Light micrograph of marine diatom Achnanthes spec. Achnanthes forms short chains, cells remain loosely connected. Achnanthes lives epiphytic on aquatic plants and any other substrates. The specimens are from the North Sea, German Bight. The relatively cool northern seas harbor very large quantities of these primary producers, which autotrophically form the base of the food chain. At the same time the diatoms of the oceans form about 45% of the oxygen worldwide. Microscopic contrast method : Differential interference contrast. Magnification 400x at a print width of 10 cm.