Chlorophyll-a and ocean productivity

Much of life on earth ultimately depends on the capture of light from the sun and its translation into energy via photosynthesis. This process is called primary production, and is performed by special pigments such as chlorophyll that exist in living plants. Although seaweeds can also photosynthesise, in the oceans most of the primary production is done by single-celled organisms called phytoplankton which drift in the water column. Satellites (specifically, SeaWifs and MODIS) can detect the concentration of chlorophyll in the oceans because it changes the colour of the water (read how it works).

Knowing the concentration of chlorophyll is useful because it allows researchers to estimate how much primary production occurs in different areas, and how this varies throughout the year. It can also be used to compare regions based on how much biological activity occurs there.

Click on the following links to view satellite-derived estimates of chlorophyll-a concentrations and see:

• how the average concentration changes between seasons
• how much the concentration varies within each season
• where primary productivity hotspots are most likely to occur in each season.

The map above shows the average ocean productivity hotspots as measured by chlorophyll-a concentrations. The lowest productivity is shown in dark blue and the highest in red.