Pediastrum algae with Spirulina cyanobacteria in the background. The little spikes on the outer cells of the Pediastrum are used to stay afloat near the surface of the water. Also, if you look closely, you can see the nucleus inside the cells.
Although both are photosynthetic microorganisms, cyanobacteria tend to be significantly smaller in size compared to eukaryotic algae (as you can see in this photo).
Edit: made a correction. the Cyanobacteria is most likely in the Spirulina genus