This is exactly right. The alga has one more organelle that originated as a bacterial symbiont, just like mitochondria and chloroplasts, which is super cool! The alga, Braarudosphaera bigelowii, is a coccolithophore, which is very cool by itself. They are important part of the carbon cycle. And they look supercool - they are covered in calcareous scales and this species is shaped like a dodecahedron!!! https://upload.wikimedia.org/wikipedia/commons/c/cb/Braarudosphaera_bigelowii.jpg