Cymbella lanceolata is a motile colony-forming diatom. Its behavior depends strongly on light exposure.
In the video above left you can see in a time-lapse the activities during the day and at night, which are very different.
In the video below you can observe how a colony is left by the diatoms at high light incidence.
Details can be found here: https://diatoms.de/en/directly-attached-cymbella-i
