The Twilight Zone | The Twilight Zone (1959 TV series) | Negative Zone | Panama Canal Zone | Eastern Time Zone | Twilight Zone | Korean Demilitarized Zone | The Dead Zone (TV series) | The Dead Zone | Pacific Time Zone | Hardiness zone | Central Time Zone (North America) | Ponce Historic Zone | Metekel Zone | Arsi Zone | The Twilight Zone (2002 TV series) | O-Zone | Mirab Welega Zone | Hadiya Zone | Gamo Gofa Zone | Debub Omo Zone | Zone | Semien Omo Zone | The Ultra Zone | Rapti Zone | Karnali Zone | Debub Wollo Zone | Dawro Zone | Central Time Zone | Agew Awi Zone |
Synechococcus has been observed to occur at concentrations ranging between a few cells per ml to 106 cells per ml in virtually all regions of the oceanic euphotic zone except in samples from the McMurdo Sound and Ross Ice Shelf in Antarctica.