Is Global Warming Reducing the Ocean's Food Supply?

We all have heard the warnings of scientist about global warming. The recent documentary by Al Gore, "A Inconvient Truth", gave us all much to think about. Many people when thinking of global warming only think about it getting warmer outside and how it will affect them. Scientist now is looking into how it is affecting the ocean food supply.

Recent NASA satellite data has shown that phytoplankton, a key to the food chain of the ocean decreases as the water temperature increases. This causes great concern to scientist about much food marine life will have as global warming progresses.

The impacts of global warming can fluctuate tremendously in different regions, due to complexities of ocean circulation. Phytoplankton is the microscopic plant life that zooplankton and other marine animals eat, essentially the grain crop of the world's oceans. The recent drop in phytoplankton production in much of the world's oceans could be a forerunner of how the oceans will respond later in the century to global warming.

As surface waters heat up, the vertical layers of seawater could mix less with each other, an effect called vertical stratification. Upwelling of cold, nutrient-rich waters would become less frequent, decreasing the amounts of phytoplankton. In addition, phytoplankton uses carbon dioxide for photosynthesis. If plankton becomes depleted, the oceans could not remove as much carbon dioxide from the atmosphere.

Small changes that happen in the bottom of the food web can have dramatic changes to certain species at higher levels of the food chain. A satellite commissioned by NASA tracked water temperature and the production of phytoplankton from 1997 to 2006, finding that for the most of the worlds oceans, when one went up the other went down and vice versa. As water temperatures increased from 1999 to 2004, the crop of phytoplankton dropped significantly, about 200 million tons a year. On average about 50 billion tons of phytoplankton are produced yearly.