 4.0-5.5 μm; striae 16-20 in 10 μm. The specimens observed are morphologically similar to Naviculadicta sp. 1 from Metzeltin & Lange-Bertalot (2007). Besides that, Naviculadicta sp. 1 from Metzeltin & Lange-Bertalot (2007) differ by the central area wider and symmetric. The population from this study resemble Sellaphora saugerresii (Desmazières) Wetzel & Mann and Navicula minima Grunow registered by Wetzel et al. (2015), however;

Naviculadicta sp. 1 differs concerning central area shape and striae density.

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake , 21.IX.2017, sediment, D. T. Ruwer (Nupélia UEM - 18073, 18085-97) .

Sellaphoraceae Mereschkowsky 1902

Sellaphora paenepupula Metzeltin & Lange-Bertalot, Iconogr. Diatomol. , 11: 66, pl. 31, figs. 9-15. 2003.

( Figs. 156-157)

Valves elliptical lanceolate, tidy. Ends subcapitate. Axial area linear and narrow. Central area laterally expanded, limited by irregular short striae. Raphe filiform. Striae radiate, more widely spaced about the central area. Length: 18.5-22.9 μm; width: 5.9-7.4 μm; striae <20 in 10 μm. The specimens were consistent and identified according to the type of Sellaphora paenepupula from Metzeltin & Lange-Bertalot (2002) and Metzeltin et al. (2005) specimens. Sellaphora pupula (Kützing) Mereschkovsky can be distinguished from Sellaphora paenepupula by the dimensions, ends short-protracted ends, and pseudoblunt shape valves ( Mann et al. 2008).

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake , 21.IX.2017, sediment, D. T. Ruwer (Nupélia UEM - 18072-75, 18083) .

Occurrence: first citation for Upper Paraná River floodplain.

Sellaphora sassiana (Metzeltin & Lange-Bertalot) Wetzel in Wetzel et al., Fottea, 15: 228. 2015.

( Figs. 158-163)

Valves elliptical lanceolate. Ends capitate. Axial area linear and narrow. Central area narrow, limited by irregular shorter striae. Raphe filiform. Striae radiate toward to central area, limited by longitudinal hyaline line. Length: 11.9-14.9 μm; width: 3.8-5.0 μm; striae <20 in 10 μm. The specimens were consistent and identified according to the type of Sellaphora sassiana from Wetzel et al. (2015), and Metzeltin & Lange-Bertalot (1998) identified as Naviculadicta sassiana Metzeltin & Lange-Bertalot. This taxon was registered in Brazilian studies of Marra et al. (2016) and Marquardt et al. (2018).

Material examined: BRAZIL, MATO GROSSO DO SUL: Batayporã, Garças Lake , 21.IX.2017, sediment, D. T. Ruwer (Nupélia UEM - 18072-76, 18083, 18086-18087) .

Occurrence: first citation for Upper Paraná River floodplain.

Some studies have already shown differences in algal communities between floodplain environments ( Algarte et al. 2006, 2009, Bichoff et al. 2018, Rodrigues & Bicudo 2001). Confirming that local environmental factors (as physical and chemical characteristics) are fundamental to determine patterns of diatom community distribution ( Algarte et al. 2009, Bichoff et al. 2018, Soininen 2007, Kahlert & Gottschalk 2014, Soininen & Weckström 2009). The relationship of the floodplain aquatic environments with hydrological periods and the dynamics created by flood pulse promote a great complexity of aquatic habitats providing a differentiated diversity in each environment ( Agostinho & Zalewski 1996, Thomaz et al. 2007). This may explain the difference in the diatom taxa present in the core sediment in each lake. Among the 47 taxa addressed, 19 were exclusive for Patos Lake, and 20 were exclusive for Garças Lake. Only eight taxa were found in both lakes: Aulacoseira ambigua , A. distans , A. granulata , Eunotia longicamelus , E. pseudosudetica , Pseudostaurosira cf. brevistriata , Achnanthidium minutissimum , and Luticola mutica .

Patos Lake is inserted in the conservation area of the Várzeas do Rio Ivinhema State Park, between two main rivers of the Upper Paraná River floodplain ( Agostinho & Zalewski 1996). Among the taxa with more than 2% relative abundance, the genera with the largest number of taxa in Patos Lake was Eunotia (13 taxa), Aulacoseira (six taxa) and Luticola (four taxa). The presence of Aulacoseira and Luticola species suggests possible periods of low waters, with moist or hydrological changes in Patos Lakes ( Devercelli 2006, Fontana & Bicudo 2009, Rodrigues et al. 2009, Ruwer et al. 2018). Whereas, the greater occurrence of Eunotia (13 taxa) taxa in the Patos Lake sediment suggest conditions of low values of pH, conductivity, and nutrients ( Moro & Fürstenberger 1997, Round et al. 1990, Vélez et al. 2005, Bicca & Torgan 2009, Burliga et al. 2013).

Gaças Lake presented a greater amount of abundant diatom species genera ( Figure 182). Fragilaroids taxa ( Staurosira , Pseudostaurosira , and Staurosirella ) were the most represented taxonomic groups in Garças Lake, among the most abundant species. The presence of fragilaroids species suggests possible periods with unstable conditions with continual changes in the environment, linked to anthropogenic impacts, hydrological and limnological changes ( Fayó et al. 2018, Gell et al. 2002, Reid et al. 2017). Algarte et al. (2016) observed the predominance of species in this same taxonomic family after changes in limnological conditions in a lake after the impact of a dam near the Upper Paraná River floodplain. Thus, both lakes have species that indicate hydrological changes, a dynamic that often occurs in floodplains.

This study provided new information about the distribution and biodiversity of tropical diatoms. From a total of 47 taxa recorded in floodplain lakes sediments, our study added 12 new citations of diatom species to the Upper Paraná River floodplain. Furthermore, were registered the other seven possible new taxa. The present study emphasizes the importance of use of sediment samples to access the diatom biodiversity of continental aquatic environments. Highlighting the need for surveying diatom assemblages in environments that present great biodiversity and that comes suffering the influence of anthropic impacts, to assist in the conservation of these environments.