Phototactic responses of Elachista antarctica (Phaeophyceae) spores of different ages across a broad irradiance range using new motion analysis software

Phototactic movements of Elachista antarctica spores were quantified across a wide range of irradiances from 10 to 800 μmol photons m-2 s-1 using the recently updated version of CellTrak 1.5 motion analysis software. Spores 0–12 h old exhibited phototactic attraction at 80 and 200 μmol photons m-2 s-1, which contributed to vertical movements up out of the boundary layer to be further dispersed hydrodynamically, but were repelled at 800 μmol photons m-2 s-1, causing spores to retreat from detrimental irradiances. No significant effects were observed among spores released 24–36 h before measuring phototaxis at 200 and 800 μmol photons m-2 s-1.