The prasinophytes
are known to be common in temperate and cold regions where they
can occur as prominent constituents of the marine picoplankton
(Throndsen, 1976). One well known genus of prasinophytes is
Ostreococcus, considered to be the smallest (ca. 0.95 μm) free-living
eukaryote, found in marine waters worldwide (Courties et al.,
1994). Two clades of Ostreococcus were thought to be distinguished
in the environment by their adaptation to light intensities, with the
high-light ecotypes being detected at warm oligotrophic sites
whereas the low-light ecotypes were present in cooler mesotrophic
and coastal waters (Rodriguez et al., 2005).