Dec. 7, 2006 — Almost ten years of unprecedented color satellite imagery of Earth’s oceans has now made one thing crystal clear: When the water gets warmer, ocean life declines.
The orbiting Sea-viewing Wide Field-of-view Sensor (SeaWiFS) has been collecting data on the colors of the oceans since 1997. That global data, combined with detailed ocean temperature data, shows an undeniable connection between the vibrancy of phytoplankton — the microscopic plants that anchor the ocean food web — and the temperature of the water, scientists announced on Wednesday.
"On a global scale there’s a very strong correlation between climate and ocean plants," said Michael Behrenfeld, an ocean plant ecologist at Oregon State University in Corvallis. "(Phytoplankton) are very sensitive to changes in climate."
Behrenfeld is the lead author of a report on the correlation in the Dec. 7 issue of the journal Nature.
The climate connection in the oceans is hugely important, Behrenfeld explained, because phytoplankton is the food of the animals that, in turn, are the mainstay of the fish we eat.
What’s more, the tiny green plants are also a gigantic player in fighting the rise in the greenhouse gas carbon dioxide in our atmosphere. It’s estimated that ocean plants account for about half the Earth’s capacity to absorb carbon dioxide, he said.
Just how warmer waters hurt phytoplankton is a tad more complex.
What happens, said Behrenfeld, is that warmer waters stay on the surface because they are more buoyant. It’s in those sunny surface waters where phytoplankton needs to be.
The problem is that when the surface waters are dramatically warmer than the waters deeper down, there's a lot less mixing of waters up and down. This hurts the phytoplankton because it’s the deeper cold waters that contain the nutrients they need to thrive.
