Step-by-step explanation:
Diatoms are chrysophytes. A photosynthetic, unicellular, eukaryotic, passive floating protist. Their wall is made up of cellulose with silica embedded in it which takes millions of years to decompose, hence they deposit in the floor of ocean known as diatomaceous earth. It is used in commercial purposes like insulation, sound proofing etc. They are also known as chief producers of ocean.
Dinoflagellates are pyrrophytes. A photosynthetic, unicellular, eukaryotic (or more precisely mesokaryotic) protists found in aquatic ecosystem. They have two flagellas: one longitudinal, one transverse which helps in their locomotion
Gonyaulax, the certain species of dinoflagellates is known for causing red tides.
No, both of them can't be considered as mixotropic. As they are only photosynthetic and can prepare their own food. Euglena shows mixotrophic nutrition.