Isolation and Cultivation of Zygnema Strains

Zygnema sp. ‘Saalach’ (SAG 2419) and Zygnema sp. ‘Elmau-Alm’ (SAG 2418) were isolated from hydroterrestrial habitats. Zygnema sp. ‘Saalach’ was obtained from the sandy littoral zone of the river Saalach (47° 47′ 8.70′′ N, 12° 56′ 42.66′′ E; 440 m above sea level (a.s.l.)) near Salzburg (Salzburg, Austria). Zygnema sp. ‘Elmau-Alm’ was collected from a sun-exposed shallow puddle in the catchment area of a subalpine pasture called ‘Elmau-Alm’ (47° 28′ 52.30″ N, 13° 14′ 48.85″ E, 1,500 m a.s.l.) near Werfenweng (Salzburg, Austria). Both strains were submitted to the Culture Collection of Algae of the Georg-August-Universität Göttingen and assigned strain numbers (see above). Samples were purified and established into unialgal cultures. Algae were cultivated on 1.5 % agar plates or in 250–500-mL Erlenmeyer flasks containing Bold’s Basal Medium (BBM; Bischoff and Bild 1963 ), respectively. Agar plates were sealed with Parafilm® to keep the moisture level constant during long-term cultivation. All algae grew in a dark/light regime of 16:8 h adjusted in a thermostat (Percival PGC 6L, Percival Scientific, Perry, GA, USA) at 20 °C and ~33 μmol photons m⁻² s⁻¹ in the light period. In the dark, temperature was reduced to 14.5 °C. Light was provided by Osram Daylight Lumilux Cool White lamps (L36W⁄840; Osram. Munich, Germany).