The Southern Ocean -- a huge water mass surrounding the Antarctic continent that comprises one-tenth of the world's oceans -- supports one of the most productive marine ecosystems on Earth.
(a huge water mass; surrounding; the Antarctic continent that comprises one-tenth of the world's oceans) (the Antarctic continent; comprises; one-tenth of the world's oceans) (The Southern Ocean; supports; one of the most productive marine ecosystems on Earth)
a huge water mass the Antarctic continent The Southern Ocean
surrounding comprises supports
the Antarctic continent that comprises one-tenth of the world's oceans
one-tenth of the world's oceans
one of the most productive marine ecosystems on Earth