Seaweeds is the common name used for

Explanation

Seaweeds is the common name for large, multicellular marine algae, most commonly referring to brown algae, which includes kelp and other similar organisms. While green algae can also be called seaweeds in some contexts, brown algae are more typically associated with the term. Diatoms and dinoflagellates, on the other hand, are not considered seaweeds as they are generally smaller and have different characteristics. Diatoms are known for their silica shells, and dinoflagellates are a type of plankton associated with red tides.