“Scientist have long understood how nutrients move from the oceans surface to its depths. As phytoplankton die, they sink and collect on the ocean floor. But if nutrients are continually sinking to the depths of the ocean, how are surface waters replenished with nutrients? Scientist discovered that in certain regions of the ocean, the nutrients-rich deep water was upwelling, or rising to the surface” which phrase from the paragraph helps you to understand that ocean health involves steady restoration