Chaetoceros diadema is a diatom in the genus Chaetoceros. The easiest way to identify this species is by finding the very characteristic diadem-like resting spores.
Cells united into chains. Very characteristic, diadem - like spores (see species image). One chloroplast. The base of the setae is short.[1]
Chaetoceros constrictus is quite similar in the vegetative stage, but its resting spores are different from C. diadema resting spores .
Jakobsen. Rasmus. Hansen. Per Juel. Daugbjerg. Niels. Andersen. Nikolaj Gedsted. The fish-killing dictyochophyte Pseudochattonella farcimen: Adaptations leading to bloom formation during early spring in Scandinavian waters. Harmful Algae. June 2012. 18. 85–95. 10.1016/j.hal.2012.04.008.