Prochlorococcus cyanobacteria are very highly abundant in sea water. Why was Prochlorococcus not discovered until the 1980s? Please select all that apply.

A) Metagenome sequencing was not available until the 1980s
B) Prochlorococcus species are photosynthetic
C) Prochlorococcus cells are hard to distinguish by light microscopy
D) Prochlorococcus cells were not easily cultured