December 09, 2006

Disappearing Phytoplankton

On Thursday NPR's Morning Edition had a segment on the bluing of the ocean which scientists have connected with the warming oceans. The color of the ocean is directly related to the amount of phytoplankton in the water. The greener the waters, the more phytoplankton, the bluer indicates less.

Courtesy of NASA
click image to visit the NASA resource page

So what does this mean? The phytoplankton is an indication of the amount of plant life in the ocean. In fact the phytoplankton is the equivalent of the grass on land. When there is more phytoplankton, the ocean has more food to support the food chain. Furthermore, phytoplankton is essential for enabling the ocean to sequester excess carbon in the atmosphere.

The sea is one of nature's "carbon sinks", which removes carbon dioxide from the atmosphere and deposits the carbon in a long-term store - dissolved in the ocean or deposited as organic waste on the seabed. The vast quantities of phytoplankton in the oceans absorb huge amounts of carbon dioxide. When the organisms die they fall to the seabed, carrying their store of carbon with them, where it stays for many thousands of years - thereby helping to counter global warming.

What scientists have found is that during the past decade, the amount of phytoplankton has tracked directly to the warming of the oceans. During the late 90s, the amount of phytoplankton increased leading to greener seas. But since then, the oceans have been growing bluer indicating a harsher environment for phytoplankton.

Ocean plant growth increased from 1997 to 1999 as the climate cooled during one of the strongest El Niņo to La Niņa transitions on record. Since 1999, the climate has been in a period of warming that has seen the health of ocean plants diminish.

The new study also explains why a change in climate produces this effect on ocean plant life. When the climate warms, the temperature of the upper ocean also increases, making it "lighter" than the denser cold water beneath it. This results in a layering or "stratification" of ocean waters that creates an effective barrier between the surface layer and the nutrients below, cutting off phytoplankton's food supply. The scientists confirmed this effect by comparing records of ocean surface water density with the SeaWiFS biological data.

The NPR report went on to say that the phytoplankton is also directly connected to the acidification of the oceans because it is the phytoplankton which is responsible for the carbonic acid in the seas. When the phytoplankton decreases, it reduces the calcium carbonate in the sea which is used to build the shells and corals so once again we see the entire complex food chain being undermined by the warming ocean.

It was only a few weeks ago that I first read about the acidification of the oceans, but now it seems like many of the articles on global warming are constantly circling back to acidification as one of the more drastic consequences of global warming. What will humans exploit when the ocean, the original source of life on earth, is once more made into a primordial stew of jelly?

Update: here's a piece from NASA about this topic. As they show, this study is part of a growing body of evidence that global warming is truly happening.

This is at least the third significant peer-reviewed research paper in the past six months showing that long-anticipated global warming biological side effects are already happening. Other studies looked at global warming connections to wildfires and die-offs of plant and animal species.

"What you're looking at is almost an avalanche of each individual effect," said Stanford University biological sciences professor Stephen Schneider. "As it gets warmer and as we measure more things, the evidence accumulates."

Posted by Mary at December 9, 2006 11:01 AM | Environment | Technorati links |

Here's a possible strategy:
Different areas of the ocean experience different types, degrees, and durations of stratification based on their location in the system of currents. The different areas have, of course, different phytoplankton populations of species well suited to that particular climate/stratification scheme. Perhaps it might be worthwhile to experiment with transplanting some species into new areas? In general, I wouldn't encourage distributing exotics, but it might be better than the alternative in this case. Some care would need to be taken to choose species that the local zooplankton could physically manage--too big or too small and the new species wouldn't get eaten. At very least, labs should be making phytoplankton "zoos" from which to start populations for those species likely to be lost.

Posted by: tjewell at December 10, 2006 01:28 PM