Diatoms and radiolaria, SEM - stock photo

Diatoms and radiolaria. Coloured scanning electron micrograph (SEM) of a circular arrangement of various diatoms and radiolaria. Diatoms are planktonic unicellular algae. They have a mineralised cell wall (frustule) divided into two halves. The frustule contains silica and provides protection and support. Radiolarians are amoeboid protozoa that produce intricate mineral skeletons. They are found as zooplankton throughout the ocean, and their skeletal remains cover large portions of the ocean bottom as radiolarian ooze.