algae vs kelp

algae

noun
  • A particular kind of algae. 

  • Algal organisms viewed collectively or as a mass; algal growth. 

kelp

noun
  • Any of several large brown algae seaweeds (order Laminariales). 

  • The calcined ashes of seaweed, formerly used in glass and iodine manufacture. 

verb
  • To gather kelp. 

How often have the words algae and kelp occurred in a corpus of books? (source: Google Ngram Viewer )