Multisizer 3 coulter cell counter

Synchronous cultures of unicellular freshwater chlorophytes Scenedesmus vacuolatus were used as the test organism. Scenedesmus vacuolatus were grown photoautotrophically in a sterile inorganic medium at pH 6.4 (modified from Grimme & Boardman, 1972 (link)). The strain (SAG 211‐15) was bought from the experimental phycology and culture collection of algae at the University of Goettingen. Algae were cultured under synchronous conditions as described by Faust et al. (2001 (link)) and Altenburger et al. (1990 (link)). Cultures were grown in sterile glass vessels (Supporting Information, Figure S4) under the following parameters: a bubbling regime of compressed air and 1.5% CO₂, at 28 °C ± 2 °C, and under illumination of saturated white light at an intensity of 400 µmol photons s⁻¹ m⁻² in a 14:10‐h light:dark cycle. Illumination parameters were achieved using 4 × Osram L36W/827 Lumilux Interna and 4 × Osram L36W/865 Lumilux Daylight fluorescent lamps. An inoculum culture in fresh medium was performed daily to allow exponential growth in the control culture throughout the incubation period without risk of nutrient depletion (maximum cell density 10⁶ cells/ml measured on a Multisizer 3 Coulter cell counter; Beckman).