For anyone interested in learning about phytoplankton and other microorganisms, I highly recommend the YouTube series Journey to the Microcosmos, https://www.youtube.com/watch?v=wS2mdmt4JPw&list=PLf3BfsFyWW...

For example this video about diatoms, which are responsible for a quarter to half of the oxygen produced on earth, https://www.youtube.com/watch?v=Ygty9HxhFK4 https://en.wikipedia.org/wiki/Diatom

Seeing high-quality video of things moving around gives a much more visceral impression than just reading text interspersed with static images, in my opinion.