Ancient Symbiosis

Emiliania, like most other phytoplankton, are autotrophic. They produce their own energy through oxygenic photosynthesis. Their photosynthetic organells are chloroplasts derived through "secondary endosymbiosis," that is, ancestral engulfment of an alga that already contained a chloroplast derived from a cyanobacterial ancestor. This is what I am referring to. 200 Million years ago cyanobacteria formed this symbiosis. E. hux became prevalent about 250,000 years ago in Quaternary Sea. The Coccoliths evolved at a time when Carbon dioxide was very high in the atmosphere and the Mg/Ca ratio was high as well. So it is a mystery as to how and why they came about under these conditions. I never said E. hux was a cyanobacteria but a symbiotic partner with a host. They do form symbiotic relationships with Coccolithophores.