Spherical cyanobacteria or algae

[Heliozian]

I'm trying to identify these green single cells using the Bellinger Freshwater Algae key which tries to narrow down to one of 250 common genera so obviously doesn't cover everything.
The cells are in freshwater, the inner green cell diameter is 20 microns, the outer diameter of the mucilage is 23.7 microns.
I can see some structures within the cells (particularly a circular structure about 4.9u in diameter)
My question is in regard to one of the key couplets "Cell pigments localized in chloroplasts" or "Cell pigments not localized in chloroplasts". I'm picking the latter as there is colour throughout the cell but I can see some differentiation within the cell so I may be wrong. The divide is, I think, between cyanobacteria and algae - a pretty mayor divide to be stumbling on and one which I'd like to crack. If I follow the not located in chloroplasts branch they key out as Gloeocapsa (which should be 1 - 17 microns) or Chroococcus (which can be 2 - 58 microns but are more likely to be in groups rather than individual)

Any help much appreciated

All the best

Ian

[Crater Eddie]

Just off the top of my head, and without looking at the measurements, this looks like it could be the green form of our old friend haematococcus.
CE

[Heliozian]

Many thanks - that looks very plausible and is an option I'd missed with my simple key following. The key has a flagelate or non-flagelate couplet. My cells are non-motile so I followed the non-flagelate branch but Haematococcus is in the flagelate end of the key as it's often flagelate. The pitfalls of simplified keys and an inexperienced operator! It does seem to be the right sort of size.
Thanks again and all the best
Ian