Subfossil and periphytic diatoms from the upper Paraná river, Brazil: last ~1000 years of a transition period¹

Diatomáceas subfósseis e perifíticas do alto rio Paraná, Brasil: últimos ~1000 anos de um período de transição

ABSTRACT

Considering the lack of knowledge regarding the paleolimnology and the diatom flora from the sediment in Brazilian aquatic environments, this study aimed to provide information about diatom biodiversity and autoecology in an environment located in the upper Paraná river floodplain. Sediment and periphytic samples were collected from a swamp located in an island of the upper Paraná river floodplain. Sediment samples were obtained by collecting a core of ~2 m with a calibrated date of 726 to 903 cal yr BP near the base. The core was sliced into layers of 2.5 cm, totaling 41 samples. Periphytic diatom samples were obtained by scraping macrophytes' petioles, totaling two samples. The community was represented by 31 species belonging to 15 genera. All of the taxa were found in the sediment record, and 15 were present in the periphyton. The three new records (Eunotia longicamelus, Planothidium bagualensis and Luticola hustedtii) reinforce the importance of paleolimnological and periphytic studies to increase information about the aquatic biodiversity.

Keywords:
bioindicators; floodplain; freshwater; paleolimnology

RESUMO

Considerando a falta de conhecimento paleolimnológico e da flora de diatomáceas do sedimento nos ambientes aquáticos brasileiros, este estudo teve como objetivo fornecer informações sobre biodiversidade e autoecologia de diatomáceas de um ambiente localizado na planície de inundação do alto rio Paraná. Amostras de sedimento e perifíton foram coletadas em um pântano localizado em uma ilha fluvial na planície de inundação do alto rio Paraná. As amostras de sedimento foram obtidas através da coleta de um testemunho de ~2 m, com uma data calibrada perto da base de 726 a 903 cal anos PB. O testemunho foi dividido em fatias de 2,5 cm, totalizando 41 amostras. As amostras perifíticas foram obtidas através da raspagem de pecíolos de macrófitas, totalizando duas amostras. A comunidade foi representada por 31 espécies pertencentes a 15 gêneros. Todos os táxons foram encontrados no registro de sedimentos, e 15 estavam presentes no perifíton. Os três novos registros para a região (Eunotia longicamelus, Planothidium bagualensis e Luticola hustedtii) mostram a importância dos estudos paleolimnológicos e da comunidade perifítica para aumentar a informação sobre a biodiversidade aquática.

Palavras-chave:
água doce; bioindicadores; paleolimnologia; planície de inundação

Introduction

Taxonomic diversity is one of the most important characteristics of biological communities that reflect evolutionary and ecological processes (Komulaynen 2009). Species richness is a basic and fundamental measurement of community and regional diversity (Magurran 1988). Several factors affect small-scale species richness. According to reviews, alteration, and loss of habitat, hydrological modification, pollution, and invasion have been identified as the main drivers of species reduction (Stendera et al. 2012).

Palaeolimnological studies are a tool to evaluate changes in the environments over time and access the ancient biodiversity. Past communities are very often the only available tool to provide information on natural biodiversity before human impacts (Smucker & Vis 2010). Therefore, the data from these studies become an important appliance for conservation actions in freshwater environments (Smol 1992, Saulnier-Talbot 2016).

Diatoms are widely used on paleolimnological studies (Gabito et al. 2013), these organisms precipitate and are incorporated in the sediment due to their biogenic structures constituted of silica (Sierra-Arango et al. 2014). Diatoms respond sensibly (directly and indirectly) to a wide range of aquatic environmental stimuli, including physical and chemical changes (Douglas & Smol 1999, Stevenson & Pan 1999). The information provided by the diatoms enables us to understand the degree of changes that have was found in the habitat, for example, variation in water level and influence of erosion, or even introduction of species and extinctions (Smol 1992, Battarbee 1999).

Regardless of the importance of these studies on biodiversity changes, these applications have been scarce in tropical environments (Rühland et al. 2015). Palaeolimnological studies addressing taxonomy and richness of diatoms are even rarer, and for Brazil there are only a few studies (Fontana & Bicudo 2009, 2012, Almeida & Bicudo 2014, Silva & Bicudo 2014, Wengrat et al. 2015, Almeida et al. 2015, Faustino et al. 2016), which concentrate focus on surface sediments of reservoirs from São Paulo State. However, there is still rare taxonomic work addressing Brazilian subfossil diatoms with sediments of more than 100 years and also from the floodplain.

Therefore, considering the lack of palaeo-limnological studies concerning diatom flora from the sediment of the Brazilian aquatic environments and given, the current transformations in the global and regional environments, this study aimed to provide information about the diatom biodiversity and autoecology from a tropical floodplain.

Materials and methods

The study area is located on a swamp on an island in the Paraná River, in the upper Paraná river floodplain, in the reach between the reservoirs of Porto Primavera and Itaipu Lake. The Mutum Island presented 15 km long, with variable width (high and low waters) between 0.5 and 1.20 km and height of 5.0 m above the average level of the River. The sampling site is located in the central region of the swamp (22°45'31.98''S and 53°17'52.60''W) (figure 1) with depth less than one meter.

Figure 1
Sampling point in the Mutum, island upper Paraná river floodplain, Brazil.

A sediment core with a length of two meters was removed with a vibrocore. The sediment was analyzed according to granulometry, structure, composition, and coloration. With this analysis, it was possible to identify 5 geomorphological zones matching the geomorphological process of the fluvial islands approached in the studies of Fernandez et al. (1993) and Steauvx (1994). According to Fernandez et al. (1993) and Steauvx (1994), the fluvial islands in the upper Paraná river floodplain are formed by coalescence processes of bars to the islands. This process begins with the formation of the original island through a deposition of sediment. After its permanent establishment, there is the formation of a lateral bar of sediment on the side of the original island. The original island and the sidebar will be separated by a channel, which due to the sediment flow will become a connected lake or backwater, consequently, in a lake, transition period and, at the end of the process will be a swamp (see figure 2 in Ruwer & Rodrigues 2018).

With small amounts of sediment from the depths 0.78 m, 1.40 m and 1.90 m, data were analyzed with radiocarbon analysis. The analyses were performed by the Center for Applied Isotope Studies - CAIS (University of Georgia, USA) and the Nuclear Energy Center in Agriculture - CENA (São Paulo University). Radiocarbon ages were calibrated (cal yr BP and cal yr AD) by CALIB7.0.4 using the SHCal13 calibration curve for the Southern Hemisphere (Stuiver and Reimer 1993, Hogg et al. 2013). The absolute dating with the isotope of ¹⁴C in the samples of depths: 78 cm, 140 cm, and 190 cm, indicated modern age, 760 ± 65 yr BP (569 to 721 cal yr BP) and 920 ± 60 ¹⁴C yr BP (726 to 903 cal yr BP), respectively. In addition, the record was separated into 2.5 cm slices with 5 cm of intervals and disregarding the first 5 cm (from the top of the core). From each 2.5 cm slice, 0.01 g of sediment was removed for the preparation of permanent slides for subsequent quantitative and qualitative analysis under a microscope. The methodology for the preparation of slides was based on Battarbee et al. (2001). Diatom analysis was carried out on 32 out of 41 samples. Nine samples were not found a sufficient number of diatoms for analysis (78307UPCB to 78310UPCB, 78318UPCB to 78322UPCB).

Given the high dominance of diatoms in periphytic samples (Biolo & Rodrigues 2013, Bichoff et al. 2016), the periphytic community was sampled in order to identify diatom communities from the current environment. The sampling of the periphytic diatom community was made in April 2016 after a period of flooding. The following abiotic parameters were measured in situ with a multi-parameter probe: dissolved oxygen (percentage saturation and g/L), pH, water temperature (°C), electric conductivity (µS/cm), turbidity (NTU), total solids (g/L) and salinity (ppt) (Mackareth et al. 1978, Wetzel & Likens 1981).

Periphytic diatom community was obtained by scraping mature petioles of an aquatic macrophyte. Two petioles were collected in the sampling site, placed in 150 ml Wheaton bottles and kept cool until further removal of the periphytic biofilm, which was performed using a stainless-steel blade wrapped in aluminum foil and jets of distilled water. After removal, periphyton was fixed and preserved in Transeau solution (Bicudo & Menezes 2017). The periphytic material was oxidized and cleaned using the Simonsen (1974) method, modified by Moreira-Filho & Valente-Moreira (1981) and prepared on permanent slides with Naphrax resin. We analyzed the samples of non-oxidized periphyton under the optical microscope, to observe the forms of arrangement and fixation of the species.

The quantitative analysis was performed according to the method of Battarbee et al. (1986) with the count of at least 500 valves in an optical microscope. The slides were analyzed qualitatively under an optical microscope (under 1000× magnification) and scanning electron microscopy (Ferrario et al. 1995). The samples were deposited in the herbarium of Botanic Department of Universidade Federal do Paraná (78280UPCB to 78322UPCB). We recorded 329 taxa in the study, and we presented here only the taxa that occurred with a relative abundance of ≥ 20%, which contributed 74% of the relative abundance of all samples. Has been adopted the Round et al. (1990) classification system.

Results and Discussion

The swamp in the current period was characterized by relatively high temperature, slightly acidic pH, low conductivity, low dissolved oxygen concentration and high turbidity (table 1).

Table 1
Abiotic variables of the swamp located in the Mutum island in the upper Paraná river floodplain, Brazil, in April 2016 (OD - dissolved oxygen; TDS - total dissolved solids).

Variables	Values
Temperature (ºC)	27.92
pH	6.19
Conductivity (mS/cm)	0.112
Turbidity (NTU)	10.8
DO (g/L)	0.0023
DO (%)	30
TDS (g/L)	0.073
Salinity (ppt)	0.1

In the total 329 taxa found in the 34 samples, 31 species had a high abundance. The community was represented by 15 genera, among which the most representative were Eunotia Ehrenberg (10), Gomphonema Ehrenberg (three) and Luticola D.G. Mann (three).

• Bacillariophyta

  • Coscinodiscophyceae

    • Aulacoseirales

      • Aulacoseiraceae

Aulacoseira granulata (Ehrenberg) Simonsen, Bacillaria, 2: 58, 1979 ≡ Gaillonella granulata Ehrenberg in Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: 127, 1843. Melosira granulata Ralfs in Pritchard, Hist. Infus. 4: 820, 1861.

Figure 2

Figures 2-29
Diatom species from Mutum Island in the upper Paraná river floodplain, Brazil (LM). 2. Aulacoseira granulata. 3-5. Aulacoseira italica. 6-7. Staurosirella crassa mf. I. 8-9. Staurosirella crassa. 10-12. Eunotia bidens. 13-15. Eunotia cf. deformis. 16-17. Eunotia formica. 18-19. Eunotia cf. intermedia. 20-21. Eunotia subarcuatoides. 22-24. Eunotia longicamelus. 25-26. Eunotia major. 27. Eunotia naegelli. 28-29. Eunotia pseudosudetica. (Scale bar: 10 µm).

Diameter: 8-17 µm; height: 14-30 µm; striae: 9-14/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27/II/2012, Ruwer et al. (78282UPCB - 78285UPCB, 78287UPCB - 78296UPCB, 78300UPCB, 78305UPCB, 78312UPCB, 78315UPCB).

Ecological information: this species generally has a planktonic habitat, but can be also found in the periphytic community. Dominant in shallow lakes, it occurs in mesotrophic to eutrophic waters but is commonly found in eutrophic waters. This species occurs in alkaline waters and tolerate temperatures of 15 to over 30ºC (Van Dam et al. 1994, Moro & Fürstenberger 1997, Taylor et al. 2007, Zalat & Vildary 2007, Kiss et al. 2012, Estepp & Reavie 2015, Bicudo et al. 2016, Faustino et al. 2016). According to some works, this species is associated with water column mixing, high flood conditions and depth variations, and physical alterations as erosion events, turbulence, and deforestation (Zalat & Vildary 2007, Dong et al. 2008, Costa-Böddeker et al. 2012, Fontana et al. 2014). This species was found in 52% of the samples, presenting greater abundance in the transition and swamp periods, with the highest abundance between these two periods.

Aulacoseira italica (Ehrenberg) Simonsen, Bacillaria, 2: 60, 1979 ≡ Gaillonella italica Ehrenberg in Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich Preussischen Akademie der Wissenschaften zu Berlin 1836: 53. 1836. Melosira italica (Ehrenberg) Kützing in Bacillarien 55, 1844.

Figures 3-5, 64

Figures 30-63
Diatom species from Mutum Island in in the upper Paraná river floodplain, Brazil (LM). 30. Eunotia rabenhorstiana var. elongata. 31. Encyonema silesiacum. 32-33. Gomphonema gracile. 34-35. Gomphonema lagenula. 36-37. Gomphonema sp. 1. 38-39. Placoneis ovillus. 40-41. Achnanthidium minutissimum. 42-44. Planothidium bagualensis. 45-46. Planothidium aff. rostratum. 47-48. Diadesmis confervacea. 49-50. Humidophila contenta. 51-52. Luticola hustedtii. 53. Luticola cf. simplex. 54. Nupela cf. bicapitata. 55-56. Luticola muticoides. 57-58. Sellaphora fusticulus. 59-60. Pinnularia brauniana. 61. Pinnularia sp. 1. 62-63. Nitzschia palea var. debilis. (Scale bar: 10 µm).

Figures 64-79
Diatom species from Mutum Island (SEM).island in in the upper Paraná river floodplain, Brazil (SEM). 64. Aulacoseira italica. 65. Staurosirella crassa. 66-68. Eunotia longicamelus. 69. Eunotia formica. 70-71. Eunotia cf. deformis (71 - internal valvar view). 72-73. Eunotia cf. intermedia. 74-76. Eunotia pseudosudetica (75 and 76 - internal valvar view). 77-79. Eunotia major (77 and 79 - internal valvar view). (Scale bar: 5 µm).

Diameter: 9-20 µm; height: 12-24 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78288UPCB, 78290UPCB - 78311UPCB, 78313UPCB - 78315UPCB, 78317UPCB).

Ecological information: species generally of planktonic habitat, but also found in the periphytic community. Dominant in shallow lakes, occurring in oligotrophic to eutrophic waters, tolerate temperatures of 0 to 30 ºC (Van Dam et al. 1994, Moro & Fürstenberger 1997, Estepp & Reavie 2015). Species of Aulacoseira genus has heavy silicified cells with a high sinking rate (characteristic clearly observed in the Aulacoseira italica of this study), therefore, this species requires turbulence to maintain its presence in the water column (Bradbury 1975). This species was found in 85% of the samples. With greater abundance in the transition and swamp periods, with the highest abundance between the transition and lake periods.

• Bacillariophyceae

  • Fragilariales

    • Fragilariaceae

Staurosirella crassa (Metzeltin & Lange-Bertalot) Ribeiro & Torgan in Ribeiro et al., Revista Brasileira de Paleontologia, 13(1): 24, 2010 ≡ Fragilaria crassa Metzeltin & Lange-Bertalot in Iconographia Diatomologica, 5: 89, fig. 1: 20-23, fig. 2:1, 1998.

Figures 6-7, 65

Length: 36-87.8 µm; breadth: 10-10.1 µm; striae: 5-6/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78296UPCB, 78299UPCB - 78302UPCB, 78304UPCB, 78306UPCB - 78317UPCB).

Ecological information: episamic species (Ribeiro et al. 2008), was found in 82% of the samples with higher values of abundance during the swamp and connected lake periods. In Brazil, it was recorded by Dunck et al. (2012) in a lentic, oligotrophic to mesotrophic environments and by Ribeiro et al. (2010) for sediment samples from a coastal zone.

Staurosirella crassa morpho. I (Metzeltin & Lange-Bertalot) Ribeiro & Torgan in Ribeiro et al., Revista Brasileira de Paleontologia 13(1): 24, 2010 ≡ Fragilaria crassa Metzeltin & Lange-Bertalot in Iconographia Diatomologica, 5: 89, fig. 1: 20-23, fig. 2:1, 1998.

Figures 8-9

Length: 14.1-58 µm; breadth: 4.8-9 µm; striae: 5-8/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27/II/2012, Ruwer et al. (78282UPCB - 78296UPCB, 78298UPCB - 78317UPCB).

Ecological information: these specimens differ from S. crassa in this study because they have rostrate to rostrate-rounded ends than just rounded ends. This species was recorded in 91% of the samples with higher values of abundance during the swamp and connected lake.

• Eunotiales

  • Eunotiaceae

Eunotia bidens Ehrenberg, Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 413. 1843.

Figures 22-24

Length: 20-72 µm; breadth: 7-11 µm; striae: 9-14/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78294UPCB, 78298UPCB - 78313UPCB, 78315UPCB - 78317UPCB).

Ecological information: periphytic species of lentic environments, occurring in acid waters, from oligotrophic to mesotrophic environments, and high temperature tolerant (Van Dam et al. 1994, Moro & Fürstenberger 1997, Lange-Bertalot et al. 2011, Faustino et al. 2016), associated with bryophytes in marsh environments (Furey et al. 2011). This species was registered in 76% of the samples, during the periods of lake and transition, but its abundance was greater during the swamp and lake.

Eunotia cf. deformis Metzeltin & Lange-Bertalot in Lange-Bertalot, Iconographia Diatomologica, 5: 57, pl. 16: figs. 9-11, 1998.

Figures 13-15, 70-71

Length: 19-62 µm; breadth: 7-9 µm; striae: 9-12/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78285UPCB, 78287UPCB - 78288UPCB, 78291UPCB - 78292UPCB, 78297UPCB - 78302UPCB, 78305UPCB - 78306UPCB).

Ecological information: taxon registered for sediment of Brazilian environments (Metzeltin & Lange-Bertalot 1998). The description of Eunotia deformis type in Metzeltin & Lange-Bertalot (1998) presents a length variation compare to the population we were found, thus this taxon was maintained as Eunotia cf. deformis. This species was found in 47% of the samples, with higher abundances during the lake period.

Eunotia formica Ehrenberg, Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 414. 1843.

Figures 16-17, 69

Length: 30-110µm; breadth: 7-11µm; striae: 10-12/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78284UPCB, 78286UPCB - 78293UPCB, 78295UPCB - 78306UPCB).

Ecological information: species with broad geographical distribution, intolerant of pollution (Bere & Mangadze 2014), of benthic habitat, present in lentic, humid environments or slow-flowing waters, occurring in oligotrophic to mesotrophic, acidic waters, tolerate to temperatures of 15 to 30 ºC (Patrick & Reimer 1966, Van Dam et al. 1994, Moro & Fürstenberger 1997, Ortiz-Lerín & Cambra 2007, Taylor et al. 2007). This species was found in 64% of the samples, during the swamp and transition period, but with greater abundances during the lake period.

Eunotia cf. intermedia (Krasske ex Hustedt) Nörpel & Lange-Bertalot in Lange-Bertalot, Bibliotheca Diatomologica, 27: 32, 1993 ≡ Eunotia pectinalis f. intermedia Krasske ex Hustedt in Rabenhorst's Kryptogamen Flora von Deutschland, Österreich und der Schweiz, 298, fig. 763 l-o, 1932.

Figures 18-19, 72-73

Length: 10-18.5 µm; breadth: 2.2-2.4 µm; striae: 12-18/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78288UPCB, 78292UPCB - 78294UPCB, 78297UPCB - 78298UPCB, 78300UPCB - 78312UPCB).

Ecological information: in the present study a population presents a variation of length smaller than the description of the species in other studies (Metzeltin & Lange-Bertalot 1998), therefore, identified the specimens as E. cf. intermedia. Species found in oligotrophic and acid environments (Van Dam et al. 1994, Ortiz-Lerín & Cambra 2007), was registered in 44% of the samples with greater abundance in the lake period.

Eunotia longicamelus Costa, Bicudo & Wetzel, Bibliotheca Diatomologica, 64: 32, pl. 73: figs. 1-17; pl. 74: figs. 108; pl. 75: 105; pl. 76: 1-4. 2017.

Figures 22-24, 66-68

Length: 17.5-85 µm; breadth: 4-7 µm; striae: 8-12/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78311UPCB, 78313UPCB - 78315UPCB).

Ecological information: species erroneously identified as Eunotia camelus Ehrenberg in taxonomic and ecological studies (Costa et al. 2017). Planktonic species of lentic and lotic acid environments, but can be found in alkaline environments. They tolerate oligotrophic to mesotrophic conditions and temperatures of 15 to more than 30 ºC (Moro & Fürstenberger 1997, Ortiz-Lerín & Cambra 2007, Faustino et al. 2016). This species was found in 91% of samples, was found in all periods, with greater abundance during the lake period.

Eunotia major (Smith) Rabenhorst. Flora europaea algarum aquae dulcis et submarinae, 1: 72, 1864 ≡ Himantidium majus Smith in A synopsis of the British Diatomaceae, 14, pl. XXXIII [33]: fig. 286, 1856.

Figures 25-26, 77-79

Length: 42-107 µm; breadth: 7.8-9 µm; striae: 8-11/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78301UPCB, 78303UPCB - 78312UPCB, 78315UPCB - 78317UPCB).

Ecological information: periphytic species of oligotrophic and acid waters, found in lentic and lotic environments (Moreira-Filho et al. 1973). Taxon with 85% frequency, with higher values of abundance in the lake period.

Eunotia naegelii Migula, Kryptogamen-Flora von Deutschland, Deutsch-Österreich und der Schweiz, 203. 1905.

Figure 27

Length: 20-85 µm; breadth: 2.7-4.2 µm; striae: 20/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78289UPCB, 78294UPCB, 78296UPCB - 78298UPCB, 78300UPCB, 78305UPCB).

Ecological information: benthic species, adhered by mucilage foot, occurring in lentic, oligotrophic and acidic waters (Van Dam et al. 1994, Moro & Fürstenberger 1997, Montoya-Moreno & Aguirre-Ramírez 2013). This species was found in 26% of the samples, with greater abundance for the current period.

Eunotia pseudosudetica Metzeltin, Lange-Bertalot, & García-Rodríguez, Iconographia Diatomologica, 15: 57, pl. 24: figs. 15-18, 2005.

Figures 28-29, 74-76

Length: 15.8-45 µm; breadth: 4-6.5 µm; striae: 11-16/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78316UPCB).

Ecological information: species registered in the Bicca et al. (2011) study, where the periphytic community was collected in environments which are characterized by slightly acidic and temperature variation of 14 to 29.8 ºC. The taxon was reported by Faustino et al. (2016) in samples ranging from meso to supereutrophic conditions. E. pseudosudetica was registered in 97% of the samples, in all periods, but with greater abundance in the lake period.

Eunotia rabenhorstiana var. elongata (Patrick) Metzeltin & Lange-Bertalot, Iconographia Diatomologica, 5: 76, pl. 64: figs. 1-13; pl. 65: figs. 17-19, 1998 ≡ Desmogonium rabenhorstianum var. elongatum Patrick in Notulae Naturae, 3, fig. 1-3, 1940.

Figure 30

Length: 77-125 µm; breadth: 5-7 µm; striae: 16-18/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB, 78285UPCB, 78287UPCB - 78301UPCB, 78303UPCB, 78305UPCB).

Ecological information: we observe through the periphytic samples that the specimens form chains, this species was found in 61% of the samples, with higher values of abundance in the transition period.

Eunotia subarcuatoides Alles, Nörpel, & Lange-Bertalot, Nova Hedwigia, 53: 188, pl. 4: figs. 1-36, 1991.

Figures 20-21

Length: 13-22 µm, breadth: 3-5 µm; striae: 16-20/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78283UPCB - 78285UPCB, 78287UPCB, 78289UPCB - 78298UPCB, 78300UPCB - 78303UPCB, 78305UPCB).

Ecological information: epiphytic species, occurring in acidic and oligotrophic environments (Van Dam et al. 1994, Ortiz-Lerín & Cambra 2007). This species was found in 58% of the samples with greater abundance during the transition period.

• Cymbellales

  • Gomphonemataceae

Encyonema silesiacum (Bleisch) Mann in Round, Crawford, & Mann, Diatoms, 667, 1990 ≡ Cymbella silesiaca Bleisch in Algen Europa's, 1802, 1864.

Figures 31, 80

Figures 80-95
Diatom species from Mutum Island (SEM).island in in the upper Paraná river floodplain, Brazil (SEM). 80. Encyonema silesiacum (internal valvar view). 81. Gomphonema gracile (internal valvar view). 82. Gomphonema lagenula (internal valvar view). 83. Gomphonema sp. 1 (internal valvar view). 84. Planothidium bagualensis (internal valvar view). 85. Planothidium aff. rostratum (internal valvar view). 86-87. Diadesmis confervaceae. 88-89. Humidophila contenta (internal valvar view). 90. Luticola hustedtii. 91. Luticola muticoides. 92. Luticola cf. simplex. 93. Nupela cf. bicapitata (internal valvar view). 94. Pinnularia brauniana (internal valvar view). 95. Pinnularia subcapitata (internal valvar view). (Scale bar: 5 µm).

Length: 28-45 µm; breadth: 7.8-10 µm; striae: 9-12/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78303UPCB, 78305UPCB, 78314UPCB).

Ecological information: E. silesiacum presented periphytic habitat, but also can be found in plankton community, is an indicator of oligotrophic water, but can be found in eutrophic waters. It occurs in lentic and lotic waters, with acidic to alkaline pH and temperature ranging from 15 to more than 30 ºC (Van Dam et al. 1994, Moro & Fürstenberger 1997, Marquardt & Bicudo 2014). The taxon was reported by Faustino et al. (2016) and Almeida & Bicudo (2014), studies of paleolimnological approach in Brazil, and was related with mesotrophic to supereutrophic conditions. This species was registered in 76% of the samples, with greater abundance in the transitional period.

Gomphonema gracile Ehrenberg, Die Infusion-sthierchen als vollkommene Organismen, 217, pl. 18: fig. 3, 1938.

Figures 32-33, 81

Length: 24-64.3 µm; breadth: 5.7-10.4 µm; striae: 12-17/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78283UPCB - 78284UPCB, 78287UPCB - 78298UPCB, 78303UPCB - 78304UPCB, 78313UPCB - 78314UPCB, 78316UPCB).

Ecological information: periphytic species from lentic environments, from oligotrophic to mesotrophic, neutral to alkaline waters, and tolerate temperatures from 15 to 30 ºC (Valente-Moreira 1975, Contin & Oliveira 1993, Van Dam et al. 1994, Moro & Fürstenberger 1997, Marquardt & Bicudo 2014, Faustino et al. 2016). This species was found in 61% of the samples with greater abundance in the current and transition periods.

Gomphonema lagenula Kützing, Die Kieselschaligen Bacillarien oder Diatomeen, 85, pl. 30: fig. 60, 1844.

Figures 34-35, 82

Length: 19-21 µm; breadth: 5-6 µm; striae: 17-18/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78306UPCB).

Ecological information: this periphytic species was related to mesotrophic and eutrophic conditions in the study of Dunck et al. (2013) and Faustino et al. (2016), and related to urban and polluted environments by Moresco & Rodrigues (2014). We have recorded the species in 79% of samples, it was absent only in the connected lake period, with higher values of abundance in the transition and current periods.

Gomphonema sp. 1

Figures 36-37, 83

Length: 22.5-44.9 µm; breadth: 5.9-7.4 µm; striae: 13-16/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78283UPCB, 78287UPCB, 78291UPCB, 78295UPCB - 78298UPCB, 78300UPCB - 78302UPCB, 78304UPCB, 78314UPCB).

Ecological information: we observe through the periphytic samples that the specimens presenting stalks for fixation. It was found in the current environment that presented a temperature of 27.9 ºC, acidic to neutral pH and low oxygen value. Occurred in 41% of the samples, more abundant in the current period.

Placoneis ovillus Metzeltin, Lange-Bertalot & García-Rodríguez, Iconographia Diatomologica, 15: 187, pl. 74: figs. 20-26, 2005.

Figures 38-39

Length: 14-24 µm; breadth: 7-10 µm; striae: 14-18/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27/II/2012, Ruwer et al. (78283UPCB, 78285UPCB - 78286UPCB, 78289UPCB, 78291UPCB - 78293UPCB, 78298UPCB - 78304UPCB, 78306UPCB - 78317UPCB).

Ecological information: this species was in 64% of the samples, with greater abundance in the period of the backwater.

• Cocconeidales

  • Achnanthidiaceae

Achnanthidium minutissimum (Kützing) Czarnecki in Kockiolek, Proceedings of the 11th International Diatom Symposium, 17: 157, 1994 ≡ Achnanthes minutissima Kützing in Synopsis diatomearum oder Versuch einer systematischen Zusammenstellung der Diatomeen, 578, fig. 54, 1833.

Figures 40-41

Length: 12.5-21 µm, breadth: 2.8-4 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB); sediment, 27-II-2012, Ruwer et al. (78284UPCB -78289UPCB, 78291UPCB - 78293UPCB, 78295UPCB, 78299UPCB - 78301UPCB, 78304UPCB, 78313UPCB - 78315UPCB).

Ecological information: the Achnanthidium minutissimum species complex is considered cosmopolitan and inhabits all freshwater habitats, mainly in lentic waters. Achnanthidium had a much wider tolerance range to various environmental factors. The Achnanthidium minutissimum is tolerant to a wide range of organic and inorganic pollution varying from oligotrophic to eutrophic conditions, although in some studies it is associated with low nutrients. It is tolerant at high temperatures (Moro & Fürstenberger 1997, Ponader & Potapova 2007, Potapova & HaMilton 2007, Faustino et al. 2016). This species was in 52% of the samples, with higher values of abundance in the transition and backwater period.

Planothidium bagualensis Wetzel & Ector, Phytotaxa, 156 (4): 201-210. 2014.

Figures 42-44, 84

Length: 12.9-30.8 µm; breadth: 6-9 µm; striae: 10-16/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78284UPCB, 78286UPCB - 78288UPCB, 78290UPCB, 78292UPCB, 78297UPCB - 78317UPCB).

Ecological information: species erroneously identified as Planothidium lanceolatum (Brébisson ex Kützing) H. Lange-Bertalot in Brazilian studies, found in the periphytic and phytoplanktonic community, mainly in lotic environments. Species with an optimum at mesotrophic waters, tolerating a large range of temperature (Burliga et al. 2005, Bes et al. 2012, Fontana & Bicudo, 2012, Bartozek et al. 2013, Wetzel & Ector 2014). This species was recorded in 73% of the samples, with greater abundance in the lake phase.

Planothidium aff. rostratum (Østrup) Lange-Bertalot in Lange-Bertalot, Iconographia Diatomologica, 6: 279, 1999 ≡ Achnanthes rostrata Østrup in Botanisk Tidsskrift 25: 35, pl. I: fig. 11, 1903.

Figures 45-46, 85

Length: 12-16 µm; breadth: 6-8 µm; striae: 12-16/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78283UPCB, 78292UPCB - 78293UPCB, 78295UPCB, 78297UPCB - 78317UPCB).

Ecological information: reported in studies by the synonym Achnanthes rostrata Østrup or by basionym Achnanthes lanceolata var. rostrata (Østrup) Lange-Bertalot. Species mainly found in the periphytic community, prostate, in lotic environments (Moro & Fürstenberger 1997, Bartozek et al. 2013), also found in sedimentary samples in Brazil (Fontana & Bicudo 2012). This species was found in 64% of the samples, with higher values of abundance during the lake and backwater periods.

• Naviculales

  • Diadesmidaceae

Diadesmis confervacea Kützing, Die Kieselschaligen Bacillarien oder Diatomeen, 109, pl. 30: fig. 8, 1844.

Figures 47-48, 86-87

Length: 12-22 µm; breadth: 5-8 µm; striae: 12-14/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78306UPCB, 78313UPCB, 78317UPCB).

Ecological information: benthic species that form long chains (observed in the periphytic samples), present in shallow water, wet and marshy environments. Occurs in eutrophic environments with high temperatures, acidic to alkaline waters (Cholnocky 1958, Hustedt 1966, Patrick & Reimer 1966, Van Dam et al. 1994, Moro & Fürstenberger 1997, Taylor et al. 2007, Torgan & Santos 2008). This species had a broader distribution in a Brazilian study with sediment samples (Faustino et al. 2016) and was related to mesotrophic to supereutrophic conditions. This species was found in 85% of samples, showed greater abundance during the transition period.

Humidophila contenta (Grunow) Lowe, Kociolek, Johansen, Van de Vijver, Lange-Bertalot & Kopalová, Diatom Research, 29: 357, 2014 ≡ Navicula contenta Grunow in Synopsis des Diatomées de Belgique, 109, 1885.

Figures 49-50, 88-89

Length: 7-15 µm; breadth: 2.2-3 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78311UPCB, 78313UPCB - 78317UPCB).

Ecological information: recently transferred of the Diadesmis to Humidophila genus (Lowe et al. 2014). Reported in paleolimnological studies in Brazilian environments (Costa-Böddeker et al. 2012, Fontana & Bicudo 2012), related to aerophilic habit and low-nutrient. Benthic species, such as D. confervaceae, occur in shallow waters and wet environments. It tolerates low luminosity and temperatures from 15 to 30 ºC, indicate mesotrophic to eutrophic environments and acid to alkaline waters (Van Dam et al. 1994, Moro & Fürstenberger 1997, Lobo et al. 2004, Taylor et al. 2007). Frequently in 91% of the samples with higher values of abundance during the transition period.

Luticola hustedtii Levkov, Metzeltin & Pavlov, Diatoms of Europe, 7: 131, pl. 24: fig. 49; pl. 166: figs. 24-37; pl. 168: figs. 7-26; pl. 170: figs. 1-7, 2013.

Figures 51-52, 90

Length: 10.5-25 µm; breadth: 5.8-8 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78296UPCB, 78300UPCB - 78306UPCB, 78313UPCB, 78315UPCB, 78317UPCB).

Ecological information: species of the genus Luticola are common in moist and swampy soils (Van de Vijver et al. 2002, Lowe et al. 2007). Luticola hustedtii was reported in Faustino et al. (2016) in sediment samples and was related to past oligotrophic conditions. This taxon was found in the epiphyton of slightly acidic waters in Straube et al. (2017). This species was found in 76% of samples, was abundant in the swamp and transition periods.

Luticola muticoides (Hustedt) Mann in Round, Crawford, & Mann, Diatoms, 671, 1990 ≡ Navicula muticoides Hustedt in Süsswasser-Diatomeen, 82, pl. 4: figs 33-36, 1949.

Figures 55-56, 91

Length: 10-23 µm; breadth: 6-9.5 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78298UPCB, 78300UPCB - 78302UPCB, 78304UPCB - 78305UPCB, 78313UPCB, 78315UPCB).

Ecological information: occurring lotic and lentic environments, in acidic to alkaline waters (Moro & Fürstenberger 1997). It was found in 70% of the samples with higher values of abundance during the transition.

Luticola cf. simplex Metzeltin, Lange-Bertalot & García-Rodríguez, Iconographia Diatomologica, 15: 116, pl. 87: figs 1-9, 2005.

Figures 53, 92

Length: 11-16 µm; breadth: 5.2-6 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sedimento, 27-II-2012, Ruwer et al. (78282UPCB - 78317UPCB).

Ecological information: this species was found in sediment samples of Faustino et al. (2016), where this taxon had a broad distribution range, related with oligotrophic and eutrophic conditions. Taxon occurring in 94% of samples with higher values of abundance during a transition and swamp periods.

• Brachysiraceae

Nupela cf. bicapitata (Hustedt) Tremarin & Ludwig, Fottea, 15(1): 78, 2015 ≡ Achnanthes bicapitata Hustedt in Botaniska Notiser, 386, figs. 68-71, 1952.

Figures 54, 93

Length: 18-20 µm; breadth: 5-6 µm; striae: 50/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78283UPCB - 78284UPCB, 78286UPCB - 78287UPCB, 78291UPCB - 78299UPCB, 78305UPCB, 78314UPCB).

Ecological information: taxon registered for the first time in Brazil by Tremarin et al. (2015), however, we consider our specimens as Nupela cf. bicapitata due to the smaller population length. This species was found in all periods, however, presented higher values of abundance in the period of the backwater.

• Sellaphoraceae

Sellaphora fusticulus (Østrup) Lange-Bertalot, Iconographia Diatomologica, 9: 216, 2000 ≡ Navicula fusticulus Østrup in Danske Diatoméer, 36; pl. 1, fig. 19, 1910.

Figures 57-58

Length: 32-46 µm; breadth: 8-9 µm; inconspicuous striae.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78283UPCB, 78286UPCB - 78303UPCB, 78313UPCB - 78314UPCB).

Ecological information: present in 70% of the samples with higher values of abundance during the transition period.

• Pinnulariaceae

Pinnularia brauniana (Grunow) Studnicka in Wein, Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft, 38: 737, 1888 ≡ Navicula brauniana Grunow in Atlas der Diatomaceen-kunde, pl. 45: figs 77-78, 1876

Figures 59-60, 94

Length: 28.1-50 µm; breadth: 5.6-8.3 µm; striae: 11-15/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78282UPCB - 78283UPCB, 78285UPCB - 78298UPCB, 78300UPCB - 78301UPCB, 78316UPCB).

Ecological information: P. brauniana was in 61% of the samples with greater abundance in the current and transition periods.

Pinnularia sp. 1

Figures 61, 95

Length: 19-23 µm; breadth: 4.8-5 µm; striae: 14-16/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, sedimento, 27-II-2012, Ruwer et al. (78288UPCB - 78298UPCB, 78300UPCB, 78302UPCB).

Ecological information: the species was found in 38% of the samples, with greater abundance during the transition period.

• Bacillariales

  • Bacillariaceae

Nitzschia palea var. debilis (Kützing) Grunow, Kongliga Svenska Vetenskaps-Akademiens Handligar, 17(2): 96, 1880 ≡ Synedra debilis Kützing in Die Kieselschaligen Bacillarien oder Diatomeen, 65, pl. 3: fig. XLV, 1844.

Figures 62-63

Length: 23-49.3 µm; breadth: 3.1-5.2 µm; fibulae: 11-13/10 µm.

Material examined: Brazil. PARANÁ: Porto Rico, Ilha Mutum, periphyton, 12-IV-2016, Ruwer et al. (78280UPCB - 78281UPCB); sediment, 27-II-2012, Ruwer et al. (78285UPCB, 78291UPCB, 78295UPCB, 78297UPCB, 78301UPCB, 78314UPCB).

Ecological information: found in periphytic and plankton community. Occurring in lentic, oligotrophic and eutrophic environments, but prefer clean or only slightly polluted waters (Tomas & Sabater 1985, Gasse 1987, Vyverman 1991, Van Dam et al. 1994, Moro & Fürstenberger 1997, Potapova & Charles 2007, Trobajo et al. 2009). A frequency of 23% with greater abundance in the current period.

Among the 31 taxa addressed, all were found in the sediment samples and 15 were present in the periphyton community, 16 were exclusive in the sediment (table 2). It is important to highlight the great exclusive diversity of diatoms that can be found in sediments. Along the temporal variation, there are consequently physical and chemical, biological and geomorphological changes in the environment. In temporal ecology, these factors and the habitat control the establishment and colonization of the species. The ability of populations to compete and persist in a habitat depends on how well species adapt to develop under specific environmental conditions (Patrick & Reimer 1966).

Table 2
Distribution and abundance of diatom species in the studied periods, Mutum island in in the upper Paraná river floodplain, Brazil (hatched area according to range of abundance values; dark gray - 30% to 100%, gray - 20% to 30%, light gray - 5% to 20%, white - 0%) * New records for the State of Paraná according to Tremarin et al. 2009, Bertolli et al. 2010, Faria et al. 2010, Silva et al. 2010, Santos et al. 2011, Moresco et al. 2011, Bartozek et al. 2013 - Table organized according to Round et al. 1990.

Taxa	Periphyton (2016)	Swamp	Transition (> 300 years)	Lake (> 760 years)	Backwater (> 920 years)
Aulacoseira italica
Staurosirella crassa
Staurosirella crassa mp. I
Eunotia bidens
Eunotia cf.deformis
Eunotia formica
Eunotia cf. intermedia
Eunotia longicamelus *
Eunotia major
Eunotia naegelli
Eunotia pseudosudetica
Eunotia rabenhorstiana var. elongata
Eunotia subarcuatoides
Encyonema silesiacum
Gomphonema gracile
Gomphonema lagenula
Gomphonema sp. 1
Placoneis ovillus
Achnanthidium minutissimum
Planothidium bagualensis *
Planothidium aff.rostratum
Diadesmis confervaceae
Humidophila contenta
Luticola hustedtii *
Luticola muticoides
Luticola cf. simplex
Nupela cf.bicapitata
Sellaphora fusticulus
Pinnularia brauniana
Pinnularia sp. 1
Nitzschia palea var. debilis

Each period was recognized in the record through the peculiar characteristics of each phase in the sedimentological material (Leli et al. 2017). In this research, some species presented greater abundance for each geomorphological period (backwater, lake, transition, and swamp). However, in the channel period (726-903 cal yr BP) was not found diatoms. The great dominance of periphytic species in swamp and transition periods could indicate the presence and abundance of macrophytes and vegetation located in the coastal region of the aquatic environment (Felisberto & Rodrigues 2010). The occurrence of some species as Diadesmis confervacea, Humidophila contenta, Luticola muticoides, Luticola cf. simplex in transition and swamp periods indicated shallow water environments, wet soils and marsh environments (Van de Vijver et al. 2002, Lowe et al. 2007, Torgan & Santos 2008). The great contribution of species of the order Naviculales in the transition period can be explained by these taxa being abundant in marshy environments as reported in the study of Vijayan & Ray (2016).

The lake period has a predominance of Eunotiaceae species (as Eunotia longicamelus, Eunotia major), which indicates a decrease of the pH, conductivity, and nutrients (Vélez et al. 2005). The occurrence of species belonging to the family Fragilariaceae (as Staurosirella crassa), in the backwater can be explained by the affinity of these taxa to unstable environments with continuous changes, characteristics that can be provided in a connected lake (Haworth 1976, Thomaz et al. 1997). Our results show a taxonomic contribution of diatoms to the region due to the three new registrations (E. longicamelus, Planothidium bagualensis and Luticola hustedtii). We showed the importance of palaeolimnological studies to increase information about aquatic biodiversity and also provided the first palaeolimnological research for a Brazilian floodplain.

• 1
  Parte da Dissertação de Mestrado do primeiro Autor

Acknowledgments

We thank the Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais (PEA), the Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupélia) and the Complexo de Centrais de Apoio à Pesquisa (COMCAP) from the Universidade Estadual de Maringá (UEM) for supplying the infrastructure. We would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for providing a master scholarship to Daiane Trevisan Ruwer, and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for a research productivity scholarship to Liliana Rodrigues. We thank Bárbara Dunck for the first corrections of the manuscript. We also thank the Grupo de Estudos do Meio Ambiente (GEMA/UEM) and Dr. José Cândido Stevaux for providing samples and data.

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Publication Dates

• Publication in this collection
  23 Aug 2018
• Date of issue
  Jul-Aug 2018

History

• Received
  04 Dec 2017
• Accepted
  06 June 2018