Earth's Journal

Biosphere Journal Entry

Chlorophyll Increases Along Coasts (April 9, 2005)

chlorophyll

From 1998 to 2003, areas in red had an increase in chlorophyll while areas in blue had a decrease. Areas in dark green had slightly lower levels, while those in light green were slightly higher. NASA.

Oceans are getting greener along the world's coasts. Chlorophyll levels increased by over 10 percent between 1998 and 2003, according to a recent NASA survey.

The chlorophyll increase is a sign that levels of microscopic plants called phytoplankton are on the rise along coastlines. At the same time, phytoplankton levels went down at the centers of the world's oceans in areas called the ocean's "deserts."

Scientists aren't sure why phytoplankton levels rose only along the coasts. It could be a sign of "nutrient stress." Water that enters the oceans with wastes from farms and factories increases the supply of nutrients like phosphorus and nitrogen that fuel the growth of plankton. Large plankton blooms can deplete the ocean's oxygen supply. This in turn harms a wide variety of marine life.

The drop in plankton in the mid-ocean is probably linked to rising sea surface temperatures. Warmer temperatures tend to create a layer of warmer water near the surface. This makes it harder for cold, nutrient-rich water from the ocean depths to make it to the surface.