By analyzing microfossils from sediment cores, scientist
have been able to track the ratio of oxygen isotopes
on both sides of the Isthmus of Panama. Changes in the
ratio of isotopes indicate how salinity levels in the
Caribbean and Pacific changed over time.
! Examine the graph carefully to interpret how salinity
changed over time.
3. Describe the changes in salinity in the Caribbean
Sea and the Pacific Ocean from six to two and a half
million years ago (mya).