Three New Diatom Species from Spring Habitats in the Northern Apennines (Emilia-Romagna, Italy)

Marco Cantonati,Olena Bilous,Liesbeth Van Wensen,Horst Lange-Bertalot,Nicola Angeli

doi:10.3390/d13110549

Abstract

Using light (LM, including plastid characterization on fresh material) and scanning electron microscopy (SEM), as well as a thorough morphological, physical, chemical, and biological characterization of the habitats, the present study aims at describing three species new to science. They belong to the genera Eunotia Ehrenb., Planothidium Round and L. Bukht., and Delicatophycus M.J. Wynne, and were found in two contrasting spring types in the northern Apennines. The three new species described differ morphologically from the most similar species by: less dense striae and areolae, and the absence of a ridge at the valve face-mantle transition (SEM feature) [Eunotia crassiminor Lange-Bert. et Cantonati sp. nov.; closest established species: Eunotia minor (Kütz.) Grunow]; narrower and shorter cells [Planothidium angustilanceolatum Lange-Bert. et Cantonati sp. nov.; most similar species: Planothidium lanceolatum (Bréb. ex Kütz.) Lange-Bert.]; barely-dorsiventral symmetry, set off ends, and lower density of the central dorsal striae [Delicatophycus crassiminutus Lange-Bert. et Cantonati sp. nov.; most similar species: Delicatophycus minutus M.J.Wynne]. Two of the three species we described are separated from the closest species by dimensions. Their description improved knowledge on two taxa (Eunotia minor s.l. and Planothidium lanceolatum s.l.) likely to be only partially resolved species complexes. We could also refine knowledge on the ecological profiles of the three newly-described species. Eunotia crassiminor sp. nov., as compared to Eunotia minor, appears to occur in colder inland waters with a circumneutral pH and a strict oligotrophy as well with respect to nitrogen. The typical habitat of Planothidium angustilanceolatum sp. nov. appears to be oligotrophic mountain flowing springs with low conductivity. Delicatophycus crassiminutus sp. nov. was observed only in limestone-precipitating springs, and is therefore likely to be restricted to hard water springs and comparable habitats where CO2 degassing leads to carbonate precipitation. Springs are a unique but severely threatened wetland type. Therefore, the in-depth knowledge of the taxonomy and ecology of characteristic diatom species is important, because diatoms are excellent indicators of the quality and integrity of these peculiar ecosystems in the face of direct and indirect human impacts.

Highlights

Using light microscopy (LM, both fresh and prepared materials) and scanning electron microscopy (SEM) observations, as well as a thorough morphological, physical, chemical, and biological characterization of the habitats, the present study aims to describe in detail three new species from the genera Eunotia, Planothidium and Delicatophycus found in two contrasting spring types in the Northern Apennines
The in-depth knowledge of the taxonomy and ecology of characteristic diatom species is important because diatoms are excellent indicators of the quality and integrity of these peculiar ecosystems in the face of direct and indirect human impacts
By applying Krammer’s [13] ratio of maximal and minimal width as a reliable means to test the quality of taxa, we find that we have contributed to improve knowledge on two taxa (Eunotia minor s.l. and Planothidium lanceolatum s.l.), which are likely to be only partially resolved complexes of species because they have a max-min width ratio of 2 and 2.2, respectively

Summary

Introduction

Rheocrenic mountain springs with low conductivity are typically high-ecologicalintegrity, oligotrophic systems with relevant discharge and current velocity They provide a habitat to many threatened-Red-List and recently discovered species (e.g., [5]), but they are sensitive to disturbance from human activities and climate and environmental change (e.g., [6,7]). Many diatom species were described from springs, and it is easy to provide examples with reference to one of the genera discussed in the present paper, namely Eunotia: E. arcofallax Lange-Bert., E. braendlei Lange-Bert. Using light microscopy (LM, both fresh and prepared materials) and scanning electron microscopy (SEM) observations, as well as a thorough morphological, physical, chemical, and biological characterization of the habitats, the present study aims to describe in detail three new species from the genera Eunotia, Planothidium and Delicatophycus found in two contrasting spring types in the Northern Apennines

Materials and Methods

Results

Discussion