the
suggestion that eukaryotic algae, most notably the
green algae, could have taken their “first steps” in the freshwater environment. First, it can be argued
that the simplest cyanobacteria were originally only
present in freshwater (Sanchez-Baracaldo et al.
2005, Blank and Sanchez-Baracaldo 2010). Such a
scenario could help explain why cyanobacterial
fossils have not been confirmed before 2,000 Ma.