Analysis of the type material of Planothidium delicatulum (Bacillariophyta) with the description of two new Planothidium species from the sub-Antarctic Region

Abstract

During a survey of the freshwater diatom flora on the sub-Antarctic islands of the southern Indian Ocean, two new Planothidium species were observed, showing some resemblance to Planothidium delicatulum. Therefore, the type material of Achnanthidium delicatulum Kützing was analysed, a common species in northern hemisphere waterbodies that was later transferred to the genus Planothidium. Additionally the material of Types du Synopsis des Diatomées de Belgique n° 234, designated in 1980 as neotype for Achnanthes delicatula was investigated. This analysis showed that the population in Types n° 234 is not conspecific with Achnanthidium delicatulum but in fact is a population of Planothidium galaicum. Both Planothidium species in the investigated Antarctic material are described as new to science: P. lilianeanum Van de Vijver sp. nov. and P. australodelicatulum Van de Vijver, C.E.Wetzel et Ector sp. nov. The new species can be differentiated based on differences in valve outline, presence of ridges and silica outgrowths on the rapheless valve, the structure of the raphe and the shape and size of the central area. Notes on the ecology and distribution of the new Antarctic species are added. Achnanthidium delicatulum is formally lectotypified.

Critical multi-stranded approach for determining the ecological values of diatoms in unique aquatic ecosystems of anthropogenic origin

“…Planothidium delicatulum was mainly recorded in salty and brackish environments with neutral or slightly alkaline conditions (Campeau, Pienitz & Héquette, 1999; Gell et al, 2005; Caballero et al, 2013; Yamamoto, Chiba & Tuji, 2017; Van de Vijver, Wetzel & Ector, 2018).…”

“…However, these findings, may not be introduced and updated in the OMNIDIA program for a number of years. The OMNIDIA system is used by state institutions in many countries around the world to assess surface water quality (Campeau, Pienitz & Héquette, 1999; Rumrich, Lange-Bertalot & Rumrich, 2000; Witkowski, Lange-Bertalot & Metzeltin, 2000; Gell et al, 2005; Potapova & Ponader, 2008; Wojtal & Sobczyk, 2012; Caballero et al, 2013; Żelazna-Wieczorek & Olszyński, 2016; Yamamoto, Chiba & Tuji, 2017; Lange-Bertalot et al, 2017; Földi et al, 2018; Van de Vijver, Wetzel & Ector, 2018). Clearly, if these assessments are based on incomplete or outdated data, assessments of aquatic environments may be fraught with error.…”

Peer Review #1 of "Critical multi-stranded approach for determining the ecological values of diatoms in unique aquatic ecosystems of anthropogenic origin (v0.1)"

“…The pH of the water in which this species was observed did not exceed 7. Planothidium delicatulum was mainly recorded in salty and brackish environments with neutral or slightly alkaline conditions (Campeau, Pienitz & Héquette 1999;Gell et al 2005;Caballero et al 2013;Yamamoto, Chiba & Tuji 2017;Van de Vijver, Wetzel & Ector 2018). Based on our findings, we suggest changing the following ecological indicator values in the Van Dam et al (1994) classification for P. delicatulum: -pH requirements: 3 (neutrophilic) (changing from 5 to 3); -salinity: 5 (brackish-marine) (changing from 4 to 5).…”

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“…However, these findings, may not be introduced and updated in the OMNIDIA program for a number of years. The OMNIDIA system is used by state institutions in many countries around the world to assess surface water quality (Campeau, Pienitz & Héquette 1999;Rumrich, Lange-Bertalot & Rumrich 2000;Witkowski, Lange-Bertalot & Metzeltin 2000;Gell et al 2005;Potapova & Ponader 2008;Wojtal & Sobczyk 2012;Caballero et al 2013;Żelazna-Wieczorek & Olszyński 2015;Yamamoto, Chiba & Tuji 2017;Lange-Bertalot, Hofmann & Werum 2017;Földi et al 2018;Van de Vijver, Wetzel & Ector 2018). Clearly, if these assessments are based on incomplete or outdated data, assessments of aquatic environments may be fraught with error.…”

“…The pH of the water in which this species was observed did not exceed 7. Planothidium delicatulum was mainly recorded in salty and brackish environments with neutral or slightly alkaline conditions (Campeau, Pienitz & Héquette 1999;Gell et al 2005;Caballero et al 2013;Yamamoto, Chiba & Tuji 2017;Van de Vijver et al 2018). Based on our findings, we suggest changing the following ecological indicator values in the Van Dam et al (1994) classification for P. delicatulum: -pH requirements: 3 (neutrophilic) (changing from 5 to 3); -salinity: 5 (brackish-marine) (changing from 4 to 5)…”