@indigomoth - People eat algae as well, and that might become a more and more important food source in the future. It can be used as a fertilizer too, I think.
What I love is when you look at a little bit of ocean water underneath a microscope. I'm training to be a teacher right now and I have plans to always have a microscope set up in the classroom. With just drops of seawater and plankton I believe I could have something different underneath the scope every day of the year. The diatoms alone are gorgeous and fascinating, and definitely worth looking up. Try searching for pictures of planktons online.