Abstract
A new benthic freshwater diatom, Fragilaria rinoi Almeida & C.Delgado sp. nov., is described from river periphyton samples in Portugal. Fragilaria rinoi sp. nov. is illustrated and discussed based on populations collected from the Vouga, Mondego and Lis river basins in central Portugal and compared with the type material of Fragilaria vaucheriae (Kütz.) J.B.Petersen. The morphological features of the new diatom species are documented through light and scanning electron micrographs, including a comparative analysis with related species of the genus (F. candidagilae Almeida, C.Delgado, Novais & S.Blanco, F. intermedia Grunow in Van Heurck, F. neointermedia Tuji & D.M.Williams, F. recapitellata Lange-Bert. & Metzeltin, F. perminuta (Grunow) Lange-Bert., F. vaucheriae and F. microvaucheriae C.E.Wetzel & Ector). Fragilaria rinoi sp. nov. is characterized by solitary cells without spines, lanceolate valves with slightly rostrate apices, a narrow, linear axial area, and a large, unilateral central area. Fragilaria rinoi sp. nov. may be confused with F. microvaucheriae in terms of length, striae density and outline, although a morphometric analysis revealed that F. rinoi sp. nov. is significantly wider. Fragilaria rinoi sp. nov. is present in rivers with high dissolved oxygen concentrations, medium to high conductivity, neutral to slightly alkaline pH and high mean values of nitrates and ammonium.
Highlights
Diatoms are very important and well represented in all freshwater ecosystems, being among the four biological quality elements required in the Water Framework Directive (WFD, The European Parliament and European Council 2000) for freshwater biomonitoring, and are known to be sensitive to a wide variety of pressures (Kelly & Whitton 1995; Almeida & Gil 2001; Nunes et al 2003)
Fragilaria rinoi sp. nov. is present in rivers with high dissolved oxygen concentrations, medium to high conductivity, neutral to slightly alkaline pH and high mean values of nitrates and ammonium
Fragilaria rinoi sp. nov. from Mogofores, the type locality (Figs 3–62: LM; Figs 78–82: SEM) and from other localities (Figs 63–77, LM: Mogofores Mar. 2012; Estarreja Mar. 2012; Foz do Ceira 20 Mar. 2012) were compared with the type material of Fragilaria candidagilae, F. recapitellata, F. perminuta, F. neointermedia, F. intermedia, F. capucina and F. vaucheriae
Summary
Diatoms are very important and well represented in all freshwater ecosystems, being among the four biological quality elements required in the Water Framework Directive (WFD, The European Parliament and European Council 2000) for freshwater biomonitoring, and are known to be sensitive to a wide variety of pressures (Kelly & Whitton 1995; Almeida & Gil 2001; Nunes et al 2003). In the years 2011 and 2012, as part of a monitoring program in the rivers of Central Portugal, the epilithic diatom flora was sampled in the Vouga, Mondego and Lis river basins. During this project, identification problems were encountered within Fragilaria species. Different authors have been using contrasting characters in order to delimitate species within this genus (Ognjanova-Rumenova et al 1994; Morales 2003), the systematic position of certain related genera is still not well resolved (e.g., Round 1984; Williams 2006)
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