Chrysophytes include diatoms and golden algae (desmids). They are found in freshwater as well as in marine environments. They are microscopic and float passively in water currents (plankton). Most of them are photosynthetic. Mycoplasma is a prokaryotic organism that completely lacks a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants. Anabaena is cyanobacteria which forms a symbiotic association with leaves of Azolla plant (Anabaena azollae) or roots of Cycas (Anabaena cycadae). It doesn't form lichens. Red dinoflagellates (Gonyaulax) undergo such rapid multiplication that they make the sea appear red (red tides). Toxins released by such large numbers may even kill other marine animals such as fishes.