Here are two diatoms. I am afraid that I do not offhand know the
names, but very pretty. Most of what I see are diatoms, of which
there are many hundreds of species. If anybody is looking for an
interesting scientific topic, I can recommend nothing more pertinent
in these days of concerns for global warming than diatoms. They occur
in fresh and salt water and are at the base of the food chain, so
essential to everything else.