what are the differences in diatoms and seaweed
Diatoms are producers within the food chain. A unique feature of diatom cells is that they are enclosed within a cell wall made of silica (hydrated silicon dioxide) called a frustule. These frustules show a wide diversity in form, but are usually almost bilaterally symmetrical, hence the group name.
Seaweed \Seaweed`\, n. 1. Popularly, any plant or plants growing in the sea. [1913 Webster] 2. (Bot.) Any marine plant of the class Alg[ae], as kelp, dulse, {Fucus}, {Ulva}, etc. [1913 Webster].